Thursday, 29 December 2011

Flickering fluorescents stress captive birds

You may not notice it, but the fluorescent lighting around you is flickering--either at a high frequency (>30 kHz) or a low one (a rate of 100-120 Hz, depending on what country you're in). Although you won't consciously notice either, the latter may cause you to experience some unpleasant side-effects, including eye strain and migraine. Many avian species, which can process visual stimuli at a higher temporal resolution, may be even more susceptible to these and other impacts of low-frequency light, which can cause "repetitive and excessive stimulation of [the] nervous system with each light flash." This could have serious negative consequences for the billions of birds worldwide that are kept on or in farms, zoos, homes, and laboratories.

There have not been many previous studies on the impacts of low-frequency lighting, and those that have been conducted have produced conflicting results. The resulting confusion inspired collaborators from the University of Bristol, Deakin University, and Cardiff University to develop a research project that might finally shed some light--so to speak--on the potential harmful effects of low-frequency fluorescent lighting. They captured 32 wild European starlings (Sturnus vulgaris) and moved the birds into an artificially-lit aviary. After 6 months of acclimation to the captive conditions, the birds underwent a three-week experiment: Half of the animals were exposed to 14 days of high-frequency lighting and then 7 days of low-frequency light, while the other half had the reverse treatment. Because the researchers hypothesized that the low-frequency light would act as a physiological stressor, they investigated avian characteristics that typically fluctuate in response to stress: body weight, behavioral time budgets, and corticosterone and hematocrit levels (the former of which is a stress hormone, and the latter of which indicates the oxygen-carrying capacity of the blood).

(European starling, Sturnus vulgaris)

Regardless of which experimental treatment they experienced, birds lost weight during the first 7 days of exposure--indicating that any change in circumstances is likely to cause birds some stress. While this was common across all animals, behavioral time budgets were not. Specifically, birds that shifted from low- to high-frequency lighting conditions jumped around more, preened less, and experienced fewer myoclonus events--involuntary muscle spasms in the head. Birds that switched from the high- to low-frequency lighting conditions demonstrated the opposite shift in behavior. Cumulatively, these patterns show that low-frequency lighting, regardless of when it is experienced, is associated with higher rates of myoclonus and preening, and lower levels of activity. The first two behaviors are considered signs of stress and reduced well-being, while the reduced rate of jumping suggests a sort of general malaise. Overall, these results indicate that the starlings were not as comfortable under the low-frequency lighting conditions.

Another interesting behavioral adjustment was related to aggression, which remained at an elevated level throughout the 3-week experiment among birds that experienced the low-frequency lighting first. This suggests not only that the lighting set the birds on edge, but that its negative effects could be felt for an extended period of time--even after the stimulus is removed. Indeed, the researchers reported that increased aggressiveness was observed in some birds up to 6 months after completion of the study.

 (Example of an indoor aviary with fluorescent lighting)

Although hematocrit levels were not affected by lighting treatment, birds exposed to high-frequency lighting had higher corticosterone levels; this was true regardless of whether the birds experienced high-frequency lighting in the first or second phase of the experiment. While it is sometimes assumed that higher levels of corticosterone indicate higher levels of stress, this is not necessarily true. One way that the birds' bodies can adjust to stress is to decrease basal corticosterone levels, such that more stressed birds actually have lower amounts of this hormone. This is an adaptive response that allows animals to deal with unexpected, and often extended, stressful situations in the wild. Previous studies on starlings have indicated that chronically stressed individuals have lower corticosterone levels, supporting the theory that low-frequency lighting is a stressor for these birds.

Hormones and behaviors are often closely linked, and it is possible that corticosterone changes drove the behavioral fluctuations observed in the light-stressed birds; however, further research will be necessary to confirm this. In general, the relationship between these two types of variable is mediated by a number of factors, including body condition, food availability, season, and social status. This may explain the conflicting results of previous lighting studies, since it is unlikely that all birds--both within and among the studies--were in exactly the same state. There may also be individual variations in responses to stressors such as low-frequency lighting; in the current study, for instance, some birds exhibited up to 60 myoclonus events during a single 20-minute observation period, while others had none at all. The researchers suggest that future experiments should attempt to elucidate the source of this individual variability, both in general and specifically with respect to myoclonus--an important behavior because of its propensity to disrupt or impair other activities.

(Aggressive interaction between wild starlings. Encounters like these were more common among captive birds caged in low-frequency artificial lighting conditions.)

Overall, the study clearly shows that caretakers of captive birds should make sure to use high-frequency lighting in their aviaries/cages; in order to be safe rather than sorry, this is a technique that should be broadly applied to all avian species, not just starlings. Additionally, the work suggests that scientific researchers should not try to compare results of studies performed under different lighting conditions, as low-frequency lighting can impact both physiology and behavior. The authors hope that these new findings will lead to an improvement of both avian welfare and interpretability of scientific data collected in aviary settings.

Evans, J.E., Smith, E.L., Bennett, A.T.D., Cuthill, I.C., and Buchanan, K.L. 2011. Short-term physiological and behavioural effects of high- versus low-frequency fluorescent light on captive birds. Animal Behaviour 83:25-33.

Thanks to the following websites for providing the images used in this post:

Tuesday, 27 December 2011

American crows learn about dangerous humans--from each other

Researchers have long known that species in the Corvidae family (including crows, ravens, rooks, jackdaws, jays, magpies, treepies, choughs, and nutcrackers) are uncommonly intelligent--not just by avian standards, but also relative to other smart animals such as many primates. The exact nature and extent of that intelligence is being revealed by a steady stream of studies covering a variety of behaviors ranging from communication to tool use to learning. One of the most recent examples of this work was recently published in the Proceedings of the Royal Society B, where scientists from the University of Washington described experiments performed on American crows (Corvus brachyrhynchos) living in Washington state.

 (American crow, Corvus brachyrhynchos)

The work followed up on previous research showing that individual crows could recognize specific humans and, when those humans had appeared threatening in some way, discriminating against them (in the form of mobbing behaviors and scolding vocalizations). These behaviors were particularly common in crows that had been captured by scientists looking to measure and band them--unsurprising, given that the imprisoned birds would be benefit from recognizing these "dangerous" humans in order to avoid them in the future. However, the researchers noticed that similar anti-predator demonstrations were also performed by crows without direct experience with captors. This suggested that the birds might be learning about potential predators from their flockmates.

In order to investigate this--and, if relevant, document the dynamics of the social learning process--the scientists performed a multi-year study associated with their efforts to capture and band crows at a variety of sites near the University of Washington Campus. During bird capture efforts, researchers wore a mask in order to condition the crows to a specific, dangerous "predator" stimulus. Later, the humans then performed walkthroughs near the capture sites--sometimes wearing the same mask, at other times wearing a "neutral" mask or none at all--in order to observe bird responses to their presence. Because captured crows were individually marked, the scientists knew when they were encountering an "experienced" individual or one that had no first-hand knowledge of the banding process. Walkthroughs were repeated multiple times (after 9, 31, and 38 exposures to trapping efforts) and were mapped, allowing researchers to measure spatial and temporal fluctuations in mobbing and scolding behaviors.

 (A crow mob--in this case, of a red-tailed hawk, Buteo jamaicensis)

Over the 5-year study period, more and more crows joined in group mobbing and scolding behaviors during banding efforts. During successive encounters, the researchers noted a linear increase in the proportion of birds that responded to the presence of the mask by scolding birds; the fact that the birds displayed these behaviors in the absence of other mobbing individuals indicated that they had previously learned that the mask signified a potential predator. Before crow trapping efforts began, only 3% of naive birds responded negatively to the dangerous mask; by the end of the study, reactions were observed in 66% of individuals--including some up to three-quarters of a mile from the capture site.

The birds may have learned about the meaning of the predatorial mask via either horizontal or vertical transmission of information--in other words, from contemporaries or from parents, respectively. During further observation efforts, the researchers uncovered evidence for both processes. Lone, unbanded adult birds were more likely to respond negatively to masks during later walkthroughs than early ones; this indicates that, during the intervening periods, they had learned about the implications of the predatorial mask. Likewise, an increasing proportion of unbanded individuals responded negatively to the masks after having observed scolding mobs, again suggesting that the crows had learned from their flockmates that the mask indicated trouble. While those patterns highlight the importance of horizontal transmission, observations of juvenile birds underscore the relevance of vertical transmission: Fledglings were much more likely to scold a masked person when they had previously observed their parents do so. This was true even when adults were absent, indicating that the juveniles were not just copying their parents, but instead had truly learned about the meaning of the mask.

 (Juvenile crow, left, begging towards an adult)

The researchers did one final analysis in order to assess the accuracy of social learning. It turns out that birds who learned their lessons the hard way also learned them best: In 91.3% of encounters, captured birds "immediately and consistently" scolded people wearing the predatory mask, but rarely scolded anyone else. On the other hand, "correct" responses to the predatorial mask were only observed 33% of time from birds that had learned from their flockmates. Although this is a much lower response than that observed in experienced individuals, it is still a significantly stronger reaction than the "learners" displayed towards neutral masks, indicating that social learning is better than no learning at all.

The scientists suggest that their results may actually underestimate the importance of the crows' social learning process, since interactions with people probably elicit weaker responses than interactions with "more typical encounters with deadly predators"--which often result in death or injury, and therefore provide additional public information that could reinforce the learning process. The ability of the crows to learn about particular classes of people may be one reason why this species does so well in human-disturbed areas: Individuals can quickly learn how to recognize, and take advantage of, friendly humans (those who provide food, for instance), while avoiding those who are less sympathetic towards crows (and may shoot or trap them); this expertise is then passed on to flockmates and juveniles, thereby increasing the number of birds that can successfully navigate the unpredictable anthropogenic landscape. On a broader scale, the results also suggest that an improved chance of predator evasion is one of the reasons why crows--and even animals in general--evolved the ability to learn from each other.

Cornell, H.N., Marzluff, J.M., and Pecoraro, S. 2011. Social learning spreads knowledge about dangerous humans among American crows. Proceedings of the Royal Society B 279:499-508.

Thanks to the following websites for providing the images used in this post:

Wednesday, 21 December 2011

eBird: a model for other citizen science projects?

Modern technology has helped scientists solve many difficult problems, but occasionally there are some achievements that can only be managed by harnessing the power of the human brain. Animal identification, for instance, is a complex process during which observers consider several characteristics--shape, size, behavior--under different circumstances, ponder which species are likely to be present at that time and place, and then choose the correct match. According to collaborators from the Cornell Lab of Ornithology, writing in a recent issue of the scientific journal PLoS Biology, this is a task that is "beyond the scope of existing artificial intelligence algorithms" and can only be accomplished by human observers. That is why, in 2002, the authors launched eBird, an Internet-based citizen science project that allows birders to report bird sightings and observations. The purpose of the team's recent journal paper was to discuss how eBird can be used as a model for the development of other successful citizen science projects.

The authors are quick to point out that their online program is only one of several that use "humans' puzzle solving abilities" to advance science: others include FoldIt, which helps predict protein structures; Galaxy Zoo, which helps pick galaxies out of celestial images; the ESP game, which labels images; and reCAPTCHA, which provides Internet security while transcribing historical printed documents. All of these are examples of "human computation," a field that "[harnesses] human intelligence to solve computational problems." These citizen science projects have two main purposes: to increase interest in, and support of, scientific efforts by actively engaging the public, and to provide data that are useful--and free of charge--to scientists, researchers, managers, and amateur naturalists.  eBird's developers believe that these goals can be achieved if developers keep 6 main goals in mind: familiarity with the focal community, maximal participation, gentle guidance of participant behavior, data quality, connection to other related datasets, and global expansion.

(Example of a protein-folding puzzle from the citizen science project FoldIt)

One of the key characteristics of eBird is that it is relatively simple to learn. When users submit data, they are asked to include information on species seen, date and location of the sighting, and whether they are reporting their entire observation list or just a random sighting. As data submitters become more familiar and comfortable with the eBird format, they can begin to include extra information, such as the age, sex, or behavior of birds--but only if they wish. This ease of use gives eBird broad appeal and increases "initial involvement"; once the program has helped users clear the hurdle of a first visit, there are many other characteristics that increase participation and keep birders returning for more. These include "personal" touches to the program, such as list-keeping features and the ability to compare observations with other users. eBird's developers included these functions after a "lukewarm" response to the program; these characteristics were designed to allow birders to do online what they were already doing, in person, in the field. The program modifications appear to have worked: Recent tallies indicate that over 1.7 million checklists will have been submitted from over 200 countries by the end of this year.

(One benefit of using eBird is receiving alerts about rare bird sightings--such as of this white-winged crossbill, Loxia leucoptera.)

Even the most experienced and knowledgeable birder may not have scientifically rigorous observation techniques, which is why eBird's creators have also tried to build in features to help "modify" users' behaviors in order to maximize data quality. For instance, they have included background information intended to educate birders about the importance of particular techniques; they have also provided incentives for being more "useful." One of the major goals is having birders report all species seen during a particular observation period, rather than just mentioning a few exciting "highlight" species. To this end, the program now includes a frequency bar chart that shows birds' seasonal patterns; this helps birders see that only complete observation reports will allow researchers to track birds' population fluctuations throughout the year. To ensure data quality, submissions are reviewed by a team of experts who identify and follow up on questionable sightings to verify their validity.

By asking birders to provide information about the time and place of each sighting, the program developers have ensured that bird observation data can be linked to a variety of other factors, including weather, land cover, stage of vegetation growth, and anthropogenic variables such as population density and traffic. None of this information needs to be provided by the birders themselves, but can be extracted from other databases established elsewhere. This is helpful not only to researchers who want to control for these environmental descriptors when using bird observation data in scientific analyses, but also to casual eBird visitors who are interested in learning more about how various factors influence the comings and goings of their feathered friends.

(Example of one way for eBird users to explore data collected by the program--a graph showing the frequency of bird sightings in a given area over a particular period of time; in this case, the chart shows information on observations of eastern bluebirds, Sialia sialis, in Athens County, Ohio, USA)

Perhaps one of the greatest achievements of eBird has been its ability to go global despite its developers' main interest in western hemisphere birds--an expansion that was fueled by the eBird audience. The program's creators have worked closely with allies in other countries in order to translate text into regional languages/dialects and to tailor the program "to the individual needs of a specific country or region." For instance, some countries have been more interested in creating a repository of historical observations, while others have placed an emphasis on establishing an online breeding bird atlas. Once these features were incorporated in each country's version of eBird, similar characteristics could be worked into other countries' programs, as well--ultimately making eBird more versatile and useful no matter where it was being used.

Although citizen science may not work for every research question or study system, it provides an exciting opportunity for scientists to harness the power of an army of research assistants while also getting laypeople interested in the scientific process. Technological advances--including ever-faster Internet connections and affordable portable devices--are helping "regular" people access and disseminate a variety of data at any time, in any place; programs like eBird help provide structure to this process of information exchange and improve both the quality and reliability of the output. The authors of the current paper advocate continued collaboration with a variety of experts--including ecologists, statisticians, and computer scientists--to develop additional ways to utilize this potentially powerful resource and determine the best method of "extracting biological insights" from citizen data.

Wood, C., Sullivan, B., Iliff, M., Fink, D., and Kelling, S. 2011. eBird: engaging birders in science and conservation. PLoS Biology 9(12):e1001220.

Thanks to the following websites for providing the images used in this post:

Sunday, 18 December 2011

Forest forensics provide details about poachers' preferences

Illegal harvesting of natural materials is a global problem, but is especially prominent in areas where poverty-stricken residents rely on these goods as sources of energy or food and as components of handicrafts, tools, and/or buildings. Although local law enforcement agencies may try to restrict harvesting, they often don't arrive at the scene of the crime until the damage has already been done. However, a team of collaborators from Kenya's University of Nairobi and Japan's Yokohama National University and Yokohama City University suggest that a bit of ecological sleuthing can reveal details about poachers' "patterns and preferences"--information that may allow the creation of better management policies that are helpful to both humans and wildlife.

The researchers tested their theory during a study in the Ngong Road Forest Reserve in Nairobi, Kenya. One side of the reserve borders the Kibera slum, where approximately 80% of the 300,000 inhabitants are below the national poverty line. Because they cannot afford to purchase wood, many of the slum residents enter the reserve each day in order to collect "forest products"--mostly kindling and wood for fires, but also raw materials for carving and bark for traditional medicines. Although forest rangers routinely patrol the reserve to discourage poaching, they frequently encounter fresh stumps and branches left by raiders. The scientists hypothesized that an analysis of these stumps could provide information about the poachers' motives and could also help researchers predict the potential ecological outcomes of continued illegal harvesting. In order to perform the analysis, the researchers divided the forest into grid cells in which they could survey both harvested and remaining trees. For each, they identified the species of focal plants, measured their sizes, and noted basic characteristics such as whether they were thorny, exotic or native, and succulent; they also measured distance to the slum, distance to the forest rangers' station, and distance to the forest fence.

(Skyline of Nairobi, Kenya)

Of nearly 15,000 stems censused across all 87 grid cells, approximately 9,000 were living and 6,000 had been cut. Stem densities were as much as 12 times higher in moderately disturbed sites as in highly disturbed areas, indicating that poachers had a significant impact on some sections of the forest. Specifically, the researchers found that stems were more likely to be cut in areas located near the slum and, especially, near the fence border. Smaller stems were especially likely to be targeted, and stems were slightly less likely to be disturbed nearer the ranger stations. Trees were more likely to grow, undisturbed, to larger sizes when they were farther from both the slum and the fence.

The most preferred species were those that grew in dense patches--a trend mainly driven by invasive timber species such as Eucalyptus trees. Poachers seemed to avoid trees with spines, thorns, or prickles; likewise, they were wary of succulent and semi-succulent plants, which were not very useful for either burning or carving. Preferences for species and size were only weakly correlated; while poachers appeared to prefer smaller stems of most species (probably for kindling), they were interested in larger stems for Brachylaena huillensis and Teclea trichocarpa--the former of which is a highly prized carving material.

 (Drought-tolerant Eucalyptus trees in Kenya)

These "forensic" investigations indicated that anthropogenic influences on wood resources were highly influenced by both accessibility and species identity: Human disturbance was "magnified" near the slum, and was particularly focused on trees that grew in high-density stands that made harvesting easier. There was a definite preference hierarchy, with lower-quality woods being utilized only after other types of wood had been depleted. Because of this lopsided interest in some species over others, growth in the forest was increasingly shifting towards the "spiny shrubbery" end of the vegetation spectrum. This is partly a result of the spread of invasive species such as lantana (Lantana camara) and kei apple (Dovyalis caffra), both of which are protected from poachers by their thorns and are happy to utilize the space left when neighboring trees are harvested. Unfortunately, these ecosystem changes are threatening the long-term safety of rare indigenous species such as Olinia rochetiana--and are likely having an impact on other types of wildlife, that utilize native trees as sources of food and shelter.

The researchers point out that wood harvesting preferences can change quickly as a result of variations in resource availability and socioeconomic circumstances. They suggest that poaching activity could be reduced via the creation of management schemes that "engage" the local community--in this case, the Kibera slum--and increase residents' "role and responsibility" in the conservation plan. The authors say that there should be three main goals to help save the Ngong Road Forest Reserve and other areas like it. The first goal is to reduce harvesting of the near-threatened B. huillensis and to begin regulating the woodcarving market to prevent the demise of this species as a result of its popularity as a source of carving material. The second goal is to remove invasive lantana before it completely chases native vegetation out of the forest. Ideally, residents could find a use for this and other exotic species--for instance, as a material for handcrafted rattan furniture; this would temporarily increase demand for the species and speed up its demise. Finally, the researchers emphasize the need to develop more sustainable techniques of harvesting fuel. This might be accomplished by deliberately planting preferred nonnative tree species in heavily trafficked areas in order to reduce pressure on indigenous vegetation while also giving the slum residents access to the wood products they need.

 (The invasive lantana, Lantana camara, quickly spreads where native trees have been removed by harvesting)

As useful as this three-pronged approach might be, though, it only targets the outcome of a larger problem, rather than the problem itself: poverty. Thus, the scientists recommend the development of city-wide plans to help the poor, improve urban planning, and make alternative sources of energy available to those who need them.

For supplemental images associated with this post, visit the Anthrophysis pin board at Pinterest.

Furukawa, T., Fujiwara, K., Kiboi, S.K., and Mutiso, P.B.C. 2011. Can stumps tell what people want: pattern and preference of informal wood extraction in an urban forest of Nairobi, Kenya. Biological Conservation 144:3047-3054.

Thanks to the following websites for providing the images used in this post:

Friday, 16 December 2011

A scientific use for model airplanes?

Censuses are an essential part of most management and conservation efforts, but may be associated with a number of difficulties. For instance, the presence of human wildlife monitors may frighten animals and potentially cause them to abandon territories; some species--especially those with cryptic coloration--may be difficult to detect during standard point count procedures; and censuses may be expensive and difficult to perform, especially in remote locations. Because of these potential problems, researchers have long been searching for new, more efficient methods of obtaining data on animals' population numbers. Several years ago, researchers suggested that remote-controlled planes might help achieve this goal, but since that time there has been little interest in testing the utility of unmanned aircraft in the field.

However, several Spanish collaborators have recently used this method to survey a Catalonian breeding colony of the locally-protected black-headed gull (Chroicocephalus ridibundus). They had two goals: first and foremost, to acquire accurate data on how many birds were living and nesting at the recently-established Estany d'Ivars i Villa-Sana gull colony, and, second, to compare data collected using the unmanned aircraft systems (UAS) technique to those obtained via a standard human visit to the colony.

(Black-headed gull, Chroicocephalus ridibundus)

Although UAS sounds like something that involves military-level complexity and precision, the device deployed in the current study comprised only a few, commercially-available products: a radio-controlled model aircraft, fitted with a radio-controlled digital camera and a GPS unit. The plane was also equipped with a "first person view flight system" consisting of a small camera in the plane's cabin that allowed the human controller to visualize the aircraft's position in real time and to keep an eye on geographical coordinates, altitude, speed, and course. Data from the GPS unit were sent straight to a computer running Google Earth. This provided a sort of air traffic control, allowing the researchers to keep an eye on the UAS's progress remotely. All in all, the entire rig weighed about 2 kg and cost less than US $2,000.

The scientists selected flight parameters that enabled them to capture the entire colony in a single image; in this case, they flew the UAS at 30-40 km/h at a height of 30-40 m above the ground. They compared three different methods of data collection. First, they examined multiple images collected at each of two different flight passes on three different survey days. Second, they examined only the first image collected on the first day. Finally, they deployed a single surveyor on foot to census the birds using "standard" survey techniques.

(A Multiplex Twin Star II, the commercial radio-controlled airplane model used by the researchers to survey gull breeding colonies)

During the UAS flyovers, most gulls (98.8%) remained stationary, indicating that the birds were not overly disturbed by the aircraft's passing. Although there were some differences between the nest counts yielded by each of the three methods, the numbers were encouragingly similar: 244 nests counted during the sequential-image method, 227 definite nests and 54 probable nests counted during the single-image method, and 229 nests counted by the on-site surveyor. Agreement between the two UAS techniques was as high as 86%, and differences between the sequential-image and direct count methods were as low as 0.8%.

These results suggest that the UAS is a useful and accurate method for obtaining counts of birds/nests without disrupting the animals. Further, it allowed the researchers to easily census a breeding colony located on an island in the middle of a lagoon--not the most accessible of research locations. Because black-headed gull nests can have a range of sizes and linings, the researchers admit that they could have made some mistakes when evaluating the UAS images. However, errors are also possible during direct counts by surveyors; the advantage of the UAS technique is that multiple flyovers can be used to quantify those errors and adjust estimates accordingly.

 (Black-headed gull breeding colony)

Although the sequential-imaging method provided more detail than the single-image method, the latter was still fairly accurate and could be useful in situations where focal animals are more easily disturbed, or where budget limitations restrict multiple flights. The researchers caution, however, that there are some potential drawbacks to the use of UAS. Both range and flight duration will be limited, requiring scientists to find a "home base" not too distant from the survey site. Another serious concern is situations that compromise image quality and resolution; wind and rain, in particular, can affect stability of the aircraft and obstruct the camera lens. As long as surveyors are willing and able to wait for clear weather, though, this should not be much of an issue. All in all, the authors of the study feel that their first attempts at "fine-scale bird monitoring" using UAS were a success, and they look forward to seeing how other scientists employ and refine the technique.


Sardà-Palomera, F., Bota, G., Viñolo, C.,  Pallaré s, O., Sazatornil, V., Brotons, L., Gomáriz, S., and Sardà, F. 2011. Fine-scale bird monitoring from light unmanned aircraft systems. Ibis 154:177-183. 

Thanks to the following websites for providing the images used in this post:

Thursday, 15 December 2011

Follow-ups to previous posts: more on turbines and chimpanzees

I've recently received feedback about two Anthrophysis posts that caught the attention of outreach specialists working on related topics. Kris Hodgson, Wind Energy Community Liaison from the Wind Turbine Technician Training Program (WTTTP) at Lethbridge College (Alberta, Canada) contacted me after I wrote about how wind turbines harm bats. Kris was eager to share information about the WTTTP's efforts to educate a variety of people--from elementary school students to economic developers and policy-makers--about wind turbine energy. He sent a link to a video of University of Calgary PhD student Erin Baerwald discussing her 2008 findings regarding the barotrauma inflicted on bats by fast-whirling turbine blades. Baerwald and colleagues were among the first to use autopsies to investigate exactly how turbines cause fatalities; their results indicated that the high pressure differentials caused by the spinning blades causes blood vessels in the bats' lungs to burst, leading to death by drowning. Fortunately, Baerwald and her collaborators at the University of Calgary and TransAlta Wind conducted further research indicating that bat fatalities can be reduced at wind energy facilities if managers make minor alterations to turbine speeds and angles. Kris also described how the WTTTP is involved in efforts to provide context and perspective for "myths [associated] with wind energy production"--such as the bat and bird deaths mentioned in my previous post, and turbine-caused nausea. Anyone interested in reading more about turbines and/or the WTTTP can visit the website of the International Wind Energy Academy or  the Wind Turbine Technician Training Program.

I also heard from Sharon Dewar, public relations director for Chicago's Lincoln Park Zoo. She had read my recent article about chimps in the media, a topic of concern for the zoo's Project ChimpCARE. As part of their efforts to bring an end to "chimpanzee commercialization," the ChimpCARE team have developed a free iPad book called Chimps Should Be Chimps. Its story follows two central characters, a venerable chimp named Poe and his granddaughter, Lulu, both of whom live in a zoo. The "multisensory book" allows young readers to interact with the illustrations and find out about the natural history of chimpanzees while also learning about the unpleasant conditions faced by many Hollywood chimps. The book's authors hope that it will serve the dual purpose of making children more interested in chimp conservation and less tolerant of the use of chimps in commercial settings. The founder of Project ChimpCARE, Steve Ross, reports that the book was inspired by his struggles "to talk to [his] own kids about chimpanzees" and emphasizes that, beyond just advocating for chimps' rights, it also "conveys to kids the importance of being yourself and believing in what comes naturally to you." Those interested in the book can read more about it--and watch several behind-the-scenes videos about its creation--on its dedicated website; it can also be downloaded for free via iTunes.

Thanks to Kris and Sharon for bringing these projects and websites to my attention. If any other readers have updates or follow-ups to previous posts, I'd love to hear about them!

Thanks to the following websites for providing the images used in this post:

Wednesday, 14 December 2011

Good for your karma, bad for your immune system?

Since the first appearance of the highly pathogenic avian influenza H5N1 virus in 1997, over 500 human cases have been reported--more than 60% of which resulted in death. Researchers are still trying to work out the many possible routes of disease transmission in order to decrease human exposure to the virus. This is not an easy task given how many wild and domestic birds may be carriers, and the variety of ways in which these animals may come into contact with both each other and the humans they can ultimately infect.

A recent study out of Cambodia highlights one unusual potential source of viral spread: the practice of "animal release," whereby Buddhists seeking to improve their karma purchase caged birds, kiss them, and then set them free. Buddhism is practiced by a high proportion of residents in the highly H5N1-affected region of Southeast Asia, which means that this practice could potentially place hundreds of millions of people at risk of infection. One common "merit release bird" is the Eurasian tree sparrow (Passer montanus), which was the focus of the current study. Collaborators from the Institut Pasteur in Cambodia, the Cambodian Ministry of Agriculture Forestry and Fisheries, and the University of Hong Kong purchased 35 of these birds from Buddhist pagodas around Phnom Penh in order to investigate three potential transmission routes: sparrow-to-sparrow, sparrow-to-chicken, and duck-to-sparrow. 

 (Eurasian tree sparrow, Passer montanus)

The researchers first determined mean lethal dose for sparrows in order to find out how "bad" an H5N1 infection needs to be before it kills a sick animal; they also observed signs and symptoms displayed by infected individuals and measured the length of time it took for sick birds to die. When exposed to other sparrows and chickens, infected sparrows were either allowed to fly freely and utilize a perch above their cage-mates (as they would in nature), or were constrained in a smaller cage and placed near the other birds (mimicking captivity conditions in Buddhist pagodas); only the "natural" caging condition was used when the sparrows were exposed to infected ducks. A variety of laboratory tests were then conducted to assay for disease transmission between focal pairs. The researchers also collected feather samples from sick sparrows in order to see whether the birds carried external contamination that might be transmissable to humans handling and kissing them during releases.

When birds were directly inoculated with H5N1, they were highly susceptible to infection, but their responses to the virus varied widely. Chickens, for instance, died very quickly. Ducks took about twice as long to die and displayed obvious neurological signs of infection. Like ducks, sparrows died approximately 4 days after infection, but showed only mild clinical signs of the disease. Thus, humans handling sick sparrows--during capture, sale, or release--might have no idea they are in contact with an ill animal.

(Domestic duck)

H5N1-inoculated sparrows did not, under any caging condition, transfer infection to other sparrows; nor did sparrows infect chickens when they were allowed to fly freely around the cage. However, when sparrows were confined to cages within the experimental enclosure, they were in much closer contact with the chickens, who frequently pecked at the sparrows through the bars. As a result, all chickens exposed under these conditions eventually died from the H5N1 virus. When exposed to sick ducks, sparrows fared slightly better: Two-thirds of the songbirds became ill, but only 50% of these cases were fatal. Of the 50 sparrows tested for H5N1 particles on their feathers, approximately half were positive, indicating that handling--and kissing--of these birds could expose humans to H5N1 infection.

The good news is that sparrows caged together in Buddhist pagodas are unlikely to spread H5N1 to each other; further, only under some caging circumstances are they likely to pass the virus on to chickens. Thus, in domestic or market situations when both species of bird may be in close quarters, humans can prevent viral exchange by keeping caged sparrows well away from the dangerous beaks of hungry or inquisitive chickens. The bad news is that chickens can be infected by sparrows, something that is particularly likely to happen when/if chickens nibble on infected sparrow carcasses encountered on the ground--a not unlikely circumstance given chickens' "propensity for pica." In fact, this particular mode of transmission may be problematic for any scavenging or carnivorous bird species.

(Chickens, Gallus domesticus)

Another piece of bad news is the finding that sparrows can become infected via exposure to H5N1-carrying ducks. Ducks have earned a reputation for causing the "silent spread" of some viruses, which means that humans may not realize when their domestic stocks have become contaminated. Since sparrows often come into close contact with humans and livestock, and since bird hunters may be particularly likely to capture sparrows near human establishments, it is possible--if not probable--that this poultry-to-sparrow transmission route could pose a threat to humans during H5N1 outbreaks. In fact, the researchers found that duck-exposed sparrows often survived for over a week before succumbing to their infection, meaning that sick birds could easily travel from one farm to another, be transported for religious practices, and/or have repeated contact with humans while carrying the infection.

However, although a recent study in Indonesia found genetic similarities between H5N1 viruses carried by humans and a single infected tree sparrow, there has not yet been a confirmed case of sparrow-to-human transmission. Thus, as far as the researchers know, it is a threat that we should be aware of, but not yet one to panic over.

Gutiérrez, R.A., Sorn, S., Nicholls, J.M., and Buchy, P. Eurasian tree sparrows, risk for H5N1 virusspread and contamination through Buddhist ritual: an experimental approach. PLoS ONE: 6(12):e28609.

Thanks to the following websites for providing the images used in this post:

Tuesday, 13 December 2011

The environmental economics of nature films

Nature documentaries are potentially valuable on a number of levels. There is the obvious monetary worth associated with fees paid by filmmakers to individuals/organizations who can provide access to certain filming locations, jobs provided to those involved in the development and production of the films, and income earned from sales of DVDs and screenings. Then there is the cultural worth of entertaining, providing information about particular species and habitats, and increasing tourism activity associated with the featured locations. And what does Nature herself get out of all this? Some would argue that documentaries enlighten, inspire interest in--and a feeling of connectedness with--the environment, and--when filmed, distributed, and/or broadcast in conjunction with ecologically-minded partners--can generate support and revenues for conservation projects.

Others would argue that it is time for Nature to receive some recompense for her role in the many nature documentaries that are produced each year. This is the stance taken by collaborators from the University of Oxford, Oxfam, and the Zoological Society of London. In an "environmental economics" essay in the latest issue of Science, the authors describe their view that documentaries are an ecosystem service (ES), comparable to natural processes such as pollination, clean water provisioning, carbon sequestration, and many more. Many organizations are now initiating efforts to pay for those services, thus generating a flow of capital that can be used to keep ecosystems healthy and functional. The authors of the current paper argue that the media should participate in similar payment schemes in order to avoid "free-riding"--not by harming nature in the course of making heir films, but by "profiting without contributing."

This is sure to anger those who feel that the media sufficiently "gives back" by creating films that bring far-flung realms and species to viewers' front rooms, thereby increasing knowledge of, and interest in, biodiversity. The authors point out that some documentaries generate phenomenal revenues: Blue Planet, for instance, earned US$62.5 million, while March of the Penguins raked in $127 million. Even a small percentage of that income could make significant contributions to conservation and management efforts. The authors feel that it is important to create a more "direct link between the use of the [ecosystem] service and the funds generated through [its] representation, broadcast, and marketing." In order to do this, they recognize that it will be necessary to develop a system in which the cost is not directly passed on to the viewer, who may then no longer find the product quite as desirable.

Their solution to this conundrum is a "trust with a certification system." The trust would consist of funds deposited by broadcasters to cover each viewer attracted or each DVD/download sold. It would be governed by a sort of conservation-oriented United Nations: an "international, apolitical" group of experts who would disperse the funds to worthy efforts. The authors propose that the certification system be put in place in order to recognize those individuals and organizations who achieved the minimal requirements--as measured by rates of payment and reports on the film-making process; this would be similar to the "Fair Trade" or "Bird Friendly" labels that can be found on other "green" products.

According to the authors, this system has several advantages. For instance, payment into the trust would be proportional to the earnings of each film, ensuring that less successful distributors would not be overburdened. Further, the monetary contributions would be made by broadcasters and distributors, who have more financial leeway than filmmakers and customers. Additionally, the certification scheme could be used to increase the "reputation and brand value" of particular broadcasters; just as some shoppers only buy Bird Friendly coffee, some viewers might limit their patronage to stations featuring "green" films.

However, the authors do also recognize some challenges associated with their proposed plan. One of the biggest hurdles would be the careful selection of the trustees in order to ensure fair and wise distribution of trust funds. Another will be determining an ES payment scheme that doesn't "stifle" film-making, but still raises a useful amount of money. The authors worry that some broadcasters might try to initiate private negotiations with filmmakers in order to offset costs.

Though they realize that the ideas in their essay may not appeal to everyone, they stress that it is important to find "innovative sources of additional finance for conservation" in order to fund the preservation of species and habitats. In other words, the authors believe that it is time to start thinking outside the box. They hope that their essay gets people thinking not just about whether and how the media might pay for ecosystem services, but also about what other professionals might be included in similar schemes. On an even broader scale, the authors also suggest that it may be time to evaluate the role of wildlife films in our society and consider the relationships that exist--or should exist--between conservation organizations and the media.

Jepson, P., Jennings, S., Jones, K.E., and Hodgetts, T. 2011. Entertainment value: should the media pay for nature conservation? Science 334:1351-1352.

Thanks to the following websites for providing the images used in this post:

Saturday, 10 December 2011

Bluebirds bring happiness to California vineyards

Wine-drinkers that want their reds and whites to also be green--in the environmental sense--may soon be able to support sustainable viticulture efforts by purchasing "bird-friendly" products. At least, that's the hope of scientists who recently investigated whether grape-growers and birds can form mutually beneficial partnerships at vineyards.

The collaborators, from the University of California--Santa Cruz and the Smithsonian Conservation Biology Institute, hope to revive the idea of "economic ornithology," a practice encouraged by a branch of the U.S. Bureau of Biological Survey from 1885-1940. This concept recognizes the fact that insectivorous birds can improve agricultural output by reducing arthropod abundances and, therefore, the damage caused to crops by pest insects. Birds have helped raise the incomes of both apple and coffee farmers, for instance, and are poised to help viticulturists, as well. In the U.S., bird-friendly vineyards could become particularly popular in California, where grapes are the second most economically important agricultural crop. In this same region, the conversion of woodland and savanna to agricultural and urban land has reduced the availability of potential breeding habitat for may species of bird. Thus, efforts to promote bird abundances on vineyards might not only help improve grape crops, but could also preserve local bird populations.

 (The Bonterra Vineyard, one of two vineyards examined in the current study)

In the current study, the scientists installed nest boxes at two vineyards in order to see whether they could be used to attract insectivorous birds during the breeding season. Each vineyard was divided in half and boxes were distributed only on one side so that the other could be used as a control to evaluate "normal" numbers of birds and associated insectivorous activities. The researchers then performed observations in all 4 areas in order to quantify avian abundance and diversity. They also conducted a "sentinel prey experiment" in which they distributed beet armyworms (Spodoptera exigua) along transects in order to assess whether predation rates were higher in the vineyard halves containing nest boxes.

Areas with an without boxes had similar amounts of avian richness. However, the two box-supplemented halves had more insectivorous birds. These included chipping sparrows (Spizella passerina), tree swallows (Tachycineta bicolor), violet-green swallows (Tachycineta thalassina), and--most notably--western bluebirds (Sialia mexicanus). Bluebirds were the predominant inhabitants of nest boxes, though their neighbors sometimes included the two swallow species and, in one case, ash-throated flycatchers (Myiarchus cinerascens).

(A beet armyworm, Spodoptera exigua, and the damage it can do to foliage.)

At the beginning of the breeding season, avian abundance doubled at the nest box treatment sites, then increased again later in the summer as fledglings emerged from the boxes to forage with their parents. Regardless of time of year, though, box-supplemented areas always contained higher avian abundances than control areas, a pattern that was predominantly driven by the presence of the western bluebirds: In treatment areas, 1.8 individuals were observed every 5 minutes, while only 0.18 individuals were observed every 5 minutes in control areas. 

In box-supplemented areas, armyworms were removed 2.4 times more often than in control sites, and were most likely to be taken when distributed along transects placed within 25 m of active nest boxes. In fact, removal rates in treatment areas were always higher when the prey were left near active boxes than when prey were placed randomly throughout the habitat. Thus, though it is impossible to confirm that bluebirds--rather than alternative predators such as squirrels, lizards, and other bird species--were the sole armyworm predator, it does seem likely that the birds were the predominant source of insectivorous activity in box-supplemented areas. 

 (Western bluebird, Sialia mexicanus)

This is good news for the grape-growers, since a pair of bluebird parents can capture well over 100 g of prey per day during the breeding season. Further, these birds found and occupied nest boxes soon after they were distributed, suggesting that growers could quickly and easily attract this species to their vineyards. All three species of bluebird in the U.S.--western bluebirds, eastern bluebirds (Sialia sialis), and mountain bluebirds (Sialia currucoides)--are willing to use, and in some places are dependent on, human-supplied nest boxes. Therefore, the authors suggest that agriculturalists across the country may be able to form partnerships with these birds in order to receive pest maintenance services in exchange for the provision of shelter. They caution that additional studies will be needed to confirm that bluebird reproductive output on vineyards is as healthy as that found in natural areas. However, bluebirds are known to respond positively to breeding conditions in other anthropogenic areas, suggesting that they should also find vineyards and other farms to be suitable.

Should viticulturists--or other types of farmers--pursue this sort of "ecologically friendly" growing practice, the authors suggest that this could be advertised via special product labels (such as the Bird Friendly stamp used by coffee-growers) or by encouraging stores to group these green products together in a particular section of the store. This will allow conservation-minded buyers to give their dollars to like-minded vendors.

For supplementary images associated with this post, please visit the Anthrophysis pin board at Pinterest.

Jedlicka, J.A., Greenberg, R., and Letourneau, D.K. 2011. Avian conservation practices strengthen ecosystem services in California vineyards. PLoS ONE 6(11):e27347.

Thanks to the following websites for providing the images used in this post:

Friday, 9 December 2011

A new perspective on overfishing

What is the state of modern fisheries, and how sustainable are current fishing practices? These are questions that can provoke heated debates among the fisheries biologists that study them, as well as among fishermen, policy-makers, the society at large. In a letter in this month's issue of Trends in Ecology and Evolution, marine conservationist Eric Palkovacs writes that answers to these questions will not be forthcoming until we can agree on a definition of "overfishing," and, further, that this will not be achievable until we start thinking about fisheries dynamics from an "eco-evolutionary" perspective--one that recognizes the integral relationship between ecological and evolutionary processes occurring "in contemporary time."

Much of Palkovacs' discussion focuses on the implications of our interest in the largest specimens of fish; whether by choice or in order to obey the law, fishermen generally throw the smallest individuals back. From an evolutionary point of view, this suggests that it should pay to be small and to reproduce as early as possible in order to improve the chances of avoiding capture and consumption, as well as maximizing the likelihood of breeding before being caught. Indeed, these are the very patterns found in fisheries around the world. While fishing bans and the creation of conservation areas might help population sizes recover from heavy fishing, these techniques will not address the evolutionary impacts of fishing practices; it may take much longer for fish to "recover" the ability to grow to larger sizes and breed later in life, since the genes that drive these traits appear to be disappearing from wild populations. Thus, fishing practices can leave a "legacy...even after demographic sustainability has been achieved."

(Industrial fishing of orange roughy, Hoplostethus atlanticus)

Although some might argue that it's better to have more, smaller fish than no fish at all, that may not necessarily be true. Palkovacs describes how aquatic food webs are highly size-structured, meaning that imbalances in the numbers of fish in each size class can have "trophic cascades" that affect a multitude of other organisms elsewhere in these complex webs. If biomass suddenly becomes concentrated at a particular trophic level--in this case, a lower level where small individuals need to eat relatively large amounts of even smaller prey in order to meet their dietary needs--then more mouths will be competing for the same amount of food. Some of these mouths will be attached to organisms that are not directly impacted by fishing but, via these trophic relationships, may suffer indirectly.

Another indirect effect of overfishing is altered ecological relationships. Palkovacs points out that potential prey species have evolved to detect, avoid encounters with, and escape from, predators. However, when fishing practices remove these predators from the habitat, former prey species will suddenly find themselves living together in rather large numbers, free from the natural selective pressures of being hunted. Under these new circumstances, vigilance and evasiveness will be less important than the ability to outcompete school-mates for access to food, shelter, and mate resources. As a result, we should see the gradual evolution of traits that help individuals outperform conspecifics. This, in turn, should also affect availability of prey items, thus further amplifying the trophic cascades initiated by removing large predators.

 (Historical image of a commercial fishing catch.)

Thus, Palkovacs writes, human-driven evolution is "intertwined" with population, community, and ecosystem processes, all of which "underlie prevailing definitions of overfishing." Without taking an eco-evolutionary view of the current status of our fisheries, he argues, it is difficult to adequately define "overfishing" and, therefore, decide whether we have achieved sustainability or still have work to do in the quest to ensure the health of our aquatic ecosystems.

Palkovacs, Eric P. 2011. The overfishing debate: an eco-evolutionary perspective. Trends in Ecology and Evolution 26(12): 616-617.

Thanks to the following webpages for providing the images used in this post:

Thursday, 8 December 2011

How similar are populations on "urban" and "natural" islands?

Although human habitats often differ from natural areas in obvious ways, there are sometimes unexpected similarities. For instance, urban "habitat islands"--or patches of suitable habitat separated by barriers such as buildings and roads--are not unlike geological islands separated by water. Among animals living on natural islands, there are usually fairly low levels of dispersal relative to continuous habitats, since it is difficult for many animals to cross water. This can lead to reductions of genetic diversity, since individuals are surrounded by, and forced to mate with, relatives who share similar genes. It seems logical to hypothesize that anthropogenic habitat islands might have similar genetic patterns as their natural counterparts, and that the the low genetic diversity found in many island-dwelling populations might represent an "end point of the genetic trajectories" of animals in anthropogenic areas. If so, it would be useful to measure and compare the genetic diversities of populations living on both types of islands in order to get an idea of how the genetics of anthropogenic populations might change over time, and over what timescale.

Such an effort was recently undertaken by researchers from the University of Western Ontario and the University of Victoria. They quantified the genetic diversity of 106 song sparrows (Melospiza melodia) breeding across 14 sites, 7 of which were coastal islands near Vancouver, and 7 of which were urban islands in the nearby city of Victoria. Because of similarities in habitat structure, breeding density, and population size at the coastal and urban sites, any genetic differences were likely to have been attributable to island type. Genetic diversity was determined by measuring the heterozygosity--the possession of two different forms of a gene (alleles), as contributed by each of an individual's parents--of each bird at as many as 7 different genetic loci. This allowed the scientists to measure genetic variation within mating pairs, within entire sites, and between sites. The researchers could also use the genetic information to investigate potential mechanisms driving the genetic structure of the different populations of birds--including dispersal between natal and breeding habitats, local population declines, and assortative mating (whereby individuals are more likely to breed with genetically-similar partners).

(Song sparrow, Melospiza melodia)

There were some similarities between the two types of site, but also some surprising differences. On both coastal and urban islands, increasing geographic distance between sites was associated with increasing genetic distance; in other words, nearby birds were more likely to be related than birds separated by large distances. Additionally, dispersal was similarly low at both types of site. Only 8 of 106 sparrows originated from a site other than where they were sampled; 4 of these were sampled on coastal islands, and 4 were sampled on urban islands. At neither site did individuals seem particularly inclined to mate with partners genetically similar to themselves. Despite these commonalities, there were also some marked genetic differences between coastal and urban islanders. Individual birds on coastal islands had significantly higher genetic diversity, and, accordingly, were significantly less inbred, than their urban counterparts. A similar pattern was found when the analysis was conducted at the level of site rather than individual: Birds in coastal areas shared fewer alleles than did birds in urban areas.

Normally, low genetic diversity is explained by the presence of low dispersal rates, differences in population history (for instance, sudden reductions in size that result from natural disasters), and demographic processes (such as assortative mating) that occur within habitats. However, the similarity of these factors between coastal and urban islands suggests that variations in song sparrow heterozygosity were influenced by some other factor. The authors believe that this other factor may be predation, which is more frequent in urban sites than in coastal sites. When conducting nest raids, predators often eat every egg or nestling in a single feeding bout, thus placing an all-or-nothing pressure on particular genetic combinations. This can have significant impacts on genetic variation within sites, especially if parents with certain genotypes are all drawn to more heavily predated territories. Another pressure that can result in chick mortality is brood parasitism by brown-headed cowbirds (Moluthrus ater). Female chicks are less likely to survive nesting with a cowbird "sibling;" this means that males have fewer potential mates to choose from when breeding, and may find themselves stuck with a closely related partner with whom they will create less heterozygous young.

(Satellite image showing the Juan de Fuca Strait, middle of photo, and the coastal islands, right center, on which half of the study birds lived)

It is also possible that urban birds are less heterozygous because this trait is simply not as favorable in urban areas. Heterozygosity is generally thought to be advantageous because the increased level of genetic diversity should equip animals with greater "flexibility" to respond to challenges--especially disease--that they might encounter during their lives. Thus, most animals are programmed to behave in ways that maximize this trait from one generation to the next. However, individuals in urban areas may be more likely to die from causes that cannot be "combated" with heterozygosity and so there may not be as much of a selective pressure on maintaining this trait in urban areas.

On the whole, the differences between coastal and urban islands suggest that anthropogenic islands are not "analogues of their naturally fragmented counterparts," as initially thought. Thus, it doesn't appear that scientists can use information on coastal birds to predict what changes might take place in birds inhabiting anthropogenic islands. However, the comparison was useful in highlighting the unexpected difference in heterozygosity between these two types of site. This will likely be an important characteristic to consider in future conservation efforts, since managers will want not only to preserve individuals, but also to maintain genetic diversity. The marked difference between urban and coastal islands also underlines the fact that animals in human areas face very different selection pressures from their natural counterparts, and therefore may adopt quite different behaviors and life history strategies.

For supplementary photos associated with this post, please visit the Anthrophysis pin board at Pinterest.

MacDougall-Shackleton, E.A., Clinchy, M., Zanette, L., and Neff, B.D. 2011. Songbird genetic diversity is lower in anthropogenically versus naturally fragmented landscapes. Conservation Genetics 12:1195-1203.

Thanks to the following websites for providing the images used in this post:

Wednesday, 7 December 2011

Lantana: friend or foe?

To many people who encounter lantana (Lantana camara L.) outside its native South America, the plant is a nuisance that threatens to overrun gardens and agricultural fields, outcompete crop species, and require almost constant pruning. To others, lantana is not only an attractive ornamental that can be used medicinally, but also creates a useful mulch that improves soil quality, helps check erosion, provides twigs that can be used as fuel, and, most importantly, is a cheap and easy method of repelling mosquitoes--including those responsible for malaria. New research recently published in the journal PLoS ONE looks at these multiple roles of lantana and asks whether the plant's anti-mosquito properties are enough to recommend its use as a malaria control tool in Africa even though it is an invasive species.

The study was conducted by an international group of collaborators from Concern Worldwide Tanzania, the London School of Hygiene and Tropical Medicine, the Ifakara Health Institute, and Durham University. The researchers conducted their study in the Kagera Region of Tanzania, which is remote and poverty-stricken. Traditional methods of malaria control--both in Tanzania and elsewhere--include long-lasting insecticidal nets and indoor residual spraying. Unfortunately, the nets cost US$5 apiece, which is a considerable sum for families that have little, if any, disposable income. As a result, over half of the households in the study village had no bednets at all, and only 9% had enough bednets for all family members. Spraying efforts, while effective, are perceived to have negative side effects (such as increasing the abundance and activity of fleas in homes); in any case, these efforts had recently been discontinued by the Tanzanian government. The researchers were therefore interested in finding a low-cost alternative that could benefit many people simultaneously, would be simple to install and maintain, and would not require much upkeep effort.

(A long-lasting insecticidal net, or LLIN)

Several mosquito-repellent plants were considered for installation as "house screens," but lantana was ultimately selected because of its "size and vigor, year round growth, and known repellency towards the African malaria vector Anopheles gambiae s.s." Its efficacy stems from the presence of particular molecules--terpines and alkaloids such as caryophylene, eucalyptol, alpha-humelene, and germacrene--that mosquitoes find unpleasant. It emits these volatile organic compounds from its leaves even in the absence of mechanical damage. Furthermore, while mosquitoes generally avoid feeding from lantana flowers, those that do have shorter lives and lower reproductive output. As an added bonus, the plants cost only US$1.50 per household.

During the study, the plants were offered to any households that wished to give them a try; ultimately, the researchers were able to compare the effects of lantana between 231 houses with, and 90 houses without, lantana screens. By the end of the research efforts, most of the lantana screens provided >25% coverage per house and had grown 40-150 cm high, often reaching homes' eaves--a particularly important point of mosquito entry. The use of light traps to capture mosquitoes within study households allowed the researchers to confirm that the majority of specimens present were A. gambiae s.s. Significantly fewer mosquitoes were caught in homes with lantana; across all mosquito-screened homes, total reductions reached 50%. For A. gambiae, 56% reductions were seen, and for the related mosquito species A. funestis, reductions reached 83%. Lantana also decreased the presence of other mosquito species that are considered a nuisance not because they transmit disease, but because they leave itchy bites.

(Lantana, Lantana camara L.)

All in all, the lantana screens appeared to be a success, and were met with fairly positive responses from the villagers. Unfortunately, some people reported that lantana invaded their agricultural fields and needed to be removed altogether, while others indicated that the plants competed for the same resources as their banana trees and therefore caused reduced output of this important crop species. These trends emphasize the fact that, for all its favorable properties, lantana is a weed, and an exotic one at that. As a result, the authors emphasize that a "thorough ecological assessment" would be needed to fully understand the potential effects of the plant in the different villages where it might be introduced; they suggest that lantana screens might only be used in areas where the plant has already been shown to coexist with local species without causing them harm.

Other drawbacks of lantana seem more serious--its leaves are toxic when eaten by cattle, which may happen when alternative foods are scarce, and, even worse, the plants may provide a refuge for Tsetse flies, which transmit sleeping sickness. Given these problems, one has to wonder whether another plant might have been more appropriate; other species initially considered include neem (Azadirachta indica A. Juss), lemongrass (Cymbopogon citratus L.), and several types of nabhengele (Ocimum spp.). Even better would be species that are actually indigenous to the region requiring antimalarial screens--though of course not every area has naturally growing mosquito-repellent plants.

(Anopheles gamibae mosquito)

One other discouraging aspect of the study was the finding that, while the vast majority of villagers knew that malaria was caused by mosquitoes, a third of individuals had mistaken ideas, or no idea at all, about how to prevent contraction of the disease. Further, only 60% of people knew that mosquitoes bred in puddles/standing water, and therefore worked to remove these features from their environments. Although knowledge cannot directly stop a mosquito from biting a human host, it could help villagers redirect their anti-mosquito efforts from, for instance, eating cleaner food, to filling in potholes where mosquitoes might lay eggs. Since a good portion of villagers were already aware of effective antimalarial behaviors, this knowledge could be shared amongst neighbors rather than requiring the intervention of outsiders.

Ultimately, it is difficult to make a recommendation for or against lantana just yet, given that much more work is needed to explore the potential ecological and economic implications of introducing this nonnative species--even with the best of intentions. In the mean time, perhaps researchers can focus their efforts on identifying a similarly useful native plant species, or working to assess the efficacy of sterile versions of ornamental lantana; although the latter might still grow with the same ferocity as "normal" plants, at least it would be unable to spread via propagation.

Mng'ong'o, F.C., Sambali, J.J., Sabas, E., Rubanga, J., Magoma, J., Ntamatungiro, A.J., Turner, E.L., Nyogea, D., Ensink, J.H.J., Moore, S.J. 2011. Repellent plants provide affordable natural screening to prevent mosquito house entry in tropical rural settings--results from a pilot efficacy study. PLoS ONE 6(10):e25927.

Thanks to the following websites for providing the images used in this post: