Thursday, 19 April 2012

Birds know where they are not wanted

Human attitudes toward wild animals are influenced by a number of factors, including demographics such as gender and age, socioeconomic status, level of education, and cultural experience. These attitudes, in turn, affect the interactions that people have with the animals around them; where some individuals might feel inclined to commune with wildlife, others might be more interested in chasing it off. In time, many animals may learn to discriminate between friend and foe, haven and wildlife war zone, and may change their behaviors accordingly. Understanding more about this process, and the links between these three factors, can be helpful in developing outreach programs, management policies, and conservation plans.

(Seattle, Washington, USA)

Two researchers--from the University of Washington and Germany's Humboldt University--recently conducted a study on this topic, focusing on attitudes toward birds along a rural-urban gradient in Berlin, Germany, and Seattle, Washington. They selected two study sites at each of four different urbanization levels (urban, dense suburban, light suburban, rural) in each city, for a grand total of 16 study sites. At each of these, they conducted house-to-house surveys in order to collect information on residents' feelings about wild birds--demonstrated by whether they feed the animals or whether they actively discourage them from coming too near--and on several other factors that can influence these attitudes (gender, age, whether or not they have children, socioeconomic status, and education level).

(Berlin, Germany)

In each area, the scientists also quantified avian responses to humans. To do this, the researchers measured flight initiation distance (FID), or the distance at which birds took off when approached by pedestrians. Rather than focusing on all local species, they examined 3 corresponding species in each city: hooded crows (Corvus cornix), house sparrows (Passer domesticus), and starlings (Sturnus vulgaris) in Berlin, and American crows (Corvus brachyrhynchos), American robins (Turdus migratorius), and starlings in Seattle. Whereas the sparrows and robins are charismatic species that are generally regarded with goodwill, the two crows are examples of species that are often persecuted; starlings are interesting because they are native to Berlin, but invasive to the US, and may therefore be associated with very different attitudes in the two cities.

(European starling, Sturnus vulgaris)

A number of factors determined whether people were more likely to feed birds or chase them away. Germans--especially those in dense suburban areas--fed birds more than Americans; however, across both cities, urban residents were less likely to feed birds than suburban and rural inhabitants. Older respondents, and those who owned their homes, were more likely to feed birds, as were people with children (regardless of their domestic status). Americans and older residents were more likely to discourage avian wildlife, but the least bird-friendly people were those in rural Seattle; Berlin residents were equally likely to discourage birds, at minimal levels, across the entire urban gradient. Although inhabitants of both cities used many of the same tactics to discourage birds--physical barriers, acoustic deterrents, and decoys, for instance--only Americans attempted to scare off and injure birds by shooting at them. As the researchers predicted, the most negative behavior was directed towards crows (60%), then starlings (20%), then all other species combined (20%).

(American robin, Turdus migratorius)

The birds showed signs of understanding where they were not wanted. In general, urban birds tolerated much closer approaches than rural birds. Bird-friendly behaviors were not significantly correlated with FID, but bird-discouraging behaviors were: While Berlin birds had similar FIDs regardless of local human activities, Seattle crows and starlings--the two most persecuted species--had significantly shorter FIDs where anti-bird attitudes were highest. The authors are not sure whether these birds are wary as a result of past experience over the lifetime of particular individuals, or whether unfriendly anthropogenic habitats have selected for greater cautiousness across the entire species; this may be an interesting area of future research.

(Hooded crow, Corvus cornix)

It is sad to think that negative behaviors have a much greater impact than positive ones, but the authors have some theories as to why this might be so. Perhaps most importantly, bird feeding is much more indirect than bird-discouraging, and so animals may never learn to explicitly associate food supplements with humans, per se, but, instead, with feeders and other anthropogenic structures; on the other hand, they are likely to remember that a tall, two-legged animal is likely to throw rocks or make frightening noises. It is also possible that any effects of goodwill are drowned out by the more obvious impacts of exposure--in other words, birds are more likely to relax as a result of habituation, caused by many repeat encounters, than because of any overt "peace offerings" made by their human neighbors.

 (American crow, Corvus brachyrhynchos)

Although the current study only focuses on five bird species in two cities, the general patterns reported here are similar to those found elsewhere in other species. Cumulatively, these results indicate that human attitudes translate into predictable suites of human behaviors that, in turn, have predictable impacts on local wildlife. This suggests that animal preservation initiatives would be greatly aided not only by improving the species' habitats and breeding success, but also by increasing human goodwill towards. Interestingly, the current results also support previous findings that Americans have more "negativistic" and "utilitarian" views towards wild animals, whereas residents are more "moralistic" and "naturalistic" in Germany and elsewhere in Europe. Thus, it will be important to keep cultural differences in mind when developing plans to alter human-wildlife relationships.

Clucas, B., and Marzluff, J.M. 2012. Attitudes and actions toward birds in urban areas: Human cultural differences influence bird behavior. The Auk 129:8-16.

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

Thursday, 12 April 2012

Conservation design: artistic solutions for biological problems

Who do you call when a pest species invades a public space--animal control? Wildlife managers? Scientists? How about...designers? That's the unique suggestion of a group of international collaborators working to solve the problem of greedy South American sea lions (Otaria flavescens) who have recently taken to begging for food in the fish market of Valdivia, Chile. Because the sea lions are both a nationally protected species and a popular tourist attraction, locals are interested in dealing with them as sensitively as possible. Unfortunately, early management measures, most notably the use of fencing around the market area, failed because they were not consistently employed.

(South American sea lions, Otaria flavescens)

Where some people might view this as a setback, local researchers saw it as an opportunity to explore the power of interdisciplinary collaboration. They placed advertisements for university design students looking to get practical work experience, then challenged applicants to design innovative solutions to human-seal conflicts. Each design was founded on background information--gleaned from newspaper articles, blogs, photographs, videos, and scientific literature--on sea lion biology and attitudes toward human-sea lion interactions. The researchers encouraged designs that would function at a variety of scales, from temporary use by affected individuals to long-term architectural projects designed to benefit the entire riverside area. They also sought ideas that could facilitate different types of human-wildlife contact, including none at all, controlled contact such as that found in zoos, or unlimited, free contact such as that found in the wilderness. In addition to looking for useful, biologically-grounded designs, the researchers wanted outputs that were aesthetically pleasing, durable, and long-lasting.

Despite having keep all of those concerns in mind at once, designers ultimately managed to come up with seven different suggestions that seemed both appropriate and feasible. These were selected as the "finalists" not only because they seemed useful on an individual basis, but also because they could be mixed and matched in different combinations in order to achieve local management goals.

(Distribution of South American sea lions. Although the designs described here were created for use in Valdivia, Chile, they could be useful throughout the sea lions' range, and also for similar species found elsewhere.)

Two of the products are fliers (also suited for poster or sign format) presenting basic information on sea lion behavior--in particular, the animals' body language and signals of agitation and aggression. The first flier is meant to be posted in areas where human-sea lion interactions are undesirable, and thus is devoted to explaining why a distance should be maintained between the two species; the second is meant for distribution in areas where interactions are permitted, and therefore provides information on how to safely engage the animals.

The next two designs are barriers that can function temporarily or can be left in place for longer-term use. Both sets of fencing are made of sturdy metal that curves towards the sea lions, preventing the animals from climbing over into areas where they are unwanted. The barriers are made in segments that can be hooked together to exclude sea lions over different amounts of space. The only difference between the two types of barrier is that one is completely solid, while the other is fitted with a slot through which humans can feed the sea lions fish; the slots have a distinctive pattern that should help the animals recognize, and frequently revisit, areas where they are likely to receive handouts.

(A sea lion visiting Valdivia's fish market)

For situations where humans can wander freely amidst the sea lions (or vice versa, depending on which perspective you take), the designers have created a "fladry umbrella" that can be quickly opened in order to scare off animals that have approached too closely or are becoming aggressive. "Fladry" are ribbons of fabric whose fluttering is unsettling to animals; here, they are combined with bright coloring and an eyespot design to produce an alarming display that should keep sea lions at bay.

The final two design solutions are both longer-term, larger-scale architectural projects that could be installed along the river where the sea lions rest and, when they are not eating handouts, hunt for fish. Both are high, smooth-walled embankments, level with the sidewalk at the top, and with the river bank at the bottom. A curvature in the walls would not only prevent sea lions from climbing up to the sidewalk, but would also provide shade for the animals during sunny days. Rest areas could be built into the bottom of the embankments, providing sea lions a place to nap--and humans a spot to do some wildlife-watching. Whereas one embankment would provide a complete barrier between humans and sea lions, the other includes feeding stations that use the same slot mechanism as above to allow visitors to pass fish through to the other side.

The authors stress that each of these designs is currently only in the "idea" stage and has yet to be made into a testable prototype. Although this will hopefully the be next phase of the project, the main point of the current paper is not to discuss which of these potential solutions will work best in Valdivia, but instead to highlight the utility of collaborations between designers and biologists. For others who wish to follow their footsteps, the authors list a number of things that should be considered both before anyone sits down at the drawing board. To begin with, it is important to research local values in order to understand what type of products will be most useful, and to whom. It is also necessary to understand the biology of the wildlife in question--in particular, what sorts of behaviors they engage in, and where; after all, these are the characteristics driving the need for management activities in the first place. Finally, designers should be aware of how much money is available to fund mitigation efforts. After all, even the most ingenious solution won't be very useful if it is too expensive to implement.

 (Sea lions wait for handouts in Valdivia's fish market)

Once potential ideas have been developed, the researchers strongly advocate the creation of prototypes and the conductance of field research. It is important not only to see how wildlife respond to the proposed designs, but also whether people approve of the products and their installation. In the case of the sea lions, for instance, the researchers indicate a need to ascertain whether the animals learn to cue in to the feeding slots, whether different patterns of fladry umbrella are more or less effective, and whether locals will find the proposed embankments to be aesthetically pleasing enough to be installed in the middle of their city. The creation of multiple different options, such as the seven generated in the current study, is useful for doing side-by-side comparisons of potential management solutions.

The researchers offer one last suggestion to future interdisciplinary collaborators: publish papers detailing the design process. Currently, they say, there is very little literature on conservation design; managers looking for solutions often have to start from scratch. If more people publish information on design proposals, assessments, concerns, and achievements, then advancements in the field will be made more quickly--to the benefit of both humans and wildlife.

Root-Bernstein, M., Rosas, N.A., Osman, L.P., and Ladle, R.J. 2012. Design solutions to coastal human-wildlife conflicts. Journal of Coastal Conservation, online advance publication.

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

Wednesday, 11 April 2012

Seabirds avoid ship traffic

Cars are the focus of conservation efforts so often that it's easy to forget there are other potentially problematic vehicles out there. Aquatic habitats, for instance, are traversed by a variety of vessels, ranging from small recreational craft to much larger fishing, freight, and military ships. Traffic from these vehicles often disturbs even the bravest wildlife, with impacts on behavior, breeding efforts and reproductive success, and distribution throughout the habitat. Surprisingly, while these general effects have been recognized for a long time, there is a dearth of the sort of species-specific data needed to create management plans allowing humans and wildlife to coexist with minimal conflict.

(The North Sea)

A group of researchers from Germany's University of Kiel recently performed a study to rectify this problem in one of the most highly trafficked marine systems in the world--the German North Sea and the nearby Baltic Sea. This area is inhabited by several species of waterbird known to be particularly sensitive to human activity: red- and black-throated loons (Gavia stellata and G. arctica, respectively), common eiders (Somateria mollissima), long-tailed ducks (Clangula hyemalis), and common and white-winged scoters (Melanitta nigra and M. fusca, respectively). By measuring whether, and how, ship traffic affects the location and behavior of these species, the researchers hoped to understand the potential affects of aquatic vehicular activity on these and other birds throughout the region--information that could then be used to develop appropriate management plans.

The researchers were interested in three major questions. First, do birds distribute themselves in such a way as to avoid the bulk of ship traffic? This was ascertained by conducting survey flights over major shipping zones and counting how many loons were present within shipping lanes and between them. Second,
at what distances will seabirds flush when approached by shipping vessels? Experimental approaches were made towards flocks of sea ducks, and the researchers noted at what distance, and under what environmental conditions, the birds took flight. Third, how quickly do birds resume their "normal" behaviors after being disturbed by ship traffic? This was also determined experimentally, with point counts conducted before and after out-and-back boat trips.

(Red-throated loon, Gavia stellata)

Loons were much more likely to be found between shipping lanes than within them, suggesting that the birds were actively avoiding ship traffic--or, perhaps, indicating that the ships had scared off prey species, requiring the loons to relocate as well. When approached by experimental vessels, sea ducks usually avoided them by taking flight rather than by diving. This, however, was the only commonality across all birds: Some species (particularly common scoters) were much more skittish than others, but there was also high variability within species. Overall, common eiders were the most likely to stand their ground (so to speak), but behavior of all birds was also influenced by flock size, proximity to shipping lanes, and sea state. Interestingly, ducks within shipping lanes flushed much later than those in surrounding areas, suggesting that these birds may have begun to habituate to maritime traffic. After ship passages, different species returned to the trafficked area at different speeds, with common eiders and long-tailed ducks arriving most quickly, and wary common scoters arriving after the greatest delay.

 (Common scoter, Melanitta nigra)

Although reactions to ship disturbances varied as a function of species identity, the overall patterns here suggest that sea birds are fairly sensitive to maritime traffic and attempt to avoid it as much as possible. For instance, while some flocks of common eiders remained in place as ships passed, other flocks flushed while vessels were still over 3 km away. The wariness displayed here has also been observed in response to offshore wind turbines, to which sea birds never seemed to habituate even after years of exposure. This suggests that the best mode of management may be to maintain a handful of shipping lanes from which large vessels never deviate, giving the birds "safe" zones in which they will not be disturbed. The only problem with this plan is that smaller recreational craft can generally travel where they like; thus, it may be necessary to introduce new restrictions for these vehicles.

Species-specific responses may stem from morphological variations that make some species better fliers (or, more specifically "flee-ers") than others. If so, then data on body size and wing shape may be useful in predicting which species will respond most negatively to human disturbance; this could be particularly helpful information when developing management plans in areas for which there are not enough funds to mount full-scale research efforts. However, the researchers caution that these behavioral data do not reflect potential physiological difficulties--such as increased heart rate and stress levels--associated with exposure to human disturbance. Likewise, birds that flee are spending time and energy on flight and relocation, when instead they could be foraging and bulking up. This trade-off is likely to have fitness implications over the long run.

(Common eider, Somateria mollissima)

Because of these other important variables, the researchers see their study as an important first step that needs to be followed with additional research. Future studies, for instance, might examine the effects of ship traffic in other seasons (when birds are in different stages of molt and have different life history motivations), under other vehicular conditions (e.g. different types of craft moving at various speeds), and on other response variables--including those related to physiology and energetics.

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

Schwemmer, P., Mendel, B., Sonntag, N., Dierschke, V., and Garthe, S. 2011. Effects of ship traffic on seabirds in offshore waters: implications for marine conservation and spatial planning. Ecological Applications 21:1851-1860.

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

Tuesday, 10 April 2012

Form and potency of urban birdsong are impacted by noise

In 1969 and 1970, the late ornithologist Luis Baptista collected recordings of white-crowned sparrows (Zonotrichia leucophrys) living in San Francisco, California. At the time he probably never suspected that, 35 years later, one of the hottest topics in the field of avian communication would be human noise-driven variations in birdsong. In 2005, however, researchers David Luther (of George Mason University and the Smithsonian Migratory Center) and Elizabeth Derryberry (of Louisiana State University), recognized that Baptista's recordings offered a treasure trove of information about historical ambient noise levels and bird song characteristics--and provided a baseline to which modern recordings might be compared.
(White-crowned sparrow, Zonotrichia leucophrys)

The two collaborators designed a study allowing them to use Baptista's data to answer three major questions: First, did urban noise levels increase between 1969 and 2005 and, if so, was it related to increases in car traffic? Second, assuming there were changes in ambient noise levels, were there any accompanying adjustments in white-crowned sparrow songs--specifically, did the sparrows show the same sort of song variations previously documented between urban and rural, or noisy and quiet territories? Finally, do current birds respond more strongly to historical or modern songs?

Eight of Baptista's recordings were collected from an area of San Francisco in which resident sparrows sang what has since (appropriately) been labeled the San Francisco dialect. This area was revisited in 2005 so that additional males (a total of 12) could also be recorded. Nearby stands the Golden Gate Bridge, with all its noisy traffic. This inspired the researchers to examine whether long-term changes in ambient noise were related to corresponding variations in traffic; information on both of these variables was extracted from documents produced by local and federal governments.

(The iconic Golden Gate Bridge: a source of noise that impacts local wildlife)

For the final part of the study, Luther visited the territories of 20 resident males and exposed them to broadcasts of both historical and contemporary recordings. Each male heard one pair of songs--only one song per day, randomly selected, and with a rest period of at least two days between each exposure. The intensity of each male's response was assessed in two ways: his general behaviors (speed to approach the speakers, closest approach to the speaker, number of flights near the speaker, number of wing waves) and vocal behavior (latency to deliver the first song, total number of songs produced).

As expected, the researchers found that San Francisco has grown significantly louder over the last 35 years. In fact, with an average increase of slightly over 5 dB (from 66 dB to 71), it has become nearly twice as loud. Over the same time period, traffic flow has increased by 19%. Likewise, male songs changed noticeably between 1969 and 2005. Of 18 song characteristics measured, five varied significantly, and four of these were related to minimum or dominant frequency--the song trait most commonly observed to change in relation to ambient noise levels. Specifically, modern males have shifted their frequencies upward. Contemporary territory holders can clearly distinguish these differences: Males responded to current songs more quickly and more intensely than to those from historical recordings.

(Great tits, Parus major--perhaps the best-studied species in the context of anthropogenic noise)

It is not easy to pinpoint the exact mechanism behind the patterns observed here. They may simply be the result of drift--or, in other words, an artifact of sampling techniques and/or random cultural survival of one type of song versus another. Alternatively, they could represent a true adaptive response to anthropogenic noise. If this is the case, though, it is not clear whether modern song is a result of cultural evolution, behavioral plasticity, or some combination of the two.

In all, though, there is strong evidence that increases in traffic led to increases in ambient noise, which, in turn, led local males to adjust their songs in order to maintain (or even improve) their ability to perform effective vocal displays clearly marking the edges of their territories. The temporal adjustments are particularly striking in comparison with changes made by the same species over the same time period in nearby rural areas. There, several populations of white-crowned sparrows actually sing lower minimum frequencies--a variation caused not by anthropogenic noise (of which there is very little), but by changes to habitat structure. Urban sparrow vocal manipulations are also strikingly similar to those observed elsewhere in several other species of city-dwelling bird, including great tits (Parus major) and song sparrows (Melospiza melodia).

(Song sparrow, Melospiza melodia--another of the growing number of avian species known to vocally respond to anthropogenic noise)

Perhaps the most intriguing finding here is that the vocalizations that are more "appropriate" for a given noise regime are also better at eliciting a response from an avian audience--in this case, potential rival males. This suggests that birds in noisy areas may need to adjust their songs to be able to communicate effectively; those that don't are in danger of being ignored, or at the very least being taken less seriously. While this was only studied here for male-male interactions, it may also be true for male-female interactions, which, obviously, play an important role in perpetuating a species. In the future, then, it will be interesting to see how signal efficacy is impacted by anthropogenic noise, and also to investigate the implications of noise pollution in species that do not display vocal flexibility.

Luther, D.A. and E.P. Derryberry. 2012. Birdsongs keep pace with city life: changes in song over time in an urban songbird affects communication. Animal Behaviour 83:1059-1066.

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

Guidelines for achieving sustainability

Although conservationists often advocate sustainability, it's not always clear how this concept can be incorporated into our lives in a practical way. It requires people and institutions to use scientific knowledge to shape (or reshape) our ideals, practices, and laws. As a result, it stands at the junction of several fields of study--including (but not limited to) biology, sociology, economics, and philosophy. Previously, the development and implementation of sustainability plans may have been held back by our lack of scientific knowledge, but, according to collaborators writing in a recent issue of Frontiers in Ecology and the Environment, the greatest barrier to sustainable living is now our lack of direction.

To combat this problem, the authors have suggested five "priority themes" that should help both governments and individuals incorporate sustainable practices into everyday living. The themes were mainly developed with industrial societies in mind, as these are considered to be "the primary origin of the sustainability crisis," and also because these are the entities "better equipped...to actively address unsustainable behaviors."

The first of the themes is "reforming formal institutions," from local interest groups all the way up to the level of federal governments. Because institutions are "the underlying rules and structures that shape the social, economic, and political transactions within society," reform of these organizations can alter the way that decisions are made and rules are enforced. Integrating environmental policy considerations into basic institutional activities could help ensure that sustainable practices are discussed (and hopefully incorporated) in many sectors, ranging from finance and trade to energy, transport, and urban development.


However, the researchers recognize that institutional changes are driven by individuals, and also that individuals are active in society outside the framework of these organizations. Thus, their second theme is "engaging community in a stronger civil society." Institutions are often focused on "traditional imperatives" that are not easily married with sustainability--for instance, businesses want to make money, but green practices sometimes require large financial investments. Individual citizens, however, are not constrained by these same concerns; just as some communities design shared pastures and parks, so too might individuals come together to develop a "green" culture.

Achieving this will be easier if people remain mindful of the authors' third theme: "curbing consumption and population growth." The researchers suggest we should be particularly careful to minimize "inconspicuous consumption," or the use of objects and practices that are not actually necessary but have been employed for so long that we think of them as such--air conditioning, for instance, or long, hot showers. In order to "reorient economic life," the authors advocate research on the topic of whether, and how, people might be persuaded to "bring their preferences into better alignment with the requirements of ethics and sustainability." Simultaneously addressing population growth will not only have ecological benefits, the researchers argue, but also social ones--improved health, well-being, quality-of-life, and gender equality, to name a few.

Speaking of equality, the fourth theme is "equity and justice," two concepts that the authors admit are often thought to be far removed from the realms of science and conservation policy. However, these are important ideas because they determine who takes responsibility for certain activities or outcomes, and who has a say when decisions are made. For example, it is good to have clear guidelines in place for the disposal of hazardous waste, otherwise the same communities or areas might end up with an unfair amount of toxic garbage; likewise, predetermining who will be tasked with any emergency cleanups will ensure there are not legal hold-ups when and if any leakage does occur.

The final theme is "value and belief systems," which, of course, will influence all of the above. Factors such as age, gender, education level, and social status will cause individual variations in values over time, while societal variations will be driven by socioeconomic development. Because such fluctuations impact "human-environment relationships," the researchers stress the need to keep these factors in mind when developing conservation plans. They hope that we can find inspirations in worldviews that emphasize sustainability--not necessarily as a replacement for current beliefs, but as a "fresh perspective on sustainability problems," and a way to find "alternatives to consumption- and growth-based society." Understanding how these philosophies and emotions will impact each of the above themes, however, will likely require some inspired interdisciplinary research.

On the whole, the authors write, "sustainability requires a social avalanche of unprecedented proportions." Although the avalanche can be started by anyone, the researchers hope that conservation researchers might help initiate change by forging more transdisciplinary alliances--not just among academics but also between academia and other societal institutions. Further, they suggest that researchers should be more vocal in advocating sustainability; by finding novel and exciting ways to discuss this topic in public, scientists might inspire the public and begin to teach by example.

Fischer, J., Dyball, R., Fazey, I., Gross, C., Dovers, S., Ehrlich, P.R., Brulle, R.J., Christensen, C., and Borden, R.J. 2012. Human behavior and sustainability. Frontiers in Ecology and the Environment 10:153-160.

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

Friday, 6 April 2012

Man's trash is a lizard's treasure?

Veterinarians admonish us not to feed our pets "people food" because it isn't good for them. A logical corollary would then seem to be that wildlife should also be kept away from human fare and the scraps thereof. Indeed, several studies have shown that urban animals nibbling on human trash wind up with some of the same health problems that plague us as a result of consuming greasy, high-carb, packaged foods. Given these patterns, it comes as a bit of a surprise to learn that Australian lace monitors (Varanus varius) may actually benefit from anthropogenic "subsidies" in the form of free meals at the local garbage dump.

(Lace monitor, Varanus varius)

These animals, also known as goannas, were the subject of a study by researchers at the University of Melbourne, Zoos Victoria, and the Australian Wildlife Health Centre. The goannas were examined in situ at four different sites: two undisturbed forests in which resident monitors consumed their natural diets, and two small garbage dumps associated with nearby rural towns. Because the dumps were located at some distance from the towns, and in the middle of small patches of forest, they closely mimicked the natural areas; the only major difference was that goannas near the dumps were able to forage on edible refuse dropped off daily by human neighbors.

In addition to performing point counts to estimate lizard density at each site, the researchers caught as many animals as possible in order to mark and measure them, and to collect a blood sample that could be subjected to a suite of laboratory analyses. Specifically, the scientists could perform counts of both red and white blood cells, assay for liver- and heart-related metabolic syndromes, measure metabolic activity and corticosterone levels, look for the hematozoan parasite Haemogregarina varanicola, and extract genetic data to sex each lizard. Cumulatively, these tests enabled the researchers to compare size, condition, physical health, and stress levels of "natural" and food-supplemented monitors.

(Lace monitor range map)

The first obvious difference between the two types of experimental site was lizard density. Not only were there 35 times as many monitors at subsidized sites, but the same individuals were repeatedly encountered over multiple visits; on the other hand, there were no resightings in natural areas. Unfortunately, it is not yet clear whether garbage dump lizard densities are high because animals from neighboring forest patches migrate there in droves, or because there were a few original colonizers who have successfully survived, reproduced, and created a large local population.
Results from the morphological and physiological measurements indicated that a life of luxury can be found in anthropogenic sites. Monitors near garbage dumps were bigger (in terms of both length and weight) and in better body condition than their counterparts in the control sites; they also had higher red blood cell counts and showed no signs of metabolic syndromes or undue stress (as indicated by aspartate aminotransferase/creatinine kinase and corticosterone levels, respectively).

(Lace monitor basking on top of a backyard BBQ)

Lower levels of plasma glucose, taken into consideration with the high body condition and low corticosterone levels, indicated that supplemented monitors were having to expend less energy to obtain their meals--a finding supported by the observation that lizards at subsidized sites could often be found basking in the sun rather than foraging for a meal. That sounds awfully similar to the sorts of patterns observed in modern humans; thus, it isn't too surprising to note that, like humans who eat highly processed foods, supplemented monitors have higher levels of phosphorous and sodium in their plasma. On the up side, though, they also have fewer blood parasites.

As with the density data, these correlations leave a major question about cause-and-effect: Are supplemented monitors morphologically and physiologically successful because of the abundant human food, or are these types of individuals simply attracted to, and able to live in, anthropogenic areas? Future research will be needed to determine the answer. Either way, these results seem to indicate that garbage dumps, and human-supplemented habitats in general, can be a paradise for wild animals.

(Head shot of a goanna)

However, the study did reveal one additional pattern that suggests there may be more to these habitats than meets the eye. Genetic data indicated that subsidized areas had sex ratios that were nearly 3 times as biased toward males; specifically, there were an average 5.3 males for each female. Unsurprisingly, this sort of bias increases competition for mates and decreases individual breeding success--with a few super-males often emerging to dominate. Not only can this reduce genetic diversity in the population, but it can also lead to higher rates of cannibalism if competitive males eat juveniles before they can grow up to be potential rivals. Cumulatively, these patterns generally render male-biased populations less successful, which means that long-term monitoring will be required to investigate whether human food subsidies are really as beneficial to goannas as they might initially seem.

Jessop, T.S., Smissen, P., Scheelings, F., and Dempster, T. 2012. Demographic and phenotypic effects of human mediated trophic subsidy on a large Australian lizard (Varanus varius): meal ticket or last supper? PLoS ONE 7(4):e34069.

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

Wednesday, 4 April 2012

Why you should eat your veggies

Many animals use carotenoid-based color signals to indicate their attractiveness, as has previously been discussed here in the context of northern cardinal breeding success. As a refresher, carotenoids are generated by photosynthetic organisms such as plants, bacteria, algae, and fungi, and are responsible for yellowish and reddish coloration--such as cardinals' bright red plumage. Although these hues are typically thought to be "sexy" because they indicate an animal's ability to forage efficiently, they also provide information on an individual's underlying physiology: Because carotenoids help protect tissues against oxidative stress, higher levels of carotenoid coloration may indicate robustness against cardiovascular disease, diabetes, cancers, and other age-related degenerative processes; carotenoids also appear to facilitate immune activity, and may therefore signal the ability to tolerate and/or fight off infection.

Given the desirability of those traits in humans, it might not surprise you to find out that we are but one of the many species expressing carotenoid pigmentation. Indeed, recent work by researchers at the University of St. Andrews' Perception Lab has revealed that even small variations in human carotenoid consumption--mainly in the form of fruits and vegetables--can lead to noticeable differences in skin color; further, these differences are associated with how attractive and healthy other people find us to be.

These findings were the result of a six-week study of 35 volunteers whose fruit/vegetable intake and skin coloration were recorded at three time points (the beginning of the study, 3 weeks in, and 6 weeks in). Coloration was measured using a spectrophotometer, which shines light onto a patch of interest and then records how much of that is reflected and what colors are present in the reflected light; this yields a metric called CIE L*a*b*, which indicates lightness, redness, and yellowness of the patch of skin (or, in this case, 7 different patches distributed across each participant's body).

(Diagram showing how a spectrophotometer works)

On average, volunteers reported eating 3.4 servings of produce per day--or 1.6 fewer servings than the UK-recommended 5 per day. Skin lightness decreased in participants who increased their produce consumption over the course of the study; in other words, these volunteers looked more tan, a pattern that was undoubtedly driven by significant increases in both redness and yellowness. This was only true for CIE L*a*b* measurements across all 7 skin patches, and not just a subset of the three on the face; additionally, these variations were only noticeable across the entire six-week period (e.g., week 0 to week 6) rather than over either of the 3-week sub-periods.

All volunteers who sunbathed, self-tanned, and applied makeup prior to the skin-tone analysis were all dismissed from the study. Still, the researchers wanted to ensure that the patterns observed here really did result from carotenoid consumption. To do this, they examined changes in skin reflectance over the range of wavelengths dominated by carotenoid coloration; experimental patterns were compared to the reflectance curves of three different carotenoids (alpha-carotene, beta-carotene, and lycopene), an average across all of these, and melanin--the pigment responsible for darkening our skin by conferring increasingly brown and black tones. The averaged carotenoid curve closely matched the reflectance curve describing the pattern observed in the study participants; this appears to have been driven primarily by lycopene, the carotenoid found in fruits such as tomatoes and papayas. The observed reflectance data were not, however, similar to the curve for melanin. Cumulatively, these findings indicate that increases in fruit and vegetable consumption--particularly of bright red produce--can result in noticeable changes in our complexions.

(Color spectrum. Carotenoids tend to absorb light most in the 400-540 nm range, but reflect light from 540 nm upwards--which is why they look yellow and red to us.)

In order to investigate the potential social ramifications of this, the researchers digitally manipulated photographs of four study subjects (two of each gender) to obtain 22 images per face. The middle face in the resulting continuum was unmanipulated and the entire spread represented a total dietary change of +/- approximately 5.6 produce portions per day. To determine which complexions were deemed most attractive, the researchers repeatedly exposed volunteers to two versions of the same face, one after the other; volunteers then picked which was yellower, healthier-looking, and more attractive. All evaluations were performed within a computer program that was aware of each photograph's actual color measurements; by keeping track of "wrong" answers, the program was able to calculate volunteers' discrimination thresholds--the point at which they were no longer able to perceive differences between photographs.

Faces that were classified as yellower, healthier, and more attractive were those with positive changes in fruit/veg consumption--in other words, those that reflected (no pun intended) higher carotenoid consumption. A difference of just under 2 fruit/veg portions per day was enough to permit discrimination of more yellow skin, while faces were perceived to be healthier and more attractive at 2.9 and 3.3 more produce portions per day, respectively.

 (Tomatoes, which are a great source of the carotenoid lycopene.)

Cumulatively, the researchers emphasize that only a "relatively modest level of dietary change" is required to achieve a yellower, healthier-looking, and more attractive skin tone. Although baseline diet was not found to impact the amount of color change observed over the 6-week study, the authors point out that original skin tone might play an important role; Asian and African individuals, for instance, are already darker than Caucasians and may therefore require larger dietary changes in order to achieve comparably noticeable differences in skin tone. Interestingly, though, a previous study from the same lab found that people of all ethnicities found yellower skin healthier-looking and more attractive, regardless of the ethnicity of the person at whom they were looking. Thus, people of all ethnic backgrounds appear likely to gain similar social benefits--assuming, that is, that looking more attractive is beneficial--from eating more produce.

Eventually, the researchers hope that their results can be used to make healthier diets more appealing. Before they start any big marketing campaigns, though, there are some additional questions they'd like to answer. For instance, do people reach a "saturation point" at which increased carotenoid consumption no longer has positive chromatic benefits? How, exactly, do carotenoids change skin color--is it purely their activity as pigments, or might the patterns also result from interactions between carotenoids and polyphenols, leading to improved blood flow? Finally, will everyone be equally aware of these diet-induced color changes? The average age of volunteers in this study was 18.9, but color vision becomes less acute as people age, suggesting that larger carotenoid fluxes may be required to catch the attention of older viewers. Whatever the answers to these questions, one thing is clear: Our parents were right to admonish us to eat our veggies.

Whitehead, R.D., Re, D., Xiao, D., Ozakinci, G., and Perrett, D.I. 2012. You are what you eat: within-subject increases in fruit and vegetable consumption confer beneficial skin-color changes. PLoS ONE 7(3):e32988.

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

Sunday, 1 April 2012

A new method for identifying habitats in need of conservation

Conservationists often call for the protection of additional wildlife habitat, and in 2010 many countries signed a pledge to increase the global protected area network from 12% to 17% by 2020. Meeting this goal will be a challenge for a variety of reasons, not least of which is the difficulty in pinpointing which locations merit protection or, when there are several worthy options, which will yield the greatest biological benefits.

(Recent map showing the extent of protected areas worldwide)

After recognizing this potential obstacle, a team of British researchers developed an objective method of "identifying priority areas for conservation," to quote the name of their recent paper in PLoS ONE. They first used pre-existing data on animal distributions in order to calculate the conservation importance of 5x5-km squares around the globe. In this case, the animals of interest were forest-dwelling birds, for which distribution data happen to be extremely detailed; additionally, forest habitats act as a sort of conservation umbrella, since these areas tend to have very high biodiversity. Impact scores indicate how many highly and moderately forest-dependent bird species inhabit each cell, and therefore offer a continuous measure of each cell's potential conservation impact--something of a novelty, since most previous measures tend to be binary or categorical.

The researchers overlaid their scores with several pre-existing datasets in order to further refine their estimates of which regions were in greatest need of conservation action. The first of these examined recent deforestation rates, and therefore pinpointed which areas were most likely susceptible to development; the next contained information on land that is already set aside for bird conservation purposes, thus pinpointing which areas are least regulated and, therefore, most vulnerable; the final dataset focused on areas with the greatest carbon stocks, allowing the researchers to determine how their results might fit in with the Reducing Emissions from Deforestation and Forest Degradation (REDD) project, an incentives program that attempts to reduce greenhouse gas emissions by avoiding deforestation.

In all, 6,077 bird species (or about 61% of the world's avian biodiversity) were considered in the analyses, and they cumulatively occupied a total of 2.2 million 5x5-km squares. Impact scores ranged from 0 to 4.01; although the average was quite low (0.0026), there was a skew such that only a handful high-scoring cells accounted for just over a quarter of the global sum. In other words, forest bird biodiversity is extremely high in a few key locations, including the Hawaiian Islands,  São Tomé and Príncipe, Indonesia, the Philippines, New Guinea, the Atlantic Forests, the northern Andes, and South America. If you examine that list closely, you'll notice that areas with high impact scores tend to be islands, coastal areas, and mountains, with a few tropical lowlands thrown in for good measure; at the other end of the spectrum are low-ranking arctic and arid regions.

(Uses of terrestrial protected areas)

The mean deforestation rate across all cells with data was 1.3%. Deforestation was not necessarily greatest in areas with the highest impact scores, though there were some regions with both high scores and high rates of deforestation; these included the Cordillera La Costa mountain forests, the Halmahera rain forests, Mount Cameroon and Bioko, and Africa's Eastern Arc forests. Perhaps more troubling is the tiny fraction of all forested habitats covered by the current protected area network: Only 9% of the study cells contain protected forest, and 7 of 20 regions with the highest impact scores did not contain any protected forest at all. The good news is that the addition of a few select areas could not only meet the 17% protected area target proposed by the world's governments, but could also preserve nearly three-quarters of the globe's most biodiverse forests.

The researchers found a weak positive relationship between impact scores and carbon stocks, indicating that REDD activities alone will not provide absolute protection to these forests, though they certainly will help. A few "super-ecoregions" had high impact scores, deforestation rates, and carbon stocks, indicating that these areas are likely to be important targets of future conservation projects. These include the Seram rain forests of Indonesia, Borneo and Sumatra lowland rain forests and Sumatran peat swamp forests, Niger Delta swamp forests, Madeira-Tapajos moist forest, and the Isthmian-Atlantic moist forest.

(Recent estimates of the distribution of global biodiversity)

The analytical techniques employed here could easily be applied to other taxa, such as mammals and amphibians; additional groups, however, will need more complete distribution maps before their habitats can be given impact scores. Multispecies analyses will be useful for investigating the extent of overlap for "rarity, endemism, and risk." Despite the likely usefulness of their method, the authors admit that there are some important factors not considered here. For instance, they have not incorporated cost management data that could indicate which areas would give them the most conservation bang for the fewest bucks; further, they have not included data on non-deforestation pressures such as hunting or chemical pollution. However, these are all factors that could be added to later analyses as more information becomes available.

Buchanan, G.M., Donald, P.F., and Butchart, S.H.M. 2011. Identifying priority areas for conservation: a global assessment for forest-dependent birds. PLoS ONE 6(12):e29080.

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