Effects of traffic noise on a highly endangered migrant bird

Conservationists and managers are not only interested in current environmental conditions, but also those that may develop in the future. Processes such as urbanization and human population expansion, for example, might eventually reduce the usefulness of some currently high-quality habitats. This possibility is particularly worrisome when the impacted species are threatened or endangered.

(A black-faced spoonbill, Platalea minor. Image courtesy of HKAEX2010.)

One such species is the black-faced spoonbill (Platalea minor), an endangered waterbird that lives along the coast of eastern Asia. In Macao, spoonbills overwinter in an area that is increasingly being developed for tourism. Although the birds can retreat to the Taipa-Coloane Wetland Reserve, which is surrounded by protective fencing and prohibits human visitors, the construction of nearby roads could rob the birds of their peace and quiet--literally. Given that anthropogenic noise is thought to have a number of negative impacts on both individuals and entire populations, these potential developments could eventually drive spoonbills from Macao and even threaten the viability of the birds' dwindling global population.

A group of Chinese researchers recently set out to investigate this possibility; specifically, they were interested in examining current levels of noise pollution  and using modeling techniques to predict how the habitat might be altered by future increases in acoustic disturbance. To do this, they conducted bird surveys in the two ecological zones contained within the reserve: an artificial lagoon and a tidal flat/mangrove swamp. The surveys were conducted 4 days a month during each month of the wintering season (October-April), over a period of two years. In addition to measuring the winter abundance of the birds (calculated here as the maximum number of individuals observed each month), the researchers also conducted behavioral observations in order to see how the birds spent their time--and how their behaviors were altered by specific human disturbance events.

In order to relate these avian parameters to noise regimes, the researchers collected acoustic recordings around the perimeter of the first zone (which has a rectangular shape) and along the edge of the second zone (which runs straight along the waterfront). The recordings were collected from 8 AM until 6 PM on working days, and so should reflect the most intense noise to which the spoonbills are regularly exposed. In order to better understand which types of noise are most alarming to the birds, the researchers examined each particular disturbance event (identified during the behavioral observations) in order to determine whether noises were generated by small cars, medium cars, heavy trucks, or motorcycles.

(Macao. Image courtesy of Abterra.)

GIS techniques were employed to investigate how the spoonbills' roosting locations related to spatial variations in noise levels. Because the researchers couldn't actually enter the reserve in order to measure noise levels next to the birds, they had to run simulations in which a variety of habitat parameters (e.g., vehicle types, average speed, traffic volume, road properties) were used to predict the actual traffic noise experienced by the birds. Predicted noise values were used to create noise distribution maps that were overlaid with maps showing where the birds actually roost.

Over the course of the study (2007-2009), the number of spoonbills typically peaked early in the year (January-February), when a maximum of 52 individuals could be seen at any one time. The birds clearly preferred the lagoon zone rather than the shore/mangrove zone, though the two zones had fairly similar average noise levels--46.5 dB(A) for the lagoon and 45.4 dB(A) for the waterfront. However, a greater proportion of the second zone contained areas where ambient noise levels were below 47 dB(A). This appeared to be a significant threshold for the spoonbills, which aggregated in these quieter areas and avoided those that exceeded 47 dB(A). Interestingly, this same apparent threshold has also been found for grassland species in the Netherlands, suggesting that the avian hearing apparatus may predispose many species to show similar responses to noise disturbance.

Spoonbills in both sections of the reserve had similar behavioral time budgets, and the researchers did not notice any significant correlations between particular spoonbill behaviors and ambient noise levels. However, they did notice that the birds were generally most active at 9 AM, which was when traffic noise was loudest. Thus, any changes to the disturbance regime that increase the amount of noise at this time of day might be particularly harmful to the birds.

The behavioral observations also revealed that spoonbills were fairly sensitive to noise events. Nearly half of their disturbance-related behaviors were associated with traffic; most of the time, the birds engaged in alarm behaviors or increased vigilance, but a flush response was observed in one spoonbill. All of these activities are known to reduce the amount of time that birds spend foraging, which, in turn, can decrease energy intake and prevent the birds from putting on adequate fat for migrating and/or breeding. An ambulance siren and a medium vehicle were responsible for two of the disturbances; the rest were caused by large trucks. While these events were, on average, approximately 82 dB(A), the loudest was a whopping 86 dB(A). Not surprisingly, the researchers noted significant relationships between noise intensity and both type and duration of spoonbill reaction.

(A flock of black-faced spoonbills foraging along the waterfront in Macao. Image courtesy of People's Daily Online.)

In one respect, these results are encouraging: Although the reserve contained areas where the ambient noise levels were fairly high, the spoonbills were able to find the quieter sections and utilize these for their overwintering activities. However, the researchers do worry about the future of the birds in Macao. They measured particularly high levels of background noise on the road separating the two zones of the reserve, which means that increasing levels of traffic could negatively impact both areas where the spoonbills are currently found. Even if noise levels remain constant, the researchers worry about the potential cumulative effects of noise from both this and other roads near the reserve; chronic noise disturbance may have implications that could not be measured in this short-term study.

Previous studies have found that traffic noise can permeate habitats over 1 km from the road, which means that the addition of more roads and/or traffic could quickly reduce the proportion of the Macao reserve that is suitable for black-faced spoonbills. It is unclear how this might impact the global population, but, given how few of these birds are left, it would be better not to perform such an experiment. In order to maintain the current quality of the reserve, the authors suggest that the government should restrict the flow of traffic--especially heavy trucks--on the roads near the spoonbill habitat. They also noted that the fencing around the lagoon zone was good for keeping out humans but not noise. Erection of a sound barrier around the perimeter might, therefore, be one way of protecting spoonbills (and other reserve inhabitants) from acoustic pollution.

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Zhang, M., Cheong, K., Leong, K., and Zou, F. 2012. Effect of traffic noise on black-faced spoonbills in the Taipa-Coloane Wetland Reserve, Macao. Wildlife Research 39(7):603-610.

Are wildcats stressed out by humans?

The last few decades have seen the rise of a new field of research known as "conservation physiology," in which researchers use endocrine approaches to investigate whether anthropogenic activities are stressful to wild animals. To quantify physiological stress, scientists collect plasma, urine, saliva, and/or fecal samples and see whether variations in hormones--glucocorticoids, in particular--are associated with changes in the external environment.

So far, glucocorticoid fluctuations have been found in a variety of species, ranging from pine martens and hyenas to wolves, elk, and bears. The sources of their stress? Activities related to ecotourism, sports, pastoralism, and even simply the presence of people in the habitat (there are natural sources of stress, too, but those aren't the focus of this particular type of research). While physiological stress responses can be adaptive over the short term, they can have negative impacts on immune and reproductive activity if maintained over the long term. Although these have been documented in species exposed to stressors such as social rivals and lengthy periods of inclement weather, there is less information on the physiological implications of extended exposure to human activities.

(Wildcat, Felis sylvestris. Image courtesy of Cryptomundo.)

Addressing this research gap was the main goal of a group of Spanish researchers working in the Natural Park Montes do Invernadeiro in northwestern Spain. Over a 5-year study period, they collected scat samples left by wildcats (Felis sylvestris) living in the park. Going into the study, the scientists hypothesized that stress levels would be higher in wildcats living in the parts of the park most heavily visited by humans. They also anticipated that the cats would be particularly susceptible to human-induced stress during the part of the year when they were engaged in the most sensitive reproductive activities--specifically, January through May, when the wildcats breed and then gestate their young.

The researchers took advantage of the fact that the park is split into three sections with different levels of human activities. The first zone is open to public visitation and contains both lodges and wildlife classrooms; this receives the greatest number of visitors. The next is a restricted zone where people can visit only on foot and only with a park biologist. Finally, the park also contains an "integral reserve zone" where visitors are not allowed; this area, obviously, receives the least amount of human traffic.

In each of these three zones, the scientists walked survey transects in order to look for wildcat scat, which they distinguished from other species' scat by means of size and shape (in case you are curious, wildcat poo is long, cylindrical, and thick, "with contiguous fragments that fit perfectly"). Because of the time required for digestion and excretion, fecal glucocorticoid levels are associated with the previous day's activities; thus, the researchers compared fecal sample information on any given day with human visitation information (provided by park officials) from the day before. In addition to looking for cortisol metabolites (the chemical components left after glucocorticoids are digested), the researchers also measured levels of three reproductive hormones (testosterone, progesterone, and estradiol) and performed genetic analyses to both confirm that all scat samples were from wildcats, and to determine how many different individuals had been encountered throughout the park.

(The Natural Park Montes do Invernadeiro in northwestern Spain. Image courtesy of Spain Tourism Guide.)

The researchers were able to collect a total of 110 scat samples over the study period; these belonged to 16 different wildcats. Three variables were found to be most closely related to variations in cortisol metabolite concentrations: progesterone and estradiol levels, and number of visitors. In other words, the most stressed wildcats were those who were primed for reproduction, and also those who lived in the high and (to some extent) low visitation zones. When the researchers plotted cortisol metabolite levels against season, they found that stress hormones peaked in the spring and autumn (during gestation and fall dispersal, respectively), while visitation rates peaked in the spring and summer. The vernal overlap means that wildcats may be particularly negatively affected by the presence of people during the time of year when they are most heavily engaged in reproductive activities.

Unfortunately, the current study was not designed to directly collect information on reproductive success, so further research will be needed to see whether higher levels of stress actually do impact fitness. In fact, there are a number of questions that this study leaves unanswered. Prime among these is the direction of the relationship between glucocorticoids and sex hormones: Does cortisol affect estradiol/progesterone (similar to patterns observed in baboons, Papio anubis), or might elevations in sex hormones drive variations in cortisol? Another unanswered question is whether wildcat stress levels in the high-visitation zone were elevated because of the number of humans they encountered or the way in which the cats were disturbed; after all, in addition to being the busiest area of the park, this zone was the only location where the cats were exposed to cars. Understanding the source of the stress will be important for making appropriate management decisions. Finally, the authors make no mention of whether the focal scat samples were evenly distributed throughout the park, or whether there were indications that the cats were actively avoiding areas with human visitors. Previous studies have indicated that wildcats attempt to avoid anthropogenic activities, and so it is possible that the cats are able to choose home ranges in order to minimize their exposure to people.

(A major aim of conservation physiologists is to facilitate ecotourism while minimizing its negative effects on wildlife. Image courtesy of Spain.net)

One clear contribution of the study is a demonstration of the potential of the conservation physiology approach. Use of scat samples enabled the researchers to collect quite a bit of information on the wildcats without adding further stress by trapping and handling the animals. Further, molecular techniques enabled the scientists to verify the identity of the scat "providers," not only to the species level but also to the level of individual cats. In the future, scat sampling could be a powerful technique for non-invasively monitoring the health of this and other protected species, measuring population growth and home range size, and examining fluctuations in stress levels in response to any number of environmental perturbations. As the authors write, however, researchers should be careful when applying this method to new animals: "...because many inconsistencies in the glucocorticoid measures are related in part to methodological problems, a careful validation for each species is obligatory."

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Pineiro, A., Barja, I., Silvan, G., and Illera, J.C. 2012. Effects of tourist pressure and reproduction on physiological stress response in wildcats: management implications for species conservation. Wildlife Research 39(6):532-539.

What's in a name?

No matter where in the world you live, chances are you've eaten "pulses" some time in the last week. These foods, otherwise known as "food legumes" or "grain legumes," have been a part of the human diet since at least 11,000 BC; they were first collected by hunter-gatherers and were then domesticated and cultivated by early farmers. Popular pulses include peas, field beans, lentils, and chickpeas; their relatives bitter vetch and grass pea were also once commonly eaten. These foods provide nutrition not only to humans, but also to livestock and even depleted soils; they can be used as feed, forage, silage, haylage, and "green manure."

(A selection of pulses. Image courtesy of GES Commodity.)

For Aleksandar Mikic, a researcher at the Serbian Institute of Field and Vegetable Crops, the story of pulses is, in many ways, also the story of modern humans. These plants were likely a vital source of nutrition to the ancestors who dispersed across Europe, bringing with them the cultures that gave rise to those we know today. One part of those cultures is language; experts believe that well over 300 different languages have emerged on the European continent, all descendents of a common ancestor known as Proto-Indo-European. Although researchers are not entirely certain where Proto-Indo-European speakers came from, it is likely that they dwelt in the Pontic-Caspian steppe from 4500 BC--after which they radiated out across the rest of the continent, taking with them both their crops and their way of speaking.

In order to try to understand the paths that migrants might have followed, as well as the preferences of different groups for particular species of pulse, Mikic performed a massive literature search investigating the etymologies of all words associated with pulse crops and leguminous plants. He targeted all languages spoken in Europe, including those in the Albanian, Armenian, Baltic, Celtic, Germanic, Hellenic, Indo-Iranian, Italic, and Slavic branches. All told, he sorted through sources associated with approximately 5 dozen current languages, as well as the ancestral forms that gave birth to them. This allowed him to compile a massive list of words indicating "pea," "lentil," "field bean," and other lesser-used pulse crops.

(The Pontic-Caspian steppe. Image courtesy of Wikipedia.)

The different "offspring" languages of Proto-Indo-European had different numbers of root words, as well as root words with different emphases. The Indo-European language family, for example, had the greatest number of original pulse crop root words. On the other hand, Uralic languages--such as Estonian, Finnish, and Hungarian--tended to borrow pulse words from their neighbors. The meanings of the roots highlight how pulses were perceived by our ancient ancestors. The Proto-Indo-European root that eventually gave rise to our modern word "bean," for instance, indicated "swollen" or "swelling," and is clearly a description of the bean pods. One Proto-Uralic root word denoting "pea" roughly translates as "hole, cavity" and "a wooden vessel," and seems to refer either to the process of plucking peas from the pod, or to the empty pod that remains once this has been done.

Overall, the prevalence of pulse-related roots throughout Europe indicates that species such as the pea, lentil, and field bean were not only well known, but also farmed, by our early ancestors. Although this had already been suggested by archaeobotanical evidence, Mikic's study provides additional support for this theory. The current work also suggests that human-pulse relationships were not the same everywhere. For example, the words for "lentil" and "field bean" in the Uralic languages tend to derive from roots meaning "pea," indicating that the pea was the initial pulse of choice among ancestral Uralic tribes. On the other hand, Caucasian languages tended to put a more even emphasis on "pea" and "field bean," with very few words uniquely indicating "lentil."

(Example of one of Mikic's etymological maps. Lens culinaris is the lentil, while Vicia faba is the field bean. The root word "*bhabh-" has one of the largest numbers of derivatives, and means "swollen" or "swelling"--clearly referring to the plant's morphology. This is the word that ultimately gave rise to our modern term, "bean." Image courtesy of PLoS ONE.)

By placing etymological information on top of geographical maps of the European continent, Mikic was able to create "routes" of linguistic evolution; these likely reflect the physical routes taken by both our early ancestors and their agricultural products. The bulk of migrants appear to have taken their languages with them, rather than arriving in their new homes and adopting native ways of speaking. In fact, natives often picked up the migrants' newly introduced phrases, and both groups of people passed these words on to their ancestors. Mikic is quick to point out that migration is only one of a number of different mechanisms driving genetic, ethnic, and linguistic development of diverse cultures; all the same, his maps provide fascinating insights into the establishment of the Europe that we know today.

While some people might consider Mikic's work to be a bit esoteric, it it actually a valuable contribution to multiple fields. Plant matter tends to degrade relatively quickly, which means that archaeobotanists have available to them only a limited number of samples for analysis. Words, however, are "remarkably well-preserved in both morphology and meaning," and can therefore help fill in the gaps left by a spotty artifact record. An improved understanding of crop evolution can help researchers who are interested in preserving rare ancestral traits and breeding variants that are likely to do well in particular climates; this genetic and evolutionary information is also valuable for those seeking to better understand biodiversity. Similarly, these sorts of studies are also interesting to those who study ancient humans, not only because these data can reveal genealogical patterns that can be useful in medical research, but also because they highlight the relatedness of diverse peoples now scattered across an entire continent. Mikic hopes that his work--which he considers only a preliminary report--will inspire collaborations among researchers from multiple fields.

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Mikic, Aleksandar. 2012. Origin of the words denoting some of the most ancient Old World pulse crops and their diversity in modern European languages. PLoS ONE 7(9):e44512.

The past and future of urban wildlife research

As you might expect given the content of this blog, there is currently quite a bit of interest in the topic of urban wildlife research. This discipline emerged in the 1970s and has been steadily growing in size and popularity since then--a reflection of humans' increasing use of urban spaces, and our growing understanding of how these habitats can provide space for species other than Homo sapiens. Research on urban wildlife seeks to answer a variety of questions, but, generally speaking, is aimed at understanding the contributions of urban ecosystems, documenting human-wildlife conflicts in urban areas, and solving ecological problems that are inherent to urban ecosystems (such as fragmentation, homogenization of species assemblages, and invasion by exotic species, to name but a few).

In the latest edition of Biological Conservation, a group of urban ecologists has sought to make recommendations about the future of urban wildlife research by looking to the past. Specifically, the authors performed a literature review aimed at illuminating long-term trends in the discipline--including the most commonly studied species, the locations where research is most often performed, and the research questions most commonly examined. They hoped that their findings would "[reveal] potential gaps in current work, [illustrate] areas of strength and weakness, and [provide] guidance for future urban wildlife research efforts."

Rather than attempt to examine every single academic journal available (a Herculean task), the authors selected up to 3 of the top-ranked journals in each of the following fields: wildlife biology, landscape ecology, animal behavior, ecology, and conservation; they also included two multidisciplinary journals (Science and Nature). Journals were only included in the final analysis if they had published at least 50 urban wildlife research articles in the year 2000 (the mid-point of the most active period for this discipline), and if they had been in print since at least 1990.

(The house sparrow, one of many species that can regularly be encountered in urban areas.)

The authors then searched each journal for use of the term "urban" (or any variation thereof) between 1971 and 2010, then examined all papers containing this word with a fine-toothed comb. The following data were collected for each manuscript: type of taxa studied, continent on which the research was performed, primary research topic (animal behavior, population ecology, community ecology, landscape ecology, conservation, human dimensions, human-wildlife conflict, wildlife management, or wildlife disease), type of research site where the study was conducted, and affiliation of first author (academic, government, non-governmental organization, or private industry).

Ultimately, 571 publications were included from 16 focal journals. Unsurprisingly, the authors found that urban wildlife literature is much more common now than when the field was first emerging; during the 1970's and 1980's, for example, there were only 14 relevant articles published in the focal journals, but this increased to a whopping 429 articles during 2000-2010. Overall, Wildlife Research published the highest proportion of urban wildlife papers and, in fact, wildlife biology journals in general tended to publish the highest percentage of urban wildlife research until the 1990's. More recently, however, urban studies are more commonly found in landscape ecology journals--a pattern resulting, unsurprisingly, from an increase in studies on this topic. Despite the fact that animal behavior was one of the most frequently addressed topics (alongside conservation and landscape ecology), there have been consistently low rates of publication in journals that specialize in animal behavior work--potential because those journals tend to be more interested in theoretical than applied studies.

Birds and mammals have been the most commonly studied species since the discipline emerged, and the bulk of work on these animals has occurred in North America, followed by Europe and then Australia; very few studies have been performed in Asia, South America, and Africa. Most studies are performed within cities themselves, with only a small portion of research conducted in suburban and exurban areas. Nearly a third of urban studies included parallel work in "natural" habitats, allowing the original researchers to make comparisons between more and less human-modified sites. The most popular urban wildlife topics are animal behavior, conservation, and landscape ecology; common combos included animal behavior-and-conservation and landscape-ecology-and-conservation. Judging from the affiliations of first authors on each paper, the people responsible for this work are predominantly academics.

The authors of the current paper note that although urban wildlife research is on the rise, papers in this discipline are published at a relatively low rate; they account for <2% of articles in the journals examined here. The authors worry that this is not enough research, given the overwhelming proportion of people now living in urban areas. They suggest a variety of reasons why urban ecosystems have not been studied intensively, including "a traditional preference to focus on native species in relatively remote, pristine, undisturbed ecosystems...as well as logistical, political, and financial obstacles to urban research."

(European robins are another species that does well in urban and suburban environments.)

The researchers also feel that more urban studies should be performed by government scientists, since it is ultimately the government that will be responsible for drafting policies and carrying out management efforts relevant to urban wildlife. The lack of work in developing areas--Asia, South America, and Africa--is also alarming, given that these are not only recognized biodiversity hotspots, but also places characterized by human population expansion and steady increases in urbanization. Further, studies from around the globe are needed if researchers are to search for broad patterns characteristic of all urban areas, rather than just one particular city or country.

Although researchers in a number of fields have engaged in urban wildlife research, the authors noted that several topics have been neglected. These include genetics, disease (particularly important given recent outbreaks of zoonotic viruses), and human-wildlife conflict (including animal-vehicle collisions, landscape damage caused by wildlife, and pet predation). In the future, it will be important to conduct studies on these topics in order to understand the full extent of the effects of urbanization and the processes that occur within urban environments. Likewise, the authors recommend that researchers perform more work in suburban and exurban areas, which likely will become increasingly common (or larger) as existing cities grow.

Overall, the authors conclude that the discipline of urban wildlife research offers--and will continue to offer--an opportunity for researchers from many fields to explore relationships between humans and animals. The results of these studies, they write, will have "tremendous and increasing importance for our urbanizing planet."

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Magle, S.B., Hunt, V.M., Vernon, M., and Crooks, K.R. 2012. Urban wildlife research: past, present, and future. Biological Conservation 155:23-32.

Conflicts over conservation on military bases

While we often think of conservation efforts as being biological in nature, they are also shaped by social issues that impact decisions on things such as goals, priorities, funds distribution, and location. Unsurprisingly, disagreements are known to arise between different groups with different values and objectives--a topic explored in a new Biological Conservation paper aimed at understanding the dynamics of conflicts on American military installations, where land that is set aside for military training purposes has also been allocated to conservation projects.

The authors of the paper report that the U.S. military utilizes more than 12 million hectares worldwide, with previous surveys indicating that there are more than 500 at-risk species sprinkled across 224 military installations. These habitats tend to be particularly wildlife-friendly because the military frequently maintains large tracts of land that are left un-managed and undisturbed save for infrequent training activities. However, these spaces may occasionally be needed--for instance, when the military is preparing troops for war or when it is necessary to build new facilities to house or care for soldiers. In these cases, tensions can arise between "training area supervisors and users" (or TASUs) and civilian "natural resource and environmental compliance managers" (or NRECMs); while each group may be aware of, and even sympathetic to, the desires of the other, they have fundamentally different goals and areas of expertise, and may therefore find themselves at loggerheads.

(Red-cockaded woodpecker, Picoides borealis. Image courtesy of Team Stewart.)

In order to better understand the tensions that arise in such situations--and to hopefully propose methods of resolving them--the authors focused on conservation efforts associated with one particular species of interest: the red-cockaded woodpecker (RCW; Picoides borealis), a vulnerable species whose population numbers have been improved thanks to its use of military lands in the southeastern portion of the U.S. Unfortunately, increases in the numbers of troops assigned to bases in these areas have left the military scrambling to make room for barracks, facilities, and training grounds, while also continuing to ensure the protection of the birds.

The authors of the study visited one affected installation and interviewed 41 personnel (23 TASU and 18 NRECM) about issues associated with conservation activities. All participants were asked the same 5 questions: 1) What do you do for the military? 2) What are the main objectives in your position? 3) Do any environmental issues influence your ability to successfully meet these objectives? 4) How do you feel those objectives should be balanced with the environmental issues? 5) Will you tell me about the most challenging environmental issue you have faced while working here? In all cases, the questioners avoided asking specifically about RCWs or endangered species management, preferring instead to see if these topics were introduced by the informants themselves. The researchers also observed both TASUs and NRECMs as they engaged in staff meetings and other relevant social encounters, and they gleaned information from literature provided by both groups of participants.

(An off-limits sign at Fort Benning, Georgia, that warns military personnel that they are close to red-cockaded woodpecker habitat. Image courtesy of USAEC.)

Overall, the researchers found that TASUs and NRECMs both avoided use of the chain-of-command conflict resolution system available for addressing any tensions on base. Instead, both parties did their best to accommodate each other on particular issues without acknowledging any broad patterns of conflict. Conflict definitely occurred, however, and because it was never directly addressed, the researchers found evidence of escalating mistrust, dislike, and "unwillingness to communicate." During one meeting between the two groups, for example, the authors observed a lack of "cues to active listening, such as verbal statements of validation, support, and reflection, as well as non-verbal signals of eye contact or appropriate facial expressions"; they even saw individuals walk out of the room, check cell phones, and look at calendars rather than engage with each other. Thanks to encounters like these, it was easy for both groups to "deindividualize" each other: Several TASUs referred to the NRECMs as "a group of environmentalist civilians" who could not understand military needs, while the NRECMs frequently reported that TASUs failed to value the environment or the conservation contributions of military installations.

Interestingly, all informants responded in the negative when asked whether any environmental issues impacted training. Later on in the conversation, however, several TASUs contradicted themselves by making comments about how the presence of RCWs impacted their ability to train in a particular way, or to utilize certain areas of the base; indeed, one commanding officer is on record making similar comments during a Senate Armed Services Committee Subcommittee meeting. The researchers feel that both TASUs and NRECMs are trapped, to some extent, by their professional responsibilities; it is not deemed acceptable to admit that training needs are not being met, but it is also unacceptable to suggest that this is being caused by conservation efforts.

(Banding of a young red-cockaded woodpecker at Fort Jackson, South Carolina. Image courtesy of USAEC.)


The authors also report that, while the TASUs tended to have a more "anthropocentric" viewpoint, the NRECMs were characterized by a more "biocentric" view--one that, in the minds of military personnel, failed to take into account the practicalities of the settings in which RCW conservation is taking place. The TASUs' distrust was so extensive that the researchers feel it could only represent the accumulation of tension over time. Further, the authors reported that the conflict they observed was "unusual in that symptoms typically associated with protracted direct conflict accrued and persisted without any direct engagement among parties."

How might this be combated? The researchers suggest some mechanism allowing "parties to release tension through multiple, small controlled conflicts [to] prevent catastrophic and unpredictable conflicts from exploding later"; perhaps there might be forum in which both TASUs and NRECMs could directly acknowledge their conflicting desires without worrying about professional repercussions. While the TASUs need to demonstrate a willingness to be more flexible, the NRECMs clearly need to persuade military personnel that their pro-environmental ideals are not necessarily also anti-military. Obviously, these goals are not easy to achieve, and will require "creativity, adaptability, [and] innovation." The authors believe that a good first step might be agreeing to "a shared definition of the problem and a shared commitment to resolution." Moving forward will be much easier once the channels of communication are (re)opened--a goal that might be more achievable in the setting of a workshop and/or under the watchful eye of a moderator.

The authors suggest that this is likely not the only example of conflict between military personnel and environmentalists; further, there may be other conservation settings in which different parties are similarly hindered by tradition, expectation, and bureaucracy. They hope that their observations might help people in tense situations identify points of conflict and work towards peaceful resolution. Ultimately, the researchers believe that improvements in communication and collaborative efforts between TASUs and NRECMs could have beneficial effects not only during times of peace, but also during post- and even mid-wartime efforts to mitigate the impacts of damage caused by military activities around the world.

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Jenni, G.D.L., Peterson, M.N., Cubbage, F.W., and Jameson, J.K. 2012. Assessing biodiversity conservation conflict on military installation. Biological Conservation 153:127-133

Nest boxes: Two birds enter, no birds leave?

Just a couple of weeks ago, a paper in Biological Conservation reported that nest boxes can be used to improve the breeding success of an endangered species. This month, nest boxes are in the news again, but for another reason entirely: This time around, they've been identified as a useful tool in the fight against invasive species; instead of being used to expand avian populations, nest boxes are now being used to shrink them.

(European starling checking out an empty nest box. Image courtesy of Birdzilla.)

Specifically, researchers in Western Australia used artificial nesting cavities to facilitate culling of common starlings (Sturnus vulgaris), an invasive species first introduced into Australia in the mid-19th century. Since that time, they've become increasingly widespread and problematic; the birds are currently held responsible for AU$300 million in crop damage each year. Because starlings are particularly choosy when it comes to nesting--reportedly even skipping breeding seasons rather than taking up residence in sub-par cavities--the researchers thought that they might be able to entice the birds into attractive artificial cavities from which both the adults and their offspring could easily be removed. Not only might this spare managers from searching for hard-to-find natural cavities, but it might also enable them to direct the starlings towards habitats that are particularly easy to access and navigate--namely, the plantation woodlots where the birds are already known to overwinter.

The first step of the study was to determine whether the birds would be interested in the artificial cavities to begin with, and, if so, whether they preferred a particular style and/or a particular type of breeding habitat. The researchers distributed a total of 180 artificial cavities across 3 types of habitat: 2 types of swamp (differing only in predominant tree species) and 1 type of plantation woodlot. The former 2 are the locations where the starlings currently breed, while the latter is where managers would like to attract them. The birds were given a choice of rectangular wooden nest boxes and terracotta pipes; both were positioned both horizontally and vertically. Boxes were checked on a monthly basis from May 2006 until June 2009, plus more frequently during the final breeding season; the authors managed a total of 5,580 observations over the course of the study. Although birds were banded and released during the first breeding season, they were culled thereafter. The researchers also performed habitat surveys aimed at measuring the abundance of natural cavities at each site.

(Cavity-loving European honeybees. Image courtesy of Wild About Britain.)

Unexpectedly, the starlings completely ignored the terracotta cavities and nested only in the wooden boxes. Even more unexpectedly, the boxes were also attractive to European honeybees (Apis mellifera), which occupied all but ~7% of the wooden cavities. Although the researchers smoked the bees out early in the study, the insects later reappeared and prevented starlings from using the boxes.  To make matters worse, starlings were not found in the artificial cavities until at least 16 months after they had been installed; this likely resulted from the birds' neophobia, or fear of new objects. Only once the birds had acclimated to the sight of the new cavities did they dare venture inside.

Thanks to the honeybee occupation, starlings were not able to utilize nest boxes in any of the woodlots. Of the remaining two habitats, they clearly preferred swamps with dead trees. These sites contained approximately three times as many natural hollows as those with live trees; thus, the starlings' use of nest boxes in these habitats suggests that the birds find man-made cavities to be superior to their natural counterparts--a good sign for managers looking to attract the birds to particular places. During the first breeding season, the birds nested in 10 of 12 available boxes; during the second season, this number fell to only 5 boxes. Starlings are smart and have good memories, so this drop-off may reflect their active avoidance of artificial cavities after being manhandled there during the first season. Alternatively, these low numbers may simply reflect the birds' declining population throughout the study area.

(A flock of starlings; groups like these can decimate crops. Image courtesy of It's Nature.)

Despite the unanticipated setbacks associated with terracotta avoidance and honeybee occupancy, the researchers were still pleased with their results. Use of the nest boxes allowed them to remove anywhere from 45-87 adult birds from the population each year, along with a dozen eggs and a half-dozen nestlings. In all cases, they knew exactly where to look for the starlings and did not have to waste precious time or manpower searching for cryptic natural cavities. However, the authors were disappointed with their inability to draw starlings to woodlots, since these habitats would have facilitated even easier access to the birds. For those considering similar control efforts elsewhere, the researchers recommend deploying the nest boxes where natural cavities are not readily available, since these are the habitats in which the man-made cavities will look most attractive and, therefore, probably have the highest occupancy rates.

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Note: I realize that this article discusses management techniques that some readers may find questionable or distasteful. For the record, this write-up does not necessarily reflect my own views on these management policies; I have merely tried to describe the original authors' methods, analysis, and conclusions as accurately as possible.

Campbell, S., Powell, C., Parr, R., Rose, K., Martin, G., and Woolnough, A. 2012. Can artificial nest-cavities be used as a management tool to assist the control of common starlings (Sturnus vulgaris)? Emu 112:255-260.

Human activities may affect social behaviors in dolphins

Indo-Pacific bottlenose dolphins (Tursiops aduncus) are known to have complex "fission-fusion" societies, in which individuals or groups of animals sometimes associate with each other, but, at other times, choose to splinter off and go their own ways. Although the reasons for different levels of dolphin sociality are not always clear, the implications are somewhat better understood; social interactions can impact the transfer of information and particular ways of doing things (i.e., "culture), affect disease transmission, alter reproductive success, and change gene flow. In other words, a population's social structure can have long-term effects on its health and stability.

Although researchers have previously suggested that anthropogenic activities might affect the social structure of exposed populations, there have been few studies on this topic--until recently, that is. A group of researchers from Australia and New Zealand were able to analyze both historical and newly-collected datasets to investigate whether anthropogenic fishing activities in Moreton Bay (southeast of Queensland, Australia) might alter the social behaviors of resident dolphins. Since the collection of the historical dataset, fishing efforts in the Bay have been reduced by nearly 50%. The researchers were interested in investigating whether this may have led to a restructuring of the dolphin population, which previously was split into 2 groups: "trawler dolphins," which sought food items tossed over the side of fishing boats, and "nontrawler dolphins," which foraged for natural sources of food.

(Moreton Bay. Image courtesy of Moreton Bay Regional.)

To investigate the effects of trawling activities, the researchers performed social network analyses--a series of examinations of which dolphins hang out together, and how often those "splinter groups" interact with each other. The scientists relied on photographic data that allowed them to make individual identifications based on size, shape, and the location/pattern of markings on the animals' fins and flanks. Dolphins were categorized as being "associated" with any neighbors who were within 100 m and with whom they were sharing similar and/or coordinated behaviors; the more often animals were seen together, the stronger their relationships were considered to be.

Other social network properties were a bit more complex. "Reach," for instance, was a variable indicating the number of indirect connections made through an intermediate (e.g., if A is connected to B, and B is connected to C, then A would be indirectly connected to C). The "clustering coefficient" indicated how well one dolphin's associates knew each other--in other words, do they hang out even when the focal individual is somewhere else, or do they all only gather together when the focal individual is there to initiate the process? "Affinity" described how strongly an individual is associated to other individuals with particularly strong relationships. Finally, "geodesic distance" was used to measure how closely connected individuals of a particular social network are. For all of these variables, the scientists were looking for differences between the historical (1997-1999) and modern (2008-2010) datasets--or, in other words, the heavy and light fishing periods, respectively.

Previously, dolphins were found in groups of anywhere from 1-45, with trawler dolphins tending to form larger groups (up to 45 individuals) and non-trawler dolphins forming smaller ones (up to 20). Modern dolphins seemed to split the difference between these two maximum values: They were found in groups of 1-35 individuals. Further, associations between individuals are currently much stronger than they were during the heavy fishing period, as demonstrated by significantly higher values of strength, reach, clustering coefficient, and affinity. Geodesic distance, on the other hand, decreased markedly, indicating that not only were the dolphins associating with each other more strongly, but they were doing so within more compact social networks.

(Indo-Pacific bottlenose dolphins, Tursiops aduncus. Image courtesy of Earth Times.)

Analysis of the historical dataset revealed almost no associations between trawler and nontrawler dolphins; modern social groups, however, contained mixtures of both type of animal (as determined by an analysis of individuals present in both the historical and modern datasets). Additionally, while the researchers did see 4 clusters of 2008-2010 individuals who tended to aggregate with each other more than with other dolphins, these groups were not nearly as distinct as the historical ones. Interestingly, most of the dolphins who were spotted in both the historical and modern studies utilized habitat where trawling no longer occurs; this suggests that they might actually prefer undisturbed spots, and simply took up trawler-associated foraging behavior because it happened to be useful at the time.

Cumulatively, the analysis revealed that Moreton Bay dolphin social structure has changed significantly over time, and suggests that the reason for this is the marked decrease in fishing activity; where once there were two disparate feeding communities, there is now only one. To understand the mechanism for this, it is useful to think about the trade-offs associated with group living. Potential benefits include predator defense and the ability to cooperate in locating and obtaining food resources; on the other hand, potential costs include competition for resources such as mates and food. The usefulness of sociality will primarily be dependent on variations in the environment--in this case, the presence and activity of fishing boats. When the boats were around, trawler dolphins had a steady, obvious source of food. Once the boats had disappeared, however, it became more difficult for these animals to locate their prey--which only occur in irregular patches throughout the habitat--and so they joined forces with the nontrawlers to locate food more quickly. The nontrawlers could afford to let this happen because, presumably, a lack of fishermen led to an increase in food supply.

(Eastern Canadian wolf, Canis lycaon. Image courtesy of Gray Wolf Conservation.)

While this study appears to be the first of its kind in an aquatic habitat, similar research has been performed on land in Eastern Canadian wolves (Canis lycaon). In that case, scientists found that the presence or absence of wolf culling practices altered the social structure of wolf packs. Although it is not yet clear whether one type of social structure is "better" than another--and whether this has any conservation and management implications--the authors of the dolphin study suggest that the more closely linked modern grouping might facilitate social learning and information sharing. This, in turn, could allow human-adapted individuals to teach other dolphins behaviors that allow them to cope with the presence of people--a pleasant prospect not only for dolphin students, but also for any humans who would like to continue seeing dolphins in the Moreton Bay area.

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Ansmann, I.C., Parra, G.J., Chilvers, B.L., and Lanyon, J.M. 2012. Dolphins restructure social system after reduction of commercial fisheries. Animal Behaviour 84:575-581.