Is sustainable seafood healthy--and vice versa?

There are many reasons to watch what you eat--nutritional value, chemical use during growth or preparation, carbon footprint, and any number of other factors related to a food's healthfulness and ecological impact. For consumers feeling overwhelmed by all these concerns, there is good news in a recent issue of Frontiers in Ecology and the Environment: A trio of American researchers has revealed that some supermarket choices allow consumers to simultaneously achieve multiple goals. Specifically, the scientists report that seafood lovers can reap health benefits from fish while also promoting sustainable fishing.

 (Atlantic pollock--healthy and sustainable. Image courtesy of Fish Watch.)

The research team initiated their study after noticing a number of public health campaigns about seafood and wondering whether the ads might be at cross purposes. Most of the education efforts focused on one of three issues: sustainability, fish nutrients (omega-3 fatty acids, in particular), and toxins. Sustainability is, of course, a positive characteristic; so is a high level of omega-3 fatty acids, which can, among other things, improve heart health. Toxins, including heavy metals and polychlorinated biphenyls (PCBs), have long been recognized as a drawback of seafood consumption. So what if consumers, in response to public awareness campaigns, buy unhealthy fish in an attempt to improve sustainability, or purchase unsustainable catch in an effort to be more healthful?

The current work aimed avoid this by determining the amount of overlap between these three characteristics. The researchers collected information on the traits from pre-existing datasets. For example, they utilized fishery sustainability rankings calculated by the Monterey Bay Aquarium and Blue Ocean Institute; another important source of information was FishBase, which provided data on each species' risk of becoming extinct as a result of being fished. Health benefits were measured as a function of omega-3 fatty acid concentrations, while mercury (one of the most extensively researched seafood toxins) was used to indicate health risk.

(A haul of orange roughy--a species that possesses high mercury levels and has been overharvested. Image courtesy of Southern Fried Science, which features an interesting article about whether these fish can ever be harvested sustainably.)

When they looked for relationships between each of these variables, the scientists discovered that the most unsustainable species were generally also those that had the highest levels of mercury contamination; further, there were no clear health benefits of these vulnerable fish. Species featured on the resulting "red list" include many tunas, swordfish, and several varieties of Pacific rockfish. Happily, the even longer "green list" features a number of healthier and more sustainable alternatives, including pollock, sole, and plaice. Since science is rarely ever black and white (or, in this case, red and green), the project also yielded a "gray list." This contains the names of several species for whom the sustainability-health relationship was more complex--animals with healthier populations but also high mercury levels, for instance. Still, this list is quite a bit shorter than the other two--both of which offer clear and useful advice for consumers looking to make purchases that are good for their own health and that of the wider ecosystem.

The researchers caution, however, that some of their information came from sources that are a few years old; it will be important to update their datasets and re-run the analyses periodically in order to generate up-to-date advice. This will be particularly vital for the data on each species' population numbers and vulnerability, since these are likely to fluctuate as ever more consumers seek the healthiest products available. There were also several species that were left out of the analysis because data were not available for all three metrics. Again, it would be valuable to re-run the analysis when and if these data are ever collected, since this information could provide further guidance on which fish can be safely eaten, and which should be avoided.

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Gerber, L.H., Karimi, R., and Fitzgerald, T.P. 2012. Sustaining seafood for public health. Frontiers in Ecology and the Environment 10(9):487-493.

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Patchy fishing efforts can create elasmobranch refugia

Elasmobranchs--sharks, rays, and skates--are among the most endangered of marine organisms, with approximately one-third of all species considered either threatened or near threatened. Fishing is the biggest threat to these animals, many of which are either targeted deliberately or are caught accidentally after becoming entangled in fishing equipment. It also doesn't help that they tend to have slow reproductive rates and inhabit areas that are being degraded or destroyed.

(A flapper skate, or Dipturus batis. This elasmobranch resident of the Celtic Sea is classified as critically endangered. Image courtesy of Arkive.)

One of the most popular techniques for elasmobranch conservation--and, indeed, for the conservation of many marine species--is the creation of marine protected areas, or MPAs. These offer wildlife a refuge where human activities are diminished or completely abolished. While MPAs have clear benefits for predominantly sessile species such as barnacles or tube worms, they may not be as effective for mobile species such as elasmobranchs; after all, sharks and their kin can quite easily swim into nearby unprotected waters where they may become bycatch.

In a new study on elasmobranchs living in the Irish Sea, a team of Irish and British scientists report that MPAs likely can protect sharks, rays, and skates, but only if the locations of the protected areas are chosen wisely. Specifically, they suggest that "de facto refugia," or naturally occurring areas where low fishing intensity overlaps with high elasmobranch density, would make very useful MPAs. In fact, they identified one such area in the northeastern portion of the Celtic Sea, where the seabed's frequently shifting sands render trawling both "inefficient and unpredictable." The general lack of fishing here--despite the area's close proximity to a port and its fairly good returns on fishing effort--has allowed elasmobranchs to flourish. Elasmobranch diversity and abundance in this habitat could be threatened by future changes to fishing policy encouraging fishermen to utilize this area more fully. Thus, creation of an MPA here would not only protect a habitat that is clearly useful to elasmobranchs, but would also ensure that it continues to act as a refuge over the long term. Since the area is already neglected by the bulk of fishermen, managers probably wouldn't need too much money or manpower to maintain the MPA boundaries, plus they likely wouldn't hear too many complaints.

(A spiny dogfish, or Squalus acanthias. This species, which can be found in heavily fished areas of the Celtic Sea, is listed as vulnerable on the IUCN Red List. Image courtesy of Fish Index.)

Researchers and managers associated with other marine habitats should be pleased to know that the methods used for the current study were relatively simple and easy to apply to other systems. The scientists utilized data collected during the Irish Groundfish Survey, a standardized bottom-trawl survey that has been conducted annually since 1997. This dataset allowed them to keep track of the total number of individuals observed, species identity (and, therefore, density and overall richness of elasmobranchs), and body size. They also examined vessel monitoring system (VMS) records in order to assess where Irish fishermen spent the bulk of their time, and how productive those areas were. The researchers' final models controlled for environmental variables such as biogeographic region, seabed substratum, water depth, and exact latitude/longitude.

As for the future of this particular refuge in the northeastern portion of the Celtic Sea, the scientists recommend further studies exploring how/why the habitat contributes to elasmobranch biomass and richness. It may act as a nursery, giving juveniles shelter during a time when they are too small and weak to adequately defend themselves. It could also protect breeding adults and give them the opportunity to produce more and/or healthier young. It is important to understand these dynamics in more detail, since differential survival of particular age/sex/size classes can influence metapopulation structure--or, in other words, have cascading effects on elasmobranch populations throughout the region.

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Shephard, S., Gerritsen, H., Kaiser, M.J., and Reid, D.G. 2012. Spatial heterogeneity in fishing creates de facto refugia for endangered Celtic Sea elasmobranchs. PLoS ONE 7(11):e49307.

Also thanks to the following for additional background information:
Polidoro, B.A., Livingstone, S.R., Carpenter, K.E., Hutchinson, B., Mast, R.B., Pilcher, N., Sadovy de Mitcheson, Y., and Valenti, S. 2008. Status of the world's marine species. In: J.C. Vie, C. Hilton-Taylor, and S.N. Stuart (eds.). The 2008 Review of the IUCN Red List of Threatened Species. IUCN, Gland, Switzerland.

Paleoecological research uncovers historical effects of humans on corals

Although we know that humans have had a significant impact on the environment and the species that dwell within it, we don't always have detailed information on when our influence was first felt, or how the effects of our activities interact with those caused by other types of perturbation. As a result, it can be difficult to establish goals associated with conservation and management efforts. For instance, if we are trying to return an ecosystem to a pre-disturbance baseline, how do we know what that baseline actually is?

(NASA image of Pelorus Island, located off the northeastern coast of Australia. Image courtesy of Tageo.)

To help answer this question for corals in Australia's Great Barrier Reef, a group of researchers recently surveyed both living and dead coral assemblages at three sites around Pelorus Island, an inshore reef located near the outlets of both the Herbert and Burdekin Rivers. Since the late 19th century, when Queensland was colonized by Europeans (and their associated livestock and agricultural crops), the rivers have delivered altered levels of sediments, nutrients, and herbicides to the Australian shore--and the corals located along it. During the recent study, researchers collected paleoecological data in order to determine the impacts of these anthropogenic influences on coral growth.

Specifically, they sent scuba divers underwater to survey both living and dead coral assemblages. The divers noted the identity, percent cover, and growth morphology of the corals. They also gathered samples of dead corals that could later be examined with computed axial tomography (CAT) scans, which can provide information on the age of each coral colony. Finally, the researchers scoured the scientific literature for information on historical climate, weather, and hydrological patterns that might have been associated with fluctuations in coral communities and growth over time.

(Australia's Great Barrier Reef. Image courtesy of GreatBarrierReef.org.)

Cumulatively, the data suggested that the Pelorus Island corals had successfully weathered a series of environmental perturbations over the years, but that they were unable to combat anthropogenic disturbances. The oldest of the three study sites was dated to the mid-3rd century; its younger neighbors sprang up in the mid-9th and early 16th centuries. While Acropora coral species dominated the reefs for several hundred years, the researchers documented a shift occurring somewhere between 1920 and 1955: Acropora were replaced with Porites, Montipora, Pavona, Millepora, and Echinopora species, with exact assemblages varying depending on the site. The researchers also observed different growth morphologies emerging over time, with modern Acropora appearing much thinner and less branched than their ancestors. This suggests that the corals had tried but failed to regenerate themselves after an environmental disturbance.

This is also indicated by the paleoenvironmental data, which revealed that the coral colonies experienced two decades of cool temperatures just prior to the beginning of their collapse; this was followed by a drought and an increase in both cyclone activity and water flow from the nearby rivers. None of these things would have been pleasant for the corals, but none of them should have been insurmountable, either. Corals are actually fairly good at recovering from "acute" environmental stressors such as weather events--except, that is, when they are also dealing with chronic stressors. In this case, the chronic stressors were influxes of chemicals resulting from human use of fertilizers. The researchers reported that nutrient flows are thought to have increased anywhere from 2.1- to 19.5-fold since European colonization, and, in particular, from 1930 onwards. Thus, in the early 20th century, corals near the Herbert and Burdekin Rivers were exposed to abnormally high amounts of sediment, herbicides, and nutrients, all of which disrupted the delicate balance of the coral ecosystem.

(An Acropora species--also sometimes known as staghorn coral. Image courtesy of Coralpedia.)

These results highlight that even the most resilient and hearty of species have limits on how many, and what type of, environmental stresses they can tolerate. Further, given the current differences observed in coral assemblages growing at the three closely situated study sites, it appears that there can be extremely fine-scale variations in how ecosystems will respond to the same set of environmental conditions. This, in turn, suggests that researchers and managers should be cautious about making generalizations about particular localities--such as "Pelorus Island" or "The Great Barrier Reef"; these might be overly simplistic and fail to take into account important local dynamics. Finally, the scientists point out that this sort of paleoecological work is very useful for more accurately determining the "baselines" to which disturbed systems should be returned. Monitoring at the Pelorus Island reefs only began in the 1980s; thus, researchers were previously unaware of how the coral colonies looked before their early-20th-century collapse. Additional paleoecological work at this and other sites should help conservationists make more appropriate targets for preservation and reclamation plans.

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Roff, G., Clark, T.R., Reymond, C.E., Zhao, J.-x., Feng, Y., McCook, L.J., Done, T.J., and Pandolfi, J.M. 2013. Palaeoecological evidence of a historical collapse of corals at Pelorus Island, inshore Great Barrier Reef, following European settlement. Proceedings of the Royal Society B 280: online advance publication.

For more on the natural history corals, check out Episode 18 of my weekly science radio show, the Wild Side (Part I, Part II).

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Artificial lighting has very real effects on invertebrates

Researchers estimate that artificial lighting is increasing at a rate of 6% each year around the world. This could dramatically reduce the amount of "naturally unlit habitat" available to wildlife, and have significant impacts on organisms that have evolved to deal with specific characteristics and regimes of light. By altering how much light is present in a habitat, where it occurs, how bright it is, what wavelengths it contains, and when it illuminates the environment, we might inadvertently impact a variety of wildlife traits, including behaviors (such as foraging, navigation, and communication), physiology (including cyclical release of hormones and other important chemicals), and interactions with other species. In fact, researchers have already gathered evidence indicating that light pollution does effect these characteristics in at least some species. Until recently, however, scientists had no information on whether artificial lighting might alter higher-level processes, such as the formation of animal communities.

(Image courtesy of Redlands Labour.)

Last summer, a team of researchers from the University of Exeter's Environment and Sustainability Institute investigated these potential higher-level effects of light pollution using an elegantly simple study design: Over a period of three days and three nights during the annual peak of insect abundance, they set out traps to collect invertebrates utilizing habitat either under street lamps or in unlit areas between two neighboring streetlamps. Traps were emptied twice a day: 30 minutes before sunrise, and again 30 minutes before sunset. This allowed the researchers to determine whether the street lamps were having a permanent impact on invertebrate communities, or whether differences were only found at night, when the lamps were switched on and were actively attracting insects from the neighboring habitat.

The scientists performed several different analyses on their data. First, they looked for differences in invertebrate abundance (measured as the total number of individuals caught per trap over the entire sampling period) between the lit and unlit patches. Second, they performed a similar analysis that took into account invertebrate community composition--in other words, not just how many organisms were caught, but what species those animals belonged to. Third, they quantified the amount of vegetation present around each trap in order to determine whether the lights were directly impacting invertebrate communities, or whether the lights were having an indirect effect by altering vegetation under each street lamp. Finally, in order to get a clearer idea of how the effects of light might impact ecosystem structure and function, they classified all trapped invertebrates more broadly, both taxonomically speaking ("harvestmen," "mites," "amphipods," etc.) and trophically speaking ("predators," "scavengers," parasites," etc.), and again tested for differences between the two types of patch.

(Example of a pitfall trap similar to those used in the current study. Image courtesy of INHS.)

The results of their work, published this autumn in the academic journal Biology Letters, were pretty emphatic. Their final analysis included data from 1,194 ground-dwelling invertebrates from 60 different taxa. On average, traps directly under the street lamps caught significantly more species (+ 5) than traps between the lamps; likewise, composition of invertebrate communities was significantly different in lit and unlit areas. These patterns were found both during the day and at night, indicating that street lamps not only impact vertebrate communities, but also that they do so permanently, and not just when they are turned on at night.

Five taxonomic groups (harvestmen, ants, ground beetles, woodlice, and amphipods) were more abundant in lit patches. For the first three of these groups, this relationship was independent of time, suggesting--again--that the lights have a permanent effect on invertebrate communities. Unfortunately, woodlice and amphipods were only captured at night, and so there is no way to determine whether they, too, are consistently more common in illuminated patches. Results of the trophic analysis also revealed long-term effects of streetlamps: Predators and scavengers were both more common under the lights, both during the day and at night.

(A harvestman, one of several taxonomic groups more common under street lamps. Image courtesy of FCPS.)

In addition to revealing the powerful effects of anthropogenic light pollution on invertebrate communities, this study is also the first to show that ground-dwelling invertebrates--and not just their aerial relatives--are attracted to human lighting. The next obvious question is whether the effects of these community shifts can be felt by organisms other than the invertebrates themselves. In order to explore this possibility, it may be particularly interesting to research the effects of light on trophic interactions, since invertebrates are an essential dietary component of many species (and, of course, are also consumers, themselves). Should this light-mediated community restructuring have wider ecosystem impacts, it will be important to identify these and determine whether they might alter essential ecosystem services provided to humans.

As researchers continue to explore the relationships between light pollution and wildlife, they will need to keep up to speed with changes in artificial lighting technology. Variations in bulb and lamp design can impact the wavelengths of light emitted, the brightness of the resulting glow, and the total area of the environment that is illuminated by light pollution. Each of these factors can contribute to the impacts of human light sources on wildlife and species assemblages.

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Davies, T.W., Bennie, J., and Gaston, K.J. 2012. Street lighting changes the composition of invertebrate communities. Biology Letters 8:764-767.

Is human disturbance good news for caribou?

Although individuals of a particular species frequently differ in a variety of characteristics, the implications of those differences are often not well understood. One exception to this general rule is the known positive impacts of size and condition, but what about the effects of certain preferences and choices--the tendency, for example, to utilize one type of habitat rather than another? A recent study on woodland caribou (Rangifer tarandus caribou) suggests that individual variations can literally be a matter of life and death--in this case not for the animals themselves, but for their offspring.

The study, performed north of Quebec City by a quintet of Canadian researchers, examined the habitat preferences of 23 adult female caribou over a 2-year study period. The researchers were interested in determining whether caribou mothers' habitat selection could affect their reproductive success by exposing calves to potential predators. The habitat in question--located within Quebec's Charlevoix region--varied widely, containing areas that were relatively undisturbed, some that had recently been logged ("cutovers"), and others that had previously been logged but where the vegetation had just begun to grow back in ("non-regenerated areas").

(Caribou calf with radio-collared bull. Image courtesy of UNBC.)

All females were fitted with GPS collars, allowing the scientists to determine where the caribou were located--and, therefore, what type of habitat they were utilizing. Monitoring efforts were particularly intense during the spring calving period, since the researchers wished to capture calves and fit them with radio collars. While the habitat usage patterns of calves could be determined from their mothers' GPS signals, the radio collars were important for allowing researchers to monitor survivorship of juvenile caribou and, when the calves died, to locate their remains. In cases of calf mortality, the researchers examined both carcasses and the surrounding habitat in order to determine the cause of death.

Pregnant females all gravitated towards habitats located on upper slopes--areas where grey wolves (Canis lupus) were less likely to be found. The usefulness of this preference was revealed by the juvenile mortality data, which showed that only 1 of 22 predated calves died from a confirmed wolf attack. However, females that showed particularly high preference for these areas--in other words, those who utilized only this habitat rather than wandering up and down the slopes--were much more likely to lose their calves to predation. This is because the high-elevation areas were also frequented by black bears (Ursus americanus), which appeared to be responsible for the other 21 predation events (only 2 calves died of natural causes, bringing the entire death toll to 24).

(A black bear, one of the caribou's two main predators. Image courtesy of Wikipedia.)

The impacts of the anthropogenically modified habitat types were interesting. Calf mortality was not strongly related to active selection of cutovers, suggesting that logging--or, at least, use of recently logged areas--may not be particularly detrimental to caribou fitness. One potential reason for this is that cutovers have not yet been repopulated by moose, the presence of which brings an influx of wolves; at the same time, there is not yet enough food here to support foraging black bears. Not only are these sites relatively empty of predators, but they also provide good cover near the ground, giving young caribou a place to hide should they need it.

Calves were, however, more likely to be predated when their mothers did not avoid non-regenerated areas. This probably stems from the fact that these patches offered more sustenance to black bears, and were therefore more likely to contain caribou predators. There was also an interesting interaction between vegetation and the presence/absence of roads, such that calf loss was more common in areas with both high road density and few (or no) mature tree stands. Again, this is probably related to the fact that these habitats support more potential predators, as well as the fact that these same predators often use roads in order to move through the habitat more easily.

(Regenerating forest at a former logging site. Image courtesy of the NW Council.)

These findings suggest not only that individual variations in habitat selection affect reproductive success, but also that caribou may actually benefit from anthropogenic activities: The ungulates appear to be safest in the most human-disturbed areas, though the researchers suggest their results should be treated with caution because the sample size was relatively low. The study also highlights the interconnectedness of organisms at different "trophic levels," or positions within the food web. Variations in the abundance of vegetation impact moose, caribou, and black bears, while differences in moose and caribou populations affect both black bears and wolves. All of these organisms can, in turn, be affected by anthropogenic activities such as logging and the creation of roads. Thus, this work is an important reminder that the effects of humans can often be subtle, complex, and indirect.

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Dussault, C., Pinard, V., Ouellet, J.-P., Courtois, R., and Fortin, D. 2012. Avoidance of roads and selection for recent cutovers by threatened caribou: fitness-rewarding or maladaptive behaviour? Proceedings of the Royal Society B 279:4481-4488.

Environmental factors associated with bird-window collisions

Every year, anywhere from 100 million to 1 billion American birds are thought to die after colliding with windows. Planners and builders have tried a variety of techniques to reduce collisions, but, according to a trio of researchers from the University of Alberta, these mitigation efforts are ultimately stymied by a poor understanding of what environmental conditions encourage collisions in the first place.

The Canadian team recently looked into this issue with the help of conservation biology undergraduate students who assisted with the study as part of their coursework. The main goal of the research was to identify the habitat characteristics associated with collisions; in particular, the research team investigated whether birds were more likely to be injured in urban versus rural environments, at houses versus apartments, near places with versus without bird feeders, and on older or younger properties (which potentially vary in the extent of surrounding vegetation). In addition to these environmental data, the research team also collected information on the number of birds hurt, the species of birds involved in collisions, and whether collision rates varied between seasons.

(The authors explored whether the presence of bird feeders, among other environmental factors, increased the likelihood of collisions with windows.)

The undergraduate students were responsible for drafting volunteers to provide all of these data. To this end, they created public-awareness pamphlets that were distributed to friends, family, and colleagues, both in paper form and via online social media. The pamphlets asked would-be participants to visit the conservation course website in order to read more about the project and enter information about avian collisions at their homes. The questionnaire covered eight "core" questions that collected information on participant demographics, observation and timing of bird collisions, length of home occupation, type of residence, presence of bird feeder, and location of home. This latter detail was provided in the form of a postal code, which was used to link the survey responses to census data (on neighborhood age) and to locate the home on Google Earth so that it could be classified as either urban or rural. The surveys also asked residents to identify which species were involved in collisions.

Of the ~1,800 people who participated in the survey over the two-year study period, approximately half remembered a bird-window collision at some point in the past; just over a third of individuals indicated that a collision had occurred within the past year alone. Although the mean collision rate was only 1.7 birds per year, this varied widely from one home to the next; several dozen collisions were reported at some residences, and the worst tally was 84 at a single home in a single year. Luckily, (known) mortality rates averaged less than 1 bird per year.

(Installation of decals may be one way to reduce the number of bird-window collisions. Image courtesy of Whispering Pines.)

Generally speaking, rural residences had more collisions and mortalities than urban residences; bird-window encounters were least common at apartments. Feeders tended to be associated with a higher number of collisions and mortalities, though dynamics varied a bit in urban and rural environments. There was some evidence that age of neighborhood influenced the likelihood of collision, but only in urban areas. Both the number of collisions and the number of deaths peaked in the summer and were lowest in the winter--perhaps because avian abundances vary greatly between these two seasons, since a large proportion of Canadian birds head south for the winter. Sparrows were the most common casualty of collisions, with chickadees and robins close behind; for all three species, a higher percentage of birds survived than died, though the difference was pretty slim for robins.

One of the reasons the authors were interested in pursuing this research was that there is a relative dearth of descriptive work on avian-window collisions. Results of the few studies that have been conducted have been used to create what the authors call a "social construction," or a widespread belief about something (in this case, the danger of windows) that is not actually based on scientific fact. Thus, the current study was developed not only to ascertain just how many birds truly are impacted by windows each year, but also to examine the environmental correlates of collisions--information that could be vital for developing useful conservation and management plans. Given the contributions of undergraduate students and members of the public, an additional benefit of the study is that it contributes to education and awareness.

(American robin, Turdus migratorius, a species that was particularly susceptible to both collisions, in general, and collision mortality. Image courtesy of Wikipedia.)

The researchers acknowledge some flaws in their work--in particular, the inaccuracies and biases associated with self-reporting--but they still feel that their results have made some useful contributions to the field. For example, their finding that feeders are associated with a higher likelihood of collision suggests that people should be careful to place seed and suet dispensers away from windows, or make their windows more obvious (e.g., by decorating them with decals and trimming back vegetation). By identifying that rural and older homes are more likely to experience collisions, the study helps show managers and planners which regions to focus on when attempting to mitigate the negative effects of windows.

Despite these important findings, more work is needed for the future. Birds that appear to survive collisions may simply fly off and die elsewhere. This makes it difficult to accurately measure the effects of windows on individual health and fitness. Thus, better demographic data are needed, as are, potentially, tracking studies that follow injured birds after they fly off. This information will also be important for understanding the long-term (population-level) impacts of collisions; it may be that the benefits of supplemental feeding outweigh the drawbacks of increased exposure to windows, but it might also be the case that birds would be better off without either the bird seed or the windows. The authors recommend that future studies move away from opportunistic observations (as made in the current project), and instead involve either experimentation or  a "snapshot" approach, during which researchers would undergo an intensive period of comprehensive data collection. Given their positive experiences with mobilizing the troops via the Internet, they recommend the use of online social network sites for increasing participation in any future work on avian collisions.

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Bayne, E.M., Scobie, C.A., and Rawson-Clark, M. 2012. Factors influencing the annual risk of bird-window collisions at residential structures in Alberta, Canada. Wildlife Research 39(7):583-592.

For more information on bird-window collisions, check out the website of the Acopian Center for Ornithology.

Were Neanderthals and modern humans birds of a feather?

Neanderthals get a lot of flack for being more "primitive" and less "advanced" than we humans, but there is an increasing evidence that they may not have been that different from our early ancestors. For example, researchers are now pretty certain that Neanderthals interbred with modern humans who shared their European habitats. While this suggests a greater degree of physical similarity than we once realized, there also appear to be cognitive overlaps between the two species as well. Recently, for instance, an international team of researchers published a paper in PLoS ONE reporting that Neanderthals, like early modern humans, harvested bird feathers for decorative purposes.

(Red-billed choughs, Pyrrhocorax pyrrhocorax, were one of several cliff-loving species found at Paleolithic sites. Image courtesy of Wikipedia.)

This finding is exciting for two main reasons. First, to quote the authors directly, "regular and systematic exploitation of flying birds for food is considered to be a hallmark of behavioural modernity, exclusive to anatomically modern Homo sapiens after 50 thousand years ago." Although there have been a few previous findings indicating that birds were an occasional prey item of Neanderthals, researchers have typically argued that use of avian species was "opportunistic and unsystematic." Thus, any evidence that Neanderthals repeatedly collected birds (regardless of how the animals were eventually used) indicates that we humans were not the only hominins capable of recognizing the potential of these particular sources of material--not to mention figuring out how to go about getting them.

The second point of interest pertains to the use of birds not for meat--or, at least, not just for meat--but for feathers and claws. Given how these bits were utilized by early humans, as well as by human descendants in nearly every known culture around the world, it is likely that the Neanderthals were collecting these features for personal ornaments or some other decorative purpose. This sort of behavior has generally been considered beyond the capacity of Neanderthals, and so the new evidence is suggestive of "unprecedented cognitive abilities."

(Cut-marks from early stone tools were found on many bird bones at three sites in Gibraltar--Gorham's, Vanguard, and Ibex Caves. Image courtesy of PLoS ONE.)

Aware that this possibility might be met with skepticism, the authors were sure to perform as comprehensive a study as possible. They first compiled a database of 1,699 archaeological and paleontological sites in which avian fossils had been identified. They were particularly interested in raptors and corvids because these two groups of birds are often seen around human settlements and so seemed particularly likely to be accessible to early hunters. An analysis of the database revealed that both Middle Paleolithic sites (those associated with Neanderthals) and Upper Paleolithic sites (those associated with modern humans) contained more raptor and corvid species than paleontological sites. Particularly common were birds that are scavengers, colonial nesters, and/or cliff-dwellers, indicating that hominin hunters were reacting to "a strong ecological signal." Also common--especially in Neanderthal-era sites--were birds with dark wing feathers. If, as this suggests, Neanderthals were specifically targeting species with certain physical characteristics, then these artifacts are evidence of "sophisticated cognitive processes" not previously attributed to these early hominins.

Detailed examinations of 604 "skeletal elements" from 21 species of bird revealed many signs of hominin processing: cut-marks made by Neanderthal stone tools, bones broken just after the birds had died, burns, tooth imprints, and--especially interesting--overextension of the ulnae and humeri. In other words, the wings had been stretched as their feathers were plucked out. The wings had received considerably more attention than other parts of the birds' bodies, and the authors found no evidence that the preponderance of wing bones at their study sites resulted from anything other than especially high levels of hominin interest in these parts of the bird anatomy.

(Map showing the Paleolithic and paleontological sites containing more than 50% of the 18 raptor/corvid species cataloged across the study area. Image courtesy of PLoS ONE.)

Although many of the examined sites were quite distant from each other--2,000 km separate Riparo Fumane and Gibraltar, for example--the authors could still see a "clear concentration across the western mid-latitude belt." The habitats in these areas are relatively similar, granting Neanderthals and early modern humans consistent access to the same types of bird species. What remains unclear, however, is what sort of forces led hominins in these areas to display similar levels of interest in the wing feathers of raptors and corvids. Did a shared ancestor of both Neanderthals and modern humans pass down this cultural characteristic? Was there behavioral convergence of two groups living in the same region? Is it possible that Neanderthals could have transmitted this trait to modern humans?

Given the current evidence, this may be difficult to determine; for now, the best the authors can do is point out that feather use is a "common characteristic of the two lineages." Further, Neanderthals arrived in Europe several thousand years before modern humans did, and therefore engaged in feather-plucking activities in isolation. Thus, no matter how they learned this behavior and regardless of whatever other mental skills they may have had, these early hominins often maligned for their lack of intellect were clearly capable of "cognitive capacities that included symbolic expression"--a characteristic that the authors feel renders them "distinctly human."

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Finlayson, C., Brown, K., Blasco, R., Rossell, J., Negro, J.J., Bortolotti, G.R., Finlayson, G., Marco, A.S., Pacheco, F.G., Vidal, J.R., Carrion, J.S., Fa, D.A., and Llanes, J.M.R. 2012. Birds of a feather: Neanderthal exploitation of raptors and corvids. PLoS ONE 7(9):e45927.