Sunday, 31 July 2011

Behavior 2011: Science outreach at Wonderlab

If you participated in or attended the Animal Behavior Society's science outreach activities at Bloomington's Wonderlab on 30 July, click here to browse through a collection of photos from the event. These comprise the 100 or so best photos of the 450 I took. If you are interested in obtaining higher-resolution copies or alternate shots, let me know and I will be happy to oblige. Check back here over the next couple days for more complete coverage of the event, including some videos!

Saturday, 30 July 2011

Saturday stuff: Websites to check out

One of the plenary speakers at the Behavior 2011 conference was the University of Cambridge's Nick Davies, whom I also heard give a plenary at last year's International Society for Behavioral Ecology meeting in Perth, Australia. Nick gives a fantastic talk--he sounds like the voiceover for a nature documentary on television. This year's talk was focused on the cuckoo (Cuculus canorus), whose singing is a harbinger of spring and who is therefore much beloved in Britain despite its nefarious deeds at other birds' nests. Unfortunately, cuckoos are on the decline in Britain, causing the British Trust for Ornithology (BTO) to attach satellite tags to several migrating adults this year in order to trace their movements from afar. Hopefully this information will provide useful information for conservation efforts. According to Nick, the cuckoo tracking scheme has caught the imagination of the British public (although I'd not ever heard of it), in part because of the BTO's webpage devoted to the project. Each of the tagged birds (all males) has been named, and readers can follow their progress and read their "blogs" online. If suitably inspired, visitors to the website can also make donations to help fund future conservation work on this and other species.

While browsing through the Behavior 2011 conference website, I ran across a link for an affiliated organization--the ISAZ. It turns out that this acronym stands for "the International Society for Anthrozoology." In other words, this is a group of researchers and professionals who study the interactions between humans and people. This includes individuals who examine the utility of therapy animals, interactions between the blind and their guide dogs, the role of pets in the home, and many other relationships that many of us experience every day but probably don't often think twice about. In the "hard-core" animal behavior world, these topics, and the researchers who study them, frequently get a reputation for being a bit "fluffy," but anyone who is a pet owner knows what an impact these animals can make in our lives. I, for one, think this is a fascinating area of research, which you can read more about here.

Finally, I'd like to give a little plug for one of my friends and colleagues, Dan Blumstein. Dan feels that stimulating discussions in the home will help pave the way for a more thoughtful, progressive, problem-solving society, and what better environment to have these discussions than over a plateful of home-cooked food? When I last saw Dan at a conference in September 2010, he was just embarking on a project to write a book that provides guidance for people who want to host good dinner parties with great food and even better conversations. During Behavior 2011, I found out that the book has been completed and is now available for Kindle/iPhone/iPad download. It's called Eating our Way to Civility, and it even has its own associated blog. Here, Dan posts discussions on important "green" topics, such as eating sustainably and saving energy. Keeping with the theme of the book, he also provides some delicious recipes. "Food for thought" has never been a more accurate phrase!

Thanks to the following websites for the photos used in this post:

Friday, 29 July 2011

Behavior 2011: Effects of childhood environment on human reproductive efforts

(Squirrel monkeys at the Colchester Zoo.)

Although we tend to overlook it, we humans are animals and, although we sometimes don't realize it, we act just like our wilder relatives. This was highlighted in a lecture today by Daniel Nettle of Newcastle University, who discussed how early-life environment affects reproductive strategies in human females. His research was inspired, in part, by previous work showing that female monkeys with more disrupted childhoods were later more interested in holding infants when given a choice between an infant and a model. In other words, these females seemed more primed to engage in reproductive behaviors than similar-aged monkeys who had experienced a normal childhood.

These results jived with several findings that have been found, separately, in studies of human reproductive behavior and stressful childhood experiences. For instance, adolescent females are likely to have an earlier first period if they are born with a low birth weight, raised without a father in the home, or are adopted; teenage pregnancy has also been linked with father absence, as well as several other early-life circumstances.

In order to tie these trends together, and see whether the monkey study showed patterns that are also present in humans, Nettle and colleagues utilized a detailed long-term database from the UK. Data collection first began in 1958 for a total of 17,416 individuals who were born that year; researchers followed up with the study participants periodically, most recently in 2004, at which point 11,939 participants remained in the study. The current study examined 4,533 females from this group in order to determine whether age at first pregnancy was affected by socioeconomic status during childhood, age of their own mother at the time of their birth, adverse experiences early in life, and emotional or behavioral issues during childhood (as previously assessed by their teachers).

Each of these variables had a significant effect on age at first birth, though the size of the effect was consistently small--often influencing age at first pregnancy by just 6 months or a year. Women who were breast-fed more started their first pregnancy later. However, women who were separated from their mothers as children gave birth earlier, and the strength of the effect was dependent on the length of separation. The only exception to this trend was among women who were separated from their mothers for more than 2 years--a situation generally linked with removal to a foster home or adoption, both circumstances in which a surrogate mother was present. First pregnancy was also earlier in women whose fathers were absent, or at least played less of a role in their upbringing; likewise, women who experienced the stress of moving as children also gave birth sooner.

The researchers performed a second layer of analysis in which they tallied how many of these stressors each woman was exposed to. It turns out that this number is highly correlated with age at first childbirth, such that women with fewer overall stressors gave birth later, and women with more stress gave birth earlier.

What drives these trends, and why? The researchers aren't sure of the answers to either of those questions just yet. However, they suspect these patterns are influenced by the hypothalamic-pituitary-adrenal axis, which controls reactions to stress and regulates a huge range of body processes--including immune function, sexuality, digestion, mood and emotions, and energy expenditure, among others. Nettle did not comment on the evolutionary advantage of these patterns--in monkeys or in humans--but I suspect it might be a good coping mechanism for animals who are living (or who think they are living) in a harsh or unpredictable environment: Producing your young earlier would certainly be one way of making sure that you leave a copy of your genes behind as some point, no matter what curve balls life throws your way.

Regardless, it's always interesting to see some research that shows humans acting like other animals, even subconsciously. It's fascinating, but a little scary--a reminder that sometimes we are just puppets dancing on the ends of strings manipulated by our genes!

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

Wednesday, 27 July 2011

Live from Behavior 2011

This week I am attending the joint meeting of the Animal Behavior Society and the International Ethological Conference, which is being held at Indiana University in Bloomington, Indiana. One of the symposia on the first day of the conference focused on the idea of "sensory pollution," a new buzz-term collectively describing the negative effects of human activities and products on the ability of animals to accurately perceive the world around them. In addition to the noise pollution that I have often described in previous posts, experts spoke on the impacts of pollution from light, chemicals, and sources of magnetism. While most of the discussion focused on the ways in which sensory pollution is harmful, there was also some mention of how "pollution" might be used to the advantage of wild animals.

(Pile-driving, one of many sources of aquatic noise pollution. I can attest from personal experience that, on land at least, it is very, very loud. Considering that sound is transmitted even better in water, I'm guessing things get quite unpleasant for aquatic animals exposed to this racket.)


Legendary aquatic bioacoustician Arthur Popper discussed recent experimental work on the physical effects of pile-driving noise on fish. He and his lab built a small indoor setup where they could mimic both the frequency (e.g., pitch) and amplitude of pile-driving sounds. Those who have heard this intense sound in the field will probably not be surprised to learn that the initial run of the testing arena resulted in vibrations so intense that they shook the entire building. After a bit of tweaking, the machinery was back on track and the researchers were able to proceed with their tests. One of their surprising findings was that, at low and moderate levels of pile-driving noise, fish were able to recover from the bleeding and tissue hemorrhaging caused by the disturbance. Further, only species with a swim bladder exhibited truly irreparable damage in response to the noise. Overall, these are fairly encouraging results, since they suggest that many animals may be more tolerant of pile-driving than expected--good news given that this particular form of aquatic sound disturbance is fairly common worldwide.

(Light pollution in the continental US.)

Next up was light pollution expert Sidney Gauthreaux, author of Ecological Consequences of Artificial Night Lighting. NPR listeners may recognize his name (and message) from a piece on bird migration that aired in 2009. Gauthreaux discussed the many sources of artificial night lighting (lighthouses, lightships, tall buildings, street lights, spotlights, flares, communication and broadcast towers) and the various ways in which they can affect birds (e.g., by causing blindness, singing feathers, increasing collisions, and leading to death). Since most birds are diurnal, lighting is a particular problem during spring and fall migrations, when many species fly through the night in order to reach their breeding and wintering grounds, respectively. Steady lights have been shown to attract three times as many birds as flashing lights. Results of studies on the effects of light color are a bit more mixed; while some findings suggest that red light and white light are not as attractive as blue lights, other research indicates that red and white light are actually worse than green and blue. One particularly interesting part of Gauthreaux's talk focused on the interaction between magnetic orientation and lighting. Evidently, birds navigate best when light is at or below the intensity of a sunset; when lighting becomes more intense, their magnetic senses are confounded and they become disoriented. Young birds appear to be particularly susceptible to light pollution, which is discouraging since these are the animals that are needed to replenish populations and carry on breeding in years to come. Another sad aspect of light pollution is that "captured" birds--those that have been drawn to a light and are too bedazzled to leave--appear to attract other birds, and many animals end up dead not only from colliding with anthropogenic structures, but also from colliding with each other midair.

(A reflective surface, which causes light to polarize. This unnatural source of polarized light can trick animals, especially insects, into thinking they are seeing water.)

One subset of light pollution is polarized light, which is light that has bounced off a surface in such a way that its wavelengths are oriented in the same direction--or, at the very least, are less randomly directed than previously. This "specialty" form of light pollution was discussed by Bruce Robertson of the Smithsonian Conservation Biology Institute. According to Robertson, there are only two natural sources of polarized light: the sky, which contains water droplets that cause polarization, and bodies of water. Many animals are sensitive to polarization because it helps them orient themselves so that the sky is above and behind them, and/or because this sensitivity enables them to seek out bodies of water where they may feed and breed. Unfortunately for these animals, humans have changed the polarized light landscape by using construction materials that are smooth and dark--the two characteristics that cause the highest levels of polarization. Objects like blacktop, crude oil spills, plastic tarps, metals, and glass all mimic water, causing animals--particularly insects--to aggregate in inappropriate places (Robertson says that an increasingly noticeable phenomenon is the presence of water insects on cars, which they mistake for ponds. Next time you go for a drive, check your vehicle for evidence of this trend!). Obviously, this is quite bad for the animals that are lured astray, but other animals may capitalize on their mistakes. Birds such as magpies and house sparrows, for instance, have been observed eating insects that are mindlessly flinging themselves at reflective windows. Fortunately, the negative impacts of polarized light can be mitigated fairly easily. Adding a bit of roughness to a surface--by faint etching in glass, for instance, or a handful of pebbles in asphalt mix--can dramatically reduce polarization. Likewise, using materials that are lighter in color or are criss-crossed by gridding in order to create many small, less attractive "islands" of habit, can also diminish the likelihood that animals will mistake anthropogenic building materials for water.
(Ocean acidification is caused by changes in carbon dioxide levels. The oceans have absorbed almost half the excess carbon dioxide we humans have pumped into the atmosphere. This has reduced the amount of carbonate in the water, which means that shellfish have fewer materials with which to make their shells.)

Recent PhD graduate Danielle Dixson discussed the effects of rising marine carbon dioxide levels on the ability of fish to use their sense of smell. She found that increases in carbon dioxide cause clownfish to prefer useless scent cues and to ignore important cues. This latter effect was seen in response to predator scents, which fish should pay attention to if they want to make sure they aren't eaten. Responses to carbon dioxide are dose-dependent, which means that as humans continue to alter global chemistry, things will only get worse for the clownfish (and probably other species, as well). Not only did the chemical pollution disrupt the fishes' sense of smell, but it also altered their "personalities": larvae treated with carbon dioxide were both bolder and more active, which means they could be more conspicuous to predators. Dixson reported that hearing and learning were also affected by carbon dioxide; cumulatively, this suggests that the chemical pollution may have an impact early on in development, and/or may affect brain functioning, thus affecting all these characteristics simultaneously. The only good news for the clownfish is that predators are similarly impacted by carbon dioxide, and under high levels of pollution they are less aggressive and quickly lose interest in their prey. Perhaps the most interesting--though very discouraging--finding was that marine larvae actively avoid scents of both oil palm and coconut, but are attracted to the scent of decomposing detritus. Why is this important? In the Pacific island archipelagos where Dixson conducted most of her research, larvae find their habitats (the shallow waters around each island) by sniffing out leaves that have fallen into the water from overhanging native trees. These species are increasingly being replaced with crops like oil palm and coconut. Thus, larvae will not only have trouble finding an attractive scent--and therefore a good home--but they will actively be repelled from the very same sites that they should be moving towards.

(Sharks can be both a type of bycatch and a deterrent to other types of bycatch.)

Some relief from all this depressing news was offered by Richard Brill of the Virginia Institute of Marine Science, a branch of my very own alma mater, the College of William and Mary. He discussed how sensory pollution has been used to discourage bycatch, and therefore preserve the health and population numbers of marine organisms such as fish, sharks, turtles, and pelagic seabirds. One early attempt at "positive" sensory pollution was the use of colored streamers on fishing lines in order to alarm potential bycatch, thereby keeping them away from fish hooks. When this failed to get the job done adequately, researchers got a bit more fancy and studied the sensory abilities of specific bycatch species. This eventually led them to discover differences between sea turtles--which fishermen don't want to catch--and edible fish such as swordfish--which they do. Specifically, sea turtles can see in the ultraviolet range, but swordfish cannot. Thus, an ultraviolet warning signal should keep turtles away from fishing lines, while leaving swordfish unaffected. Because turtles have a strong panic reaction to sharks, researchers came up with the idea of creating a UV shark silhouette that can be placed periodically along fishing lines in order to send the turtles running (or, in this case, swimming). Since plexiglass reflects UV light, it seems to be a good candidate material for the cut-outs. This particular plan is hot off the press,and researchers haven't yet had a chance to test whether it really works--but stay tuned. Another potential technique that hasn't been investigated is the use of electropositive metals to create a "zone of repulsion" around fishing lines. This should cause electrosensitive animals--namely sharks, another unwanted species--to avoid becoming snagged on a fishing hook. Magnets could also be used for this purpose, but so far they appear to cause avoidance behavior over the short-term, whereas the metals cause longer-term avoidance. One added bonus of the metals is that they are small, abundant, and cheap, which should make this technique easy to employ if it turns out to work well.

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

Sunday, 24 July 2011

Sunday Stuff: Citizen Science

If you've ever listened to reports about "scientific evidence" and wondered how those data were collected and analyzed, you might be interested to know that there are many opportunities for everyday people to get involved in real science projects.

Last year, one of the UK's radio stations, BBC Radio 4, encouraged non-scientists to investigate interesting phenomena and conduct small-scale experiments in a competition called "So You Want to Be a Scientist?" The winner was 69-year-old grandmother Ruth Brooks, who investigated homing behavior in common garden snails. As a result of her work, Ruth was named Britain's Amateur Scientist of the Year. Click on the links above to find out more about the competition and Ruth's experiment, and to hear her acceptance speech.

In the wake of the recent disastrous crude oil leak in the Gulf, developers at CrisisCommons created a phone app called "Oil Reporter," which allows anyone with an iPhone or a Google Android phone to report the presence of oil patches, oil-covered animals, or any other oil-related problems along the Gulf. The data are stored by San Diego State University and can be used by any member of the public interested in analyzing the spread of oil or the extent of the damage it has caused (or is causing).

The Smithsonian Institution has begun an initiative called "Shout," which connects classrooms with each other and with scientific experts around the world. Its ultimate goal is to help the environment while simultaneously teaching students about how to conduct scientific experiments. One Shout initiative is the Tree Banding Project, in which students install dendrometers so they can monitor tree growth. Among other things, this allows them to measure biomass and compare growth rates in different locations and different times of year.

US birders are probably familiar with Cornell's eBird initiative, which involves many projects geared towards making everyday bird observations scientifically useful. Anyone can log in and report sightings of rare birds or unusual bird behaviors, and people with backyard feeders can submit tallies of the animals they've seen visiting their property. Although these reports are not always scientifically rigorous in the strictest sense--not all observers are collecting data in a uniform way--they can still be very useful in highlighting patterns that merit further research by the experts. After all, professional scientists don't have an inexhaustible supply of time and energy, so an army of citizen scientists is bound to be helpful.

One last tidbit isn't strictly citizen science, since it also involved a handful of experts, but it's close enough to count. The BBC News has recently reported the discovery of a new aphid species in Cornwall, the most southwesterly county in England. It was found at the Duchy College in Camborne during a survey effort called the "BioBlitz," which involved college students, staff, members of the Cornwall Wildlife Trust, and wildlife specialists. The aphid is native to Italy, where it is only found on Italian alders. These trees are commonly planted in Cornwall to act as windbreaks, and clearly a few Italian aphids arrived in the UK as stowaways. Discovery of the aphid just goes to show that anyone with a sharp eye can make important observations--even in somewhere as familiar as their own backyard or a campus just down the road.

Thanks to http://www.pdphoto.org/PictureDetail.php?mat=&pg=5612 for providing the snail photo used in this post. All other images came from the websites linked to within the main body of the post.

Friday, 22 July 2011

Are lions responsible for our fear of the dark?

The great apes--gorillas, chimpanzees, humans, and orangutans--have always lived near large carnivores that hunt predominantly at night. One such carnivore is the lion, which was once the most widely distributed mammal in the world. Lions are so important to human history that they are featured in cave paintings from as long as 36,000 years ago. But it turns out that there is another indelible mark they have made on human history: Research out this week suggests that humans' innate fear of the dark, as well as our unease with full moons, may have been driven by the cats' hunting practices.

(Female lions at Lake Nakuru, Kenya, shortly after a daytime feast.)

Scientists from the University of Minnesota and the Tanzanian Wildlife Research Institute took advantage of several excellent long-term datasets in order to investigate which parts of the lunar cycle are associated with lion hunting success and human attacks. They examined one subset of African lions--those living in the Serengeti and Ngorongoro Crater in southern Tanzania. These animals have been studied in detail for over thirty years; one measurement that has consistently been taken during this time is "average belly size," which indicates how well fed the lions are. In addition to astronomical data on lunar cycles, the researchers also had access to meteorological records, which allowed them to look for effects of season (since there are more clouds during the rainy season and, thus, more darkness). They obtained information from the Tanzanian government on all lion attacks on humans between 1988 and 2009, then followed up with the victims or the victims' families in order to get further details about each event. Cumulatively, all this information allowed the researchers to find out when lions fed the most, when those feeds were associated with successful hunts, rather than scavenging, what time of month and day humans were most frequently attacked by lions, and whether any of these parameters varied during different seasons of the year.

(Waning moon on a mostly cloudless night.)

Overall, more than 1000 Tanzanians were attacked during the 21-year study period. More than two-thirds of these attacks were fatal, and victims were not only killed but also eaten by the lions. Unsurprisingly, given that lions are predominantly nocturnal hunters, the majority of victims were attacked after dark. The researchers excluded information from retaliatory lion hunts, which narrowed their dataset down to 474 victims from 450 separate attacks.

Among lions in the Serengeti and the Ngorongoro Crater, belly size was larger on days after moonless nights, indicating that food intake was higher when nights were darker. Further, belly size was related to the amount of ambient light, regardless of whether it occurred during the waxing or waning of the moon. As found in previous studies in South Africa and Uganda, lion hunting success was highest on dark nights--in other words, the full bellies noted after moonless nights were not a result of scavenging, but of successful capture of fresh prey. During the period around the full moon, when the lions had reduced hunting success at night, they spent more time killing and scavenging during the daylight hours in order to supplement their diet.

Human victims were more likely to be attacked during the darkest days of the cycle and during the darkest part of the night. Nearly 60% of victims were attacked between 6 and 9:45 PM--the post-sunset time period during which humans are most active and, therefore, most exposed to predation. More than 3 times as many people were attacked during the wet season than during the dry season, since clouds obscure moonlight and provide optimal hunting conditions for lions.

(Slumbering male lion. They look so innocent with their eyes--and mouths--shut.)

Based on these data, the researchers conclude that human feelings towards both darkness and full moons are adaptive responses geared toward increasing survival in habitats with large, nocturnal carnivores. Our surviving ancestors were those that learned to fear the dark and stay inside their shelters at night, away from predators; this fear became so ingrained that it is in our genes even now, when the majority of us live in environments where these predators no longer exist. Our feelings toward the full moon have similar origins. Even though illumination from the full moon afforded some measure of protection, by enabling our progenitors to see better and by making it more difficult for predators to sneak up on them, it was also a portent of the time when lions would be hungriest and most active (due to their lack of hunting success during the brightest evenings of the month). Thus, human cultures around the world developed stories and superstitions about this dangerous time--arguably the most famous of which is the idea that humans might morph into toothy, clawed beasts (such as werewolves) during this phase of the moon.

Next time you see Teen Wolf on TV or feel the need to plug in a night light when it's a bit too dark, you'll know who to blame.

Packer, C., Swanson, A., Ikanda, D., and Kushnir, H. 2011. Fear of darkness, the full moon and the nocturnal ecology of African lions. PLoS one 6(7): e22285.

Thanks to the following website for the moon photo featured in this post:


"Greener" neighborhoods may not necessarily make for happier residents

(A neighborhood with decent amounts of "green." Does the green make the residents happier?)

An increasingly popular area of conservation research focuses on measuring the psychological value of nature. Studies in several locations have shown that people are happier in greener environments and those with more animals (in terms of both numbers of individuals and numbers of species). Some environmentalists have expressed concern that increasing levels of urbanization will lead to both physical and emotional separation between people and nature, one consequence of which might be a skewed perception of "biodiversity"--with subsequent impacts on whether or not people will support conservation initiatives that aim to improve species abundance and richness in various habitats.

While most of the previous studies have focused on areas such as parks, where people temporarily relocate for recreational purposes, recent work by scientists at Australia's Charles Sturt University has investigated for the first time how human well-being and "connectedness" with nature vary in relation to different levels of urbanization in the neighborhoods where they reside. The authors collected data on demographics and psychological status using a survey distributed to residents by mail. In order to characterize the habitat, they measured species richness, species abundance, vegetation cover, vegetation density, and level of urban development in each of the neighborhoods surveyed.

(A typical "peri-urban" neighborhood--one that is between the suburbs and the countryside, and therefore has a fair amount of vegetation in addition to anthropogenic development.)

In contrast to previous research, this study found that residents were not overwhelmingly impacted by the "greenness" of their environment. Both personal and neighborhood well-being were predicted more by demographic variables such as age, number of years the resident had lived in the neighborhood, and social/economic status. Likewise, "connectedness" to nature was less affected by levels of urbanization than by general activity levels and demographics such as gender and, again, length of residency, and social/economic status.

However, using separate analyses, the researchers did find that the odds of both personal and neighborhood well-being increased with increases in "greenness." For instance, the odds of higher personal well-being increased by 55% from the lowest to the highest levels of vegetation cover measured in the surveyed neighborhoods. There were also some interesting trends within certain demographic groups. For example, well-being among females decreased by 124% from the lowest to the highest levels of urbanization, indicating that women were more sensitive to a lack of nature in their environments--potentially because they were more likely to spend more time at home. Another intriguing trend was related to education: Residents with more advanced degrees reported stronger feelings of "connectedness" at higher levels of abundance.

Given that the findings of this study were so at odds with previous reports, the authors have pondered what additional factors may have influenced their results. They conjectured that residents' feelings may be influenced by the proximity of other natural areas that are near, but not in, their neighborhoods--perhaps an urban dwelling is more tolerable when you know you can easily escape to a park located down the road. The scientists also noted that there was substantial variation in the amount and use of yard/garden space at each residence, which may have obscured patterns that would have been found had they distributed the surveys across more uniform environments. One question the researchers are particularly interested in investigating in the future is whether residents respond differently to native and non-native species. Regardless, one thing seems clear: The relationship between humans and nature is not an easy one to describe or predict.

Luck, G.W., Davidson, P., Boxall, D., and Smallbone, L. 2011. Relations between urban bird and plant communities and human well-being and connection to nature. Conservation Biology 25(4):816-826.

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

Tuesday, 19 July 2011

Exeter Tuesday: Effects of small-scale fishing efforts on marine turtle populations

(La Islilla Port, Pira, Northern Peru)

Those who eat canned tuna may be familiar with the "dolphin safe label" used to indicate that no dolphins were harmed when the fish were harvested. But dolphins are only one of many marine animals that may be negatively impacted during the fishing process--for example, sharks, sea birds, and turtles are all known to suffer injuries or even death after being caught in nets or on hooks. Although large, industrial fishing outfits are most often blamed for this damage, the combined efforts of smaller parties (known as small-scale fisheries or, sometimes, artisanal fisheries) may also have significant effects on animal populations.

(Leatherback turtle, Dermochelys coriacea, caught in a gillnet boat)

New research published today in the Journal of Applied Ecology describes the effects of small-scale fisheries in Peru on 5 species of marine turtles that forage (and, in rare cases, breed) along the Peruvian coast: green turtles (Chelonia mydas), leatherback turtles (Dermochelys coriacea), olive ridley turtles (Lepidochelys olivacea), hawksbill turtles (Eretomocheyls imbricata), and loggerhead turtles (Caretta caretta). Although outright turtle fishing has been banned in Peru since at least 1995 (green and leatherback turtles have been protected since 1976), these species are often caught accidentally, at which point they are sometimes released, but may also be kept for personal consumption or sale.

(Fishing boats along the Peruvian shoreline.)

The researchers (collaborators from the Marine Turtle Research Group at the Cornwall Campus of the University of Exeter, Pro Delphinus, and NOAA--National Marine Fisheries Service) analyzed 7 years' worth of data collected by observers on fishing boats in each of 4 Peruvian fisheries. Over a total of 264 fishing trips, 807 turtles of 4 species (loggerheads, green, olive ridley, and leatherback turtles) were captured. Using these numbers, the researchers estimated that the annual turtle bycatch across all 4 fisheries is approximately 5900 turtles.

(A bycaught leatherback turtle is released into the wild...after the fishermen are convinced not to keep it.)

"Fishing effort" can be measured as total number of hooks or total length of net deployed, depending on capture technique. The 807 turtles captured here comprise 635 caught with an effort of 900,000 hooks and an additional 172 caught with an effort of 838 km of nets. These represent only a fraction of the estimated 80 million hooks and 100,000 km of nets deployed across Peru each year. Because turtles are not spread evenly across all Peruvian fisheries, it is unlikely that these figures could be used to make a direct extrapolation in order to calculate the total number of turtles captured each year in Peru. All the same, it doesn't take an expert at math to recognize that the fishermen are probably hauling in a lot of turtles along the country's coast.

(A leatherback turtle is brought to shore in northern Peru.)

One additional problem is which turtles are being caught. Adults accounted for approximately 35% of the green turtle bycatch, 71% of leatherbacks, and 67% of olive ridley turtles; the vast majority of loggerheads were juveniles. Because adults are potential breeders, and are therefore responsible for sustaining, or even increasing, the population, it can be particularly damaging if fishermen are catching a disproportionately large number of this age class, as it appears they are.

(Release of the leatherback, "Odiseo" back to the wild.)

There are several potential mitigation techniques available to reduce the impacts of fishing on turtle populations. These include fishery closures, the establishment of marine protection areas, and the use of alternative or additional fishing equipment such as circle hooks, dehookers, net illumination, and nets without flotation devices. However, because fishing is both a livelihood and a direct way of putting food on the table, managers and conservationists will ultimately need to employ techniques that simultaneously save turtles and prevent the locals from going hungry.

To listen to The Journal of Applied Ecology's podcast containing an interview with authors Joanna Alfaro-Shigueto and Brendan Godley, click here. To see the Science Daily write-up of the paper, click here. To see the associated Youtube video, click here.
Alfaro-Shigueto, J., Mangel, J.C., Bernedo, F., Dutton, P.H., Seminoff, J.A., and Godley, B.J. Small-scale fisheries of Peru: a major sink for marine turtles in the Pacific. Journal of Applied Ecology, online advance publication.

All pictures provided by Jeffrey Mangel.

Monday, 18 July 2011

Birds' tolerance to urbanization is influenced by their biogeographic range

Of all the places impacted by urbanization, tropical habitats rank near the top of the list. Because these areas are often "hot spots" for biodiversity, containing many different species in a single place, even small amounts of urbanization threaten to wipe out whole species. Unfortunately, because of the diversity and ecological complexity of tropical habitats, there is still much to be learned about the species that live in these areas and, especially, about their habits. Entirely new species are discovered each year, and only a small portion of all species have been studied in detail. Yet, without more species-specific information, it is difficult to develop good management and conservation plans, since it is hard to predict exactly how and why different species will be impacted by human developments.

This is the conundrum addressed by recent work from a scientist at the Universidad de las Américas Puebla in Puebla, Mexico. He investigated diversity of songbird assemblages throughout Mexico in order to determine if they are less diverse than in rural areas--as has been found in other, non-tropical, countries. He then examined whether particular types of bird species seem to be particularly sensitive to urbanization, or, conversely, particularly common in urban habitats. A bird's "type" was determined by its biogeographical range--in other words, what sort of habitat the bird prefers, and how much space that habitat covers. Thus, classifications (there were a total of 7) indicated whether the birds were from, say, the Nearctic area (basically, all of North America above the Yucatán Peninsula), or whether they occurred only in Mexico. The study compared urban and non-urban bird assemblages at both local (within Puebla) and national (across Mexico) levels, in an attempt to investigate whether diversity patterns are influenced by the spatial scale at which they are measured.

(The skyline of Puebla, Mexico)

In non-urban sites, the most common birds were those that are found only, or mostly, in Mexico, as well as Neotropical birds (those from the Neotropical region, which covers all of the western hemisphere below the Nearctic zone). In other words, the birds that were most "distinctive" to the region were most threatened by increased human development. On the other hand, urban sites were dominated by non-native species, birds with a wide distribution (found across both the Neotropical and Nearctic zones, and, in some cases, the Palearctic zone (which comprises Europe, North Africa, Russia, and much of Asia and the Middle East), Nearctic birds, and semiendemics (which only live in Mexico during one season).

At both regional and national levels, songbird assemblages in urban areas were less diverse than expected by chance, with Neotropical species and endemics (those found only in Mexico) being particularly underrepresented. Thus, urbanization leads not only to similarity between cities within a single country, but also, to some extent, between countries, since regional "specialties" disappear and are replaced by species that can be found in many places (think of pigeons, Columba livia, and house sparrows, Passer domesticus).

(The great-tailed grackle, Quiscalus mexicanus)

Interestingly, the only species found at all urban study sites in the nationwide survey was the great-tailed grackle (Quiscalus mexicanus). This is not, as you might expect, a non-native species, or even a species classified as having a wide distribution. In fact, it is a Neotropical species--one of the few to do well in the face of urbanization. Along with house finches (Carpodacus mexicanus), lesser goldfinches (Carduelis psaltria), and house sparrows, the great-tailed grackle has previously been identified as an "urban exploiter." This probably doesn't surprise anyone who has seen grackles, finches, and sparrows happily put up with house cats, lawnmowers, passing cars, playing children, and any number of other disturbances, in order to visit bird feeders or peck at food scraps on the sidewalk.

The author conjectures that one of the reasons that native tropical species don't respond well to urbanization is their "slow pace of life"--they lay fewer eggs per breeding attempt, their nestlings grow slower, their juveniles are dependent on their parents for longer, and they have longer life spans. All of these characteristics make them less flexible to changes in their immediate environment, and if there is anything urban tolerance requires, it is adaptability. Although much more species-specific research will need to be conducted to determine the exact reason for each species' sensitivity to urban development, the author suggests that, for now, biogeographical origin can be used to predict which species will likely be affected by anthropogenic disturbance. This should help conservationists develop management plans to preemptively help these species before they become threatened, endangered, or extinct.

González-Oreja, J.A. Birds of different biogeographic origins respond in contrasting ways to urbanization. 2011. Biological Conservation 144:234-242.

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

Saturday, 16 July 2011

Saturday stuff: Bio videos

Because even the most hard-core science fans need a break from the scientific literature every now and then, I am beginning a weekend tradition of posting multimedia resources that are informative and fun. Today I am taking the opportunity to promote the efforts of people and organizations that I know personally.

First up is a short documentary about the University of Exeter--Tremough Campus's annual field course in Kenya. I was lucky enough to be included on the trip this year as a lecturer (thanks, Brendan Godley!), so I got to see the documentarian, Bryony Stokes, diligently collect hours of video and thousands of still shots chronicling our travels around the country. Our trip marked my first time in Africa, and it was incredible to see in person things that most of us have watched on television all our lives. Kenya is a fascinating place from a biological perspective, but also from cultural, economic, and conservation perspectives. As much as we scientists want to ensure that Africa's biodiversity is preserved, we cannot deny the fact that the African countries are also home to people who need to make a living, even though that may cause their needs to conflict with those of the wildlife. Our students, who are studying to become conservationists and managers, got a first-hand look at how difficult it can be to balance the needs of humans and the environments in which they live.

On a completely different note, I've also posted a video shared with me by Jan Wouter Kruyt, a fellow biologist that I recently met at the Science Communication Training Day held in conjunction with the Society for Experimental Biology's 2011 conference in Glasgow, Scotland. The video was produced as part of a larger project called Flight Artists. Jan and his colleagues study the biomechanics of flight and initiated Flight Artists in order to put video cameras in the hands of citizen scientists and artists. The only demand was that the filmmakers produce video of naturally flying objects--including birds, insects, airborne seeds, etc. It is a great program that gives everyday people the opportunity to work with advanced technology, as well as to observe flight up close and personal (thanks to high magnification and super-slow-motion filming techniques). Jan is currently trying to make the following video go viral, so if you like it, please share it with everyone you know.

Finally, I'm also including a video produced by Jes Therkelsen, a filmmaker who is about to become a postdoctoral researcher in my former lab at the College of William and Mary in Williamsburg, Virginia, USA. At the time I left the campus, we did not even have on-campus recycling, though an effort was under way to initiate a recycling scheme, as well as to begin many other "green" projects. The massive improvements that have been made at William and Mary since my time are documented in the following video, and demonstrate not only that being green doesn't have to be hard, but also that it can be achieved by anyone, anywhere.

Friday, 15 July 2011

Mercury contamination affects birdsong

(The South River, Shenandoah Valley, Virginia, USA)

Although mercury can be found naturally throughout the environment, local concentrations may be increased by pollution from industries and mines. Once mercury atoms join together with a carbon and three hydrogen atoms, they form a compound known as methylmercury, the most "bioavailable" type of mercury--in other words, the type most capable of doing damage to a variety of organisms. Concentrations of mercury increase at each subsequent stage in the food chain. So, for instance, a wren will contain more mercury than the spiders it eats, while a snake will contain more mercury than the wrens it eats. In habitats exposed to mercury contamination, this can be a big problem, since even relatively small concentrations of mercury can cause damage to the nervous system.

A team from the College of William and Mary recently demonstrated how this mercury-driven nervous system damage can lead to behavioral abnormalities. They studied birds along the South River in Virginia, an area that had been contaminated by industrial mercury during 1929-1950. Previous work in the area had shown elevated levels of mercury in both the blood and the feathers of resident birds. The levels were similar to those known to cause behavioral abnormalities in common loons (Gavia immer), inspiring the William and Mary researchers to take a closer look at their birds. Specifically, they investigated song performance in four species:

(Song sparrow, Melospiza melodia)

(House wren, Troglodytes aedon)

(Carolina wren, Thryothorus ludovicianus)

(Eastern phoebe, Sayornis phoebe)

The first three species, all learn their songs as are juveniles. In the phoebe, on the other hand, song is innately programmed, and juveniles grow up knowing how to sing a "species-normal" song regardless of what they hear when they are young--even if they hear nothing at all.

For all three of the song-learning species, song parameters were significantly different in contaminated sites than in reference sites. Specifically, contaminated wrens sang shorter songs with fewer notes. They also sang at a lower peak frequency, meaning that they placed most of their volume emphasis at a lower pitch. Contaminated sparrows sang songs with fewer note types. Their "buzz note," a special syllable that is used by males to advertise their attractiveness, was lower-pitched and covered a smaller bandwidth--in other words, it was less complex, and therefore probably a bit easier to perform, than buzz notes sung by males at clean sites. Notably, mercury levels had no effect on any parameters measured for phoebe songs, indicating that song performance is not impacted by mercury contamination in this species.

Although it is possible that mercury contamination could somehow make song performance more difficult--for instance, by impacting muscle control--the marked difference between song-learners and the phoebe suggests that mercury has an effect during the song-learning stage. Previous laboratory work in monkeys has shown that mercury can lead to deafness in the upper frequency range. A similar trend in birds would certainly help explain why the sparrow and both wrens produced songs that emphasized lower frequencies--perhaps these are the only notes they could hear, and therefore memorize. The authors stress that future work will be needed to develop a more detailed understanding of how mercury could alter singing behavior by impacting growth and developmental pathways, or perhaps by disrupting birds' physiology.

Males use song to attract females and warn off rival males--two behaviors that have significant impacts on breeding success. Thus, regardless of the mechanism by which it affects individual birds, mercury contamination poses a clear risk to avian populations, and probably many other species that share their habitat--even as long as 60 years after the pollution has ceased.

Hallinger, K.K., Zabransky, D.J., Kazmer, K.A., and Cristol, D.A. 2010. Birdsong differs between mercury-polluted and reference sites. The Auk 127(1):156-161.

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

Thursday, 14 July 2011

Urbanization alters food consumption patterns among lake-dwelling crayfish

You've probably heard of the saying, "You are what you eat," but what about "You are where you eat"? Using a method called carbon stable isotope analysis, which looks at the ratios of two forms of carbon (13C and 12C), scientists can tell where an animal's food comes from. In lakes, for example, food from open water areas has a depleted 13C:12C, food from the lake bed near the shoreline has an enriched ratio, and food from terrestrial resources (also called "subsidies," indicating items that fall, or are washed, in from land) has a ratio intermediate between these two values. Thus, by collecting tissues from animals throughout a lake, researchers can determine which area of the lake provides the food the animals are eating.

Recently, this technique was utilized by collaborators from the University of Washington in Seattle, Washington, USA, and Niigata University in Japan, in order to evaluate the impacts of shoreline urbanization on food resources in lakes of different sizes. The researchers collected samples from 14 lakes in the US and Japan and looked for relationships between 13C:12C, degree of urbanization, and size of lake. They focused their efforts on the signal crayfish, Pacifastacus leninusculus, a long-lived, omnivorous crustacean that likely plays an important role in "ecosystem engineering" because of the amount of detritus that it processes while feeding. Thus, any effects of urbanization on the diet of this species probably has wide-ranging impacts on the whole lake.

(A signal crayfish, Pacifastacus leninusculus. Although this species is native to western North America, it can now be found around the world.)

The researchers found that shoreline urbanization had an effect on 13C:12C, indicating that it influenced the amount of terrestrial resources entering the aquatic environment. However, the effects of urbanization differed depending on lake size. In large lakes, there was little impact on 13C:12C. However, in small lakes, crayfish had more enriched 13C:12C, indicating that they were eating more locally-generated food than food that was being washed in from land. This suggests that urban development had either diminished the availability of potential food items, or had prevented them from being deposited into the lakes (for instance, as a result of retaining walls or other blocking structures)--or both. Given that anthropogenic habitats are generally characterized by lower levels of plant material and high levels of impervious surface such as cement and blacktop, this is probably not surprising.

The authors report that these results are consistent with another recent study that found reductions in terrestrial subsidies to lake consumers in areas with shoreline development. These subsidies are important for stabilizing populations, communities, and food webs. When these are not available, organisms in lakes may face more competition for the resources that are generated within the lake itself, potentially leading to shortages. This can affect not only individual species, but also the ecosystem function of the lake as a whole. If the price of lakeside property wasn't already enough to put you off the idea of settling there, maybe the negative impacts of shoreline developments will be.

Larson, E.R., Olden, J.D., and Usio, N. 2011. Shoreline urbanization interrupts allochthonous subsidies to a benthic consumer over a gradient of lake size. Biology Letters 7:551-554.

Thanks to http://www.essexbiodiversity.org.uk/Default.aspx?pageid=148 for providing the image used in this post.

Wednesday, 13 July 2011

Spiders and mosquitoes like the scent of humans

An apparent example of convergent evolution has just been reported for Anopheles gambiae, an African mosquito species that can spread the human malaria vector, and Evarcha culicivora, an East African jumping spider that feeds (indirectly) on vertebrate blood.

After noticing the abundance of E. culicivora in and around human dwellings, collaborators from the University of Canterbury (Christchurch, New Zealand) and the International Centre of Insect Physiology and Ecology (Mbita Point, Kenya) decided to test whether the spiders used human scent to locate, and move towards, these areas. The goal of the spiders would not be to feed directly on humans, but instead to capture recently-gorged mosquitoes and consume human blood second-hand. Previous work has shown that the spiders have excellent eyesight, but also that they are capable of using olfaction alone to identify prey. Thus, it seemed possible that they might use their sense of smell to locate the food of their food, positioning themselves not only near mosquitoes, but specifically near ones that were full of blood.

(Anopheles gambiae taking a drink)

To test this, the researchers built a set of interconnected stimulus and test chambers. The stimulus chamber was connected by a set of hoses to 16 separate holding chambers, which were then connected to exit chambers. The entire system was ventilated, such that scent from the stimulus was blown into the holding chambers, in each of which sat a spider. Once the ventilation had begun, the researchers measured how long it took each spider to move from its holding chambers into its exit chamber. Spiders that found the ventilated stimulus scent interesting/attractive would be more likely to linger in the holding chamber for a longer period of time. Each spider was subjected to two trials: one in which the stimulus was a pair of white cotton socks that had been worn continuously for 12 hours preceding the trial, and one in which the stimulus was a pair of clean, unworn socks. The researchers studied 109 spiders altogether--27 adult males, 21 adult females, 32 small juveniles, and 29 large juveniles. This allowed them to investigate potential differences related to sex and age.

(East African jumping spider, Evarcha culicivora)

The results were pretty dramatic. All types of test animals spent significantly more time in the holding chamber when worn socks were used as a stimulus than when clean, unworn socks were used. Further, there were no behavioral differences between males and females, small and large juveniles, or adults and juveniles. Given the universality of the response to human scent, and the fact that the test spiders were captive-bred and had not been exposed to similar scents in the past, these results suggest that the spiders do not learn over time to associate human odors with a meal. Rather, this appears to be an innate response--one that helps attract them towards areas where they will find food.

If there is any lesson to be learned here, it is that you should try to smell as clean as possible if you are visiting Africa and don't want to run in to too many jumping spiders. Unfortunately, though, Anopheles mosquitoes locate their victims using not only human scent compounds, but also carbon dioxide emissions, heat, and moisture. So no matter how clean you plan to be, if you want to avoid mosquitoes, you'll need to pack some bug spray--and quinine pills.

Cross, F.R. and Jackson, R.R. 2011. Olfaction-based anthropophily in a mosquito-specialist predator. Biology Letters 7:510-512.

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