Category: Environment

{The first documented evidence of wild chimpanzee mothers teaching their offspring to use tools has been captured by video cameras set to record chimpanzee tool-using activity at termite mounds in the Nouabalé-Ndoki National Park in the Republic of Congo, according to new research from anthropologists at Washington University in St. Louis.}

“Wild chimpanzees are exceptional tool users, but in contrast to humans, there has been little evidence to date that adult chimpanzees teach youngsters tool skills,” said Stephanie Musgrave, the study’s first author and an anthropology graduate student in Arts & Sciences.

“We found that mother chimpanzees in the Goualougo Triangle teach by transferring termite-fishing probes to their offspring,” Musgrave said. “In this population, chimpanzees select specific herb species to make their fishing probes, and they produce probes that have a particular brush-tipped design. By sharing tools, mothers may teach their offspring the appropriate material and form for manufacturing fishing probes.”

Published in the journal Scientific Reports, the study is based on research conducted in partnership with the Wildlife Conservation Society, the Lincoln Park Zoo, the Max Planck Institute and Franklin and Marshall College. The findings have important implications for the evolution of teaching.

“It is easy for us to take for granted the importance of sharing information to learn complex skills, as it is ubiquitous in humans,” said Crickette Sanz, associate professor of biological anthropology in Arts & Sciences at Washington University and co-author of the study. “Our research shows that the evolutionary origins of this behavior are likely rooted in contexts where particular skills are too challenging for an individual to invent on their own.”

Musgrave, Sanz and colleagues used video to capture examples of wild chimpanzee mothers transferring specialized termite-gathering tools to less-skilled, immature chimpanzees. These transfers, which are costly to tool donors but beneficial to tool recipients, meet the scientific criteria for teaching in wild apes.

“Tool transfers are costly for mothers, whose ability to forage for termites is reduced, but are beneficial for offspring, who gain increased opportunity to learn tool skills and gather termites. This is the first such evidence satisfying these criteria for teaching in wild apes,” Musgrave said.

“Identifying teaching among wild animals is difficult because one has to quantify the impact of possible teaching behaviors on both the teacher and the learner,” Musgrave said. “Using video footage from remote camera traps placed at termite nests in the chimpanzees’ home range, we were able to observe and quantify how sharing tools affected those who relinquished their tools as well as those who received them.”

Chimpanzees are exceptional among animals for their remarkable propensity to make and use tools. Since different groups of chimpanzees use different types of tools, the teaching process also may need to be customized to address local conditions.

“Studying how young chimpanzees learn the tool skills particular to their group helps us to understand the evolutionary origins of culture and technology and to clarify how human cultural abilities are similar to or different from those of our closest living relatives,” Musgrave said.

The findings have interesting implications for identifying the cognitive underpinnings of teaching. In humans, teaching involves an understanding of others’ abilities and the intention to help them learn. In this study, chimpanzee mothers both anticipated the youngsters’ need for a tool and devised strategies to reduce the effort necessary to provide them.

In examples captured in this study’s videos, mothers sometimes bring multiple tools to a termite nest; they may also divide their fishing probe in half lengthwise, giving one-half to their offspring and keeping the other half. This strategy provides their offspring with a usable tool without compromising their own ability to gather food, Musgrave said.

Washington University pioneered the use of remote video technology to study the behavior of wild chimpanzees in Congo, and now it is used at nearly every ape research site across Africa. “It is a very effective means of monitoring wildlife without increasing human impact. Our camera array also provides a means of monitoring the health of the forest, as other endangered species such as western lowland gorillas, forest elephants, and leopards are ‘captured’ on film,” Sanz said.

“In addition to our traditional tracking of wild chimpanzees through the forest each day, this remote video technology has been a force multiplier in expanding the scope of our research to several other chimpanzee communities,” Sanz said. “We have observed a generation of chimpanzee kids learn how to use these tool sets, without having to spend a decade habituating them to human presence or risk exposing them to anthropogenic diseases.”

{The tuneful behavior of some songbirds parallels that of human musicians.That’s the conclusion presented in a recent paper published by an international team of researchers, among them David Rothenberg, distinguished professor of philosophy and music in NJIT’s Department of Humanities. Other members of the team are from the City University of New York (CUNY), the Freie Universität Berlin and Macquarie University in Australia.}

“Temporal regularity increases with repertoire complexity in the Australian pied butcherbird’s song” was published online in Royal Society Open Science.

{{A Very Musical Species}}

The pied butcherbird, a very musical species, provided a wealth of intriguing data for analysis by co-author Eathan Janney, a Ph.D. candidate in the Department of Psychology at CUNY’s Hunter College. Janney based his analysis upon years of data collected and also analyzed by violinist and biomusicologist Hollis Taylor of Macquarie University, who has previously published extremely detailed analyses of butcherbird songs. “Since pied butcherbird songs share so many commonalities with human music,” Taylor writes, “this species could possibly revolutionize the way we think about the core values of music.”

In the past, claims that musical principles are integral to birdsong were largely met with skepticism and dismissed as wishful thinking. However, the extensive statistical and objective analysis of the new paper demonstrates that the more complex a bird’s repertoire, the better he or she is at singing in time, rhythmically interacting with other birds much more skillfully than those who know fewer songs. The accompanying video includes a sample of a butcherbird’s solo song, as well as the song of another butcherbird and an Australian magpie.

Co-author Ofer Tchernichovski, professor in the Hunter College Department of Psychology, finds that the butcherbirds “balance their performance to keep it in a sweet spot between boredom and confusion.” Constance Scharff, a co-author who directs the animal behavior laboratory at the Freie Universität Berlin, says “pied butcherbirds, not unlike jazz musicians, play around with their tunes, balancing repetition and variation.” This finding suggests that such musical virtuosity may signify more than just the evolution of a way for birds to establish territorial dominance and facilitate mating. It may also provide evidence that musical ability in birds was a precursor to the evolution of the many dimensions of musical ability in humans.

{{Inclusive Multidisciplinary Research}}

The paper is the product of inclusive multidisciplinary research. It integrates input from biologists, neuroscientists, musicians and engineers, including co-author Lucas C. Parra, a member of CUNY’s Department of Biomedical Engineering.

Rothenberg, who provided his unique perspective, says, “Science and music may have different criteria for truth, but sometimes their insights need to be put together to make sense of the beautiful performances we find in nature.”

Rothenberg has written extensively about the bond between humans and our surrounding natural world, a world we share with myriad other creatures. An earlier paper that he co-authored, “Investigation of Musicality in Birdsong,” published in Hearing Research touched upon aspects of the same topic explored in the recent Royal Society publication. Rothenberg’s book Why Birds Sing is an in-depth look at the subject that challenges neuroscientists to seriously consider music as a tool to help understand birdsong.

As a musician — he plays the clarinet and saxophone — Rothenberg has added the dimension of music to research connecting the living sounds of the natural world to traditions of global rhythmic innovation and improvisation. His book Thousand Mile Song is about making music with whales, and Bug Music, How Insects Gave Us Rhythm and Noise offers the provocative premise that listening to cicadas, as well as other humming, clicking and thrumming insects, fostered an innate sense of musical rhythm and synchronization over the long history of human evolution.

{Washington State University researchers say the world’s reservoirs are an underappreciated source of greenhouse gases, producing the equivalent of roughly 1 gigaton of carbon dioxide a year, or 1.3 percent of all greenhouse gases produced by humans.}

That’s more greenhouse gas production than all of Canada.

Writing in next week’s journal BioScience, the WSU researchers say reservoirs are a particularly important source of methane, a greenhouse gas that is 34 times more potent than carbon dioxide over the course of a century. Reservoir methane production is comparable to rice paddies or biomass burning, both of which are included in emission estimates of the Intergovernmental Panel on Climate Change, the leading international authority on the subject.

John Harrison, co-author and associate professor in the WSU Vancouver School of the Environment, last month attended a meeting in Minsk, Belarus, to discuss including reservoir emissions in a planned 2019 IPCC update of how countries report their greenhouse gas inventories.

Methane accounts for 80 percent

“We had a sense that methane might be pretty important but we were surprised that it was as important as it was,” said Bridget Deemer, WSU research associate and lead author. “It’s contributing right around 80 percent of the total global warming impact of all those gases from reservoirs. It’s a pretty important piece of the budget.”

The BioScience analysis, which drew on scores of other studies, is the largest and most comprehensive look to date at the link between reservoirs and greenhouse gases, Harrison said.

“Not only does it incorporate the largest number of studies,” he said. “It also looks at more types of greenhouse gases than past studies.”

Acre per acre, reservoirs emit 25 percent more methane than previously thought, he said.

The researchers acknowledge that reservoirs provide important services like electrical power, flood control, navigation and water. But reservoirs have also altered the dynamics of river ecosystems, impacting fish and other life forms. Only lately have researchers started to look at reservoirs’ impact on greenhouse gases.

“While reservoirs are often thought of as ‘green’ or carbon neutral sources of energy, a growing body of work has documented their role as greenhouse gas sources,” Deemer, Harrison and their colleagues write.

Gases from decomposing organic matter

Unlike natural water bodies, reservoirs tend to have flooded large amounts of organic matter that produce carbon dioxide, methane and nitrous oxide as they decompose. Reservoirs also receive a lot of organic matter and “nutrients” like nitrogen and phosphorus from upstream rivers, which can further stimulate greenhouse gas production.

In 2000, BioScience published one of the first papers to assert that reservoir greenhouse gases contribute substantially to global warming. Since then, there has been a nine-fold increase in studies of reservoirs and greenhouse gases. Where earlier studies tended to be confined to reservoirs behind power stations, the newer studies also looked at reservoirs used for flood control, water storage, navigation and irrigation.

The WSU researchers are the first to consider methane bubbling in models of reservoir greenhouse gas emissions. Also, while previous papers have found that young, tropical reservoirs emit more methane than older, more northern systems, this study finds that the total global warming effect of a reservoir is best predicted by how biologically productive it is, with more algae and nutrient rich systems producing more methane.

The authors also report higher per-area rates of methane emission from reservoirs than have been reported previously. This means that acre-for-acre the net effect of new reservoirs on atmospheric greenhouse gases will be greater than previously thought. Reservoir construction around the globe is expected to proceed rapidly in coming decades.

Largest study of reservoir greenhouse gas emissions

“There’s been a growing sense in the literature that methane bubbles are a really important component of the total emissions from lake and reservoir ecosystems,” said Deemer. “This study revisited the literature to try and synthesize what we know about the magnitude and control on methane emissions and other greenhouse gases — carbon dioxide and nitrous oxide.”

The result is that, in addition to being the largest study of reservoir greenhouse gas emissions to date, it is the first to comprehensively look at the flow of all three major greenhouse gases — carbon dioxide, methane and nitrous oxide — from reservoirs to the atmosphere.

{Bumblebees can learn to pull strings for food and pass on the ability to a colony, according to researchers at Queen Mary University of London (QMUL).}

Pulling strings to obtain food is an experiment often used to test the intelligence of apes and birds, but it is the first time this technique has been discovered in an insect.

Moreover the cultural spread of such a technique from a single informed individual has also been described for the first time in an invertebrate animal.

The results, published in PLOS Biology, show that rare innovator bees were able to solve the problem of pulling the string to reach a sugar water reward by themselves while most others could learn to pull the string when trained.

Naïve bees were then able to learn the task by observing a trained demonstrator bee while this skill was passed down through several generations of learners, ensuring its longevity in the population.

Dr Sylvain Alem, lead author of the study, said: “We found that when the appropriate social and ecological conditions are present, culture can be mediated by the use of a combination of simple forms of learning. Thus, cultural transmission does not require the high cognitive sophistication specific to humans, nor is it a distinctive feature of humans.”

Dr Clint Perry, another lead author of the study, added: “Despite the obvious differences between humans and other animals, understanding social learning and culture in animals holds a key to understanding the evolutionary roots of the peculiarities of social learning and culture in humans.”

To test the bees’ capacity for learning string pulling, they were presented with three artificial blue flowers with a string attached to each flower and placed under a small transparent Plexiglas table.

Initially 23 bees, of a group of 40, were able to be trained in a stepwise manner by placing the flowers and strings at progressively distant positions under the table. Another group of bees were given the opportunity to solve the task spontaneously, without any training, and only two of 110 were successful suggesting it is a rare occurrence.

Naïve bees were then allowed to observe trained bees pulling the string from a distance and 60 per cent of them successfully learned the skill. Finally trained bees were placed in colonies and researchers observed that the technique spread successfully to a majority of the colony’s worker bees.

Professor Lars Chittka, project supervisor, said: “We are ultimately interested in finding out what might be possible neural solutions to underpin such refined skills in bees. How can they do it with such small brains, and how can their miniature nervous systems manage such a diversity of behaviours and cognitive tasks?

“We are exploring this through modelling information processing in parts of the insect brain, and we find that often, exceedingly difficult tasks, for example in visual pattern recognition or floral scent learning, can be solved with extremely simple neural circuits. We are still a long way from understanding the required neural circuitry for string-pulling, however.”

{An incredibly advanced hearing system which enables a group of insects to listen to the same sound twice with each ear, helping them to locate the sound’s origin with pinpoint accuracy, has been discovered by scientists at the University of Lincoln, UK.}

The new Leverhulme-funded research set out to explore how Copiphora gorgonensis — a bush-cricket native to Colombia, South America — is able to hear sound signals from potential mates and to detect the sound source.

Unlike vertebrates, bush-crickets’ ears are located in their forelegs. Each front leg exhibits a single ear below the knee with two eardrums (also known as tympanic membranes), which are backed by a narrow cylindrical tube (the acoustic trachea) running along the leg internally and opening out on the side of the insect’s body.

The researchers found that a single sound actually arrives at the bush-crickets’ ears twice, at different times and with different amplitudes, using the external and internal paths. The eardrums in each leg receive sound from the external side, and internally via the tracheal tube, making this type of ear a ‘pressure difference receiver’. This dramatically improves their ability to locate the sound source.

This significant new discovery helps to explain how these nocturnal insects use their advanced hearing systems to successfully locate their mating partners in the dark.

Dr Fernando Montealegre-Z from the University of Lincoln’s School of Life Sciences led the study. He explained: “Our research used advanced technologies to show how these bush-crickets receive sound signals in a way that enables them to detect their original source. We showed that the sound arrives at each tympanal membrane twice; externally at the normal speed of sound in air and then again internally via the acoustic trachea inside the animal, at a slightly slower speed. Curiously, the sound travelling inside the tracheal tubes is also amplified because the tube has the effect of an acoustic horn, a bit like an ear trumpet. Taken together, this means this tympanal membrane is receiving the signal twice — the first time at normal sound speed and with no amplification, and the second time slower but louder.

“In mammals, ears are located on the sides of the head and their position and distance is enough to cause slight differences in the time a signal arrives, and also to produce amplitude differences between both ears. As these insects are too small to have ears in their heads, their location in the legs coupled with the tubing system allows the insect to hear a sound four times; twice in each ear. As they are nocturnal and the males sing to attract distant females for mating, these findings explain how females are so good at finding the best singing males in the dark and helps us to really understand how such sensitive and efficient hearing systems work.”

The research was conducted as part of a pioneering project funded by the Leverhulme Trust to examine how insects have evolved incredible ultrasonic hearing abilities. A grant of £250,000 was awarded to support Dr Montealegre-Z’s work, which aims to develop an integrated understanding of the evolution of ultrasonic hearing in bush-crickets.

The findings are published in the Journal of the Royal Society Interface in a new paper authored by Dr Thorin Jonsson, also from Lincoln’s School of Life Sciences.

Dr Jonsson said: “Scientists previously had relatively little knowledge about the workings of the acoustic trachea and what happens to a sound signal when inside this part of the ear. The results we gathered are therefore extremely interesting, as they show just how the speed of the sound is slowed down to delay it reaching the internal surface of the eardrum. This produces a time-lag and ultimately means the insect has the opportunity to hear the same sound twice.

“Understanding this highly sensitive and very delicate mechanism provides a fascinating insight into how these insects use their ears to locate potential mates and might also inspire other areas of research, such as engineering or micro-robotics.”

{Doubling of the carbon dioxide concentration will cause global plant photosynthesis to increase by about one third, according to a paper published in the journal Nature.}

The study has relevance for the health of the biosphere because photosynthesis provides the primary food-source for animal life, but it also has great relevance for future climate change.

Vegetation and soil are currently slowing down global warming by absorbing about a quarter of human emissions of carbon dioxide. This land carbon sink is believed to be in part due to increases in photosynthesis. It is widely accepted that plant photosynthesis will increase with carbon dioxide, so long as nutrients, such as nitrogen and phosphorus, are not limiting.

Global Earth System Models (ESMs) all predict that global photosynthesis will increase with carbon dioxide, but they differ by a factor of three in the size of this ‘CO2 fertilization’.

The authors of the Nature study, which are based at DLR in Germany and the University of Exeter in the UK, have discovered that the size of the CO2 fertilization is revealed by how the seasonal cycle in carbon dioxide concentration varies in the atmosphere.

Lead author of the study, Sabrina Wenzel of DLR explains: “the carbon dioxide concentrations measured for many decades on Hawaii and in Alaska show characteristic cycles, with lower values in the summer when strong photosynthesis causes plants to absorb CO2, and higher-values in the winter when photosynthesis stops. The peak-to-trough amplitude of the seasonal cycle therefore depends on the strength of the summer photosynthesis and the length of the growing season.”

The measurements made on Hawaii and in Alaska show an increasing amplitude of the seasonal cycle, but what does this mean for the future? The Wenzel et al. study answers that question, by showing a link between the increase in CO2 amplitude that a model simulates and the CO2-fertilization that it predicts.

This in turn means that the observed increase in the CO2 amplitude can be converted into a much improved estimate of the CO2-fertilization, which the authors call an Emergent Constraint.

Co-author Professor Peter Cox, of the University of Exeter, summarises the consequences of the study: “despite nutrient limitations in some regions, our study indicates that CO2-fertilization of photosynthesis is currently playing a major role in the global land carbon sink.

“This means that we should expect the land carbon sink to decline significantly when we begin to stabilize CO2.”

{Princeton University researchers have compiled 30 years of data to construct the first ice core-based record of atmospheric oxygen concentrations spanning the past 800,000 years, according to a paper in the journal Science.}

The record shows that atmospheric oxygen has declined 0.7 percent relative to current atmospheric-oxygen concentrations, a reasonable pace by geological standards, the researchers said. During the past 100 years, however, atmospheric oxygen has declined by a comparatively speedy 0.1 percent because of the burning of fossil fuels, which consumes oxygen and produces carbon dioxide.

Curiously, the decline in atmospheric oxygen over the past 800,000 years was not accompanied by any significant increase in the average amount of carbon dioxide in the atmosphere, though carbon dioxide concentrations do vary over individual ice age cycles. To explain this apparent paradox, the researchers called upon a theory for how the global carbon cycle, atmospheric carbon dioxide and Earth’s temperature are linked on geologic timescales.

“The planet has various processes that can keep carbon dioxide levels in check,” said first author Daniel Stolper, a postdoctoral research associate in Princeton’s Department of Geosciences. The researchers discuss a process known as “silicate weathering” in particular, wherein carbon dioxide reacts with exposed rock to produce, eventually, calcium carbonate minerals, which trap carbon dioxide in a solid form. As temperatures rise due to higher carbon dioxide in the atmosphere, silicate-weathering rates are hypothesized to increase and remove carbon dioxide from the atmosphere faster.

Stolper and his co-authors suggest that the extra carbon dioxide emitted due to declining oxygen concentrations in the atmosphere stimulated silicate weathering, which stabilized carbon dioxide but allowed oxygen to continue to decline.

“The oxygen record is telling us there’s also a change in the amount of carbon dioxide [that was created when oxygen was removed] entering the atmosphere and ocean,” said co-author John Higgins, Princeton assistant professor of geosciences. “However, atmospheric carbon dioxide levels aren’t changing because the Earth has had time to respond via increased silicate-weathering rates.

“The Earth can take care of extra carbon dioxide when it has hundreds of thousands or millions of years to get its act together. In contrast, humankind is releasing carbon dioxide today so quickly that silicate weathering can’t possibly respond fast enough,” Higgins continued. “The Earth has these long processes that humankind has short-circuited.”

The researchers built their history of atmospheric oxygen using measured ratios of oxygen-to-nitrogen found in air trapped in Antarctic ice. This method was established by co-author Michael Bender, Princeton professor of geosciences, emeritus.

Because oxygen is critical to many forms of life and geochemical processes, numerous models and indirect proxies for the oxygen content in the atmosphere have been developed over the years, but there was no consensus on whether oxygen concentrations were rising, falling or flat during the past million years (and before fossil fuel burning). The Princeton team analyzed the ice-core data to create a single account of how atmospheric oxygen has changed during the past 800,000 years.

“This record represents an important benchmark for the study of the history of atmospheric oxygen,” Higgins said. “Understanding the history of oxygen in Earth’s atmosphere is intimately connected to understanding the evolution of complex life. It’s one of these big, fundamental ongoing questions in Earth science.”

{Free-roaming dogs can spread disease and kill wildlife}

Man’s best friend can sometimes be wildlife’s worst enemy. Free-roaming dogs, both feral and owned animals that run loose, spread rabies and other diseases, kill wild animals and have caused extinctions. They’re even to blame for thousands of human deaths every year. And yet dogs get little of the hatred aimed at feral cats — and only a fraction of the attention from scientists.

Perhaps that needs to change.

A new study places the domestic dog among the four invasive mammals that have caused the most extinctions of native species. Cats and rodents are the worst, responsible for 63 and 75 extinctions, respectively — mostly birds. Dogs have caused around 10 extinctions and threaten another 156 species, Tim Doherty of Deakin University in Australia and colleagues report September 16 in the Proceedings of the National Academy of Sciences.

So while dogs aren’t as bad as cats on the extinction scale, their impact shouldn’t be ignored, especially when you look more closely at the harm they can do. Though that can be a little difficult, Izabela Wierzbowska of Jagiellonian University in Krakow, Poland, and colleagues note in a study published in the September Biological Conservation. There is a “paucity of scientific studies on the ecological impact of domestic dogs,” especially at the national level, they note.

The researchers tried to rectify that by tallying up the wildlife killed by free-roaming dogs in Poland (a nation roughly the size of New Mexico). Wierzbowska and her team took advantage of Poland’s strict management of its rural lands, which are divvied up into 49 hunting districts where the mortality of game species must be reported every year. This meant the researchers could count kills by free-roaming dogs, both feral and owned.

From 2002 to 2011, the records showed that dogs killed an average of 33,000 wild animals each year, plus 280 or so livestock. That’s probably an underestimate, though, since it is unlikely that hunting district managers recorded every kill made by a stray dog.

Unlike cats, which tend to go for small prey, the dogs often took on much larger animals, such as deer and boar. But the dogs also killed plenty of smaller animals, including brown hare (which accounted for half of their kills), badgers and grouse. Dogs also killed animals protected from human hunters, such as the European hamster and the black grouse.

The scale of the killing was dwarfed by that done legally by humans, so it’s unlikely the dogs are going to drive Polish deer to extinction anytime soon. But there are plenty of other ways that dogs can harm wildlife, the researchers note. They carry and spread pathogens such as rabies and canine distemper virus (which threatens Siberian tigers, among other animals). Their very presence can change the behavior of wild animals, and not for the better. They compete with native wildlife for prey. And when they kill livestock, local wolves may take the blame, increasing wolf-human conflict.

Free-roaming dogs are also a huge threat to people. In India, where millions of dogs roam the streets, more than 20,000 people die each year from rabies. And even in the United States, free-roaming dogs can be a huge problem in cities, and especially in poor areas. I once heard a frightening story: A woman I met in the waiting room of the vet hospital explained that she was there after having to choose whether to save her child or her pet from a free-roaming dog that attacked them. She whisked her kid to safety on top of a car and hoped that the vet could save the pet dog she had to leave to take the brunt of the attack.

So before we start exterminating the world’s feral cat population (good luck with that), perhaps we should turn some of that energy on figuring out what to do about the dogs. Or even the rodents — since they’re the biggest problem of them all when it comes to driving other species extinct.