Mathematics predicts a sixth mass extinction

In the past 540 million years, the Earth has endured five mass extinction events, each involving processes that upended the normal cycling of carbon through the atmosphere and oceans. These globally fatal perturbations in carbon each unfolded over thousands to millions of years, and are coincident with the widespread extermination of marine species around the world.

Scientists have analyzed significant changes in the carbon cycle over the last 540 million years, including the five mass 
extinction events. They have identified 'thresholds of catastrophe' in the carbon cycle that, if exceeded, would lead
 to an unstable environment, and ultimately, mass extinction [Credit: MIT]

The question for many scientists is whether the carbon cycle is now experiencing a significant jolt that could tip the planet toward a sixth mass extinction. In the modern era, carbon dioxide emissions have risen steadily since the 19th century, but deciphering whether this recent spike in carbon could lead to mass extinction has been challenging. That's mainly because it's difficult to relate ancient carbon anomalies, occurring over thousands to millions of years, to today's disruptions, which have taken place over just a little more than a century.

Now Daniel Rothman, professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences and co-director of MIT's Lorenz Center, has analyzed significant changes in the carbon cycle over the last 540 million years, including the five mass extinction events. He has identified "thresholds of catastrophe" in the carbon cycle that, if exceeded, would lead to an unstable environment, and ultimately, mass extinction.

In a paper published in Science Advances, he proposes that mass extinction occurs if one of two thresholds are crossed: For changes in the carbon cycle that occur over long timescales, extinctions will follow if those changes occur at rates faster than global ecosystems can adapt. For carbon perturbations that take place over shorter timescales, the pace of carbon-cycle changes will not matter; instead, the size or magnitude of the change will determine the likelihood of an extinction event.

Taking this reasoning forward in time, Rothman predicts that, given the recent rise in carbon dioxide emissions over a relatively short timescale, a sixth extinction will depend on whether a critical amount of carbon is added to the oceans. That amount, he calculates, is about 310 gigatons, which he estimates to be roughly equivalent to the amount of carbon that human activities will have added to the world's oceans by the year 2100.

Does this mean that mass extinction will soon follow at the turn of the century? Rothman says it would take some time -- about 10,000 years -- for such ecological disasters to play out. However, he says that by 2100 the world may have tipped into "unknown territory."

"This is not saying that disaster occurs the next day," Rothman says. "It's saying that, if left unchecked, the carbon cycle would move into a realm which would be no longer stable, and would behave in a way that would be difficult to predict. In the geologic past, this type of behavior is associated with mass extinction."

History follows theory

Rothman had previously done work on the end-Permian extinction, the most severe extinction in Earth's history, in which a massive pulse of carbon through the Earth's system was involved in wiping out more than 95 percent of marine species worldwide. Since then, conversations with colleagues spurred him to consider the likelihood of a sixth extinction, raising an essential question:

"How can you really compare these great events in the geologic past, which occur over such vast timescales, to what's going on today, which is centuries at the longest?" Rothman says. "So I sat down one summer day and tried to think about how one might go about this systematically."

He eventually derived a simple mathematical formula based on basic physical principles that relates the critical rate and magnitude of change in the carbon cycle to the timescale that separates fast from slow change. He hypothesized that this formula should predict whether mass extinction, or some other sort of global catastrophe, should occur.

Rothman then asked whether history followed his hypothesis. By searching through hundreds of published geochemistry papers, he identified 31 events in the last 542 million years in which a significant change occurred in Earth's carbon cycle. For each event, including the five mass extinctions, Rothman noted the change in carbon, expressed in the geochemical record as a change in the relative abundance of two isotopes, carbon-12 and carbon-13. He also noted the duration of time over which the changes occurred.

He then devised a mathematical transformation to convert these quantities into the total mass of carbon that was added to the oceans during each event. Finally, he plotted both the mass and timescale of each event.

"It became evident that there was a characteristic rate of change that the system basically didn't like to go past," Rothman says.

In other words, he observed a common threshold that most of the 31 events appeared to stay under. While these events involved significant changes in carbon, they were relatively benign -- not enough to destabilize the system toward catastrophe. In contrast, four of the five mass extinction events lay over the threshold, with the most severe end-Permian extinction being the farthest over the line.

"Then it became a question of figuring out what it meant," Rothman says.

A hidden leak

Upon further analysis, Rothman found that the critical rate for catastrophe is related to a hidden process within the Earth's natural carbon cycle. The cycle is essentially a loop between photosynthesis and respiration. Normally, there is a "leak" in the cycle, in which a small amount of organic carbon sinks to the ocean bottom and, over time, is buried as sediment and sequestered from the rest of the carbon cycle.

Rothman found that the critical rate was equivalent to the rate of excess production of carbon dioxide that would result from plugging the leak. Any additional carbon dioxide injected into the cycle could not be described by the loop itself. One or more other processes would instead have taken the carbon cycle into unstable territory.

He then determined that the critical rate applies only beyond the timescale at which the marine carbon cycle can re-establish its equilibrium after it is disturbed. Today, this timescale is about 10,000 years. For much shorter events, the critical threshold is no longer tied to the rate at which carbon is added to the oceans but instead to the carbon's total mass. Both scenarios would leave an excess of carbon circulating through the oceans and atmosphere, likely resulting in global warming and ocean acidification.

The century's the limit

From the critical rate and the equilibrium timescale, Rothman calculated the critical mass of carbon for the modern day to be about 310 gigatons.

He then compared his prediction to the total amount of carbon added to the Earth's oceans by the year 2100, as projected in the most recent report of the Intergovernmental Panel on Climate Change. The IPCC projections consider four possible pathways for carbon dioxide emissions, ranging from one associated with stringent policies to limit carbon dioxide emissions, to another related to the high range of scenarios with no limitations.

The best-case scenario projects that humans will add 300 gigatons of carbon to the oceans by 2100, while more than 500 gigatons will be added under the worst-case scenario, far exceeding the critical threshold. In all scenarios, Rothman shows that by 2100, the carbon cycle will either be close to or well beyond the threshold for catastrophe.

"There should be ways of pulling back [emissions of carbon dioxide]," Rothman says. "But this work points out reasons why we need to be careful, and it gives more reasons for studying the past to inform the present."

Author: Jennifer Chu | Source: Massachusetts Institute of Technology [September 20, 2017]

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North Atlantic right whale population decline confirmed

NOAA Fisheries researchers and colleagues at the New England Aquarium have developed a new model to improve estimates of abundance and population trends of endangered North Atlantic right whales, which have declined in numbers and productivity in recent years. The findings are published in the journal Ecology and Evolution.

A North Atlantic right whale mother and calf, sighted June 8, 2014, during an aerial survey by the Northeast 
Fisheries Science Center [Credit: NOAA Fisheries/Christin Khan, NEFSC]

Between 1990 and 2010, the abundance of North Atlantic right whales increased just under three percent per year, from about 270 animals in 1990 to 482 in 2010. After relatively steady increases over that time, abundance has declined each year since 2010 to 458 animals in 2015. The analysis shows that the probability that the population has declined since 2010 is estimated at 99.99 percent. Of particular concern is decline of adult females in the population, estimated at 200 in 2010 but 186 in 2015, the known deaths of 14 North Atlantic right whales this year, and the widening gap between numbers of males and females.

"Although our work directly reveals a relatively small decrease, the subtext is that this species is presently in dire straits," said lead author Richard Pace.

Pace is a large whale researcher at NOAA's Northeast Fisheries Science Center. Other authors include NEFSC whale researcher Peter Corkeron, and Scott Kraus of the New England Aquarium.

The new statistical method reported today provides a clearer and timelier picture of North Atlantic right whale numbers. While both existing methods and the new statistical method for estimating North Atlantic right whale numbers show a decline in the population since 2010, the new estimates are less affected by changes in whale distribution, less reliant on sighting frequency, and better account for animals that are still alive but are not frequently seen.

Right whale (Eubalaena glacialis) skim feeding, with baleen clearly visible 
[Credit: NOAA Fisheries/Elizabeth Josephson, NEFSC]

In the past few years, these whales have not aggregated as consistently at the times and places where they have in the past. This reduces the likelihood that they will be sighted since survey efforts are most efficient when conducted while whales are coming together in larger groups to feed, calve, and care for young. This change in behavior has made the census-based estimate of their populations less reliable than in the past, and led to development of the new statistical model for estimating abundance.

The New England Aquarium has conducted research on right whales for more than three decades and also maintains the North Atlantic Right Whale Catalog. All methods for estimating abundance rely extensively on this record. The catalog combines information on individually identified North Atlantic right whales collected through annual surveys undertaken by a variety of researchers. The result is a comprehensive photographic census of the population for at least the past 25 years.

For this study, data from more than 61,000 sightings were reviewed. Analysis included sighting histories from 658 whales, including 280 females, 328 males and 50 animals of unknown sex. Of the 658 whales seen during the study period of 1990 to 2015, 247 were first seen before 1990.

NOAA Fisheries works directly with fishermen and shipping companies to reduce harm that can be caused if whales entangle in gear or collide with ships, two well-documented causes of whale deaths and serious injuries, and with researchers throughout the region to understand the biology and condition of animals in the population. The agency is also assisting Canadian officials and scientists with their efforts to reduce risks to these whales in Canadian waters.

Source: NOAA Northeast Fisheries Science Center [September 19, 2017]

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Emerging disease further jeopardizes North American frogs

A deadly amphibian disease called severe Perkinsea infections, or SPI, is the cause of many large-scale frog die-offs in the United States, according to a new study by the U.S. Geological Survey.

This tadpole shows signs of a severe Perkinsea infection [Credit: William Barichivich, USGS]

Frogs and salamanders are currently among the most threatened groups of animals on the planet. The two most common frog diseases, chytridiomycosis and ranavirus infection , are linked to frog population declines worldwide. The new study suggests that that SPI is the third most common infectious disease of frogs.

Scientists with the USGS studied 247 frog die-offs in 43 states from 1999 through 2015. The researchers found that SPI caused 21 of the mass mortalities in 10 states spanning from Alaska to Florida, all involving tadpoles. Up to 95 percent of the tadpole populations died during the SPI mortality events.

"Amphibians such as frogs are valuable because they serve as pest control by eating insects like mosquitos, and they are food for larger predators," said Marcos Isidoro Ayza, a USGS scientist, University of Wisconsin-Madison post-doctoral fellow and the lead author of the study. "They're also exceptional indicators of ecosystem health. Like the proverbial canary in a coal mine, amphibians let us know when something in our environment is going awry."

This photomicrograph shows a liver of a frog with a severe Perkinsea infection [Credit: ​​​​​​(USGS]

The SPI die-offs occurred in tadpoles of 11 frog species, including the critically endangered dusky gopherfrog in its only remaining breeding locations in Mississippi. Most of the SPI events occurred in states bordering the Atlantic Ocean and Gulf of Mexico. However, SPI was also detected in Alaska, Oregon and Minnesota.

"Habitat loss, habitat fragmentation and disease are among the factors that contribute to amphibian declines," said Jonathan Sleeman, director of the USGS National Wildlife Health Center. "This study indicates that SPI is an additional disease that can further threaten vulnerable frog populations."

SPI is caused by a tiny one-celled parasitic organism called a protist. The SPI-causing protist, called Perkinsea, is highly resistant to disinfection agents such as common bleach. As a result, it is difficult to prevent the spread of Perkinsea, and SPI is able to reoccur at known locations.

"SPI in frogs may be under-diagnosed because it is not a disease for which they are typically screened," Isidoro Ayza said. "Incorporating routine screening of critical habitats for infected frogs is crucial to help understand the distribution of this destructive disease."

The disease kills tadpoles by causing multi-organ failure, and there is no cure or treatment for SPI at this time. SPI is not known to affect humans or pets.

Source: US Geological Survey [September 19, 2017]

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When it comes to the threat of extinction, size matters

Animals in the Goldilocks zone -- neither too big, nor too small, but just the right size -- face a lower risk of extinction than do those on both ends of the scale, according to an extensive global analysis.

Extinction risks are greater for animals at the small and large ends of the scale 
[Credit: Oliver Day, Oregon State University]

Reporting today in the Proceedings of the National Academy of Sciences, researchers who determined body masses for thousands of vertebrate animal species showed that the largest and smallest species face a greater risk of extinction than do mid-sized animals.

Disproportionate losses at the large and small ends of the scale raise the likelihood of significant changes to the way natural ecosystems function in forests, grasslands, oceans and even rivers and streams -- "the living architecture of the planet," the researchers wrote.

"Knowing how animal body size correlates with the likelihood of a species being threatened provides us with a tool to assess extinction risk for the many species we know very little about," said William Ripple, a distinguished professor of ecology at Oregon State University and lead author of the study.

Ripple and colleagues from the United States, Australia and Switzerland looked at the more than 27,000 vertebrate animal species assessed by the International Union for the Conservation of Nature in the so-called Red List. About 4,400 are threatened with extinction.

Among the groups of animals evaluated were birds, reptiles, amphibians, bony fishes, cartilaginous fishes (mostly sharks and rays) and mammals.

The largest animals are threatened principally with harvesting by humans. "Many of the larger species are being killed and consumed by humans, and about 90 percent of all threatened species larger than 2.2 pounds (1 kilogram) in size are being threatened by harvesting," said Ripple.

"Harvesting of these larger animals takes a variety of forms including regulated and unregulated fishing, hunting and trapping for meat consumption, the use of body parts as medicine and killing due to unintentional bycatch," the authors wrote.

Meanwhile, threats to the smallest animals may be grossly underestimated. The smallest species with high extinction risk consist of tiny vertebrate animals generally less than about 3 ounces (77 grams) in body weight. These diminutive species are mostly threatened by loss or modification of habitat. Examples include the Clarke's banana frog, sapphire-bellied hummingbird, gray gecko, hog-nosed bat and the waterfall climbing cave fish. Small species that require freshwater habitats are especially imperiled.

Different conservation strategies will be needed to address threats to the largest and smallest animals, the scientists said. Well known mammals at the large end of the scale -- whales, elephants, rhinos, lions -- have been the target of protection programs, but conservation attention is also needed for large-bodied species that are not mammals. They include large fish, birds, amphibians and reptiles such as the whale shark, Atlantic sturgeon, Somali ostrich, Chinese giant salamander and the Komodo dragon.

Human activity seems poised to chop off both the head and tail of the size distribution of life, the authors added, which will fundamentally restructure many ecological communities.

Source: Oregon State University [September 18, 2017]

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Old fish few and far between under fishing pressure

Like old-growth trees in a forest, old fish in the ocean play important roles in the diversity and stability of marine ecosystems. Critically, the longer a fish is allowed to live, the more likely it is to successfully reproduce over the course of its lifetime, which is particularly important in variable environmental conditions.

A large, old yelloweye rockfish [Credit: Victoria O'Connell]

A new study by University of Washington scientists has found that, for dozens of fish populations around the globe, old fish are greatly depleted -- mainly because of fishing pressure. The paper, published in Current Biology, is the first to report that old fish are missing in many populations around the world.

"From our perspective, having a broad age structure provides more chances at getting that right combination of when and where to reproduce," said lead author Lewis Barnett, a UW postdoctoral researcher at the School of Aquatic and Fishery Sciences and the Joint Institute for the Study of the Atmosphere and Ocean.

In forestry, a tree farm with only 20-year-old trees may be healthy and productive, but the loss of old-growth trees should not go unnoticed. The giant trees have unique traits that support a number of animal and plant species and make for a diverse, robust ecosystem. In a similar sense, the same is true for old fish.

"More age complexity among species can contribute to the overall stability of a community," Barnett said. "If you trim away that diversity, you're probably reducing the marine food web's ability to buffer against change."

The designation of an "old fish" varies from species to species, depending on life history. Some types of rockfish might live to 200 years, while few herring live past age 10.

After female fish release eggs, many factors must align for a healthy brood to hatch and grow to adult size. Because the marine environment is so variable, species might go a whole decade between successful broods. Older fish in a population have more years to produce eggs, increasing the chance for success over time.

The face of an old halibut fish [Credit: Andrea Pokrzywinski]

"In the marine world, the success rate of producing new baby fish is extremely variable," said co-author Trevor Branch, a UW associate professor of aquatic and fishery sciences. "I think of old fish as an insurance policy -- they get you through those periods of bad reproduction by consistently producing eggs."

In addition to having more opportunities to reproduce, older fish also behave differently than younger fish. As they age, some fish change what they eat and where they live in the ocean. They also take on different roles in the marine food web, sometimes becoming a more dominant predator as they get older, and bigger.

When you take old fish out of the mix, the diversity and stability of an ecosystem can suffer, the authors explain.

"Big fish are in a lot of ways different from smaller fish," said co-author Tim Essington, a UW professor of aquatic and fishery sciences. "Having that diversity acts as a hedge against risk and helps stabilize the system a bit."

The researchers looked at model output gathered from commercial and recreational fisheries and scientific observations that describe the status of fish populations over the years. In their analysis of 63 populations living in five ocean regions worldwide, they found that the proportion of fish in the oldest age classes has declined significantly in 79 to 97 percent of populations, compared with historical fishing trends or unfished figures, respectively. The magnitude of decline was greater than 90 percent in 32 to 41 percent of the groups.

This is mainly due to fishing pressure, the researchers say. In general, the longer a fish lives, the more encounters it has with fishing gear, and the greater the likelihood it will be caught. However, some environmental factors like disease and pollution might also contribute to the loss of old fish.

These findings could inform fisheries management, which often sets limitations based on the total weight of fish caught over a season without considering factors such as the size or age of a fish. The authors suggest fishing methods to protect young and old fish by prohibiting the harvest of fish below and above a specific size range. Other solutions include closing certain areas to fishing permanently, or rotating areas where fishing can take place each year to let fish grow older and bigger -- similar to agricultural crop rotations that allow the soil to recover between planting cycles.

Author: Michelle Ma | Source: University of Washington [September 14, 2017]

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Climate change challenges the survival of fish across the world

Climate change will force many amphibians, mammals and birds to move to cooler areas outside their normal ranges, provided they can find space and a clear trajectory among our urban developments and growing cities. But what are the chances for fish to survive as climate change continues to warm waters around the world?

Fish species in many river systems, including the John Day River pictured, will face the challenge of coping 
with warmer waters in the future [Credit: University of Washington]

University of Washington researchers are tackling this question in the first analysis of how vulnerable the world's freshwater and marine fishes are to climate change. Their paper, appearing online in Nature Climate Change, used physiological data to predict how nearly 3,000 fish species living in oceans and rivers will respond to warming water temperatures in different regions.

"Climate change is happening. We need tools to try to identify areas that are going to be the most at risk and try to develop plans to conserve these areas," said lead author Lise Comte, a postdoctoral researcher in the UW's School of Aquatic and Fishery Sciences. "It's important to look at the organisms themselves as we cannot just assume they will all be equally sensitive to these changes."

The researchers compiled data from lab experiments involving nearly 500 fish species, conducted over the past 80 years by researchers around the world. These standardized experiments measure the highest temperatures fish are able to tolerate before they die. This analysis is the first time these disparate data from lab experiments have been combined and translated to predict how fish will respond in the wild.

The researchers found that overall, sensitivity to temperature changes varied greatly between ocean-dwelling and freshwater fish. In general, marine fish in the tropics and freshwater fish in higher latitudes of the Northern Hemisphere were the most at risk when water temperatures warmed, the analysis showed.

This figure shows the risk that freshwater fish (top) and marine fish (bottom) could exceed their thermal limits 
by the year 2070. Blue indicates a low risk and red shows a high risk [Credit: University of Washington]

"Nowhere on Earth are fish spared from having to cope with climate change," said senior author Julian Olden, a UW professor of aquatic and fishery sciences. "Fish have unique challenges -- they either have to make rapid movements to track their temperature requirements, or they will be forced to adapt quickly."

Using years of data -- and relying on the fact that many fish species are taxonomically related and tend to share the same thermal limits -- the researchers were able to predict the breaking-point temperature for close to 3,000 species. Regional patterns then emerged when those data were paired with climate-model data predicting temperature increases under climate change.

For example, fish in the tropical oceans are already living in water that is approaching the upper range of their tolerance. They might not have much wiggle room when temperatures increase slightly. By contrast, in freshwater streams in the far north, fish are accustomed to cooler water temperatures but have much less tolerance for warming waters. Since the effects of climate change are acutely felt in high latitudes, this doesn't bode well for fish in those streams that have a small window for survivable temperatures.

Fish will either migrate, adapt or die off as temperatures continue to warm, the researchers explained. Given past evolutionary rates of critical thermal limits, it's unlikely that fish will be able to keep up with the rate at which temperatures are increasing, Olden said. The ability to move, then, is imperative for fish that live in the most critical areas identified in this analysis.

Currently, dams and other infrastructure may block fish from getting where they might need to be in the future; fish ladders and other means to allow fish to circumvent these barriers could be more readily used, although the effectiveness of these structures is highly variable.

Additionally, actions to restore vegetation along the edges of streams and lakes can help shade and reduce water temperature for the benefit of fish.

"Fishes across the world face mounting challenges associated with climate change," Olden said. "Looking forward, continued efforts to support conservation strategies that allow species to respond to these rapid changes are needed."

Author: Michelle Ma | Source: University of Washington [September 13, 2017]

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Back from the dead: how to revive a lost species

Scientists from around the world are hoping to return a lost species of giant tortoise to one of the world-famous Galápagos islands.

In 2008 the researchers found tortoises with the distinctive saddleback shells such as the adult tortoise, right, 
on Isabela Island in the Galápagos [Credit: Luciano Beheregaray, Flinders University]

The discovery of DNA links or ‘high ancestry’ to extinct Floreana species of giant tortoise means the mega-herbivore could one day be returned to the island for repatriation via a captive-breeding program – perhaps within the next five years.

Professor Luciano Beheregaray, Head of the Molecular Ecology Group at Flinders University, says the conservation effort will be a major milestone in jump-starting the recovery of the Foreana Island’s exotic ecosystem which critically depends on the mega herbivore.

The exciting discovery, outlined in Scientific Reports, describes how the discovery was made after an international expedition to a remote volcano on Isabela Island in the Galápagos found many giant tortoises with high ancestry from the extinct Floreana Island tortoise (Chelonoidis elephantopus).

Giant tortoises were transported by helicopter and then ship from the volcano’s slopes to the Galápagos National Park Breeding Center on the central island of Santa Cruz.

DNA analyses used by the experts from the US, Belgium, Ecuador, Greece, Italy and Australia, then assigned the ancestry of the relocated tortoises using reference databases containing data from all extant and extinct species of Galápagos giant tortoises.

The 23 relocated tortoises found to have high ancestry to the extinct Floreana species are now being used in a genetically-informed captive breeding program that aims to repatriate this species to Floreana Island.

“Our discovery and the captive breeding program raises the possibility that the extinct Floreana species could be revived,” says  ARC Future Fellow Professor Beheregaray, from Flinders University’s College of Science and Engineering (Biological Sciences).

Charles Darwin wrote about the harvesting of the species of tortoise found only on Floreana Island, which was exterminated within 15 years of his visit to the Galápagos in 1835.

Tortoises were removed from Floreana more than two centuries ago by mariners looking for food.

However, in 2008 the researchers found tortoises with the distinctive saddleback shells on Isabela, an island where native species have dome-shaped shells (see photo).

Several DNA-based analyses were then used to show that these animals were descendants of the Floreana species.

The latest study’s coordinator Adalgisa Caccone, from Yale University, says it was ironical that the haphazard translocations by mariners killing tortoises for food some 200 years ago has now created the unique opportunity to revive this lost species today.

As a result of that discovery, the Galápagos National Park, together with the Galápagos Conservancy, carried out an ambitious, logistically complex, and strenuous expedition in late 2015 to find and relocate genetic relatives of the extinct species of tortoise and to launch a breeding program aimed at restoring them to their native island.

“That expedition was a success,” says Professor Beheregaray.

Species are being lost at an unprecedented rate due to human-driven environmental changes. The cases in which species declared extinct can be revived are rare.

The geneticists are now working together with the Galápagos National Park and the Galápagos Conservancy to implement a monitored breeding program with the animals relocated from Isabela Island.

This program will strive to preserve in future generations the diversity of the breeders and to maximise the Floreana species’ genomic representation in their offspring.

The current plan is to release young tortoises on the island within five years.

Source: Flinders University [September 13, 2017]

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Monkey tool use threatens prey numbers, say researchers

Using tools to search for food is affecting primate prey numbers and could potentially lead to prey species extinction, new Oxford research suggests.

Using tools to search for food is affecting primate prey numbers and could potentially lead to prey species extinction, 
new Oxford research suggests [Credit: Amanda Tan]

Once thought to be a skill unique to humans, recent studies have shown that some animals, such as monkeys, apes, birds and otters, are able to use tools to find food that would otherwise be inaccessible to them.

Tool use has been a gift and a curse for human society, on the one hand allowing people to progress to become one of the most successful species on the planet, but on the other endangering and pushing many prey species to the brink of extinction, particularly in the case of ocean overfishing.

In new research published in the journal eLife and funded by the European Research Council, scientists from the Department of Anthropology and Archaeology at Oxford University have assessed whether tool use can negatively affect prey species in the same way it does in human society. Using the primate species macaques (Macaca fascicularis) as an example, the findings reveal that these monkeys not only use tools but experience the same adverse effects, such as prey decline, which could eventually lead to a loss of tool skills. The paper was presented today at the British Science Festival.

Led by Dr Lydia Luncz, a postdoctoral researcher at Oxford, the team used archaeological evidence to demonstrate that the macaques' use of tools to forage for shellfish in Khao Sam Roi Yot National Park in Thailand is affecting prey availability.

The researchers compared the availability, size and maturation stages of groups of shellfish between two islands inhabited by different-sized macaque populations against the stone artefacts uncovered on the island. In doing so, they were able to show how tool use has affected prey reproductive biology over time.

The findings show that this foraging behaviour has caused the monkeys to enter an 'ecological feedback loop', influencing both the size and amount of prey available over time. The evidence revealed an emerging pattern: both the size of the shellfish and the tools used to open them were found to be smaller on the island with many predators. If it continues, the researchers have speculated that these prey populations are likely to decline.

Without prey to forage on, the monkeys will also have no need to use the technique so might even experience a social regression and 'unlearn' how to use tools altogether.

Dr Luncz said: 'People often say that practice makes perfect – the more you do something the better you get at it. But the less you do it, the harder it becomes and the more you are likely to forget that skill completely. Our study shows that it is the same for monkeys. With no need to use the stones for foraging, the technique might be lost.

'As this is a learned social behaviour, in the long term there will be a generation of macaques that do not know how to use tools, and any associated benefit or trade with other species will be lost. Potentially, one day tool use might get reinvented by later generations, and it will be interesting to see how the skill is discovered and who they learn it from.

'This has interesting parallels to the evolution of human stone use, where stone technology might also have been lost and reinvented throughout history.'

The team will next build on this knowledge by visiting islands with monkey populations that do not currently use stone tools to dig for evidence that they may have done in the past.

Dr Luncz said: 'In archaeology, generally the deeper you dig the further you go back in time. The same methods used for human artefacts can tell us a lot about how species have evolved and adapted to environmental change over time.'

Source: University of Oxford [September 08, 2017]

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