Animal populations are shrinking due to their high-risk food-finding strategies

It hasn't been clear why certain animal populations are taking a hit, until now

Date:  November 15, 2018

Source:  Swansea University

A study using animal-attached technology to measure food consumption in four very different wild vertebrates has revealed that animals using a high-risk strategy to find rarer food are particularly susceptible to becoming extinct, as they fail to gather food for their young before they starve.

In the first study of its kind, a team of researchers led by Swansea University used thumbnail-sized electronic tags to record the movement of a number of individual condors, cheetahs, penguins and sheep in Argentina, South Africa and Northern Ireland over a six-year period.

Nicknamed the "Daily Diary," the tags record a mass of data -- everything from the animal's minute movements through space and time, to the temperature of its environment and light levels.

The results from the tags were used to measure:

The probability that each animal finds food items.

The size of the food items.

The effort used to find the food.

The effort used for all other activities such as rest, play etc.

Professor Rory Wilson of Swansea University, a world-leading expert on animal movement and lead author of the study, said: "We know that animal populations across the world are taking a hit, with the most charismatic animals like lions and cheetahs being among the worst affected, but up until now it hasn't been clear why.

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Humanity has wiped out 60% of animal populations since 1970, report finds

The huge loss is a tragedy in itself but also threatens the survival of civilisation, say the world’s leading scientists

Damian Carrington Environment editor

Tue 30 Oct 2018 00.01 GMTLast modified on Wed 31 Oct 2018 16.53 GMT

Humanity has wiped out 60% of mammals, birds, fish and reptiles since 1970, leading the world’s foremost experts to warn that the annihilation of wildlife is now an emergency that threatens civilisation.

The new estimate of the massacre of wildlife is made in a major report produced by WWF and involving 59 scientists from across the globe. It finds that the vast and growing consumption of food and resources by the global population is destroying the web of life, billions of years in the making, upon which human society ultimately depends for clean air, water and everything else.

“We are sleepwalking towards the edge of a cliff” said Mike Barrett, executive director of science and conservation at WWF. “If there was a 60% decline in the human population, that would be equivalent to emptying North America, South America, Africa, Europe, China and Oceania. That is the scale of what we have done.”

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Managed hunting can help maintain animal populations

May 21, 2018, University of Cambridge

Researchers studying the hunting of ibex in Switzerland over the past 40 years have shown how hunts, when tightly monitored, can help maintain animal populations at optimal levels.

The international team of researchers, led by the University of Cambridge and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), studied the hunt of Alpine ibex – a type of wild goat with long, curved horns – in the eastern Swiss canton of Graubünden by examining the horn size of more than 8,000 ibex harvested between 1978 and 2013, to determine whether average horn growth or body weight had changed over the last 40 years.

Their results, published in the Journal of Animal Ecology, reveal that unsurprisingly, ibex with longer-than-average horns are more likely to be shot than animals of the same age with shorter horns. However, due to tight controls placed on the hunt by the Swiss authorities, hunters tend to shoot as few animals as possible, to avoid violating the rules and incurring large fines.

Hunting for specific traits can place selective pressure on certain species, resulting in a negative evolutionary response. In their study, the researchers investigated whether the targeting of ibex with large horns would lead to a lower average horn size across the entire population.

They found that while even tightly-managed hunts cannot prevent hunters from targeting longer-horned animals, no long-term changes were found in the horn length of male ibex in Graubünden, which is most likely related to the fact that the numbers of ibex removed from the population by hunters is too small to have an evolutionary effect.

"Our most important finding is that ibex hunting over the last 40 years has not had a negative effect on the constitution of the animals," said WSL's Kurt Bollmann, the study's senior author.

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'Black swan' events strike animal populations

Date: March 7, 2017
Source: University of Washington

Black swan events are rare and surprising occurrences that happen without notice and often wreak havoc on society. The metaphor has been used to describe banking collapses, devastating earthquakes and other major surprises in financial, social and natural systems.

A new analysis by the University of Washington and Simon Fraser University is the first to document that black swan events also occur in animal populations and usually manifest as massive, unexpected die-offs. The results will appear online March 7 in the Proceedings of the National Academy of Sciences.

"No one has really looked at the prevalence of these black swan events in animal population abundance before," said lead author Sean Anderson, a UW postdoctoral researcher in aquatic and fishery sciences. "People associate the phrase with financial market crashes, and being able to take that term and apply it to another system gives context about what we're seeing in animal populations."

The researchers analyzed data from more than 600 animal populations, including mammals, birds, fishes and insects. They found that drastic changes in populations occurred in about 4 percent of the animals they surveyed, most commonly in birds.



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Aboriginal Hunting Practice Increases Animal Populations

Oct. 24, 2013 — In Australia's Western Desert, Aboriginal hunters use a unique method that actually increases populations of the animals they hunt, according to a study co-authored by Stanford Woods Institute-affiliated researchers Rebecca and Doug Bird. Rebecca Bird is an associate professor of anthropology, and Doug Bird is a senior research scientist.

The study, published today inProceedings of the Royal Society B, offers new insights into maintaining animal communities through ecosystem engineering and co-evolution of animals and humans. It finds that populations of monitor lizards nearly double in areas where they are heavily hunted. The hunting method -- using fire to clear patches of land to improve the search for game -- also creates a mosaic of regrowth that enhances habitat. Where there are no hunters, lightning fires spread over vast distances, landscapes are more homogenous and monitor lizards are more rare.

"Our results show that humans can have positive impacts on other species without the need for policies of conservation and resource management," Rebecca Bird said. "In the case of indigenous communities, the everyday practice of subsistence might be just as effective at maintaining biodiversity as the activities of other organisms."

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