Ear-generated Doppler shifts in bat biosonar

Date:  June 4, 2019

Source:  Virginia Tech

Anybody who has been passed by an ambulance at high speed has experienced a physical effect called the Doppler shift: As the ambulance moves toward the listener, its motion compresses the siren's sound waves and raises the sound pitch. As the ambulance moves away from the listener, the sound waves get dilated and the pitch is lowered. A listener wearing a blindfold could use this Doppler shift pattern to track the motion of the ambulance.

In a paper published by the Proceedings of the National Academy of Sciences, the authors, Rolf Mueller, professor of mechanical engineering in the College of Engineering, and his doctoral student, Xiaoyan Yin, demonstrate that the ears of bats come with a "built-in ambulance" that creates the same physical effect. Yin and Mueller think the study of ear-generated Doppler shifts in bat biosonar could give rise to new sensory principles that could enable small, yet powerful sensors. An example of this type of sensor would be for drones that can operate in dense foliage or autonomous underwater vehicles navigating near complex underwater structures.

"The animals move their ears fast enough so that sound waves that impinge on the ears are transformed by the motion of the ear surfaces and shifted to higher or lower frequencies," said Mueller. "In fact, the bat species studied (horseshoe bats and Old World Roundleaf bats) can move their ears so fast that Doppler shifts of around 350 Hz can be created. This is about seven times larger than the smallest Doppler shift the animals haven been shown to be able to detect."

Doppler shifts have long been known to play an important role in the biosonar system of bats such as the species studied by Mueller and Yin. The bats have the enviable ability to hunt in very dense vegetation, but to accomplish this, they have to solve the problem of how to distinguish a moth, their preferred prey, from hundreds of leaves that surround it.

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Koala drinking stations can reduce impact of climate change

Expert calls for urgent action to conserve iconic Australian species

Date:  June 5, 2019

Source:  University of Sydney

A long-held view that koalas get all their hydration from eating leaves has been overturned by new research published today from Dr Valentina Mella and colleagues at the University of Sydney.

The study in PLOS ONE offers hope in the fight to conserve this threatened species, with researchers finding that koalas will regularly use artificial water stations, particularly during hot and dry conditions.

"Drinking stations could help koalas during heat and drought events and might help mitigate the effects of climate change," said Dr Mella from the School of Life and Environmental Sciences.

Dr Mella also said drinking stations could prove a useful strategy to support other arboreal folivores such as gliders and possums in Australia and sloths, lemurs and some monkeys on other continents.

Koala populations along Australia's east coast have been declining due to lost habitat from deforestation, diseases such as chlamydia, attacks from feral animals, fire and vehicle collisions.

The Australian Department of Environment estimates that combined koala populations in Queensland and New South Wales declined from 326,400 in 1990 to 188,000 in 2010, a drop of 42 percent.

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Northeastern U.S. deer more susceptible to wasting disease than those to the west

Date:  June 6, 2019

Source:  Penn State

Some deer are more susceptible to chronic wasting disease that is spreading through herds of white-tailed deer across much of the United States, according to Penn State researchers, who have identified a panel of genetic markers that reliably predict which animals are most vulnerable to the contagious neurological disorder.

"The genetic variants that would make deer less susceptible to chronic wasting disease are in much lower frequency in the East, likely because they weren't needed," said David Walter, adjunct assistant professor of wildlife ecology. "Over a long period of time, their survivability may have been somehow favored by losing these genotypes. They weren't important until a disease like chronic wasting disease showed up. We have seen that deer with the more susceptible genotypes are in the majority."

Over the last decade or so, Walter's research group in the College of Agricultural Sciences has been studying how the movement, behavior and genetics of wild deer are affecting the spread of chronic wasting disease. Often referred to as CWD, it is a fatal prion disease affecting the deer family, and belongs to a group of similar diseases, such as mad cow disease and scrapie in sheep, called transmissible spongiform encephalopathies.

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New model predicts impact of invasive lionfish predators on coral reefs

Date:  June 6, 2019

Source:  University of Alberta

A new model is providing insight into the impact of invasive lionfish on coral reefs in the Atlantic Ocean and Caribbean Sea. The venomous predatory fish has invaded more than 7.3 million square kilometres in the Atlantic and Caribbean, wreaking havoc among native fish populations.

The method, developed and tested with coral reef fish in the Bahamas through an international collaboration of scientists in Canada, the United States, and United Kingdom, is based on the behaviours used by prey to avoid being eaten by predators that use different hunting tactics.

"Many scientists have speculated that invasive lionfish are so successful in the Atlantic because prey don't recognize them as a predator," explained Stephanie Green, assistant professor in the University of Alberta's Department of Biological Sciences and lead author.

Stephanie Green, assistant professor in the Department of Biological Sciences, swims alongside a lionfish.

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To see how invading predators change an ecosystem, watch the prey, say researchers

Date:  June 5, 2019

Source:  Princeton University

Invading predators can devastate an ecosystem. In fact, a leading cause of extinction is the introduction of predators into an isolated system like an island or a lake. The destruction is usually blamed on the predator's eating choices, but sometimes the key lies in the prey animals' responses, according to an international team of researchers led by Princeton's Robert Pringle.

"You really can't understand predator-prey interactions -- or how predators will affect biodiversity and ecosystems -- without understanding the behavior of the prey," said Pringle, an associate professor of ecology and evolutionary biology. "The ways in which prey change their behavior to avoid getting eaten is a hard thing to predict, but without understanding that, you can't predict anything else. Most theory in ecology simply assumes that predators eat prey, end of story. The real world is more complicated. But it's not so complicated that we can't get to the bottom of it."

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