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An unusual creature is coming out of winter’s slumber; here’s why scientists are excited

Duke Lemur Center recreates the seasonal swings of native habitat, helping to unlock the secrets of hibernation

dwarf lemurs
The fat-tailed dwarf lemurs are our closest hibernating relative. Researchers at the Duke Lemur Center have been changing up their care to more closely match the seasonal fluctuations they experience in the wild. Researchers at the Duke Lemur Center have been changing up their care to more closely match the seasonal fluctuations they experience in the wild. Photo by David Haring, Duke Lemur Center

DURHAM, N.C. — If you binged on high-calorie snacks and then spent the winter crashed on the couch in a months-long food coma, you’d likely wake up worse for wear. Unless you happen to be a fat-tailed dwarf lemur.

This squirrel-sized primate lives in the forests of Madagascar, where it spends up to seven months each year mostly motionless and chilling, using the minimum energy necessary to withstand the winter. While zonked, it lives off of fat stored in its tail.

Animals that hibernate in the wild rarely do so in zoos and sanctuaries, with their climate controls and year-round access to food. But now our closest hibernating relative has gone into true, deep hibernation in captivity for the first time at the Duke Lemur Center.

“They did not disappoint,” said research scientist Marina Blanco, who led the project. “Indeed, our dwarf lemurs hibernated just like their wild kin do in western Madagascar.”

The researchers say recreating some of the seasonal fluctuations of the lemurs’ native habitat might be good for the well-being of a species hardwired for hibernation, and also may yield insights into metabolic disorders in humans.

“Hibernation is literally in their DNA,” Blanco said.

Blanco has studied dwarf lemurs for 15 years in Madagascar, fitting them with tracking collars to locate them when they are hibernating in their tree holes or underground burrows. But what she and others observed in the wild didn’t square with how the animals behaved when cared for in captivity.

Captive dwarf lemurs are fed extra during the summer so they can bulk up like they do in the wild, and then they’ll hunker down and let their heart rate and temperature drop for short bouts — a physiological condition known as torpor. But they rarely stay in this suspended state for longer than 24 hours. Which got Blanco to wondering: After years in captivity, do dwarf lemurs still have what it takes to survive seasonal swings like their wild counterparts do? And what can these animals teach us about how to safely put the human body on pause too, slowing the body’s processes long enough for, say, life-saving surgery or even space travel?

To find out, Duke Lemur Center staff teamed up to build fake tree hollows out of wooden boxes and placed them in the dwarf lemurs’ indoor enclosures, as a haven for them to wait out the winter. To mimic the seasonal changes the lemurs experience over the course of the year in Madagascar, the team also gradually adjusted the lights from 12 hours a day to a more “winter-like” 9.5 hours, and lowered the thermostat from 77 degrees Fahrenheit to the low 50s.

The animals were offered food if they were awake and active, and weighed every two weeks, but otherwise they were left to lie.

It worked. In the March 11 issue of the journal Scientific Reports, the researchers show for the first time that fat-tailed dwarf lemurs can hibernate quite well in captivity.

For four months, the eight lemurs in the study spent some 70% of their time in metabolic slow-motion: curled up, cool to the touch, barely moving or breathing for up to 11 days at a stretch, showing little interest in food — akin to their wild counterparts.

Now that spring is afoot in North Carolina and the temperatures are warming, the lemurs are waking up. Their first physical exams after they emerged showed them to be 22% to 35% lighter than they were at the start but otherwise healthy. Their heart rates are back up from just eight beats per minute to about 200, and their appetites have returned.

“We’ve been able to replicate their wild conditions well enough to get them to replicate their natural patterns,” said Erin Ehmke, who directs research at the center.

Females were the hibernation champs, out-stuporing the males and maintaining more of their winter weight. They need what’s left of their fat stores for the months of pregnancy and lactation that typically follow after they wake up, Blanco said.

Study co-author Lydia Greene says the next step is to use non-invasive research techniques such as metabolite analysis and sensors in their enclosures to better understand what dwarf lemurs do to prepare their bodies and eventually bounce back from months of standby mode — work that could lead to new treatments for heart attacks, strokes, and other life-threatening conditions in humans.

Blanco suspects the impressive energy-saving capabilities of these lemurs may also relate to another trait they possess: longevity. The oldest dwarf lemur on record, Jonas, died at the Duke Lemur Center at the age of 29. The fact that dwarf lemurs live longer than non-hibernating species their size suggests that something intrinsic to their biological machinery may protect against aging.

“But until now, if you wanted to study hibernation in these primates, you needed to go to Madagascar to find them in the act,” Blanco said. “Now we can study hibernation here and do more close monitoring.”

This research was supported by the Duke Lemur Center.

CITATION: “On the Modulation and Maintenance of Hibernation in Captive Dwarf Lemurs,” Marina B. Blanco, Lydia K. Greene, Robert Schopler, Cathy V. Williams, Danielle Lynch, Jenna Browning, Kay Welser, Melanie Simmons, Peter H. Klopfer, Erin E. Ehmke. Scientific Reports, March 11, 2021. DOI: 10.1038/s41598-021-84727-3.

 

Press release from Duke University, by Robin A. Smith.

Alien frog invasion wreaks havoc on natural habitat

A warning on World Environment Day

The spotted-thighed frog is easily identified by the distinct spots on its thighs. Credits: UniSA/Christine Taylor

Indiscriminate feeding by an alien population of the carnivorous spotted-thighed frog – could severely affect the native biodiversity of southern Australia according to a new study by the University of South Australia.

The invasive amphibian – Litoria cyclorhyncha – which has hitchhiked across the Nullarbor from Western Australia – has now established a community of 1000-plus in Streaky Bay, South Australia, with sightings also confirmed on the Eyre Peninsula and at the Adelaide airport.

This is the first study of the spotted-thighed frog’s diet in its invaded range with the findings providing important biological information about the impact of the alien species on natural ecosystems.

Ecology experts, UniSA’s Associate Professor Gunnar Keppel and Christine Taylor, say the potential of the spotted-thighed frog spreading to other parts of Australia is very concerning given its destructive eating patterns.

“This frog is an indiscriminate eating machine that will devour just about anything it can fit into its mouth,” Taylor says.

“We’re talking about a relatively large, predatory tree frog that, as a species is alien to South Australia, and it could have devastating impact on invaded habitats.

“As it eats away at local species, it’s impacting the natural ecosystem, which can displace or destroy local food webs, outcompete native birds, reptiles and mammals for resources, and potentially change natural biodiversity.”

Biodiversity is the theme of this year’s United Nations World Environment Day.

Published in the Australian Journal of Zoology, the study examined the stomach contents of 76 spotted-thighed frogs across three habitats – an artificial wetland, seminatural bushland and an urban setting.

The carnivorous spotted-thighed frog will indiscriminately devour just about anything it can fit into its mouth. Credits: UniSA/Christine Taylor

On average, each frog had at least six prey items in its stomach, with prey estimated to include 200 different species, 60 per cent of which were beetles, spiders and insects. Native geckos, young frogs and mice were also identified as prey.

Introduced species can have terrible outcomes for Australia, if not understood well. The infamous introduction of the cane toad in the 1930s as a mechanism to control sugar cane beetles, is just one example. The failure of that initiative continues to ravage Australia’s ecology, with the cane toad now listed as a threatening pest under the Environment Protection and Biodiversity Conservation Act.

Assoc Prof Keppel says it is important that people understand how detrimental introduced species can be for whole environments. He warns that if the spread of the spotted-thighed frog is not kept under control they could dominate many ecosystems in south-east Australia, at the expense of the local flora and fauna.

“The spotted-thighed frog is obviously very mobile. Already it’s managed to travel more than 2000 kilometres and set up a colony in Streaky Bay. But its considerable tolerance of salinity and potential ability to withstand high temperatures could lead to further geographic spread, and if not controlled, it could extend further eastward into the Murray-Darling Basin,” Assoc Prof Keppel says.

“It’s vital that we continue to protect Australia’s biodiversity. Preventing further dispersal of the spotted-thighed frog is a high conservation priority.

“The state government should consider managing the invasive population of spotted-thighed frogs at Streaky Bay. This should include education programs to inform people about what to do if they find a frog, as well as the feasibility of exterminating the population in South Australia.

“Importantly, if you do see one of these critters in your travels – leave it be. We don’t want it hitchhiking any further.”

spotted-thighed frog
The spotted-thighed frog is native to southwestern Australia. Credits: Christine Taylor

Press release from the University of South Australia