Sleepyhead: The stripe-faced dunnart, an Australian mammal which maximises its survival in winter by going into a daily state of torpor – whereby it remains idol and lowers its body temperature. This may be a top tactic to protect against the changing environment, say scientists.
Credit: University of New England/Fritz Geiser
SYDNEY: Mammals that hibernate or burrow are less likely to become extinct than other mammals, according to research from Scandinavia.
The study, published in The American Naturalist, has found that mammals which use these tactics – such as bats, bears and squirrels, which lower their metabolic rate for extended periods, and moles or chipmunks, which tunnel underground – are less likely to crop up on endangered species lists.
Less stressed
The authors, from the Universities of Oslo, in Norway, and Helsinki, in Finland, looked at data on 4,500 mammal species and found that 443 of them hibernated, burrowed, or lived in caves and trees.
These mammals were then compared against the Red List of threatened species, compiled by the World Conservation Union (IUCN), and found to be endangered less frequently than species that didn't exhibit these behaviours.
The researchers controlled for the effect of other factors know to influence rates of extinction, such as body size and geographic location.
"[These mammals] have a greater propensity to survive in the current extinction crisis and probably also in past crises because of reduced exposure to environmental stress," said Lee Hsiang Liow, lead author and a biologist with the University of Oslo.
The "sleep-or-hide" tactics – also including other forms of dormancy, such as aestivation or torpor – are thought to offer extra cushioning against the risks posed by climate change, habitat loss and other negative environmental changes, said Liow.
The study is bolstered by previous research by the same team, which showed that species that sleep or hide are also likely to appear for longer periods in the fossil record.
Cryptic behaviour
However, Mikael Fortelius, co-author and palaeontologist from the University of Helsinki, believes these mammals are in a "catch 22" situation: "They survive longer, but in a changing world they run the risk of eventually becoming seriously obsolete," he said. "Species that don't sleep or hide may be short-lived, but they are also more likely to leave successful descendants."
Fritz Geiser, a zoologist from the University of New England, in Armidale, Australia, said that hibernating or burrowing mammals have a better chance of survival because they are able to conserve more energy.
"Animals that burrow or hibernate are able to conserve energy, and have a much better chance of survival… animals that run around all the time are hammered," he said. "Their cryptic behaviour also makes them very hard to find.
Geiser's own research, slated for publication in the German journal Naturwissenschaften, shows that the stripe-faced dunnart, a species of Australian marsupial, is able to maximise it's survival during winter by going into a daily state of torpor, where it conserves energy by remaining idol and lowering its temperature.
"Evidence suggests that the use of torpor, and the resulting reduction in energy requirements, can contribute to predator avoidance because less time is required for [risky] foraging," he said. "Avoidance of predators in turn increases lifespan, and results in selection of long-lived individuals and species."
