

Thursday, February 19, 2009

Hibernators Are Better Survivors

This is something I think I've known all along. Hibernators are indeed better at surviving, and this article explains why. I thought this would be a great discussion here. I remember back in 1992, I watched a documentary about dinosaurs and one of the things I remember was Bob Bakker's theory that dinosaurs were killed off by diseases. While it could be a plausible theory, I never bought it. I think he has since changed his way of thinking, but the things that kept me from believing his theory was that ammonites also died out and so did a lot of sea creatures, who could not catch land-based diseases. And they all died out at the same time as the dinosaurs. But I've quoted Bakker from a comment he made on one of the documentaries he did when he compared dinosaurs to frogs and frogs to elephants. Frogs were around when the dinosaurs were, and they managed to survive. Bakker asked, "What does an elephant do that a frog doesn't?" His answer was that elephants spread, meaning they migrate. I thought the more appropriate question was what does a frog do that an elephant doesn't? My answer was that frogs go underground and hibernate when times get tough. Who knows if any dinosaurs hibernated? Most likely not because they lived in such a lush landscape, except for maybe the species confined to the Antarctic region. But I don't know, my theories are 17 years old. What do you think? Here is the article:


Hibernating Animals Face Less Extinction Risk
Emily Sohn, Discovery News

Feb. 19, 2009 -- A spell of bad weather might send you running to bed. Plenty of animals act the same way, and it turns out the reclusive behavior can be a remarkably good way to avoid extinction.

Mammals that regularly hunker down, hibernate, or otherwise hide from the world are better at weathering environmental change than are less hermitic species, according to a new study. The finding offers a window into which animals might thrive as the climate changes and habitats vanish.

"Just imagine yourself in a war zone," said lead researcher Lee Hsiang Liow, a paleobiologist at the University of Oslo. "Having some food storage and a place to avoid harsh environmental conditions would help you survive that period while there was bombing outside in your habitat."

Liow and colleagues from both the University of Oslo and the University of Helsinki were originally looking in the fossil record for a link between body size and extinction rates among mammals.

An unexpected outcome of the study, published last year in the Proceedings of the National Academy of Sciences, was the hint that hibernation-like behaviors, which are more common in smaller animals, might help explain why smaller animals tend to be better survivors.

To test the idea, the scientists tapped into a database of more than 4,500 living mammal species. For most species, they looked at nine so-called sleep-or-hide behaviors -- including hibernation, using burrows or tunnels, and going into a state of torpor or dormancy. Next, the team looked up each species' category of conservation, as listed by the International Union for Conservation of Nature (IUCN).

The analyses, published this month in the American Naturalist, found that having at least one sleep-or-hide behavior made a species less likely to appear on the IUCN Red List as threatened or endangered. The category included black bears, hedgehogs, and raccoon dogs native to Asia.

The scientists used statistics to account for body size and range size -- both are strong predictors of an animal's risk of extinction. And still, the findings held.

"You can always find unique explanations or stories about why things happen to certain animals," Liow said. "What we're seeing here is that sleep-or-hide related traits are extra characteristics that could help predict extinction risk."

Conservation biologist Bill Toone was not surprised by the study's results.

"These animals are spending a lot of time in very insulated and protected areas," said Toone, executive director of EcoLife Foundation, a conservation group in San Diego. "Someone behind a cement wall would survive better than someone standing in the road when a big truck came by."

But, he said, identifying a group of animals that is especially good at surviving environmental change is an important finding. To him, the study also points to a scary future -- full of animals that spend lots of time underground.

"I see a world with far less diversity and probably more pest-level species," Toone said.

"When I think sleep-or-hide, my mind goes to gophers and rats."


Metalraptor said...

Many of the other known K-T survivors have been known to hibernate, such as crocodilians (the American and Chinese Alligators have been documented going into torpor), mammals (perhaps the reason why they fared better than the rest of the archosaurs), and squamates (hibernations has been documented in both snakes and lizards). And of course turtles hibernate too, can't forget turtles.

Metalraptor said...

They do know that bears don't go into true hibernation, just a state of torpor...right?

Anyway, if this idea is true, our next mass extinction might promote a world dominated by bats, since they are excellent hibernators...weird.

Dee TimmyHutchFan said...

A World dominated by bats, that's pretty much the World I had in mind in the future. At least in the skies.

Anonymous said...

This is Metalraptor...

You also do know that some scientists believe some ornithopods, such as Oryctodromeus and Leanellasaura hibernated, right?

Dee TimmyHutchFan said...

Hi Metalraptor.

No, I wasn't aware of any hibernating dinosaurs. I'm shocked they didn't make it.

Anonymous said...

Wait, wait, be careful of that assumption. The south australian small ornithopods _may_ have been burrowers, but not necessarily hibernators. That may explain why the small ornithopods went extinct during a chilling episode where much of southern Australia became closer to Montreal than lowland Oregon in climate.

Metalraptor said...

Other way around. Growth rings similar to those found in hibernating mammals have been found in Leanellasaura, but Oryctodromeus is the burrower (hence the name, Oryctodromeus).