全球变暖有益捕鼠蛇的生存

Speculation about how animals will respond to climate change due to global warming led University of Illinois researcher Patrick Weatherhead and his students to conduct a study of ratsnakes at three different latitudes -- Ontario, Illinois, and Texas. His findings suggest that ratsnakes will be able to adapt to the higher temperatures by becoming more active at night. "Ratsnakes are a species with a broad geographic range so we could use latitude as a surrogate（代理的） for climate change," Weatherhead said. "What are ratsnakes in Illinois going to be dealing with given the projections for how much warmer it will be 50 years from now? Well, go to Texas and find out. That's what they're dealing with now. Snakes are ectotherms, that is, they use the environment to regulate their body temperature. We were able to compare ratsnakes' ability to regulate their temperature in Texas as compared to Illinois and Canada."

The research showed that ratsnakes in Canada, Illinois, and Texas would all benefit from global warming. "It would actually make the environment thermally better for them," Weatherhead said. "Texas is already too hot for much of the day so it may cause them to shift to even more nocturnal foraging there and stay active at night for more of the season."

As the higher temperatures associated with global warming begin to be more challenging for snakes in Illinois, will they be able to switch to nocturnal（夜的） foraging? "We think that won't be a problem for them," Weatherhead said. "We already know that Illinois snakes show some limited amount of nocturnal activity because there is anecdotal evidence for nocturnal nest predation by snakes."

Weatherhead said that as temperatures increase there are a lot of potential scenarios of what might happen in the ecosystem.

"If we start with the premise that with a thermal increase snakes will do better, the snake population may increase, but snakes are also facing diminished habitat and have a high road mortality. They are not a universally well-loved group of animals. People are known to purposely swerve（转弯） in the road to kill them. So, just because temperatures may become more beneficial for snakes it doesn't necessarily mean we'll have a plague of snakes. We may, however, have northern expansion of ranges," he said.

Weatherhead inserted tiny transmitters that emit radio pulses into ratsnakes to track their location and behavior. In order to save battery life through the winter months while the snake was hibernating, the transmitters were designed to slow its pulse rate (not the pulse rate of the snake) as the temperature dropped. "The relationship between the change in temperature and how it affects the transistor's pulse rate is pretty precise. We learned that we could predict the temperature of the snake from the pulse rate of the transmitter," he said.

Weatherhead's team also created snake models using a piece of copper pipe filled with water and painted black with a transmitter inside it. They placed the simulated snakes in various microhabitats--under a log, up in a tree, and on bare ground. This provided representative samples of all of the places that are available to a real snake while exposed to a range of weather conditions.

"We got the weather data from standard weather stations, then developed predictive equations from the weather conditions and the model snake's body temperature under each condition," Weatherhead said. "After you've sampled the environment once, then it's just the physical relationship between those environmental factors and the inanimate snake model which very closely mimics a real snake in those same circumstances.You plug the weather data into these equations and you can tell what temperature a snake in each of those environments would be at any time," he said.