Thursday, January 24, 2013

University of Illinois researchers study fate of snakes in a warming climate

University of Illinois researchers study fate of snakes in a warming climate

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I’m fonder of snakes than most people are. My family and I enjoy finding garter snakes in our yard, and I consider it an added bonus to see water snakes in a river when I’m fishing. My daughter even keeps a cornsnake for a pet. Attached as I am to snakes, however, I had never wondered much about how climate change will affect them. University of Illinois researcher Patrick Weatherhead has, though.

In a collaboration that included three graduate students over the course of about ten years, he assessed the likely consequences of a warming environment on ratsnakes. Ratsnakes are beautiful, nonvenomous creatures that can grow to six feet long and feed primarily on small rodents, although they also feed on birds and bird eggs when the opportunity presents itself.

Fortunately for purposes of the study, the researchers did not need to figure out how to create a warmer environment for their subjects in order to test their hypotheses. Instead, they took advantage of the fact that ratsnakes occupy a broad geographic range, and used latitude as a surrogate for climate change. That is, they compared the ability of ratsnakes to regulate their body temperature through behavior in three populations representing the north-to-south extent of their range: Ontario, Illinois and Texas. What they found was that ratsnakes in all three places will derive some benefit from a warmer climate.

Say, for example, future daytime temperatures in Illinois warm beyond the range that ratsnakes prefer for activity.

What would they do?

For an answer, Weatherhead and colleagues looked to the behavior of ratsnakes in Texas, where the climate of the present is approximately the same as the climate projected for Illinois within 50 years or so.

[Photo: Jinelle Sperry, who collaborated on the project, with Texas ratsnake at Fort Hood, Texas.]

When daytime temperatures in Texas get too hot for foraging, the researchers found, ratsnakes there wait until the cool of the night to go looking for food. Weatherhead expects that ratsnakes in Illinois will follow suit, although the ones in his study were still active strictly during the day. (He notes that there is already other anecdotal evidence of snakes raiding bird’s nests at night in Illinois.)

Increased nocturnal foraging may even provide a benefit to ratsnakes. At night they are more likely to catch adult birds on the nest and so eat them along with their eggs. In addition, ratsnakes hunting at night might be less vulnerable to the animals that prey on them when they’re active by day.

While the capacity to shift from hunting during the day to hunting at night may enable ratsnakes in Illinois to cope with global warming, Weatherhead emphasizes that it’s not likely to result in a plague of them. “They are not,” in his phrase, “a universally well-loved group of animals.” Their populations will still have to contend with diminishing habitat, high road mortality and the fact that people sometimes still kill them on purpose.

And what’s good for ratsnakes might be bad for other animals, especially the ones they eat and the ones that eat them. In Texas, for example, ratsnake predation is already a problem for two species of endangered birds. “Things don’t live in isolation,” Weatherhead emphasizes. “It’s crucial that we understand how the components of various ecosystems might be affected if we’re going to work effectively to protect them in the face of global warming.”