Listen to the commentary
Real Audio : MP3 download
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.
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.]
[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.
