Newswise — The Olympic Games are not just for humans anymore. Researchers in Australia put two species of venomous snakes through a competition that included sprint trials in a racetrack and wrapping around, thrashing, tongue flicking, and biting when held—and then scored the snakes’ responses. The results? If you were to come across one of these snakes in the wild, you might prefer it to be the small-eyed snake—it is more likely to flee than fight.
The study is reported in the March 2010 issue of the journal Herpetologica. Researchers used the controlled conditions of laboratory trials to test whether temperature, time of day, and type of encounter can predict a snake’s defensive responses.
Two species of Australian elapid snakes, small-eyed snakes (Cryptophis nigrescens) and broad-headed snakes (Hoplocephalus bungaroides), were selected to participate in these trials. Both are nocturnal but vary widely in their foraging patterns, which might explain differences in their defensive responses. The small-eyed snake travels widely to forage for food, while the broad-headed snake will lie in ambush within sun-warmed rocky retreats.
To test their speed, snakes were poked in the tail with a paintbrush to urge them to move forward. Their behavioral responses to a predator were observed after being seized around the middle by a gloved hand. These reactions were tested at three different temperatures—10, 20, and 30 degrees Celsius—and during both darkness and bright illumination, simulating night and day.
The data collected from these tests showed that snakes vary their defense responses based upon their environment at the time of encounter.• Because they are nocturnal creatures, the snakes displayed more intense antipredator behavior at night than during daylight hours.• When cold, both species of snakes tried immobility as a defense, becoming more vigorous in their responses at warmer temperatures.• Small-eyed snakes experienced less decline of their sprint speed and alertness at lower temperatures than did broad-headed snakes. This would be expected of an active nocturnal forager like the small-eyed snake and gives it a better chance to flee.• The wait-and-pounce habits of the broad-headed snake would leave it less prepared to flee, but also in a better location to make a stand, such as in a crevice or near rocks rather than out in the open.
Both species of snakes most often chose to flee from the perceived predator, but the broad-headed snake more consistently switched to retaliatory behavior and responded more intently at higher temperatures.
Full text of the article “Flexible Defense: Context-Dependent Antipredator Responses of Two Species of Australian Elapid Snakes,” Herpetologica, Volume 66, Issue 1, March 2010 is available at http://www2.allenpress.com/pdf/herp_66_1_1-11.pdf.
HerpetologicaHerpetologica is a quarterly journal of The Herpetologists' League, containing original research articles on the biology of amphibians and reptiles. The journal serves herpetologists, biologists, ecologists, conservationists, researchers, and others interested in furthering knowledge of the biology of amphibians and reptiles. To learn more about the society, please visit: http://www.herpetologistsleague.org.
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