Monday, October 11, 2010

How Do Snakes Know When to Stop Feeding?

Feeding strategies in snakes have yet to be fully investigated. Feeding frequency is one of the more poorly understood aspects. While field studies suggest snakes ambush, actively search, or use a combination of both hunting strategies, little is known about the motivation for hunting behavior. A few studies on vipers suggest snakes may feed as few as five or six times per year. This however, cannot be applied to all snakes, particularly those species that consume numerous small prey items, such as the social insect-eating threadsnakes and blindsnakes, the earthworm-eating uropeltids, the small fish-eating homalopsids, and the fish egg-eating sea snakes. These species must feed much more frequently. Boas and pythons are well known for eating relatively few large prey and capable of fasting for long periods of time (as long as 36 months). One aspect of feeding is satiety, it has been studied extensively in other groups of vertebrates but it is poorly understood in reptiles. Torben P Nielsen and colleagues have now investigate time-dependent satiation in two species of constricting snakes the Ball Pythons (Python regius) and Yellow Anaconda (Eunectes notaeus). They show that satiation depends on both fasting time and prey size and they define satiation as the state achieved when a snake would not voluntarily consume a second prey presented to it Ball Pythons fed with mice of a relative small prey mass (the mice were 15% of the snake’s mass), satiety response occurred 6 to 12 hours after feeding, but 24 hours after feeding the pythons regained their appetite. When the pythons were give mice that were 10% of their body mass the snakes feed continually during the experiment. The Yellow Anacondas did not show the satiety response until they had been fed prey that was 20% of their mass, and the response develop between 6 to 12 hours after feeding, but it was statistically not significant. The anacondas remained satiated for 24 hours. Handling time (from strike until prey swallowed) increased with the prey’s body mass and handling time decrease between the first and the second prey, there was also a positive correlation between handling time and the mass of the snake.

Nielsen T. P., M. W. Jacobson, T. Wang 2010. Satiety and eating patterns in two species of constricting snakes. Physiology and Behavior. 2010 DOI: 10.1016/j.physbeh.2010.09.001

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