Article Review: Female Eastern Hog-Nosed Snakes (Heterodon platirhinos) choose nest sites that produce offspring with phenotypes likely to improve fitness

This article is about a study done to determine if female Eastern Hognose snakes actively choose their nesting sites based upon temperature to promote the development of healthier offspring. To do this, the researchers first had to determine the average temperatures of nest sites in the wild.  So, they located 21 nests and placed temperature recording devices next to the eggs.  They also placed one of these devices at a similar location 50 m away from each nest, but at the same depth as the actual nest.  This was done to find the temperatures of other possible nest sites in which the snakes could have laid their eggs.  This research led the scientists to determine that the average temperature of actual nest sites was 24.6 degrees Celsius, while the average temperature of the possible nest sites was 22.2 degrees Celsius.

During the second year of the study, the researchers collected eggs from 8 nests.  Half of the eggs were then incubated at 24.6 degrees Celsius and the other half at 22.2 degrees Celsius.  Just after hatching, the snakes were taken from the nests and their responses at being handled were recorded and scored.  No response by the snakes was given a score of 0, hissing was scored a 1, body flattening was scored a 2, an attempt to flee was given a 3, striking at the handler was given a 4, and the trick of playing dead was given a 5.  If the baby hognose snake did more than one of these responses, it was given the cumulative score of both.  Therefore, each snake could score up to 15 points.  At 3 days after hatching, snout-vent length, weight and swimming speed was also recorded to determine the physical fitness of each hatchling. 

From this research, the scientists determined that both the over-all average temperature and the hourly average temperatures were higher for actual nest sites than for the other possible nests sites, showing that the females hognose snakes probably do attempt to lay their eggs in warmer locations.  The second part of this research showed that the two different incubation temperatures did not affect hatching success rates or cause differences in the number of responses due to handling.  However, the eggs that were incubated at the lower temperature did hatch an average of 13 days later than the eggs in the higher temperature.  Also, the snakes from the higher temperature incubator swam faster and were on average longer than the snakes from the lower temperatures.

This research is significant because it shows that female hognose snakes can choose warmer locations to lay their eggs.  This can lead to larger-hatching and faster snakes, which have a better chance of survival from predators.  They also hatch earlier, which will give them more time to eat and store energy in preparation for hibernation, which occurs pretty soon after hatching for this species. 



Title:  Female Eastern Hog-nosed Snakes (Heterodon platirhinos) choose nest sites that produce offspring with phenotypes likely to improve fitness
Authors:  C. A. Peet-Pare and G. Blouin-Demers
Journal:  Canadian Journal of Zoology

http://www.nrcresearchpress.com/doi/abs/10.1139/z2012-091#.UYHiO-rD_mJ