Article Review: Tail breakage frequency as an indicator of predation risk for the aquatic snake Natrix maura

Tail breakage frequency as an indicator of predation risk for the aquatic snake Natrix maura

Authors:  Xavier Santos, Mónica Feriche, Raúl León, Aikaterini Filippakopoulou, Marta Vidal-García, Gustavo A. Llorente, Juan M. Pleguezuelos

In this article, the viperine snake (Natrix maura) was studied.  N. maura is native to the Iberian Peninsula and can be found in a variety of aquatic habitats.  This species has a large number of natural predators including a variety of birds, some mammals, and other snakes.  The viperine snake is frequently found living in fish farms which protect the snakes from predation as the fish pools are covered with wire mesh.  Since the snake populations found in the fish farms are not exposed to predators like natural populations are, they offered the researchers an opportunity to study predation factors in this species.  

A common feature of this species is the ability to break off their tails as a way to get away from their many predators.  The researchers wanted to test their hypothesis that different N. maura populations would have intraspecific variation in terms of tail breakage.  The researchers recorded sex, size measurements, and tail breakage in three different natural populations and compared them all to a population found at a fish farm.  They found that the data did support their hypothesis.  They found that larger individuals had a higher frequency of tail breakage and that sex did not have any significance.  Most importantly, the results showed that the frequency of tail breakage was significantly lower in the fish farm population compared to the three natural populations.  In the fish farm population 5.1% displayed signs of tail breakage, where as in the three natural population 18.7% showed signs of tail breakage.  Since there were no differences found between the three natural populations, they concluded that tail breakage was a good way to measure predation risk for N. maura.

This article was well written, however I think the experiment needs to be replicated.  There were not as much data for the snakes found in the natural habitats, and the fact that the snakes found in the fish farm were preserved and studied later adds more room for error.  I think the researchers may need to back up their findings with more raw data.

Article:  

Santos X, Feriche M, Pleguezuelos J, et al. Tail breakage frequency as an indicator of predation risk for the aquatic snake Natrix maura. Amphibia-Reptilia [serial online]. August 2011;32(3):375-383. Available from: Academic Search Complete, Ipswich, MA. Accessed April 28, 2013.

Link: 

http://ehis.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=96946360-e246-429f-8d4a-4afdff6d5c26%40sessionmgr11&vid=2&hid=110