Thursday, March 7, 2013

Two sand-dune dwelling snakes avoid direct competion


Sand Viper, Cerastes vipera.

The Saharan sand viper, Cerastes vipera , and the crowned leafnose, Lytorhynchus diadema  belong to different clades but well adapted to life in desert sand dunes. In Israel, and in all Saharan countries both coexist in sand and dune systems.   The two species have several characteristics in common: they are sand-dwelling; active under the same climatic conditions; nocturnal; feed mostly on lizards; and are relatively small – 35 cm for the sand viper and 50 cm for the crown leaf-nose snake. However, they differ in that the sand viper moves by side-winding  while the crowned leafnose snake uses serpentine movement; and the sand viper is a ambush predator, while the crowned leafnose snake is an active forager.

In a forthcoming article Sivan et al. (2013) test the hypothesis that sympatric sand vipers and crown leaf-nose snakes partition niches in terms of temporal activities and diet. They predicted that the two species would differ in their seasonal and daily patterns of activity as well as in the composition of their diets. To test these predictions they determined temporal activities, for both. Both were active from early spring until late fall but displayed  different seasonal activity patterns, the sand viper was bimodal with activity peaks in spring and autumn. The crowned leafnose was unimodal with a peak in summer. The sand viper was active  during the first three hours of darkness while the crown leaf-nose snake was  active during the first seven hours of darkness. Also the two species showed different patterns of nocturnal behavior: the sand viper moved up to 50 m while the crowed leafnosed snake moved several hundred meters each night. Prey included the Nidua fringe-fingered lizards (Acanthodactylus scutellatus) for both species. But the viper also consumed the skink Chalcides sepsoides and the crowned leafnosed snake gecko ate the gecko Stenodactylus petrii as well as reptiles eggs. The authors concluded that temporal partitioning in above-ground activity, distinctly different foraging strategies, and slightly different diets contribute to the coexistence of the two species.

Citation
Sivan, J., M. Kam, S. Hadad, A. A.Degen, I. Rozenboim,A. Rosenstrauch. 2013. Temporal activity and dietary selection in two coexisting desert snakes, the Saharan sand viper (Cerastes vipera) and the crowned leafnose (Lytorhynchus diadema). Zoology, http://dx.doi.org/10.1016/j.zool.2012.09.002

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