The turtleheaded sea snake, Emydocephalus annulatus.
Drawing by Ethel King, Australian Museum.
A mark and re-capture study of the turtleheaded sea snake, Emydocephalus annulatus, in New Caledonia suggests that snakes living in two bays less than 1.15 kilometers apart are separate populations. Lukoschek and Shine (2012) found that while the snakes could swim from one bay to the other, they rarely do so. More that eight hundred snakes were recaptured and only two individuals had moved between the bays. 136 snakes were genotyped for eleven microsatelite loci and the two populations were found to have statistically significant genetic divergence. The sedentary behavior of these sea snakes has ecological and evolutionary implications but is also important for their conservation and management. The authors suggest that sea snakes may be poor colonists and this may account for their highly heterogeneous distributions across several spatial scales, but perhaps most importantly coral reef habitats. Populations of snakes associated with reefs operate as separate ecological units and, as such, local disturbances will have mostly local impacts. However, once a local population has been damaged establishing a new population is likely to be slow. Thus sea snakes may be vulnerable to habitat disturbances brought about by huamn activities or environmental factors, and explain the recent precipitous population declines and local extinctions of turtleheaded sea snakes, as well as other reef-associated species. These local extinctions include a previously large population of turtleheaded sea snakes at Ashmore Reef in the Timor Sea. The results of this study also raise concern about the potential for this population to recover, as well as for the recovery of critically endangered and endangered small-range endemics in the genus Aipysurus, which have undergone similar local extinctions at Ashmore Reef. The entire article is available on-line.