The Distribution and Dispersion of the Alsophis rufiventris on the Quill, Sint Eustatius

The Lesser Antilles are home to four different colubrid snakes of the Alsophis genus. Alsophis used to be common around the Lesser Antilles, but has declined dramatically. The Red-bellied Racer snake (Alsophis rufiventris) is one of those four endemic Alsophis species of the Lesser Antilles. The islands St. Eustatius (Statia), Saba, St. Kitts and Nevis used to be home to A. rufiventris, when in the 1900s A. rufiventris got extirpated on St. Kitts and Nevis. Only two subpopulations exist today, on 10.9% of its original range. Therefore, A. rufiventris is now classified as endangered on the IUCN red list. A better understanding of these animals can help in effectively protecting them. To get an idea of the distribution and dispersion on the trails of the western slope of the Quill was investigated, because the abundancy of A rufiventris was thought to be the highest there.

In total 66 snakes were PIT tagged, over a three month period, of which 34 males and 32 females, suggesting a sex ratio of 50:50. Every snake was measured to see if there was a difference in tail length between males and females, to create an easy, costless and harmless way to distinguish both sexes, other than from the look of the exterior. Males had a significant longer tail, making it possible to use this method to identify the sexes.

Encounters and reencounters were mapped to give an idea about the dispersion of A. rufiventris. There were 43 reencounters, of which 4 snakes where reencountered three times after initial tagging. Different snakes were reencountered several times within a 80 meter range. Only one snake was reencountered about a kilometre from the first three encounters of that individual. Therefore, over this short period A. rufiventris seemed to have a certain home range, though the behaviour of other Alsophis species suggest that they will be rather nomadic over a longer time period. For that reason, long time study is suggested, to learn more about the specific behaviour of this species.

[Student report]

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