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Habitat fragmentation effects on annual survival of the federally protected eastern indigo snake

August 23, 2012

The eastern indigo snake (Drymarchon couperi) is a federally listed species, most recently threatened by habitat loss and habitat degradation. In an effort to estimate snake survival, a total of 103 individuals (59 males, 44 females) were followed using radio-tracking from January 1998 to March 2004 in three landscape types that had increasing levels of habitat fragmentation: (1) conservation cores; (2) conservation areas along highways; (3) suburbs. Because of a large number of radio-tracking locations underground for which the state of snakes (i.e. alive or dead) could not be assessed, we employed a multistate approach to model snake apparent survival and encounter probability of live and dead snakes. We predicted that male snakes in suburbs would have the lowest annual survival. We found a transmitter implantation effect on snake encounter probability, as snakes implanted on a given occasion had a lower encounter probability on the next visit compared with snakes not implanted on the previous occasion. Our results indicated that adult eastern indigo snakes have relatively high survival in conservation core areas, but greatly reduced survival in conservation areas along highways and in suburbs. These findings indicate that habitat fragmentation is likely to be the critical factor for species' persistence.

Citation Information

Publication Year 2012
Title Habitat fragmentation effects on annual survival of the federally protected eastern indigo snake
DOI 10.1111/j.1469-1795.2012.00524.x
Authors D.R. Breininger, M. J. Mazerolle, M.R. Bolt, M.L. Legare, J.H. Drese, J. E. Hines
Publication Type Article
Publication Subtype Journal Article
Series Title Animal Conservation
Index ID 70039690
Record Source USGS Publications Warehouse
USGS Organization Patuxent Wildlife Research Center