Head-starting as a tool for the reintroduction of extirpated watersnake populations

Michael R Frank, Purdue University

Abstract

Habitat loss and fragmentation are factors leading to declines in many faunal populations. Restoring habitats to support the rebound of local populations may help to remedy these declines, but in cases where a species has been extirpated, natural recolonization is unlikely. Translocation has proven to be a successful strategy for the repatriation of some extirpated populations, but its effectiveness is unclear and understudied in snakes. Using the Northern Watersnake ( Nerodia sipedon) I directly translocated individuals to a recently restored nature preserve from a nearby site in 2008. I also raised neonates in simplistic laboratory enclosures (“head-starts”) until they were large enough to be translocated to the same preserve. These experimental release groups were compared to resident snakes. Compared to residents, translocated snakes selected aquatic habitats with a more open canopy, moved more extensively, and used areas outside of reserve boundaries more frequently. Head-starts showed restricted movements and used habitats in ways atypical of residents. Translocated and resident snakes grew at similar rates, but headstarts failed to grow appreciably. Both experimental groups had low survivorship relative to residents. Much of the mortality in head-starts occurred during the overwintering period, while mortality in directly translocated snakes was limited to the active season. Due to the poor performance of head-starts, I also examined alternative approaches by releasing head-starts directly into constructed hibernacula and older head-starts that were raised for two years in captivity. Head-started snakes released into constructed hibernacula failed to overwinter successfully and ultimately all died. Although head-starts did not survive, constructed hibernacula were similar in water table characteristics when compared to sites chosen by resident snakes. Head-starts raised identically to head-starts in 2008 but for an additional year, as well as an additional sub-set of head-starts that were given enriched captive conditions, selected habitats similar to snakes resident to the preserve. Both head-started groups had similar growth rates and were able to successfully overwinter as well. At the end of the study, these head-started snakes had higher survivorship rates than residents. Ultimately, successful techniques, like those for two year old head-started snakes, might one day be employed in repopulation efforts of imperiled species.

Degree

M.S.

Advisors

Kingsbury, Purdue University.

Subject Area

Ecology|Conservation

COinS