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ICCB Poster R Ward 1.pdf (3.96 MB)

In search of snakes: Conservation and distributional modelling of a declining island population of grass snakes (Natrix natrix)

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posted on 2015-07-31, 18:20 authored by Robert WardRobert Ward

Within Europe a fifth of reptile species are thought to be threatened with extinction, however evidence of snake declines is poor due to several life history traits and limited study. Snakes are linked with their environment at varying spatial scales and typically exhibit negative responses to anthropogenic habitat change, serving as indicators of ecosystem health. The grass snake (Natrix natrix) is found across much of Europe. Although relatively common in mainland Britain, they are thought to be undergoing declines in some areas due to a dependence on landscape-level features such as oviposition sites. Within the Channel Islands grass snakes are only found in Jersey where they have declined, with little known about the causes and the population's subsequent distribution and status. Furthermore they are undoubtedly the rarest of the island's four reptile species. Earlier research has found grass snakes to be abundant in the north-west and south-west of Jersey, and historically the species occurred throughout the remainder of the island at a low density. Further declines are likely, and so to assess the population a combination of directed transect walks utilising both visual and refugia survey methods took place in 2014 at 19 sites. An intensive survey effort revealed low detection with the species occurring at 58% of study sites even though suitable habitat was available. A citizen science project encouraging public recording provided further sightings. The resulting distributional data suggests the population is largely restricted to the west and south-west of the island. A Maxent species distribution model based upon these data highlights a lack of suitable habitat throughout much of the island, with poor connectivity between quality habitat. Furthermore, localities with south-westerly aspects, ponds, scrub and bush, grassland, gardens, coniferous woodland, a close proximity to prey populations, and lower elevations had greater likelihood of species presence.

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