Habitat matrix effects on pond occupancy in newts

In farmlands, the population viability of many amphibians is suspected to d epend on the resistance the matrix of crop fields presents to movements bet ween ponds and terrestrial sires and movements among ponds. Over recent dec ades the increase in cereal grouping at the expense of cattle breeding has caused a drastic change in habitat matrix in many European regions. We inve stigated the effect of such change on populations of three newt species (Tr iturus helveticus, T. alpestris, and T. cristatus) by comparing their abund ances in sites that varied in amount of cultivated ground. A multivariate r egression analysis of the relationship of newt abundance to both Pond and l andscape variables demonstrated the negative influence of cultivated ground on abundance. The width of the uncultivated sector linking the pond to the forest was a good predictor of abundance after the influences of both pond area and fish presence were removed Moreover, newt presence was positively related to the number of ponds within that 50-ha surrounding area, highlig hting the role of metapopulation functioning in newt occupancy of ponds. Th e relationship between newt abundance and width of uncultivated sectors agr ees with present knowledge of the orientation mechanisms that underlie migr ation movements in urodeles Such a relationship between connectedness and s ector width shows that narrow linear corridors such as hedgerows may not be useful in newt conservation. Our study, also highlights the need to incorp orate a behavioral component of habitat use into models of connectivity in conservation biology.