Movements and habitat choice of resident and translocated adult female Grass Snakes (Natrix natrix) during the egg-laying period

We used externally applied transmitters to study movements of female grass snakes (Natrix natrix) during the egg-laying period in a near-urban landscape in Sweden. Half of the studied snakes were residents while the other half were translocated individuals with no previous experience of the area. As predicted, resident females moved more goal-oriented and shorter distances than did translocated individuals. Habitat use did not differ between resident and translocated snakes; they were typically found in bushes, reeds, and tall vegetation. Habitat preference (use in relation to availability) showed that bushy habitats, tall grassy vegetation and reedbeds were over-used in proportion to availability, whereas forest and open grass lawns were used less than expected based on availability. Our study highlights the importance of preserving and restoring linear habitat components providing shelter and connectivity in conservation of grass snakes. We suggest that externally applied transmitters are a better option than surgically implanted ones in movement studies of grass snakes, and that translocation as a conservation method for snakes has drawbacks.

Removal of American mink increases the success of simulated nests in linear habitat

Alien species of predators may negatively influence the breeding success of waterfowl. Previous studies have tested whether predator removal causes an increase in nest success and breeding densities; however, conclusions have been contradictory. Here we examine the impact of the removal of introduced American mink, Mustela vison, on the survival of simulated waterfowl nests in two treatment and two control transects, in a linear section of habitat along the Jihlava River, Czech Republic. Nest survival was recorded during two periods (June and July), with minks removed after the first replicate. In total, eight minks were removed from treatment transects. Whereas nest survival in control transects slightly decreased from June to July, the opposite trend, i.e. an increase in nest survival, was apparent in the treatment transects. On the basis of the results, we suggest that a local reduction in mink populations is an effective short-term tool for the conservation of protected waterfowl species. Our study adds to others, reporting potentially adverse effects of alien, introduced, carnivorous species on local biota.