From what I gather, adults hibernate in the same areas each year and young snakes apparently select hibernation dens at random, perhaps by following scent cues from adult snakes. During the breeding season adders are reported to remain in the vicinity of hibernation areas, where breeding females will be courted by amorous males. The gravid females will then stay close to hibernaculas for the rest of the active season, whereas all other adders will move off into the surrounding habitat to feed throughout the summer.
So does anyone have an explanation as to why today I found one of the adders from my local site, individual M9, so far from where he was 2 years ago? I came across him on a wall around 450m as the crow flies from where I last saw him, mating, in April 2011. If he avoided going through the conifer forest and took the more 'adder-like' habitat of brambles and grass the the distance is more like 700m. My understanding of this species was that the mating and associated behaviour takes place close to hibernaculas, not half a kilometre away.
The site were these snakes live seems to be divided into 2 sub-populations, separated by around 700m of seemingly suitable habitat. Could it be that this year, if there are no breeding females in one sub-population, male snakes may move from one area to the other in search of a receptive female? Andren et al. (2007) stated that berus males were able to detect female pheremones at a distance of 500m, so as the crow flies these two sub-populations are within this limit. However, the Phelps paper does note that "over the years ... the adults, both male and female, were found to exhibit total site fidelity". I'm not so sure what to think, and would like to hear your opinions and thoughts on this.