Characterisation of Eurasian lynx Lynx lynx den sites and kitten survival

We retrospectively investigated characteristics of den structures and den sites used by female Eurasian lynx Lynx lynx in the Jura Mountains and the northwestern Alps of Switzerland. During 1983-2000, we discovered 30 natal and 40 maternal dens belonging to 26 females. Important den structures were closed, i.e. provided good shelter, had few entrances, and measured 1 m(2). Dens were found in rocky places, eaves and wooden surroundings. Most dens were located in mixed forests with relatively open vegetation allowing for a visibility of 10-20 in. Contrary to our expectations, natal and maternal dens were equally exposed to human disturbance and were found in terrain which could be dangerous for the kittens. Overall, the two den types barely differed. While concealment did not seem to play a very important part at natal dens and while natal dens were almost never open structures, maternal dens were surrounded by a large number of hiding places and the dens and surroundings were rich in visual contrasts providing good camouflage options. Dens in the Alps and in the Jura Mountains were located in steeper terrain than available on average. The quality of the den sites did not seem to affect the survival of young lynx. Well-suited den sites are so abundant in the Alps and the Jura Mountains that females obviously have no problems finding good den sites.