Anja Molinari-Jobin

Significance of lynx Lynx lynx predation for roe deer Capreolus capreolus and chamois Rupicapra rupicapra mortality in the Swiss Jura Mountains

Prey class selection and kill rates by lynx Lynx lynx were studied in the Swiss Jura Mountains from March 1988 until May 1998 to evaluate the significance of lynx predation for roe deer Capreolus capreolus and chamois Rupicapra rupicapra. We found clear differences in the kill rates and prey class selection between lynx of different age, sex and breeding status. Male lynx killed more chamois than female lynx, and chamois was never found in kill series of subadult lynx. Family groups had the highest kill rate. They killed an ungulate every 5.0 days, compared to an average of 6.2–6.6 days for single lynx. During our 10-year study, the density of independent lynx was rather stable, ranging within 0.94–1.01 individuals/100 km2. Based on the observed kill rates and the estimated lynx population structure we calculated that lynx killed 354 ± 13 roe deer and 87 ±13 chamois annually in the 710 km2 study area. The magnitude of lynx predation on roe deer and chamois was primarily shaped by the lynx population structure. A decline in the number of resident male lynx reduced the number of chamois killed in the study area by ¼ of the previous number due to the difference in prey selection of male and female lynx. There was a difference in the most frequently killed age and sex classes between roe deer and chamois: lynx killed more male chamois (39%) than females or fawns, whereas in roe deer, does (38%) were most often killed. By altering adult survival, lynx predation has a significant impact on prey population dynamics. Lynx killed a maximum of 9% of the roe deer and 11 % of the chamois spring population. Considering the differences in the recruitment potential of the two prey species, lynx has a greater impact on chamois than on roe deer.

Spatial and Social stability of a Eurasian lynx Lynx lynx population: an assessment of 10 years of observation in the Jura Mountains

Abstract A total of 18 Eurasian lynx Lynx lynx were radio-tagged between March 1988 and June 1998 in the Swiss Jura Mountains, and during 1995-1997 eight animals were radio-tagged on the French side of the mountain chain. Adult males occupied larger long-term home ranges than adult females (283 km2 vs 185 km2). Neighbouring males shared 7.3% of their home ranges and females 0.2%. The mean distance between males and females living in the same area for fixes taken the same day was 10.94 ± 8.61 km, underlining the solitary character of the species. Consecutive individual annual home ranges overlapped 71.7 ± 7.3% for females and 77.5 ± 7.9% for males, indicating high spatial stability over time. In the Swiss study area, two adult animals were followed for seven and nine years, respectively, and another two lynx were observed in the study area for nine years. Range size did not vary across three distinct periods, P1-P3, but the sex ratio did. Generally, males covered the ranges of 1-2 females, but during the second period, P2, the range of a single male overlapped with those of six females. Dead females were all immediately replaced, but dead males were not. Two poached males were only replaced after three and five years, respectively. Population density, ranging within 0.7-0.8 adult resident lynx/100 km2, did not vary significantly over time in Switzerland. Including kittens and subadults, the density was 1.1-1.6 lynx/100 km2. Our study in the Jura Mountains indicated that there is long-term stability in the social and spatial structure of the lynx population, but this stability was temporarily disturbed by the lack of adult resident males.

Variation in diet, prey selectivity and home-range size of Eurasian lynx Lynx lynx in Switzerland

Abstract To analyse the factors responsible for the interplay of Eurasian lynx Lynx lynx predation and home-range size, we reviewed patterns of lynx predation in Switzerland by comparing the prey spectrum of lynx in five studies performed in the following study areas: the northwestern Alps, where lynx were studied both in the 1980s and 1990s, the central Alps, the Jura Mountains, and northeastern Switzerland. We then compared home-range size of female lynx with two indirect measures of prey abundance, roe deer Capreolus capreolus and chamois Rupicapra rupicapra harvested per km2 and habitat suitability for roe deer and chamois as derived from a GIS model. Lynx diets were similar among sites. Roe deer and chamois made up 90% of prey items in all five studies. Comparing the proportion of roe deer and chamois in the diet with availability, Manlys preference indices indicated selective predation in all studies. Roe deer were preferred over chamois in all areas except in the Jura Mountains where relatively few chamois were present. Predation was least selective in northeastern Switzerland, where the initial phase of recolonisation by lynx was studied. Variation in prey availability is often identified as an important factor explaining intraspecific variation in home-range size. Due to differences in roe deer and chamois abundance from one study area to another, we expected female lynx home ranges to decrease with increasing prey abundance. The predictors for Minimum Convex Polygon (MCP) and Kernel home-range estimators differed. MCP home-range sizes were best explained by the interactions of study with the number of locations per lynx, roe deer harvested per km2, and good roe deer habitat, whereas Kernel home-range sizes were best explained by the interactions of study with good roe deer habitat, good chamois habitat, and the interaction of good roe deer and chamois habitat plus an additive effect of the study. Contrary to our expectations, there was no simple correlation of prime roe deer and chamois habitat nor between the number of roe deer and chamois harvested per km2 and the size of female lynx home ranges. The comparison of the five studies suggested that this expectation may only be valid if lynx populations are close to carrying capacity (e.g. the Jura Mountains and the northwestern Alps in the 1990s). For predictions of home-range size both habitat (spatial factor) and the status and dynamic of the predator/prey populations (temporal factor) need to be taken into account.

Conservation of the lynx Lynx lynx in the Swiss Jura Mountains

Abstract Lynx Lynx lynx returned to a semi-natural, human dominated landscape in the Jura Mountains in France and Switzerland after reintroductions in the early 1970s. Controversy has resulted from lynx attacking sheep and preying on game species such as roe deer Capreolus capreolus and chamois Rupicapra rupicapra. We review the history of the lynx, the transition of the landscape and fauna in the Jura Mountains, and recent findings from long-term field studies on the species. Possible threats to the survival of the population are assessed. The ecological conditions for the existence of the lynx in the Jura Mountains have improved since the species was eradicated in the 19th century. Both habitat and prey base are suitable for maintaining the population. Immediate threats include traffic accidents and illegal killings. Long-term threats include small population size and genetic impoverishment as a result of the post-reintroduction bottleneck. We recommend conservation and management that involve local people and cooperation at national and international scales. Fragmentation of the habitat and the management system should be avoided, and landscape linkages from the Jura Mountains to adjacent mountain ranges should be established to promote a lynx metapopulation.

Characterisation of Eurasian lynx Lynx lynx den sites and kitten survival

Abstract 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 m2. Dens were found in rocky places, caves and wooden surroundings. Most dens were located in mixed forests with relatively open vegetation allowing for a visibility of 10-20 m. 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.

Behavioural observations of interactions in a free-ranging lynxLynx lynx family at kills

The behaviour of a free-ranging female lynxLynx lynx Linnaeus, 1758 and her kittens at 12 different kills was studied for 44 hours of observation from September 1996 to March 1997. The development of interactions at kills of a lynx family group showed the following pattern: until the end of September we often observed two lynx, usually both kittens, feed from the kill at the same time. After the age of four months aggression between kittens was observed frequently, with the bigger kitten being dominant. From September the kittens were never again seen feeding together at the kill. However, we never observed fighting, and aggressive behaviour did not increase with the age of the kittens. Whereas until December one of the kittens was always first at the kill, from January onwards it was mostly the adult female who ate first. She introduced her kittens to the home range of a neighbouring female where the family break-up occurred. The kittens were last seen together with their mother on 26 March. Dispersal seemed to be initiated by the female abandoning the kittens.