Fridolin Zimmermann

Recovery of large carnivores in Europe’s modern human-dominated landscapes

The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape. Many populations of brown bears, lynx, grey wolves, and wolverines persist successfully outside protected areas in Europe. Success for Europes large carnivores? Despite pessimistic forecasts, Europes large carnivores are making a comeback. Chapron et al. report that sustainable populations of brown bear, Eurasian lynx, gray wolf, and wolverine persist in one-third of mainland Europe. Moreover, many individuals and populations are surviving and increasing outside protected areas set aside for wildlife conservation. Coexistence alongside humans has become possible, argue the authors, because of improved public opinion and protective legislation. Science, this issue p. 1517

Testing expert groups for a habitat suitability model for the lynx Lynx lynx in the Swiss Alps

Abstract Modelling species distribution is an important aspect of conservation ecology. Empirical models are most commonly used. However, collecting data for these models is time-consuming and expensive. Expert models may be a good alternative method, though previous studies have found mixed results. The purpose of our study was first to create an expert model and evaluate it with independent lynx data, and second to use two discrete types of experts to control for prior radio-tracking experience. Two habitat suitability expert models (scientific and local experts) were constructed in a Geographical Information System using the Analytical Hierarchy Process and Compromise Programming. The models were evaluated with lynx data, taken from the study area in the northwestern Swiss Alps, using Resource Selection Index and Spearman correlation. The correlations showed that both models fitted the data well. However, the local expert model was better (rs  =  0.964, P < 0.001) than the scientific expert model (rs  =  0.833, P < 0.001). The models were also evaluated in the Jura Mountains to test the local nature of the models. It was found that the local expert model performed less well (rs  =  0.939, P < 0.001) than the scientific expert model (rs  =  0.967, P < 0.001) as expected. Comparison between weights for each expert group revealed some interesting differences, which showed the local nature of answers and how personal experience and theoretical knowledge can lead to different answers. Our study shows that expert knowledge, and especially local knowledge, can be employed to create a good habitat suitability model. This has important implications for conservation and science because it shows not only that expert knowledge may be used when no other data exist, but also that local ‘ground workers’ should be employed more often in the development of habitat suitability models or conservation plans. However, there are limitations to the models and, as expert models are relatively new in ecology, more research is needed. Nevertheless, in a climate where there is pressure to keep up with human exploitation of natural resources and to adopt a more strategic approach to conservation, the findings of our study are encouraging.

Potential distribution and population size of the Eurasian lynx Lynx lynx in the jura Mountains and possible corridors to adjacent ranges

Abstract To estimate the potential population size of the Eurasian lynx Lynx lynx in the Jura Mountains and to assess possible corridors between this population and adjacent areas (the Vosges Mountains, the Black Forest and the Alps), we adapted a previously developed Geographic Information system (GIS) probability model for lynx distribution and extrapolated it over the entire mountain range. The model was based on knowledge of the habitat use and land tenure system of resident animals from the central part of the Jura Mountains, where lynx were followed by means of radio-telemetry. Corridors were computed in the GIS using a friction grid and a cost distance function. The friction value attributed to each land use variable was assessed from our observations of lynx dispersal. Our model predicts a breeding population in the Jura Mountains of 74-101 individuals and 51-79 individuals when continuous habitat patches of < 50 km2 are disregarded. The Jura population lies within the range of a viable population if only demographic aspects are taken into account, but is rather small from a genetic point of view. Genetic viability would be assured if the Jura lynx population were part of a larger metapopulation. Potential corridors exist from the Jura Mountains to the Vosges Mountains, the Black Forest and the Alps (Chartreuse and Salève, respectively). The length of these corridors range within 7.3-37.3 km, and their costs are all within the range of radio-collared lynx roaming outside their prime habitat. The best corridor leads south to the Chartreuse, an isolated part of the French Alps, which is itself connected to the rest of the Alps by two corridors of 4.5 and 6.5 km, respectively. Observations in the Chartreuse indicate that lynx may have immigrated from the Jura Mountains, but there is no evidence for the use of northern corridors, as the species has not yet completely occupied this area. We conclude that the monitoring of the population size, its spatial expansion, and the genetic surveillance in the Jura Mountains must be continued, as the status of the population is still critical. Only good surveillance would allow the necessary conservation measures to be initiated in time.

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.

Density estimations of the Eurasian lynx (Lynx lynx) in the Swiss Alps

Abstract Use of photographic capture–recapture analyses to estimate abundance of species with distinctive natural marks has become an important tool for monitoring rare or cryptic species, or both. Two different methods are available to estimate density: nonspatial capture–recapture models where the trap polygon is buffered with the half or full mean maximum distance moved by animals captured at more than 1 trap (1/2 MMDM or MMDM, respectively); or spatial capture–recapture (SCR) models that explicitly incorporate movement into the model. We used data from radiotracked Eurasian lynx (Lynx lynx) in the northwestern Swiss Alps (NWSA) during a low (1.0 lynx/100 km2) and a high (1.9–2.1 lynx/100 km2) lynx population density to test if lynx space use was density dependent. Second, we compared lynx density estimates resulting from these 2 different methods using camera-trapping data collected during winters 2007–2008 and 2009–2010 in the NWSA. Our results indicated lynx space use was negatively correlated with density. Lynx density estimates in all habitats using MMDM (0.86 and 0.97 lynx/100 km2 in winters 2007–2008 and 2009–2010, respectively) were significantly lower than SCR model estimates, whereas there was no significant difference between SCR model (1.47 and 1.38) and 1/2 MMDM (1.37 and 1.51) density estimates. In the NWSA, which currently harbors the most abundant lynx population in Switzerland, 1/2 MMDM and SCR models provided more realistic lynx density estimates compared to the MMDM, which lies in the lower range of densities. Overall, the SCR model is preferable because it considers animal movements explicitly and is not biased by an informal estimation of the effective sampling area.

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.

Demography of lynx Lynx lynx in the Jura Mountains

Abstract We radio-collared a total of 29 lynx in the Swiss Jura Mountains and collected data on demography during 1988-1998. We were able to observe 10 2-14 year-old females for 32 female years. Lynx kittens were born between 12 May and 13 June (26 May ± 9 days). One female gave birth to a litter on 26 August after she had lost her first litter born in May. The average litter size was 2.00 ± 0.75 kittens (range: 1-3). The sex ratio of 1.67 females:1 male did not differ significantly from the expected ratio of 1:1. On average, 81% of adult females reproduced each year. The overall reproduction rate was 1.67 kittens/female year. Of 49 kittens, 43-49% survived until independence at the age of about 10 months. The survival rate of subadults and adults was 53 and 76%, respectively. Litter size and survival of kittens and subadults varied considerably between three observation periods, i.e. P1-P3 (P1: 1988-1991, P2: 1992-1994, P3: 1995-1997), characterised by substantial changes in the social structure of the population. During P2 only one resident male was present in the main study area, and during this period, the average litter size was lowest with 1.50 kittens only. The survival of kittens was with 37-44% lowest as well, mainly because of the high proportion of litters where all kittens were lost. However, the survival of subadults was highest during P2, when observed animals survived to adulthood. During 1974-2002, 124 mortalities were documented for the whole of the Jura Mountains. Human related mortalities were responsible for 70% of known losses. An estimation based on the radio-collared lynx suggested that poaching may have been responsible for as much as 32% of total mortality. In contrast to other study areas, traffic accidents were very important in the Jura Mountains. They might represent as much as 29% of mortality. During our 10-year study period, no significant spatial expansion of the population was recorded in Switzerland. We suppose that the high human-related mortalities limited the population, which also would explain the lack of a numerical response to an increase in prey abundance observed during the same period in the study area in Switzerland.

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.

Optimizing the size of the area surveyed for monitoring a Eurasian lynx (Lynx lynx) population in the Swiss Alps by means of photographic capture-recapture

We studied the influence of surveyed area size on density estimates by means of camera-trapping in a low-density felid population (1-2 individuals/100 km(2) ). We applied non-spatial capture-recapture (CR) and spatial CR (SCR) models for Eurasian lynx during winter 2005/2006 in the northwestern Swiss Alps by sampling an area divided into 5 nested plots ranging from 65 to 760 km(2) . CR model density estimates (95% CI) for models M0 and Mh decreased from 2.61 (1.55-3.68) and 3.6 (1.62-5.57) independent lynx/100 km(2) , respectively, in the smallest to 1.20 (1.04-1.35) and 1.26 (0.89-1.63) independent lynx/100 km(2) , respectively, in the largest area surveyed. SCR model density estimates also decreased with increasing sampling area but not significantly. High individual range overlaps in relatively small areas (the edge effect) is the most plausible reason for this positive bias in the CR models. Our results confirm that SCR models are much more robust to changes in trap array size than CR models, thus avoiding overestimation of density in smaller areas. However, when a study is concerned with monitoring population changes, large spatial efforts (area surveyed ≥760 km(2) ) are required to obtain reliable and precise density estimates with these population densities and recapture rates.

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.