Habitat availability is not limiting the distribution of the Bohemian–Bavarian lynx (Lynx lynx) population
1.6.2016, Carnivores.cz
After decades of persecution and extermination of large carnivores in Europe, their populations have started to recover. This is partially due to the improved legal protection in most European countries. We now see that large carnivores are recolonizing their former ranges both naturally and through reintroduction; however, they are confronted with a human-dominated landscape, where their habitats are diminished and fragmented as a result of direct destruction and the development of roads and railways. Large carnivores are particularly vulnerable to local extinction in fragmented environments because they require large contiguous spaces, and their populations are low in density. This can increase the risk of local extinction.
The study published in the magazine Oryx (with the contribution of Czech experts Luděk Bufka and Jaroslav Červený) focused on the Bohemian–Bavarian population of lynx along the Austrian–German–Czech border which originated from lynx captured in the Carpathian Mountains and reintroduced to the Bohemian Forest in the 1970s and 1980s. Because of its central geographical location, this population has the potential to act as a link between other small and isolated populations. The latest status report on the population, therefore, gives rise to conservationists’ concerns. The data indicate that the population, which is currently estimated to comprise of 47–67 individuals, has stagnated since the late 1990s.
Human induced mortality – particularly mortality caused by road traffic or illegal killing – may be the reason. Habitat availability and connectivity may also influence population dynamics and thus may be the factor limiting the distribution of the Bohemian–Bavarian lynx. The present study aimed to assess the availability of suitable habitat along the Austrian–German–Czech border.
The authors used novel techniques for species distribution modelling and global positioning system (GPS) telemetry data available for 10 lynx of the Bohemian-Bavarian population (6 males and 4 females) radio-collared during 2005–2012. In accordance with results of previous studies, the new habitat suitability model indicated that lynx avoid areas close to human settlements or with intense anthropogenic disturbance. Similarly, lynx were reported to avoid agricultural areas. On the other hand, the importance of forest have been highlighted, the three forest types – broad-leaved, coniferous, and mixed – as well as transitional woodland shrub and wetlands all providing suitable habitat. The results of modelling also indicated that lynx preferred areas of lower altitude, which matches the increasing density of roe deer – the main prey of the regional lynx – with decreasing altitude.
The authors considered spatial requirements of lynx, and the size and connectivity of suitable habitat patches, using the least-cost path analyses. Based on these data, they estimated a potential population size for the area along the border of Germany, the Czech Republic and Austria at 90–160 individuals.
(a) The study area along the borders between Germany, the CzechRepublic and Austria, for which MaxEnt predictions were obtained for distribution of Eurasian lynx Lynx lynx.
(b) MaxEnt prediction of habitat suitability for Eurasian lynx in the study area. Patches with habitat suitability index > 0.35 and a coherent area > 120 km2 are considered suitable. Least-cost paths between these patches are indicated. White circles denote records of lynx of Status and Conservation of the Alpine Lynx Population categories C1 and C2 in Bavaria, Germany.
A spatial comparison of potential and actual lynx distribution with the latest status report revealed permanent lynx presence only in four of 13 suitable habitat patches within the study area (Bohemian Forest, Upper Palatinate Forest, Brdy and Forest Quarter). Of these, there is a permanent patch-wide distribution of lynx only in the Bohemian Forest. This represents the source of the population and includes the Bavarian Forest National Park and the Šumava National Park, which have been shown to be of significant importance for lynx conservation in the region.
Assessing connectivity between suitable habitat patches, the authors found that lynx are able to access all suitable habitat patches in the study area. Existing road network – mostly main roads and municipal roads – poses risks but not barriers for lynx. However, the authors highlight that habitat fragmentation needs to be considered in landscape planning to prevent degradation of connectivity for large carnivores.
It is alarming, that despite relatively good connectivity, lynx do not occupy a significant proportion of suitable habitat. This indicates that the distribution of the Bohemian–Bavarian population is limited by factors other than habitat.
One of the conclusions of the study is that, despite good connectivity, the current distribution of the Bohemian–Bavarian lynx population is not in equilibrium with available habitat. Illegal killing is considered the most likely cause.
However, even the potential carrying capacity of habitat in the study area (90–160 individuals) is not sufficient for a long-term viable population, which according to an expert opinion should comprise about 500 individuals. The long-term aims should, therefore, include enhancing the connectivity to other lynx populations (i.e. Czech Carpathian, German Harz, and Austrian Alpine populations).
Additionally, the authors recommend focusing future research on dispersing sub-adult lynx, with the aim of increasing acceptance of lynx by people. Suitable habitat distribution also needs to be taken into account when locating sites for future lynx reintroduction. But most importantly, preserving the landscape connectivity must be considered in landscape planning and road development to prevent any further fragmentation.
The author is a translator.
Sources:
N. Magg et. al: Habitat availability is not limiting the distribution of the Bohemian–Bavarian lynx Lynx lynx population, Oryx, August 2015
