Endangered mammals in the cultural landscape

The reduction of natural habitat in Austria has induced some mammalian species to invade suburban areas, often causing ambiguous responses of the public. Especially small mammals may exhibit exceptionally high population densities in areas such as parks and sporting grounds, which potentially produces conflicting interests of conservationists and the general public. Information on sustainable development of such colonies is hence essential for efficient, practicable and publicly acceptable conservation measures. The European ground squirrel (Spermophilus citellus) is a model species for appropriate investigations, because it occurs on a range of nearly natural to strongly altered habitats. Actually it is a typical inhabitant of the pannonian region. Well into the second half of the 20th century, it was locally so abundant that rural communities offered rewards for squirrels` ears or tails. Today, the species is considered endangered on both the national and the international level. The aim of this project is to determine the causes and consequences of this unsteady state of existence in man-made environments. To this end, we propose to investigate the distribution and abundance of S. citellus in Austria while simultaneously surveying landscape fragmentation and habitat availability. These data will be completed by comparing five selected sites according to their differing exposure to human interventions. Data on the demography, behaviour, physiology and genetics of these focal populations will help to reveal limiting environmental factors. At the same time, it will be possible to clarify the causes and effects of population dynamics including the consequences of isolation on group sizes, densities and inbreeding. This interdisciplinary approach will contribute to a better understanding of interdependencies among habitat fragmentation, population size, density, behaviour, individual condition, stress, and genetic attributes. Moreover, associations among habitat characteristics, presence of ground squirrels, and abundance and numbers of further pannonian species can be identified. Ultimately, a concept may be derived based on the European ground squirrel as a bio-indicator for the state of natural communities in the pannonian region. As a result, our study may be of crucial importance not only for the European ground squirrel, but also for other endangered species: The exposure to human impact is a substantial factor threatening the existence of rare species in the modern landscape. On the other hand, artificially shaped areas might offer the opportunity to supply refuge areas and to manage the persistence of natural communities, provided that efficient conservation plans are implemented.

While sometimes near to extinction in their natural habitat, colonies of European ground squirrels in close spatial association with humans often achieve exceptional densities. In an effort to clarify this phenomenon, we investigated the current distribution and the environmental conditions ground squirrels have to cope with in the modern landscape. The main finding was that 90% of the mapped ground-squirrel sites occurred in agricultural areas (vineyards, fallow land, field margins). Complex, patchy cultivation patterns represent a considerable part of available ground-squirrel habitat in the modern landscape. Conservation measures should be aimed at promoting and preserving agricultural mosaics, and connecting such heterogeneous habitat clusters with dispersal corridors. Further research emphasized the investigation of five focal populations by capture-mark-recapture and observations. To my knowledge, this was the first research comparing several populations exposed to different levels of human alteration. Three of the five habitats were in or near Vienna north of the Danube, one in Vienna south of the Danube, and one west of Lake Neusiedl. Along with data on demographic attributes, life-history traits and behaviour, we collected faecal samples to extract Cortisol: European ground squirrels usually defecate at capture; therefore these samples offer a non-invasive opportunity to compare stress load of different populations. It turned out that the focus populations varied in virtually every aspect studied. The most conspicuous finding was that population densities increased with habitat alteration (individuals/ha - secondary steppe: 9.3, semi-arid grassland: 11.9, renaturated lawn: 25.9, vineyards: 33.8, alfalfa meadow: 42.6). Dense populations in close association with humans are nowadays a typical characteristic of European ground squirrels, but to date, it has not been stated explicitly that rather undisturbed, continuous populations may exhibit pronouncedly low densities. Cortisol levels increased with population densities. They seemed to reflect stress load to both the number of conspecifics and the frequency of human presence, and to a lesser extent to the presence of predators. Although stress levels were high in anthropogenic habitats, population densities indicate that ground squirrels benefit from the close proximity of humans because less predators approach and attack when people are present. This was also reflected in vigilance behaviour, as animals in the steppe were significantly more vigilant than in other areas. Consequently, squirrels in anthropogenic habitats could spend more time foraging and thus were heavier than in the steppe. Home ranges varied among the study sites and decreased with population density (m - steppe: 7369; semi-arid grassland: 13562; renaturated meadow: 4577; vineyards: 3536; Alfalfa meadow: 1619). This may indicate that European ground squirrels reduce their home ranges with increasing competition and probability of social conflict, and explore preferably less densely populated areas. Genetic diversity increased with population size and density, indicating that isolation may lead to genetic depletion of sparse population fragments. European ground squirrels virtually adapt to intensity and quality of habitat alterations and may to a certain degree benefit from human influence. However, long-term investigations are required to monitor the persistence of colonies exposed to artificial disturbance.