Spatial ecology of the Scottish wildcat, domestic cat and hybrids
The Scottish wildcat is threatened by introgression with the domestic cat. Introgression is the gene flow between two species, subspecies or populations that results from the repeated backcrossing of hybrids. Based on current knowledge, it has been calculated that off an estimated 3,500 wild-living cats in Scotland, as few as 400 of these may be pure wildcat, with the remainder consisting of feral domestic cat and cats that are hybrid between domestic cat and wildcat1. The wildcat is facing similar threats across its range in mainland Europe2. Such genetic mixing may result in individuals that are less well adapted3. If changes in population density or forging behaviour arise from introgression, changes the structure of the remaining ecological community via interactions across trophic levels may also result4. It is therefore imperative that we make every effort to reduce introgression and seek to understand it’s causes and consequences.
A better understanding of the process of introgression may aid conservation of wildcat by targeting efforts to break the link in the causal chain of introgression. For example, if there is a sex-bias in hybridization, such as a greater likelihood of male wildcats mating with domestic females than vice versa, then neutering efforts could be targeted to female domestic cats. Alternatively, hybrid cats may act as a bridge between domestic cat and wildcat5 and therefore removal of hybrids will reduce the chance of continuing introgression. Finally, there may be environmental characteristics that favour encounters between domestic cat and wildcat. There is some evidence for example that domestic cat favour more open habitat and wildcat prefer more wooded habitat5,6, suggesting that a more fragmented landscape would increase the rate of introgression. Thus changes in habitat management could influence introgression and provide refuges where wildcat are not in competition with domestic cat.
If we cannot evict all domestic cat genes from wild-living cats in Scotland, we need to establish, on the domestic cat – wildcat spectrum, where a line can be drawn that distinguished domestic cats from functional ‘wildcats’. To do this, we need to compare the behavioural ecology of cats from across this spectrum within the same geographical area. While a previous study in Scotland comparing the ranging behaviour of cats found no evidence for a difference in habitat use7, studies from other areas in Europe have found evidence for differences in diet5,8. A detailed comparison of the foraging behaviour of cats in Scotland is still needed to answer whether non wildcats can be considered functional wildcats.
The aims of this study are to: 1) investigate the process of introgression between domestic cat and wildcat; 2) identify any habitats that are preferential to wildcat over domestic cat; 3) gain insight into the impact that domestic cats and hybrids have on the ecosystem and 4) provide further detail on the behavioural ecology of wildcats in Scotland. We will use simultaneous GPS based tracking of cats from across the wildcat – domestic cat spectrum to achieve these aims.
The project is jointly funded by the Peoples Trust for Endangered Species, WildCRU and the Royal Zoological Society of Scotland.
1 Macdonald, D.W., Daniels, M.J., Driscoll, C., Kitchener, A.C. & Yamaguchi, N. 2004. The Scottish Wildcat: analyses for conservation and an action plan. Wildlife Conservation Research Unit, University of Oxford, 67pp.
2 Pierpaoli, M., Biro, Z.S., Herrmann, M., Hupe, K., Fernandes, M., Ragni, B., Szemethy, L., Randi, E. 2003. Genetic distinction of wildcat (Felis silvestris) populations in Europe, and hybridization with domestic cats in Hungary. Molecular Ecology 12, 2585-2598.
3 Rhymer, J. M., Simberloff, D. 1996. Extinction by hybridization and introgression. Annual Review of Ecology and Systematics 27, 83-109.
4 Hairston, N. G., Smith, F. E., Slobodkin, L. B. 1960. Community structure, population control, and competition. The American Naturalist 94, 421-425.
5 Germain, E., Ruette, S., Poulle, M.-L. 2009. Likeness between the food habits of European wildcats, domestic cats and their hybrids in France. Mammalian Biology – Zeitschrift fur Saugetierkunde 74, 412-417
6 Weber, D. 2007. Monitoring Wildcats (Felis silvestris silvestris): Guidance for a systematic survey of the distribution of wildcats and for monitoring population changes over time. Translated from German by H Schnell, H Armour and R Maier. Hintermanweber.ch, Ecological consultancy, Rodersdorf, 20pp.
7 Daniels, M. J., Beaumont, M. A., Johnson, P. J., Balharry, D., Macdonald, D. W., Barratt, E., 2001. Ecology and genetics of Wild-Living cats in the North-East of Scotland and the implications for the conservation of the wildcat. Journal of Applied Ecology 38, 146-161.
8 Biro, Z. S., Lanszki, J., Szemethy, L., Heltai, M., Randi, E., 2005. Feeding habits of feral domestic cats (Felis catus), wild cats (Felis silvestris) and their hybrids: trophic niche overlap among cat groups in Hungary. Journal of Zoology 266, 187-196.