The mere presence of a domesticated cat in the wild causes fear in other animals. This affects their physiology, behavior and movements. In addition, cats transmit diseases that are dangerous to humans, wildlife and domestic animals, such as rabies and toxoplasmosis, writes Marko Mägi, an ornithologist-ecologist at the Institute of Ecology and Natural Sciences at Tartu University’s blog. 2.0.
There is not enough research on the impact of cats on wildlife. In addition, they took place mainly in the developed countries of North America or Europe. Therefore, the question arises whether it is possible to draw conclusions for the whole world based on the data collected.
To find the answer, the scientists analyzed 2,245 scientific studies in cats. Of these, 332 found the data accurate enough to provide an overview of the global impact of cats on wildlife.
The study of cats is uneven and varies greatly from continent to continent. For example, 37.1% of studies were conducted in Australia, 28.5% in Europe and 25.3% in North America. At the same time, cats from Asia (1.6%), Africa (3.2%) and South America (4.3%) have been poorly studied.
There has been relatively much research in Australia because cats are an invasive species there. This is the only country in the world where stray cats are killed to protect other animals.
But the lack of adequate research in Asia, Africa and South America worries scientists, because these areas are important biodiversity sites for the whole world and cats are predators. The lack of research is largely due to the legacy of colonialism, which left these areas with a lack of resources and scientists, without access to data and without a delivery of scientific research.
Friend or weight?
Most often, studies on the impact of cats on wildlife were conducted on the islands (41.9%). This is due to the fact that in areas surrounded by water on all sides, cats caused the most damage and became the cause of the extinction of local species. In addition, it is easier to deal with the spread of wild pets on the islands.
The studies concerned islands located mainly in the tropics or in temperate latitudes. However, as the climate warms, islands at large latitudes may also become suitable for cats – and scientists should keep their ears open.
Most of the research (62.2%) concerns stray cats. Regarding the species threatened by these animals, only in 43.1% of the studies the scientists evaluated their effect on all the endangered, in the rest – on one or two species of birds (47.1%) or mammals (36% ), namely amphibians (1.1%), invertebrates (0.5%) or reptiles (4.2%).
The focus is on cat hunting and impacts on populations or communities are rarely assessed. When these studies were performed, in 88.9% of cases, cats were found to adversely affect the abundance of certain animal species or increase their risk of extinction. Only 11.1% of studies did not reveal a significant effect of cats on wildlife.
Although there were no positive environmental impacts, eight studies found a correlation between cats and control of invasive species such as birds and rats.
Scientists have mainly studied the effect of cats on nature in rural areas, less often in cities, and even there, for the most part, in parks and other green areas. However, as cities expand, the role of domestic cats in conserving biodiversity becomes more important because they can quickly destroy other animals and birds.
What to do?
In addition to field research, which is invaluable, laboratory experiments are also required to gather accurate information and simulate different situations, as many factors affect wildlife at the same time.
One of the daily solutions to the problem is to make the cats visible with bells or other means. However, the effect of this measure is still questionable, as studies are insufficient and the available results are contradictory.
Cat-castration-release-style cat population control programs have not shown good results so far. There is also the view that fat or neutered cats hunt other animals less often, but there is also evidence to the contrary – they hunt even more often. However, the political pressure to maintain these programs is very high, because this way is considered humane.
And although the effect of cats on nature is usually negative, do not forget that these animals are used to control pests, they are considered family members and companions that evoke positive emotions. It is therefore not surprising that stakeholders – pet owners, animal rights activists and environmentalists – see them differently and have opposing views on the need to control the cat population.
Therefore, the collection of high quality data on restraint measures is essential, as this is the only way to check the competence of policy decisions and, if necessary, to make recommendations.