Why Do Feral Cats Live Where They Live?
Wherever humans go, we bring other species with us. Dogs, rats, pigs, and sheep have colonized the world with our help. One of the most recognizable species that has accompanied with us around the world are cats.
Unfortunately, introduced animals often leave captivity, and invade and destroy native animal populations. One example of this problem can be found in Australia, where cats are believed to be responsible for a sharp decline in the populations of native small mammals – a favorite food of cats. However, the effect of feral cats appears to be reduced in topographically-diverse areas, with rocky outcrops and hills, compared to topographically-simple areas like flat grasslands. A team of researchers believes that feral cats in Australia avoid these complex areas, making them important refuges for small mammals threatened by overpredation.
To test this theory, the researchers deployed four camera arrays across two natural preserves in Western Australia: northern Kimberly and central Kimberly. Each preserve had one camera array in a topographically-diverse area and one in an adjacent topographically-simple area. Each array was comprised of between 14 and 21 cameras deployed in dry creek beds for 3 to 5 weeks. There was a distance of 800m to 1km between each camera, to avoid multiple cameras being placed in the same cat’s range. Each camera was baited with the urine of a sterilized female cat, and was programmed to take three images per trigger. The researchers also placed non-harmful traps to estimate the prevalence of small mammals in these environments.
In the northern Kimberly preserve, cats were detected in the topographically-simple environments on 14 occasions, but no cats were detected in complex environments. In the central Kimberly, simple environments had 53 cat sightings, but only 7 were recorded in complex environments. Both complex areas had much higher populations of small native mammals than did either simple environment.
The results of this study suggest that topographically-complex environments, particularly those with rocky outcroppings, elevation changes, and dense understory vegetation, serve to protect small native mammals from invasive feral cats. The reasons for cats’ avoidance of these areas are not discussed here, but the researchers note that cats may have less success hunting in complex environments. Regardless of the reasons, protecting biodiversity in Australia will likely require protection of these topographically-complex environments; they are one of the last areas of the continent that is somewhat safe from invasive species.