Our cats regularly bring home live mice as playthings. Whenever possible we free the mice and put them outside again, after which they disappear. If the mice were caught a long way away, do they have any chance of survival miles from their nests?
鈥� The house mouse Mus musculus domesticus is certainly capable of surviving on release. Some 20 years ago I was involved in an experiment that included tracking populations by genetic markers. This showed that a fair proportion of released animals both survived and successfully integrated with the local population.
Of course, your cat could be catching other local mouse species, such as wood mice 鈥� Apodemus sylvaticus. These have a much lighter belly and should, in theory, be more robust in the wild. Whether they have a similar social flexibility I do not know.
Advertisement
The time of year will be important because the chances of the mice surviving after being released in winter would be much lower. Cat-induced trauma could also affect survival rates, but human handling appears to have little effect.
Ray Nash, Frome, Somerset, UK
鈥� Mice do not live permanently in nests. They use them only to raise their young. Adults feed on seeds and insects wherever they find them.
Tomcats do range widely, sometimes travelling several kilometres from where they live, but they are not usually looking for mice when they do this. Rather, they are seeking a suitable mate, so it is unlikely that they would bother to carry a live mouse a couple of kilometres. Female cats, however, rarely travel more than a few hundred metres from their territory, and it is females that do most of the hunting.
Capture-and-release experiments have shown many times that mice can find their way home from at least 1.5 kilometres away, even when this means crossing rivers or surmounting obstacles that prevent them returning in a direct line.
So in the first instance, the probability that the freed mouse is lost is very low; and even if it were, it wouldn鈥檛 have much difficulty, cats aside, in finding food.
Terence Hollingworth, Blagnac, France