Watch out there's a stoat about

The Stoat is one of those animals that I only see occasionally, perhaps running across a track or working the base of a hedgerow in search of small mammals or other prey. As such, I tend to take notice of where and when I see Stoats, noting them in my field book to report at the end of the year. It seems that I am not alone in this; look at the Norfolk Mammal Report (available from the Norfolk & Norwich Naturalists’ Society) and you will see the species features more often than others that you would consider to be more common across the county. Does familiarity breed contempt and are we ignoring the commonplace?

There is something mesmerising about a Stoat that is working an area in search of prey. Ever alert, it searches opportunistically, pausing every now and then to scan for other predators and would-be prey. I have only seen a Stoat tackle prey on a handful of occasions, usually a vole or mouse, but on once a Rabbit considerably larger than the Stoat in size. Stoats are reputed to mesmerise their prey by dancing but this is unlikely to be the case. The few incidents where observers have reported such behaviour may, in fact, be observations of a Stoat suffering from an infestation of a parasitic nematode, which causes skull deformity and spasms.

Although the Stoat is one of the smaller European carnivores, it is not the smallest and shares the British part of its wide range with the even smaller Weasel. The two species can be told apart fairly readily; the Stoat larger, with a long black-tipped tail; the smaller Weasel with a shorter tail and no black tip. Additionally, in Stoat, the chestnut back and flanks meet the cream belly in a straight line, whereas in Weasel this line is irregular and sometimes spotted.

There is one other aspect of Stoat ecology that fascinates me and that is its breeding system. Both male and female Stoats are territorial, with each male holding a territory within which there may be one or more smaller female territories. During the breeding season each male will adopt one of three strategies, the choice dependent upon his age and social status. Older dominant males adopt a roaming strategy, expanding the size of their territory massively. They then roam around the territory in search of females, spending a few days with each before moving on. Younger males stay within their smaller territories and the youngest males remain fully transient, unable to hold a territory of their own. Although mating occurs from April to June, the females delay implantation, so the resulting young are not born until the following spring.