Proving That Size Is Not All That Matters
For this edition of the Tomorrow wildlife column, we turn our attention to a species that, although most of us are familiar with its name, remains largely unknown in terms of its biology and behaviour: the least weasel (Mustela nivalis) or more commonly referred to simply as the weasel.
Weasels have a wide distribution across the northern hemisphere, including North America, Asia and Europe. In the southern hemisphere, they have been introduced by humans to Australia and New Zealand as a form of pest control against the also-introduced rabbit and are now a serious threat to local wildlife. In Portugal, they are consistently found throughout the country, with a preference for habitats such as meadows, prairies, farmlands and woodlands.
Part of the mustelid family – a group of animals that include stoats, martens, polecats, otters, badgers and wolverines – the weasel is an animal of small dimensions. In fact, weasels are the smallest true carnivores in the world. These creatures weigh as little as a bar of soap and are roughly the size of a pet hamster. Their bodies are slender and their legs are short, common traits amongst the smaller cousins in the mustelid family.
The weasel’s fur ranges slightly from a cinnamon color to reddish-brown, always with a bright white underside. Both male and female weasels are identical in appearance, but adult males can be 10–20% larger than females. Weasels can live up to ten years and can have multiple litters in a year, raising up to five newborns each time.
Despite their small size, weasels are fierce and energetic predators. Insatiable creatures, what they lack in size, they make up for in voracious appetite, so it’s not a surprise that they spend most of their time hunting. Their diet is varied, but their favorite prey is mice and voles. Even after catching a substantial meal, they often snack on it briefly and then resume the relentless hunt. This behavior sees weasels hoarding carcasses in their burrows, sometimes in their dozens!! Opportunistic feeders, they will attempt to catch anything they can tackle, including eggs, adult birds, and even rabbits or leverets (young hares). This is remarkable considering that a rabbit is about ten times heavier and much larger than a weasel. For comparison’s sake, it’s like a beagle taking down a fully grown black bear.
Territorial animals, weasels live around their burrows, which are often chambers in stone walls, tree stumps and even suitable spaces found in barns and cellars. Here is where you are most likely to see them in action, darting quickly in and out of bushes and crevasses, or running across a field.
As for identification, the weasel is often mistaken for its larger cousin, the stoat (Mustela erminea). Stoats have similar bodies, colour and markings, and also share the same habitats; even their behavior is very similar. Most sightings of both species happen in a flash, making it difficult to differentiate between the two. However, the stoat is considerably larger and has a longer tail with a distinct black tip. The smaller weasel, in contrast, has a much shorter tail and lacks any black markings on its body.
Fun fact
In 2015, a particular individual was spotted in a London Park riding on the back of a green woodpecker. This weasel attacked the much larger bird that took flight, but the undeterred weasel clung to its back. The moment was captured by amateur photographer Martin Le-May.
Photo © MartinLe-May
