Norwegian Lemmings stand out in a crowd and scream to deter predators
Conspicuous, boldly coloured fur and loud barks warn would-be predators that little Norwegian Lemmings are not to be messed with, researchers have discovered.
The findings of the team headed by Malte Andersson from the University of Göteborg in Sweden appears in Springer’s journal Behavioral Ecology and Sociobiology.
The Norwegian Lemming (Lemmus lemmus) is endemic to northern Finland, Norway, Sweden, and the Kola peninsula in Russia.
The animals have a red-brown back, yellow flanks, white breast, chin and cheeks and a large black patch on the head, neck and shoulders.
They are unique among small rodents in their ferocity, and will readily fight back the aerial attacks of predators such as the Long-tailed Skua with loud screams, lunges and bites.
Most smaller rodents rarely aggressively protect themselves from predators; a willingness to have a go, therefore, is worth advertising.
Through five field tests, Andersson noted that the Norwegian Lemming’s remarkable traits can be ascribed to aposematism: the use of warning colours and other methods to signal to predators that the potential prey has some form of defence, for example being toxic.
Aposematism is unusual in herbivorous mammals, however, being much more common among insects, snakes and frogs.
In one of the experiments, 18 observers found it easier to spot Norwegian Lemmings in their natural habitat than their main rodent neighbour, the Grey-sided Vole.
In another test, Andersson noted that Brown Lemmings only gave anti-predatory warning calls in one out of 39 instances when a human (seen as a potential predator) was near.
Norwegian Lemmings, on the other hand, did so in 36 of 110 cases.
Black and white or yellow are classic warning colorations, which some birds instinctively know to avoid.
Andersson explains that such calls and coloration are often useful at close range, where a lemming is likely to be discovered even if silent.
They signal to a predator that the rodent will put up a fight if attacked.
“The Norwegian Lemming combines acoustics with visual conspicuousness, probably to reduce its risk of becoming prey,” says Andersson, who believes that such aposematism could help explain why the long-distance movements of Norwegian Lemmings are so conspicuous.