The Truth Behind The Mask
June McNicholas tells us how the polecat got his distinctive 'bandit' mask.
It may sound like a 'just-so story' from Rudyard Kipling but it's actually the research focus of an academic article recently published by a team of zooologists from the University of Oxford and the University of Memphis. To be precise, their article discusses reasons for the prevalence of facial masks in many 'mid-guild' (ie: small to medium sized) carnivores.
Raccoons, civets, red pandas, several species of polecat, including our own European polecat from whom our ferrets are probably descended, black-footed ferrets and some small weasel species all have 'bandit' masks.
Many other similar sized carnivores like badgers and skunks have stripes faces - in other words masks that go vertically rather than horizontally. Why? Evolution of colours and patterns is rarely random so what benefit is there in having a mask? The scientists looked at a number of masked/striped animals and their unmasked/unstriped relatives to identify possible reasons.
Do dark masks act as an anti-glare device?
Dark colouration around the eyes can reduce glare from bright light. After all, footballers use dark paint under the eyes when playing on very bright days and Eskimo/Inuit people rub soot around their eyes to prevent snow blindness, so maybe masks do the same for some animals? Probably not, concluded the scientists, as many of the masked animals live in deep forest, underground or are nocturnal so they would not be exposed to bright light. (I don't know if the scientists considered that polecat ferrets may need anti-glare devices to carry on playing in an electrically lit living-room - I suspect not!)
Are masks useful for recognising each other in a social group?
This is certainly true for many types of facial marking in various antelope species. However, the scientists felt it was an unlikely use for masks in carnivores because so many of the species were solitary-living so they would have little need of social identification except during breeding.
Do masks make an animal sexy to a potential mate?
Does a big mask mean a big...well, let's just say sex appeal? Not very likely, say the scientists, because most masked species are either born with the markings or acquire them very early in life rather than at the times they are mature enough to breed. Also, there are a lot of related species that breed at the same time etc but do not have masks.
At this point it looked as if there was a good line in rejection of possible explanations for why polecats and similar species have masks but not real progress in why masks had evolved. However, the scientists have turned their attention to looking at why some species had masks while similar or related species did not. The main factor seemed to be how different animals avoided being attacked by predators. 'Mid-guild', or medium sized, carnivores obviously do prey on other animals, but, as they are only medium-sized themselves, they can be vulnerable to being preyed upon by larger carnivores if they have no defences.
Examination of how species avoid being attacked seemed a very worthwhile avenue of investigation. For example, pine martens, beech martens, mink, weasels and other members of the mustelid family that do not have masks have easily available avenues of escape from predators. Mink take to the water, martens are extremely fast climbers, weasels bolt for cover in small holes. The majority of masked mustelids and masked members of other species did not have such easy ways of avoiding predators. In fact, the mask seemed to signal a message of: 'You wouldn't want to catch me, I could hurt you' in that all masked animals are very strong and aggressive for their size and could inflict considerable injury on any predator.
Polecats, wolverines, raccoons, badgers and civets and no shrinking violets where fights are concerned. Maybe they don't have the speed to escape or the ready refuges like water or trees that some of their unmasked relatives have but they do have the all-important message through their mask: 'Don't make me angry, you wouldn't like me if I was angry' - which may well have made their masks the main feature of their successful existence.
So the next time your little poley looks up at you defiantly through his mask just remember that part of his behaviour is daring you to defy thousands of years of evolution!
Reference: Newman, C., Buesching, C.D. & Wolff, J.O. (2005). The function of facial masks in 'mid-guild carnivores'. 0IK0S 108:623-633,2005.