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Why do rabbits have white, furry bottoms? Does this not make them easier for predators to spot? Lupodod

Rabbits certainly have their fair share of predators. Fully-grown rabbits are taken by foxes, cats, stoats and polecats while young rabbits are preyed on by badgers, buzzards and weasels. Over 90 per cent of baby rabbits die in the first year of life, most of these in the first three months. Some may die of disease, but a huge number are eaten. This high mortality rate is the main reason why rabbits are so fecund and, well, breed like rabbits! The female can have two or three litters per year, giving birth to about ten young each time. Producing lots of young increases the chance that some will make it through to adulthood and successfully reproduce.

As they are on the menu of so many predators, rabbits are very vigilant, constantly on the lookout for danger. They have eyes set wide on the sides of their skull which give them a broad field of vision, and sit on their hind legs to see further. With so many enemies around, it might seem counter-intuitive for a prey animal like a rabbit to make itself more visible by having a white rump. However, the white underside of a rabbit’s stubby tail (called a scut) is not that easy to see when the rabbit is grazing or moving slowly. It’s most noticeable when the rabbit is running, probably heading away from danger. This has led to several theories why rabbits have white tails.

Firstly, it acts as a warning to other rabbits in the warren. If a rabbit senses danger it raises its tail and thumps its foot to alert other members of the warren. Rabbits are mostly active in the low light conditions of dawn and dusk so a white flash would stand out, alerting other rabbits to run. Another theory suggests that by having a white tail, predators are attracted to the ‘right’ end of the rabbit and aim for the rear instead of the head, giving the rabbit a greater chance of escaping.

Rabbits also have a strict hierarchy and there can be a lot of aggression within the colony. Males, called bucks, will fight for access to females, known as does. The most dominant buck gains mating rights while the does compete for nest sites. Fights between the females can lead to serious injuries and even death. So one theory suggests that the tails are used like a white flag in surrender, to show submission to other rabbits and avoid potentially deadly fights. Dominant rabbits tend to be caught by predators more often than those lower in the hierarchy, perhaps because they are distracted by fights or because chasing off other rabbits makes their white tails more visible.

The rabbit’s tail probably has several functions, but the costs of having a white, fluffy bottom must be outweighed by the benefits or natural selection would have led to something a bit less conspicuous.