THE FAMILY LIFE OF THE RED FOX
Fox cubs are born deep in the earth in spring and pressure then mounts on the adult foxes to find enough food to go round the ever-hungry family. In some family groups, non-breeding vixens lend valuable assistance in rearing the young and by the end of the summer the young are able to fend for themselves.
During the winter dog foxes and vixens often shelter underground in an earth. Normally each fox regularly uses only a few earths within its territory.
With the approach of spring, however, the behaviour of the vixen changes. She is pregnant, having mated in late January, and carries her young for an average of 53 days. As her pregnancy advances, she excavates many disused earths – sometimes old badger or rabbit holes – throughout her home range, and makes exploratory diggings’ at potential sites for new earths.
These burrows, begun along sandy banks and ridges, often reach no more than 10-20cm (4-8in) into the ground. You can spot where they have been started from the surrounding soil, which bears deep gouges from the vixen’s claws. These exploratory diggings are often abandoned, but why is not always obvious. Sometimes the fox encounters a sturdy root which impedes progress, but at other times she simply seems to change her mind about the site.
Birth in the earth
The earth the vixen eventually chooses to house her cubs-which are generally born at the end of March – usually has two or three entrances and may stretch for several metres underground, through a series of ramifying tunnels.
When the cubs are born the vixen is confined within the earth, staying there for several days and sometimes for more than a week. During this time, the dog fox’s behaviour may be critical to the vixen’s well-being. On the whole the dog fox is a conscientious father and regularly provides food for his mate. You can sometimes find a small offering of food lying outside the entrance to the earth, where the doe fox has left it.
In some areas, foxes live in social groups made up of one dog fox and several vixens. By radio-tracking it has been possible to discover that each of these group members shares roughly the same range of territory. There is little overlap with the range of similar neighbouring groups.
Although vixens are reproductively mature in their first year, it seems that where social groups develop some vixens within the group particularly the younger members-do not breed. In some places, perhaps as few as one third of those able to do so, actually breed. This figure varies greatly from place to place. World-wide research shows that in certain areas well over 90% of vixens conceive and give birth in their first year.
From observation of fox groups in captivity it seems that the dog fox males with only one vixen, showing no interest at all in any others in the group. In the wild it is likely that more vixens mate and conceive than in captivity. But only a minority succeed in reaching a full-term pregnancy or rearing offspring. In a survey in which radio-tagged non-breeding vixens were followed at night, it appeared that these individuals visited the vicinity of the breeding earth each night-and several times in some cases. The ‘barren’ vixens were apparently participating in rearing the cubs, sitting and playing with them and even providing them with food.
At first sight, this seems to be an extra-ordinary act of altruism. The vixens which do not have the opportunity to bear young themselves instead help to rear those of another vixen. Since the success of an individual, in evolutionary terms, is measured by the number of offspring which survive to breed subsequent generations, this behaviour is paradoxical.
A clue to the reason for this apparently selfless behaviour may lie in the observation that all the vixens in a given group commonly look alike. They may share features such as a blaze of white on the legs or a heavily marked muzzle. It seems that the female members of fox groups are at least sometimes close relatives-daughters, sisters, aunts. This provides a possible explanation. They have a stake, an evolutionary investment, in the survival of their relative’s cubs, since those cubs will carry some of the genes shared by the whole family. Helping to rear a relative is breeding by proxy.
Why don’t the helpers simply breed themselves? The answer may be that they have no choice. Evidence suggests that helpers are often socially subordinate to the breeding female. It may be that their failure to breed is a direct consequence of low status and thus beyond their own control. The mechanism could be equivalent to a sort of inbuilt family planning.
The young vixen may be faced with the dilemma of staying at home, with no opportunity of breeding, or of leaving home in the hope of surviving long enough to find a territory of her own. Staying at home as a helper – at least for a time – may be the best compromise. There is, after all, a chance that she will inherit the territory when the dominant vixen dies. There may even be opportunities to breed before then, since not infrequently there are cases of two vixens within one group breeding, and even sharing the same earth.
Feeding the cubs
Up to the age of about three weeks, fox cubs are fed on their mother’s milk. After that they begin to gnaw at scraps of meat. This heralds a change in the behaviour of the non-breeding vixens. They start to spend much more time with the cubs, grooming them and sometimes even splitting the litter up into two or three hiding places, each guarded by a different vixen. The most striking thing of all is the extent to which non-breeding vixens aid the young cubs by feeding them. In some cases, they carry more food back to the cubs than the real mother. On one occasion, it was found that when a vixen, the mother of a litter, was taken seriously ill, her cubs survived with the help of several non-breeding females. It is a major task for the adult foxes to provide enough food for the growing cubs, even though the labour for parents which have the benefit of helpers is reduced. In areas where foxes maintain large territories – some well over 400 acres – the task of carrying the food home is substantial. There is some evidence that the diet of growing cubs comprises more large prey than does that of the adults during the same period. This could result if parents were deliberately economising on travel by carrying larger prey to the cubs. Certainly, it is more efficient to carry back one hare than to make several dozen trips with mice and voles.
By early summer the cubs have grown sufficiently to follow the adults out of the earth. It often looks as though the adults lead a cub deliberately on a tutorial expedition. Every time one adult fox sniffs at something, a cub rushes up and also sniffs at it, closely imitating its parents’ behaviour in everything. Sometimes the cubs wander away from the earth by themselves and this-when they are out in daylight — is a good time to see them.
As the cubs grow increasingly independent, they forage more and more for themselves, often choosing quite different prey from that fed to them by their parents. Three or four-month-old cubs scour the grass for beetles and at night, if weather conditions permit, they catch earthworms. Adults catch the worms without difficulty, but the cubs seem to take a while to learn the technique of stabbing the snout down into the vegetation to grab the worms. At first they are more inclined to try to catch them by the so-called mouse leap – a movement the cubs exhibit almost as soon as they can run. The fox leaps high off the ground, then lands on a mouse with both forepaws. This may be an adaptation to thwart the escape response shown by wood mice which leap upwards when threatened. By landing from above the fox forestalls the mouse’s escape. Cubs trying to catch earthworms with such leaps fail miserably because the worms slip away between their paws. However, the correct technique is soon learned.
Some young dog foxes begin to disperse in early autumn, although others wait until mid-winter. Although members of a group may spend little time together as the summer draws to a close, and even though they rarely hunt together, they may well still be in close contact. As they criss-cross the territory by night, members of a family not only meet quite frequently, but can also keep in touch through scent and sound.