For much of the year, foxes are difficult to see in the wild. But when their cubs are born between May and July, they are vocal and more active during the day, hunting, playing or just relaxing in the sun.
Here Stephen Harris describes their key characteristics and some of the behaviour you are likely to see.
Male or female?
Dog foxes and vixens are hard to tell apart, though dogs are generally about one fifth heavier. The dogs also have broader, slightly more domed heads.
During winter (when mating), the male’s testes visibly protrude between his hindlegs, but these regress and are hard to see in summer.
When lactating, the vixen’s eight teats are obvious, and her belly fur is brick red (it’s normally white or grey).
In late winter, the vixen digs out several potential breeding earths. In rural areas, these will be in banks, at woodland edges or under piles of sticks or drystone walls. In urban areas, they can also be in or under sheds and buildings.
Growth of cubs
Newborn fox cubs are blind, deaf, dark-grey in colour and weigh about 120g.
After 14 days, their eyes open. Their pupils are slate-blue. Guard hairs appear, giving cubs a fuzzy appearance. They have small, floppy ears and weigh about 350g.
After four weeks, the cub’s pupils are grey flecked with brown. The muzzle starts to lengthen. White fur appears around the mouth and patches of red on the face.
The coat is still woolly, but the ears are now erect.
After eight weeks, the pupils become amber-coloured and the cub’s face approaches adult proportions. Its fur is largely adult colour but still looks woolly
Throughout the summer, cubs are very similar to adults but have thinner coats and a lankier appearance. They become indistinguishable from the adults by late September or early October, once their winter coats are fully grown.
From late September, the family group breaks up and some or all of the cubs disperse.
Cubs are suckled for the first four weeks, then progressively weaned until seven weeks old (though they are occasionally still suckling at 14 weeks).
They hunt earthworms and insects as soon as they emerge from their earth (at four weeks), but these form only a very small proportion of their diet.
Adults bring back larger mammals and birds for the cubs, but they themselves feed more on small prey such as mice and voles.
Cubs are cautious until they start foraging for themselves.
In gardens, they may hide in flowerbeds while the adults collect food. Youngsters have high energy-needs – adults caring for a litter can look very thin.
Both dogs and vixens provision their cubs, who beg for food by rushing over excitedly. They hold their bodies low to the ground, wag their tails rapidly, nuzzle the adult’s mouth and whine.
Cubs fight over access to food. They arch their backs, raise their hackles and hold their heads low while making high-pitched ‘kek-kek-kekking’ noises. Tugs-of-war help to break open carcasses – the cubs’ teeth are too weak to tackle intact prey.
Cubs start to forage for themselves in July. Thereafter, they compete with adults for food, who may push them off a kill. They tend to go for easy-to-catch prey such as insects and earthworms while slowly developing their hunting skills.
There is a strict dominance hierarchy within social groups.
A subordinate approaches a dominant with its body held low. It often crouches or even wriggles on its back at the feet of the dominant animal in a puppy-like appeasement gesture.
Cubs start to establish a dominance hierarchy even before they emerge from their earth, when fights are particularly vicious. About 20 per cent of cubs die underground, often as a result of spats with siblings. Dead cubs are generally consumed by littermates.
Hierarchy is largely established within seven or eight weeks, and thereafter serious fights are rare.
Dominant cubs have preferential access to food and thus grow much faster. In larger litters, dominant cubs may look four weeks older than subordinates, often leading to the mistaken impression of two pooled litters.
Dominant cubs receive more social grooming from adults, are more strongly integrated into the social group and less likely to disperse in autumn.
As cubs get older, they fight by standing on their hindlegs and placing their forelegs on their opponent’s chest. They try to push each other over in a trial of strength. The loser is often chased and may be badly bitten on the rump or base of the tail.
Foxes live in social groups – three or four adults are quite common (though 10 were recorded in one Bristol group). These consist of equal numbers of dogs and vixens.
Generally, only one vixen breeds, but occasionally up to three do. Cubs can be reared separately, but may also be pooled together in one large litter.
Mid-March is the peak time for births. The average litter size is four or five, but eight is not uncommon. For the first few weeks, the vixen spends most of her time with the cubs and relies on the male to bring her food.
There is no obvious sign as to which earth has been used for breeding until the cubs emerge at about four weeks old – usually late April or early May. Food remains then accumulate around and inside the earth.
Unless disturbed, cubs stay in their natal earth until early June, though they may abandon it earlier in hot weather. From early June, they lie up above ground at rendez-vous sites in dense cover such as a bramble or thorn patch or in piles of rubbish.