At the height of the breeding season, this phenomenon is known as "March madness", when the normally nocturnal bucks are forced to be active in the daytime. In addition to dominant animals subduing subordinates, the female fights off her numerous suitors if she is not ready to mate. Fights can be vicious and can leave numerous scars on the ears. In these encounters, hares stand upright and attack each other with their paws, a practice known as "boxing", and this activity is usually between a female and a male and not between competing males as was previously believed. When a doe is ready to mate, she runs across the countryside, starting a chase that tests the stamina of the following males. When only the fittest male remains, the female stops and allows him to copulate. Female fertility continues through May, June and July, but testosterone production decreases in males and sexual behaviour becomes less overt. Litter sizes decrease as the breeding season draws to a close with no pregnancies occurring after August. The testes of males begin to regress and sperm production ends in September. Does give birth in hollow depressions in the ground. An individual female may have three litters in a year with a 41- to 42-day gestation period. The young have an average weight of around at birth. The leverets are fully furred and are precocial, being ready to leave the nest soon after they are born, an adaptation to the lack of physical protection relative to that afforded by a burrow. Leverets disperse during the day and come together in the evening close to where they were born. Their mother visits them for nursing soon after sunset; the young suckle for around five minutes, urinating while they do so, with the doe licking up the fluid. She then leaps away so as not to leave an olfactory trail, and the leverets disperse once more. Young can eat solid food after two weeks and are weaned when they are four weeks old. While young of either sex commonly explore their surroundings, natal dispersal tends to be greater in males. Sexual maturity occurs at seven or eight months for females and six months for males. European hares are large leporids and adults can only be tackled by large predators such as canids, felids and the largest birds of prey. In Poland it was found that the consumption of hares by foxes was at its highest during spring, when the availability of small animal prey was low; at this time of year, hares may constitute up to 50% of the biomass eaten by foxes, with 50% of the mortality of adult hares being caused by their predation.