Throughout most of Europe, the testes that have been involuted during hibernation begin reactivating about midway through hibernation. Full spermatogenesis (sperm production) can be present from March or April and continue into August; sperm production has declined to a minimum by late September. In the UK, the main breeding season, sometimes called the rut, runs from about mid-May until September. Some populations, in France for example, exhibit clear spring and summer phases to the rut, while it appears to be a continual process in Britain. In New Zealand, hedgehogs breed from November to March or April.
During his Ph.D. studies, Nigel Reeve observed courtship among hedgehogs inhabiting his London golf course study area to peak during August, which tallies with Pat Morris’ findings of a peak pregnancy rate in September – 52% females studied in England and Wales were pregnant during this time, compared to an average of 44% between May and July. In his Complete Hedgehog, Les Stocker notes that births may continue until early October, but most litters are born by July. Similarly, Pat Morris considered most young are probably born in June and July in his New Hedgehog Book.
The Art of Woo: Courtship
Courtship can be aggressive; the female often reacts to the male with lowered forehead, bristling spines and a loud, rapid snorting that sounds like a sharp exhalation of breath. Despite the female’s aggressive response, the male will approach and try to either herd or circle her while she butts at his flanks – often made with sufficient force to knock the male off his feet. While circling, the male will intermittently change direction and make attempts to mount the female. Maurice Burton was the first to publish a description of hedgehog courtship in the English literature, it having only been previously documented in the German literature, based on courtship he was alerted to by his gardener on 18th May 1965. Burton published a short article in the Illustrated London News during June of the same year in which he wrote:
“The sequence in hedgehogs starts when the boar approaches the sow, puffing or snuffling loudly. The two meet face to face, stand like this for a while and then the boar may turn and trot away through the herbage. But he seldom goes further than three feet away from the sow. He returns to face her once more, then he begins to walk round her, she pivoting so that her nose is directed towards him, and for most of the time the two are almost nose to nose. She may snap at him from time to time, or strike at him with a front paw; or she may roll up, completely or partially, in which even the boar may try to push his snout under her, as if seeking to unroll her.”
Courtship may be broken off and resume many times, continuing for several hours. Burton noted that the snuffling serves a definite function, with the sow being almost mesmerised by the tempo. This is a particularly interesting observation because although it is often thought that the snorting and grunting are a mutual exchange, they actually seem entirely the product of females hissing at the males; males apparently make very little noise during courtship. Snorts are emitted by the female every three seconds or so and each is accompanied by a jerk of the body.
It is not uncommon for several males to vie for the attentions of a single female and in some cases the female wanders off while the males are busy fighting over her! Females are polygamous and males polygynous, meaning each sex will mate with several partners, although it should be remembered that courtship does not always lead to copulation. In a short paper to the Journal of Zoology in 1986, Nigel Reeve and Pat Morris described a total of 27 males courting 20 different females. One female in particular was courted by at least 10 different males, eight of whom also courted at least one other female. Two of the males each courted at least eight different females. Only five (7%) of the courtships Reeve and Morris observed ended in mating. That 93% of courtships didn’t end in mating led the authors to suggest:
“Thus, although there may appear to be no selection of partners, it is still possible that some form of exclusivity might operate by sexual selection or inbreeding avoidance. This may in part be the function of the protracted and often inconclusive courtship behaviour.”
A female hedgehog shorting during courtship. Hedgehog courtship involves the male persistently circling the female while she turns to face him snorting every second or so. The male's circling, and the female's snorting, can continue uninterrupted for an hour or more. - Credit: Marc Baldwin
A protracted courtship may also help a female judge the vigour of potential suitors, with less tenacious individuals giving up more readily. In Ireland Amy Haigh and her colleagues documented 39 courtships between 16 individuals, none of which ended in successful copulation. The average bout of courtship lasted about an hour, although one observation went on for 2 hours and 20 minutes. Courtship always ended with the male seeming to lose interest and moving away to start foraging. Haigh and her co-workers also observed promiscuity among the hedgehogs – females were found with up to seven different males and males with up to three different females.
Observations of matings are rare, but there are some genetic data suggesting that females will mate with several partners. A team from the Waterford Institute of Technology in Ireland, led by Siobhan Moran, conducted a small-scale genetic analysis on five litters of hoglets brought into rescue centres, one litter from Devon and four from Jersey; in total, five females and 25 hoglets. Their results, published in the Journal of Zoology in 2009, showed evidence of multiple paternity. The Devon litter and one of the Jersey litters each yielded three paternal alleles, representing the mother and two different males.
Interestingly, Haigh and her co-workers also observed that hedgehogs moved into poorer quality pasture habitat (where food was less abundant) to breed, suggesting that less food in the area may mean fewer distractions from mating – at the end of the breeding season they moved back into neighbouring invertebrate-rich habitats.