In Europe and wider in Eurasia between wolf researchers and in the circle of other wolf-related people (e.g. hunters specialising in killing wolves, wolf pup searches) there is a widely spread belief on wolf reproduction that wolves are strictly monogamous species with a certain way of breeding and family pattern of pack formation. Actually, in my study in Belarus since the late 1990s there have been found so many abnormalities in those, that I start to think about what actually prevails in the wolf reproduction and packing: the “rules” or “exceptions”. Such “abnormalities” occurring too often are a very interesting phenomenon and they need to be further investigated.
Among such “rules” or maybe “common beliefs” may be mentioned:
(1) The first breeding of female wolves happens, when they are about two years old or older;
(2) During breeding season a wolf pack has merely one litter or there are no pups in the pack;
(3) Usually a wolf pack consists of parent wolves and their pups of the current and previous biological years as a normal maximum; additionally, such a pack may subordinate some non-relative wolves that may be evaluated as a norm, too;
(4) Usually, offsprings disperse from a pack at mating season on the second year of their life being 20-22 months old.
(5) When wolves are more or less common, usually wolves kill and even consume stray dogs, but do not incorporate them into a pack and do not interbreed with them. Pairing with stray dog happens in a rarefied wolf population; and both sexes of stray dog may be paired with wolves
(6) There was nearly nothing mentioned about a great negative role of the lynx (Lynx lynx) and wild ungulates (mostly elk Alces alces, red deer Cervus elaphus and bison Bison bonasus) concerning low survivorship of wolf pups. So, it looks like it is a norm that these animals do not impact the wolf reproduction markedly.
In my study there was found that (2), (3) and (4) are only half-right, there are exceptions of (1) and (5), while (6) is entirely opposite.
Pack multi-breeding was found as a usual phenomenon in Belarus. Indeed, in Naliboki Forest and Paazierre Forest by investigating breeding in wolves for about 20 years and having found myself 70 dens with pups, there were revealed 14 cases of double breeding and two cases of triple breeding. So, pack multi-breeding happened in 49% of the cases. The main reason for multi-breeding was mating of the dominant male (perhaps, father) not only with the dominant female (mother), but with subdominant females (mainly daughters). Taking into account that not all cases were checked sufficiently for a chance of multi-breeding i.e. the other possible litters could be not discovered, we assume that actually multi-breeding happens in 60-80% of cases of reproduction in wolf packs. Pup survivorship is very low, and the whole litters die quite often.
Having discovered 70 wolf dens with pups, breeding of yearling females was revealed for two of these 70 cases (3%). Taking into account the ratio between yearling and other females in the wolf population, the data suggests that approximately 5-8% of yearling females already breed.
The timing of giving birth in the wolf population is getting more prolonged. In the 2000s among 61 giving births, which we well documented, there were registered one parturition in the mid-January, 4 parturitions in the late March-early April and 4 parturitions in the last decade of May. The majority of the registered parturitions in wolves were dated within a normal seasonal period, i.e. the last decade of April till the mid-May.
Also, we gained enough proofs that lynxes suppress wolf reproduction a lot by deliberately hunting on weakened individuals such as pups of the year, yearling females and heavily pregnant females. Wild ungulates kill many wolf pups, too.
There were found frequent peculiarities of pack formation. It was revealed that offsprings often stay with parents 3-5 years without breeding. Quite opposite trend is connected with pack deterioration through the wolf persecution by human or/and because of extremely low survivorship of pups. Both situations lead to a non-family pack formation somewhen during autumn, when strong one or several wolves gradually subordinated other non-relative wolves that ranging around. So, in such situations during winter the majority of wolf packs mostly consisted of non-relative individuals.
Among seven well-documented cases of hybridization between wolf and stray dog, three cases were registered in Naliboki Forest, when the wolf population was quite dense (about 2 inds per 100 km2). In all seven cases only female stray dog (naturalised one) and male wolf create a hybrid family.
As to the wolf population in Belarus, it is mainly exploited (heavy persecution of wolves is carried out every year in the most of the country), but in reserves the wolf is under protection nowadays. Prey supply is sufficient and even rich in many areas.
Wolf reproduction ecology and in particular the species breeding is one of the main studies I do. Getting more and more material on the wolf reproduction, I started to think that maybe the many peculiarities found are actually the norm, while the wolf monogamous family is one of the options.
Zoology by Vadim Sidorovich 