Too early giving birth in wolves got common in Naliboki Forest

Co-author Irina Rotenko

In this post we address to a newly registered trend in breeding of wolves in Belarus, in particular relating to the earlier giving birth in wolves in Naliboki Forest, the central-western Belarus and in the whole country.

While starting a detailed study on reproduction in wolves in Belarus in the 1990s, I (Vadim Sidorovich) visited all wolf-related local people (in total there were seven persons), who have relatively large experience in wolf pup searching in the country. Two of them (Lienard Jurevich and Baliaslaw Sadowski) lived in the core area of Naliboki Forest. Taking altogether the den findings of those seven wolf pup searchers, it appears that  they found more than three hundred of actual wolf dens with pups. During our meetings I raised them many wolf-related questions, and one of the questions was timing of giving birth in wolves. Their answers were more or less like the following one.

Usually female wolves give birth in the period from the end of April till the end of May, and two third of wolf litters appear till 10th of May. Also, from those wolf-related people said me some anecdotal messages, that they heard about some cases of wolf giving birth earlier even in the late of March, but nobody from those respondents themselves discovered a wolf litter so early. Moreover, in my own experience alone till 2007 as well as from the joint experience that was gained together with wolf pup searcher Victar Staliarow in 1990s there was no evidence of such early breeding in wolves in Belarus. Such situation with timing of giving birth in wolves continued till the beginning of the 2000s.

Approximately since 2010 and particularly during the last 4-6 years the situation with timing of breeding in wolves in Belarus seemingly changed considerably to the direction of earlier breeding. We investigated this trend in Naliboki Forest, the central-western part of Belarus.

It is worthwhile to notice that we mean breeding of real wolves, which look like normal ones. In this post we do not include our material about breeding of pairs, in which one looked like a normal wolf, whereas another one was an evident stray dog. During our long-term study on wolves we faced such hybrid breeding or heard about someone’s such findings for many  times. Some of our material on the wolf-dog breeding is given in the earlier post in this blog as well as in our book on the wolf reproduction (Sidorovich & Rotenko, 2019).

A total, in Naliboki Forest since 2015 by investigating (by finding of den with pups and/or by camera-trapping) 3 to 6 wolf breeding groups per year, and  we registered the following cases of too early giving birth: (1) mid-January; (2) late January; (3) late February; (4) mid-March; (5,6) 2 cases in late March; (7-9) 3 cases in the early April. An early giving birth in wolves is defined as when wolf parturition happened before 10th of April. So, during the last nine years (since 2015) in Naliboki Forest we registered nine cases of early breeding in wolves. A total during these nine years we investigated stories of 38 parturitions and raising of litters in wolves in the area. Thus, too early breeding in wolves in Naliboki Forest got really common during the last decade and constitutes 23.7% of cases.

Hypothetically, we connect this trend with more intensive hybridization of wolves with stray dogs that frequently  happened since 2010, and we do not see any other cause that could affect the timing in wolf breeding in Belarus so dramatically.

It looks like nowadays in Belarus wolves are genetically polluted by on-going hybrydisation with stray dogs, while two decades ago wolves were almost unpolluted in the country. In the early 2000s we sampled wolves in Belarus for a genetic study, and none of these wolves showed even a dog ancestry (Stronen et al., 2013).

Father wolf with a pup of the year in the late May. The pup was born in the late January.

You can support the research on large carnivores in Naliboki Forest by buying just a coffee. It will help to keep the study going.