Coauthor Irina Rotenko
In May 2020 we traced four breeding groups of wolves in the model area (about 1000 square km) of Naliboki Forest, the central-western part of Belarus. There were mating registered in all these wolf groups in the period from the late January till the mid-March. According to the obtained information from the camera-traps and by reading of activity signs, it looked like all the adult females of wolves got into heat and mated.
One breeding group of those wolves consisted of two adult females and founding male. In this breeding group one female gave birth definitely, while another one was registered having no pups (aside the nipples were not visible on her belly that was almost without hair) already since the ealy May. It is hard to say there was denning behaviour in this adult female without pups or not (creating of dens, first of all).
The second breeding group of wolves was quite large (see another post for details). Initially we registered two breeding females with pups and two adult males that served for them: mainly one male serving to one female. However, sometimes two adult males were photographed in the close proximity of active den of one female. In the late May we got convinced that in this breeding group there was one more breeding couple that stayed with pups fairly close (approximately 1-2.5 km apart) to the two above denning couples. All these three couples from one large breeding group of wolves were characterized by pronounced denning behavior.
Other two groups of breeders were just couples. The first of these couples was documented that they have no pups on 10th of May: no pregnancy and aside the nipples were not visible on the belly that was almost without hair. The same was documented in relation to the second of these couples on 6th of June. Nevertheless, both wolf couples were characterized by denning behavior with digging of burrows and taking much attention to any siutable burrows.
Actually in the range of our activity in May in Naliboki Forest there was one more breeding group that consisted of male wolf and female hybrid (spotted and with white tail), but still we did not succeed to gather enough information about their breeding this year. Nevertheless, it looked like they have pups. We will get know that during this June.
In all the three cases we have no idea, when pregnancy of the three adult female wolves collapsed or they have lost pups in early days. The last winter in Naliboki Forest the wolf population density was lower: 30-50 inds per about 2700 square km in January-March versus 70-90 inds before (Sidorovich, 2016). In our book on the wolf reproduction biology (Sidorovich and Rotenko, 2018, 2019) we present data on the frequency of breeding in adult female wolves and its density-dependent variation. There was not much variation of this parameter along the gradient of food supply, but the population density was quite essential factor: low density – 93% of pregnant adult females in March till mid-April; medium – 89%; high – 74.
The last winter in Belarus the wolf population density was at fairly low level, and it could be expected that in Naliboki Forest having rather rich prey supply almost all adult female wolves would breed. But actually let’s say 3 out of 8 of them had no pups even had no any marks of presence pups of early days (some nipple visible aside) already in the mid-May. This information suggests only 60-70% breeding in adult female wolves in Naliboki Forest this year. That is rather low taking into account the population density level and supply with prey. Perhaps there were other factors like the possible disease that was acting in wolves (generally in carnivores) during the summer and autumn of 2019 that played a negative role in the wolf breeding in Naliboki Forest.