Zoology by Vadim Sidorovich

Is there a relationship between initial litter size and survival to the first winter in wolf pups in Belarus?

Co-author Irina Rotenko

High mortality in wolf pups is a well‑known demographic bottleneck that strongly shapes wolf populations worldwide. Belarus is no exception: as documented in Sidorovich & Rotenko (2019) and in several posts on this blog, pup mortality here is particularly severe. In Belarus survival of wolf pups to the first winter is a crucial stage in the species population dynamics.

The Reproductive Struggle of Wolves and Brown Bears: Next Steps in Our Study

Co-author Irina Rotenko

Introduction: Bear Recolonization and Lack of Reproduction

Since April 2011 brown bear began re-colonizing Naliboki Forest, where in the past the species was common. During the summer of 2018, consistent observations (mainly via camera traps) revealed seven large male individuals and one or two smaller ones of uncertain sex (presumably females, inferred from the lack of visible testes). From 2020 to 2022, in the Naliboki Forest, we identified ten to twelve brown bears, about half of which (4–7 individuals) did not have visible testes, indicating they were likely females. Despite detailed tracing of the local bear population, no reproduction (i.e. no cubs) in summer has been observed, although mating pairs have been recorded every mating season from May to June.

At least ten-year-old female lynx Aurelja has two kittens this year

Co-author Irina Rotenko

Eight years ago, we began following an adult female lynx in the central-southern part of Naliboki Forest, in the localities of Jamna, Budy, and Barki, covering an area of about 40–60 square kilometers. We named her Aurelja. A Belgian volunteer once snow-tracked her with a kitten for several days. The volunteer’s name was Aurelja, and she asked us to name this mother lynx after her. We agreed.

Some findings on the development of a wolf reproduction clan

In Naliboki Forest in May-June 2025 within an area of only about 140 km², we recorded three distinct wolf families (each with pups) living in exceptionally close proximity throughout the denning season. One of these families had two simultaneously breeding females (double-breeding), two of them had one litter each, while a separate group of four non-breeding adults and subadults lived there, ranging between the families. We define this newly observed social structure during breeding season as a breeding clan.

Footage of a wild boar attempting to attack an adult wolf

Co-author Irina Rotenko

Recently, we captured an interesting moment when a large wild boar tried to attack an adult wolf just after it had crossed a river via a beaver dam.

Again, higher survival of wolf pups in the conditions of lower numbers of lynxes and brown bears in summer 2025

Co-authors: Louise Giovannelli and Irina Rotenko

From mid-August to the end of October, we closely monitored the wolf families that had been registered as denning in Naliboki Forest (central-western Belarus) in late spring of this year. In addition to our spring findings, we discovered in early autumn that one breeding group had previously gone unnoticed. This group exhibited double-breeding behavior.

Outstandingly frequent marking by wolves in summer and early autumn: what does it mean?

Co-authors: Louise Giovannelli and Irina Rotenko

Usually, from May until the end of September, wolves engage in territorial marking only sparingly. Breeding individuals, in particular, tend to avoid excessive marking. Non-breeders continue territorial marking at levels similar to those in the cold season, or even noticeably less.

One Important Factor Overlooked in the European Mink’s Demise

As a former researcher of wild European mink populations, I should have published these findings two decades ago. But better late than never. Back then, my attention was consumed by large carnivores and their conservation challenges, and I regret having neglected other essential topics. That oversight still weighs on me.

Wolf breeding clan under conditions of surplus prey abundance in Naliboki Forest: a new phenomenon

Co-author: Irina Rotenko

Over the last decades in Naliboki Forest (central-western Belarus), we have repeatedly documented multi-breeding wolf packs — most often double broods, occasionally triple broods. We now estimate that roughly two-thirds of wolf packs in this region reproduce in this intensive, multi-breeding strategy. This is likely driven by a combination of abundant prey and continued human persecution of wolves.

Another brown bear attack on wolf pups discovered

Co-author Irina Rotenko

In late April of this year, we discovered a wolf den where the pups had been extirpated by a brown bear. Just yesterday, a new incident was recorded – another brown bear attacked wolf pups.