Co-author Irina Rotenko
Historic Context and Present State of Brown Bears
Throughout the Nice Lithuanian interval, from the sixteenth to the 18th centuries, brown bears have been considerable within the Naliboki Forest and surrounding forest massifs. Studies of searching these animals incessantly seem within the sport husbandry paperwork of the Radziwills and different magnates. Up till the First World Conflict, the brown bear remained an ordinary sport species and a comparatively widespread trophy within the searching collections of the native elite, indicating a high-density inhabitants within the Naliboki Forest.
Throughout the First World Conflict, brown bears within the Naliboki Forest have been almost eradicated. Within the Twenties, the species started to recolonize the world. By the late Nineteen Thirties, data present that 30-50 brown bears inhabited the Naliboki Forest. Nevertheless, in the course of the Second World Conflict, they have been hunted to extinction by locals and guerrillas for his or her meat. Within the late Nineteen Fifties, after the struggle, migrating brown bears began to repopulate the Naliboki Forest, and by the Nineteen Sixties, a steady inhabitants of roughly 20-30 bears had been re-established.
Within the Seventies, the brown bear inhabitants was progressively poached. Native searching wardens, Baliaslaw Sadowski, Lienard Yurevich, and Edzik Khmara, noticed a major decline within the bear inhabitants, attributing it to a scarcity of replica throughout the species. Over a decade, they recorded just one sighting of a mom bear along with her cubs.
Throughout the Nineteen Sixties and Seventies, the forest was densely populated by wolves, resulting in hunters culling 30-70 wolves every winter. Sadowski and Yurevich reported two situations of wolf packs attacking hibernating brown bears, chasing them over a number of kilometers. It’s unclear if the bears had cubs throughout these hibernation intervals.
Between the Seventies and 2011, brown bears have been seldom seen in Naliboki Forest, with solely occasional appearances. Typically, these transient brown bears didn’t keep in Naliboki Forest for lengthy, often residing there for lower than a yr.
In April 2011, across the identical time, two grownup bears made their method into Naliboki Forest and progressively settled within the space. After hibernation, within the heat season of 2012, these identical bears have been noticed in the identical areas of Naliboki Forest.
Throughout the summer season of 2018, constant observations (primarily through digicam traps) revealed seven giant male people and one or two smaller ones of unsure intercourse (presumably females, inferred from the dearth of seen testes). From 2020 to 2022, within the Naliboki Forest, we recognized ten to 12 brown bears, about half of which (4-7 people) didn’t have seen testes, indicating they have been doubtless females. Regardless of detailed tracing of the native bear inhabitants, no breeding has been noticed, though mating pairs have been recorded each mating season from Might to June.
Reevaluating Assumptions of Replica Failure
Initially, we attributed the absence of brown bear cubs in Naliboki Forest to disturbances brought on by antler searchers throughout February and March. Throughout late winter and early spring, when shed hunters have been significantly energetic, mom bears had already given beginning to cubs of their dens. In accordance with a number of brown bear researchers, beneath such circumstances, mom bears are sometimes hesitant to return to their dens, resulting in the loss of life of the cubs. At first look, this rationalization appeared believable.
Over time, we gathered proof suggesting that our preliminary assumption was incorrect, and one other issue performs a major function within the reproductive failure of brown bears in Naliboki Forest. Firstly, on 4 events, we discovered it difficult to disturb brown bears from their hibernating dens by merely strolling close by. Throughout these situations, we handed inside 8 to twenty meters of the hibernating bears 7-20 occasions over the winter, with out realizing how shut they have been, and none have been frightened away by our presence. Moreover, we occurred to startle brown bears (solely males) from their dens 3 times, after we often approached the sleeping brown bears for a number of metres and delayed close by. The brown bears fled solely a brief distance (300-500 meters) and returned to hibernate in the identical space, albeit at totally different websites. This led us to consider that disturbance from shed hunters and others is unlikely the reason for the brown bears’ reproductive points in Naliboki Forest.
We additionally thought of the chance that searching canines would possibly disturb hibernating mom bears, resulting in cub mortality and driving them away. Nevertheless, within the Naliboki Forest reserve (which constitutes half of the forest space), searching with canines and different types of searching is strictly prohibited. Moreover, in different components of Naliboki Forest, searching usually ceases by mid to late January, coinciding with the beginning of brown bear births.
Regardless of dismissing the preliminary speculation associated to shed hunters’ winter actions, we remained puzzled by the decline in brown bear replica. Nevertheless, a selected incident prompted us to formulate a brand new, extra believable speculation—one which we proceed to discover in our ongoing analysis.
Wolf Predation as a Potential Think about Reproductive Failure
In mid-January 2021, 5 grownup wolves launched an assault on a medium-sized brown bear at its open hibernation web site. The bear mounted a protection beneath a spruce tree, urgent its again towards the trunk earlier than fleeing. It took cowl in a dense thicket of younger spruces, weaving by means of willow bushes, reeds, and fallen bushes. The pursuing wolves halted the bear’s escape seven occasions in clearings or sparsely wooded areas. Every time, the bear counterattacked, utilizing giant bushes and willow bushes for cover. After a 3-kilometer chase, the bear entered a small space throughout the thicket, marked by fallen birches, the place it appeared to wound one of many wolves, stripping pores and skin from its again. Subsequently, the bear discovered refuge in a bigger thicket, prompting the wolves to desert their pursuit.
Reflecting on the incident described earlier, we recalled two comparable situations reported by native searching wardens (Baliaslaw Sadowski, Lienard Yurevich, and Edzik Khmara) within the Naliboki Forest in the course of the Seventies. This led us to contemplate the chance that robust wolf packs might intimidate a mom brown bear, drive her to desert the world, and prey on her cubs. Given the substantial wolf inhabitants in Naliboki Forest, such occasions might happen a number of occasions every winter. This frequency of wolf aggression in the direction of mom brown bears may be adequate to halt the replica of the species throughout the forest.
Our evaluation has progressed additional. Within the Nineteen Nineties and early 2000s, I, Vadim Sidorovich, spent intensive time within the forested areas of European Russia—particularly Pskov, Tver, Vologda, Smolensk, and Novgorod. Apparently, I noticed a close to absence of wolves roughly 100 km from the Belarusian border. Wolf tracks on forest roads and riverbanks have been sporadic, not day by day. The hassle required to search out wolf footprints in Naliboki Forest in Belarus was disproportionately larger in comparison with these Russian areas—a stark distinction.
In these Russian areas, wild ungulate density was remarkably low, doubtless leaving wolves food-deprived and stopping them from establishing a dense inhabitants. Nevertheless, I encountered many brown bears in those self same areas of Russia. Tracks of mom brown bears with cubs occurred surprisingly usually. Their scats primarily consisted of natural stays and bugs, indicating herbivorous and entomophagous habits. Notably, the low numbers of untamed ungulates didn’t considerably have an effect on brown bears. In these Russian forest massifs, the place wolves have been scarce, mom brown bears efficiently reproduced, and the brown bear inhabitants thrived.
The persistent absence of brown bear cubs in Naliboki Forest, regardless of the presence of mating pairs, factors to a posh interaction of things influencing reproductive success. Our observations counsel that the excessive density of wolves and their aggressive interactions with brown bears, significantly throughout denning intervals, could also be a major deterrent to profitable breeding. This speculation aligns with contrasting eventualities in European Russia, the place decrease wolf populations correlate with thriving brown bear replica.