Added: Derel Benning - Date: 27.12.2021 07:45 - Views: 16966 - Clicks: 6892
Swedish researchers studying bears arrive at the site of a horrific battle in a deep forest. Dead bear cubs and s of a fight leave no doubt that a female and cubs-of-the-year have been attacked by a male. Some of the students and volunteers helping in the research work are appalled. Steyaert's study addresses infanticide, the killing of young offspring within a species, among brown bears.
The study is part of the Scandinavian Brown Bear Research Project, which has attracted scientists from several countries. When researchers find the corpses of bear cubs in the forest, they are sometimes partly eaten. This is just one of the indications that the female bear has defended her cubs fiercely.
They use these biological remains to identify the bears using DNA tests. Sometimes a mother bear manages to escape with her cubs. In others, the entire brood or individual cubs are killed. In two cases, researchers observed that female bears were also killed. Females are smaller than adult male bears and not much of a match when it comes to brawls like these.
This allows the scientists to follow their every move in detail. When scientists see a female bear with cubs veering from her normal roaming pattern, or if they see that a male is in the same place at the same time, they begin to suspect there may have been a fight. Out in the woods they rely on a low-tech approach as well, finding the exact spot of the battle with the help of dogs.
The reason for this male bear aggression is under dispute. Cubs are born in January or February. The cubs then follow their mother for one or two years. She will not mate as long as she is lactating and nursing them. But she can come in heat again in just a few days once the cubs disappear. By killing the cubs the male is removing a hamper against successfully mating with the female.
Thirteen cases of infanticide have been registered in a three-year period. Much remains unknown about the phenomenon. Steyaert stresses that it is a hard subject to study despite the space-age gadgets at hand. The technology fails now and then. The GPS collars can also simply fall off as the bears roam far and wide in rough terrain. The death of an entire brood of cubs is costly lost for a female. She has invested her time and resources into the cubs and will defend them with all her might. One strategy females with cubs use is simply to shy away from areas where males might be.
GPS tracking from an earlier study by the bear project showed that females with cubs stay away from areas of the forest where male bears and single females are found during the critical mating season. In autumn, when the rutting and the oestrus period is over, the bears all roam in the same areas.
These are areas where food Single females Bear are poorer. Bears eat a lot of grass and herbs at this time of year. The droppings of males as well as females with and without cubs have been analysed. These showed that mother bears had diets that had less protein and more fibre compared to the fare enjoyed by males and single females. Once the mating season ends in the summer and the cubs are out of danger from aggressive males, the protein content in the droppings of these females improved. The researchers see this as a smart strategy by the mother bears — they make a sacrifice by picking areas with slimmer pickings for part of the year when they and their offspring are vulnerable, compensating by eating better in the fall.
However, this study is based only on observations of a limited of bears in just one season. This kind of strategy is known from the relationship between animal predators and their prey. In periods where the prey are particularly at risk they prefer to withdraw to areas with a scantier food supply than to chance being eaten. Mother bears with cubs also risk going closer to human habitats, houses and cabins, in the spring and summer.
The bears are clever at hiding in these areas. In several cases the researchers have observed mothers Single females Bear cubs less than 1, metres from human habitats. None of the locals were aware of their proximity. Sweden has more brown bears in total and greater density in its forests than neighbouring Norway — there are only about brown bears in Norway versus upwards of 3, in Sweden.
Nevertheless, these are all the same stock and have common behaviour patterns on either side of the border. There would be no genetic advantage in killing cubs they have sired.
Researchers think males generally avoid doing so. But if this is true, how do the males know which cubs are their own offspring? Males that wander into a new area are not likely to be the father of any cubs they encounter, and these newcomers are often the most aggressive bears. The Eurasian elk, or moose, is filling in for cows as a forest browser. While Bessie is in the barn or an enclosed pasture, this big herbivore ensures continuity in the overall amount of browsing in outlying land in Norway.
A Scandinavian study indicates that females with cubs often stay away from the choicest feeding grounds from May to mid-July to avoid running into males.
Photo: Ilpo Kojala. October - Partly eaten When researchers find the corpses of bear cubs in the forest, they are sometimes partly eaten. Sam Steyaert. Nord University. University of Oslo.
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