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By Sascha Pare

 published 1 day ago

https://www.livescience.com/animals/bears/half-asleep-bears-are-wandering-around-siberia-because-its-too-hot-to-hibernate

Bears that are struggling to hibernate due to abnormally warm weather in Russia’s Amur region are wandering around in a daze, having suppressed their metabolism in preparation for winter.

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Bears in Siberia are wandering around “half-asleep” following abnormally high temperatures this fall, according to the Department for the Protection of Wildlife of the Amur Region.

The bears are ready to hibernate, having accumulated the fat reserves needed to sleep through the winter, but warm temperatures in November have kept them up past their bedtime, the government department said in a translated Telegram post on Nov. 21.

“In some areas, half-asleep bears still walk around the dens,” representatives wrote in the post. Bears were spotted traipsing around in a daze a month past the time they usually enter hibernation — toward the end of October, according to the post.

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The sleepless bears were mainly males, while females with cubs took to their dens “strictly on schedule,” the post said.

Bears normally spend winter asleep in dens, emerging in the spring when food becomes available again. Unlike other hibernating animals, bears decide for themselves when to begin their long seasonal sleep based on a number of cues, including food supply and temperature. Research has linked warmer weather and shorter winters to a reduction in the time bears spend hibernating, with bears leaving their dens 3.5 days earlier with every rise in temperature of 1.8 degrees Fahrenheit (1 degree Celsius).

Related: Bear linked to multiple attacks in Japan found dead alongside its final victim 

This fall, the Amur region, which shares a border with China in the Russian Far East, experienced abnormally high and record-breaking temperatures in October and November, The Moscow Times reported. And this could be delaying the bears’ hibernation.

Soggy dens could also be to blame, Oivind Toien, a zoophysiologist and research assistant professor at the Institute of Arctic Biology at the University of Alaska Fairbanks, told Live Science in an email. “Temperatures above freezing in wet snowy conditions could cause melt-water to enter dens [and] that could make it uncomfortable for bears to stay in,” he said.

Hibernation timing problems appear to impact males more than females and cubs.

“The denning period in females with cubs serves the additional purpose to protect the cubs,” Toien said. Bear cubs are more susceptible to frigid temperatures than adults due to their smaller size, as their bodies store less energy and lose heat more quickly, he said.

Cubs also have a higher base metabolism per unit of body mass than adults during both the summer and hibernation months, “so smaller bears might have to be extra careful in not spending extra energy on activity during this transition period into hibernation,” Toien said.

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Large adult bears, however, can maintain daytime activity during the early winter months by elevating their metabolism when they are on the move, then slowing it down again when they are resting, Toien said. Bears that are wandering around “half-asleep” may have already triggered the physiological transition to a hibernation state, and are thus going about their business with a suppressed metabolism, he added.

Bears in Alaska may also be losing sleep due to warm temperatures, Toien said. “Bears walking around in winter is well known for instance from coastal areas of Alaska,” he said. “Both the size of the bears and the mild climate in those coastal areas and continued availability of some food sources might play a role here.”

Sleepless bears are especially common in urban areas, where trash cans offer plentiful and accessible food throughout the winter, Toien said. Unlike the bears in the Amur region, those that habitually scavenge on human leftovers don’t typically build up fat reserves in preparation for hibernation, he added.

by Cell Press

Researchers report December 5 in the journal Neuron that mice display behavior that resembles self-recognition when they see themselves in the mirror. When the researchers marked the foreheads of black-furred mice with a spot of white ink, the mice spent more time grooming their heads in front of the mirror—presumably to try and wash away the ink spot. However, the mice only showed this self-recognition-like behavior if they were already accustomed to mirrors, if they had socialized with other mice who looked like them, and if the ink spot was relatively large.

The team identified a subset of neurons in the hippocampus that are involved in developing and storing this visual self-image, providing a first glimpse of the neural mechanisms behind self-recognition, something that was previously a black box in neurobehavioral research.

“To form episodic memory, for example, of events in our daily life, brains form and store information about where, what, when, and who, and the most important component is self-information or status,” says neuroscientist and senior author Takashi Kitamura of University of Texas Southwestern Medical Center. “Researchers usually examine how the brain encodes or recognizes others, but the self-information aspect is unclear.”

The researchers used a mirror test to investigate whether mice could detect a change in their own appearance—in this case, a dollop of ink on their foreheads. Because the ink also provided a tactile stimulus, the researchers tested the black-furred mice with both black and white ink. Though the mirror test was originally developed to test consciousness in different species, the authors note that their experiments only show that mice can detect a change in their own appearance, but this does not necessarily mean that they are “self-aware.”

https://www.youtube.com/embed/jVM62d3ODjk?color=whiteMouse during the mark test. Credit: Neuron/Yokose et al.

They found that mice could indeed detect changes to their appearance, but only under certain conditions. Mice who were familiar with mirrors spent significantly more time grooming their heads (but not other parts of their bodies) in front of the mirror when they were marked with dollops of white ink that were 0.6 cm² or 2 cm².

However, the mice did not engage in increased head grooming when the ink was black—the same color as their fur—or when the ink mark was small (0.2 cm²), even if the ink was white, and mice who were not habituated to mirrors before the ink test did not display increased head grooming in any scenario.

“The mice required significant external sensory cues to pass the mirror test—we have to put a lot of ink on their heads, and then the tactile stimulus coming from the ink somehow enables the animal to detect the ink on their heads via a mirror reflection,” says first author Jun Yokose of University of Texas Southwestern Medical Center. “Chimps and humans don’t need any of that extra sensory stimulus.”

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Using gene expression mapping, the researchers identified a subset of neurons in the ventral hippocampus that were activated when the mice “recognized” themselves in the mirror. When the researchers selectively rendered these neurons non-functional, the mice no longer displayed the mirror-and-ink-induced grooming behavior. A subset of these self-responding neurons also became activated when the mice observed other mice of the same strain (and therefore similar physical appearance and fur color), but not when they observed a different strain of mouse that had white fur.

Because previous studies in chimpanzees have suggested that social experience is required for mirror self-recognition, the researchers also tested mice who had been socially isolated after weaning. These socially isolated mice did not display increased head grooming behavior during the ink test, and neither did black-furred mice that were reared alongside white-furred mice.

The gene expression analysis also showed that socially isolated mice did not develop self-responding neuron activity in the hippocampus, and neither did the black-furred mice that were reared by white-furred mice, suggesting that mice need to have social experiences alongside other similar-looking mice in order to develop the neural circuits required for self-recognition.

“A subset of these self-responding neurons was also reactivated when we exposed the mice to other individuals of the same strain,” says Kitamura. “This is consistent with previous human literature that showed that some hippocampal cells fire not only when the person is looking at themselves, but also when they look at familiar people like a parent.”

Next, the researchers plan to try to disentangle the importance of visual and tactile stimuli to test whether mice can recognize changes in their reflection in the absence of a tactile stimulus—perhaps by using technology similar to the filters on social media apps that allow people to give themselves puppy-dog faces or bunny ears. They also plan to study other brain regions that might be involved in self-recognition and to investigate how the different regions communicate and integrate information.

“Now that we have this mouse model, we can manipulate or monitor neural activity to comprehensively investigate the neural circuit mechanisms behind how self-recognition-like behavior is induced in mice,” says Yokose.

More information: Visuotactile integration facilitates mirror-induced self-directed behavior through activation of hippocampal neuronal ensembles in mice, Neuron (2023). DOI: 10.1016/j.neuron.2023.10.022. www.cell.com/neuron/fulltext/S0896-6273(23)00803-6

Journal information: Neuron 

https://phys.org/news/2023-12-mice-mirror-classic-indicator-self-recognition.html