As safe habitats for polar bears continue to shrink rapidly due to the climate crisis’ impact on polar regions, scientists carried out a study to understand whether these majestic creatures can adapt to new environments.
Over three weeks in summer, Canadian researchers closely monitored 20 polar bears, employing collars equipped with video cameras and GPS to gain insights into their behaviour and energy expenditure when stranded on land.
The results, published in the journal Nature Communications on Tuesday, reveal a grim reality for these creatures as they grapple with the challenges of a changing environment.
Despite the bears attempting various strategies to maintain energy reserves, such as resting, scavenging, and foraging, nearly all of them experienced rapid weight loss, averaging around 1 kilogram, or 2.2 pounds, per day.
This weight loss occurred regardless of whether the bears were actively foraging or conserving energy through extended periods of rest, researchers from western Hudson Bay region of Manitoba, Canada, said.
Charles Robbins, the director of the Washington State University Bear Center and co-author of the study, says adapting to land like their grizzly bear relatives seems unlikey for polar bears.
“Neither strategy will allow polar bears to exist on land beyond a certain amount of time,” Mr Robbins says.
“Polar bears are not grizzly bears wearing white coats. They’re very, very different.”
Some adult male polar bears opted to conserve energy by resting, and burning calories at rates similar to hibernation. Others actively searched for food, consuming bird and caribou carcasses, as well as berries, kelp, and grasses.
Despite this diversity in behaviour, the bears faced a common challenge – the inability to replace the energy-rich fat of seals, their preferred prey, during the ice-free season.
“We found a real diversity of bear behaviours, and as a result, we saw a diverse range of energy expenditures,” Anthony Pagano, the lead author and research wildlife biologist with the US Geological Survey Polar Bear Research Program, said.
Although terrestrial foods provided some energetic benefit, the bears had to expend more energy to access these resources. Even those bears that went for long swims, covering distances up to 175 kilometres, faced challenges in feeding while swimming and bringing their finds back to land.
Only one bear out of the 20 managed to gain weight after stumbling across a dead marine mammal on land, highlighting the difficulty polar bears face in finding sufficient food during the extended ice-free period.
“As polar bears are forced on land earlier, it cuts into the period that they normally acquire the majority of the energy they need to survive,” Dr Pagano says.
The polar bear population in the area has already declined by an estimated 30 per cent since 1987. Researchers warn that these findings likely extend to polar bear populations across the Arctic, putting them at an increased risk of starvation as the ice-free period continues to grow.
Kwa kuwa maeneo salama ya kubaki kwa dubu wa barafu yanaendelea kupungua kwa kasi kutokana na athari za mgogoro wa hali ya hewa katika maeneo ya barafu, wanasayansi walifanya utafiti ili kuelewa kama viumbe hawa wakuu wanaweza kukabiliana na mazingira mapya. Kwa wiki tatu, watafiti wa Canada walifuatilia kwa karibu dubu 20 wa barafu, wakitumia kola zilizo na kamera za video na GPS kupata ufahamu wa tabia zao na matumizi ya nishati wakati wa kukwama kwenye nchi kavu. Matokeo ya utafiti huo, yaliyochapishwa katika jarida la Nature Communications, yanafunua hali mbaya ya viumbe hawa wanaopambana na changamoto za mazingira yanayobadilika. "Licha ya mbinu mbalimbali za kubaki na nguvu kama vile kupumzika, kutafuta chakula, na kutafuta chakula, karibu wote walipoteza uzito kwa kasi, kwa wastani wa kilo moja kwa siku.""" Kupungua kwa uzito kwa dubu hufanyika bila kujali kama walikuwa wakitafuta chakula au kuhifadhi nishati kwa muda mrefu, watafiti kutoka eneo la magharibi la Hudson Bay la Manitoba, Canada, walisema. Charles Robbins, mkurugenzi wa Kituo cha dubu cha Chuo Kikuu cha Jimbo la Washington na mwandishi mwenza wa utafiti huo, anasema kubadilika kwa ardhi kama jamaa zao wa dubu wa kijivu inaonekana kuwa isiyo ya kawaida kwa dubu wa barafu. "Hakuna mkakati wowote utakaoruhusu dubu wa barafu kuishi kwenye nchi kavu zaidi ya muda fulani", anasema Bw Robbins. <unk>Dubu wa barafu si dubu wa rangi ya kijivu wanaovaa makoti meupe. Wao ni tofauti sana, tofauti sana. Baadhi ya dubu wa kiume wazima walichagua kuhifadhi nishati kwa kupumzika, na kuchoma kalori kwa viwango sawa na usingizi wa majira ya baridi kali. Wengine walitafuta chakula kwa bidii, wakila mifupa ya ndege na caribou, pamoja na matunda, mwani, na nyasi. Licha ya tofauti hii katika tabia, dubu walikabiliwa na changamoto ya kawaida - kutokuwa na uwezo wa kuchukua nafasi ya mafuta yenye nishati ya sili, windo lao la upendeleo, wakati wa msimu usio na barafu. "Tumepata utofauti wa kweli wa tabia za dubu, na kama matokeo, tuliona aina mbalimbali za matumizi ya nishati, ""Anthony Pagano, mwandishi mkuu na mtaalamu wa biolojia wa wanyama wa porini katika Programu ya Utafiti wa Bear ya Polar ya Utafiti wa Kijiolojia wa Marekani alisema." Ingawa chakula cha ardhini kilitoa faida fulani ya nishati, dubu walilazimika kutumia nishati zaidi ili kupata rasilimali hizo. Hata dubu waliotembea umbali wa kilomita 175 walipata changamoto za kupata chakula na kuiburuta. Dubu mmoja tu kati ya 20 aliweza kupata uzito baada ya kukumbana na mnyama wa baharini aliyekufa kwenye nchi kavu, ikionyesha ugumu wa dubu wa barafu kupata chakula cha kutosha wakati wa kipindi kirefu cha barafu. "Kwa kuwa dubu wa barafu wanalazimishwa kufika ardhini mapema, inapunguza kipindi ambacho kwa kawaida hupata nishati nyingi wanazohitaji ili kuishi", anasema Dakt. Pagano. Idadi ya dubu wa barafu katika eneo hilo imepungua kwa asilimia 30 tangu mwaka 1987. Watafiti wanasema matokeo hayo yanaweza kuathiri idadi ya dubu wa barafu katika eneo la Arctic, na kuwaweka katika hatari ya kufa njaa wakati barafu haipo.