Mella Valentina S A, Cooper Christine E, Karr Madeline, Krockenberger Andrew, Madani George, Webb Elliot B, Krockenberger Mark B
Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales 2006, Australia.
School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia.
Conserv Physiol. 2024 May 27;12(1):coae032. doi: 10.1093/conphys/coae032. eCollection 2024.
Thermoregulation is critical for endotherms living in hot, dry conditions, and maintaining optimal core body temperature () in a changing climate is an increasingly challenging task for mammals. Koalas () have evolved physiological and behavioural strategies to maintain homeostasis and regulate their but are thought to be vulnerable to prolonged heat. We investigated how weather, behaviour and disease influence for wild, free-living koalas during summer in north-west New South Wales. We matched with daily behavioural observations in an ageing population where chlamydial disease is prevalent. Each individual koala had similar rhythms (average = 36.4 ± 0.05°C), but male koalas had higher amplitude and more pronounced daily rhythm than females. Disease disrupted the 24-hr circadian pattern of . Koala increased with ambient temperature (). On the hottest day of the study (maximum = 40.8°C), we recorded the highest ( = 40.8°C) but also the lowest ( = 32.4°C) ever documented for wild koalas, suggesting that they are more heterothermic than previously recognized. This requires individuals to predict days of extreme from overnight and early morning conditions, adjusting regulation accordingly, and it has never been reported before for koalas. The large diel amplitude and low minimum observed suggest that koalas at our study site are energetically and nutritionally compromised, likely due to their age. Behaviour (i.e. tree hugging and drinking water) was not effective in moderating . These results indicate that and koala are strongly interconnected and reinforce the importance of climate projections for predicting the future persistence of koalas throughout their current distribution. Global climate models forecast that dry, hot weather will continue to escalate and drought events will increase in frequency, duration and severity. This is likely to push koalas and other arboreal folivores towards their thermal limit.
体温调节对于生活在炎热干燥环境中的恒温动物至关重要，而在气候变化的情况下维持最佳核心体温（）对哺乳动物来说是一项越来越具有挑战性的任务。考拉（）已经进化出生理和行为策略来维持体内平衡并调节体温，但它们被认为易受长期高温影响。我们调查了天气、行为和疾病如何影响新南威尔士州西北部夏季野生自由生活考拉的体温。我们将体温与衣原体疾病流行的老龄种群中的每日行为观察结果进行了匹配。每只考拉个体都有相似的体温节律（平均体温 = 36.4 ± 0.05°C），但雄性考拉的体温波动幅度更大，且每日节律比雌性更明显。疾病扰乱了体温的24小时昼夜模式。考拉的体温随着环境温度（）升高。在研究中最热的一天（最高温度 = 40.8°C），我们记录到了野生考拉有记录以来的最高体温（ = 40.8°C），但也记录到了最低体温（ = 32.4°C），这表明它们比之前认为的更具异温性。这要求个体根据夜间和清晨的状况预测极端天气的日子，并相应地调整体温调节，而此前从未有过关于考拉的此类报道。观察到的较大昼夜温差幅度和较低的最低体温表明，我们研究地点的考拉在能量和营养方面可能因年龄而受到损害。行为（即抱树和饮水）在调节体温方面并不有效。这些结果表明体温和考拉体温密切相关，并强化了气候预测对于预测考拉在其当前分布范围内未来生存状况的重要性。全球气候模型预测，干燥炎热的天气将持续加剧，干旱事件的频率、持续时间和严重程度将会增加。这可能会将考拉和其他树栖食叶动物推向其热极限。
