Alaska Department of Fish and Game, Kenai Moose Research Center, 43961 Kalifornsky Beach Road Suite B, Soldotna, AK 99669, USA; Department of Wildlife and Fisheries Sciences, Texas A&M University, TAMU, 2258 Bldg. 1537, 534 John Kimbrough Blvd., College Station, TX 77843, USA.
Alaska Department of Fish and Game, Kenai Moose Research Center, 43961 Kalifornsky Beach Road Suite B, Soldotna, AK 99669, USA.
J Therm Biol. 2020 May;90:102581. doi: 10.1016/j.jtherbio.2020.102581. Epub 2020 Apr 5.
We tested the concept that moose (Alces alces) begin to show signs of thermal stress at ambient air temperatures as low as 14 °C. We determined the response of Alaskan female moose to environmental conditions from May through September by measuring core body temperature, heart rate, respiration rate, rate of heat loss from exhaled air, skin temperature, and fecal and salivary glucocorticoids. Seasonal and daily patterns in moose body temperature did not passively follow the same patterns as environmental variables. We used large changes in body temperature (≥1.25 °C in 24hr) to indicate days of physiological tolerance to thermal stressors. Thermal tolerance correlated with high ambient air temperatures from the prior day and with seasonal peaks in solar radiation (June), ambient air temperature and vapor pressure (July). At midday (12:00hr), moose exhibited daily minima of body temperature, heart rate and skin temperature (difference between the ear artery and pinna) that coincided with daily maxima in respiration rate and the rate of heat lost through respiration. Salivary cortisol measured in moose during the morning was positively related to the change in air temperature during the hour prior to sample collection, while fecal glucocorticoid levels increased with increasing solar radiation during the prior day. Our results suggest that free-ranging moose do not have a static threshold of ambient air temperature at which they become heat stressed during the warm season. In early summer, body temperature of moose is influenced by the interaction of ambient temperature during the prior day with the seasonal peak of solar radiation. In late summer, moose body temperature is influenced by the interaction between ambient temperature and vapor pressure. Thermal tolerance of moose depends on the intensity and duration of daily weather parameters and the ability of the animal to use physiological and behavioral responses to dissipate heat loads.
我们检验了这样一个概念，即在环境空气温度低至 14°C 时，驼鹿（Alces alces）就开始出现热应激的迹象。我们通过测量核心体温、心率、呼吸率、呼出空气的热损失率、皮肤温度以及粪便和唾液中的糖皮质激素，来确定阿拉斯加雌性驼鹿在 5 月至 9 月期间对环境条件的反应。驼鹿的体温季节性和日间变化并没有被动地遵循与环境变量相同的模式。我们使用体温的大幅变化（24 小时内变化≥1.25°C）来表示对热应激源有生理耐受的天数。热耐受与前一天的高环境空气温度以及季节性的太阳辐射峰值（6 月）、环境空气温度和蒸气压峰值（7 月）相关。在中午（12:00 小时），驼鹿表现出体温、心率和皮肤温度（耳动脉和耳廓之间的温差）的每日最低值，这与呼吸率和通过呼吸丧失的热量的每日最大值相吻合。在早晨从驼鹿身上采集的唾液皮质醇与在采样前一小时内空气温度的变化呈正相关，而粪便中的糖皮质激素水平随着前一天太阳辐射的增加而增加。我们的研究结果表明，在温暖季节，自由放养的驼鹿没有一个环境空气温度的静态阈值，在这个温度下它们会受到热应激的影响。在初夏，驼鹿的体温受到前一天环境温度与太阳辐射季节性高峰相互作用的影响。在夏末，驼鹿的体温受到环境温度和蒸气压之间相互作用的影响。驼鹿的热耐受能力取决于每日天气参数的强度和持续时间，以及动物利用生理和行为反应来散发热量负荷的能力。
