Behavioral thermoregulation in mammals: a review

Abstract

In mammals, thermoregulation is a key feature in the maintenance of homeostasis. Thermoregulatory capacities are strongly related to energy balance and animals are constantly seeking to limit the energy costs of normothermia. In case of thermal changes, physiological mechanisms are enhanced, increasing rates of energy expenditure. However, behavioral adjustments are available for species to lower the autonomic work, and thus reduce the energy costs of thermoregulatory responses. Hence, thermogenesis-induced metabolic costs can be reduced during cold exposure, and hyperthermia associated to dehydration can be avoided during heat exposure. Hypothermia avoidance consists in a concomitant decrease in heat dissipation and increase in heat production. Inversely, heat exchange is enhanced and body heat production is reduced when avoiding hyperthermia. The different behavioral strategies available for mammal species to cope with both decreased and increased levels of ambient temperature are reviewed. Moreover, thermoregulation function is under the control of central, metabolic, energetic and endocrine systems, which induces that parameters such as hour of the day, season, gender or aging may affect thermoregulatory adjustments. Some examples will be given.

A remarkably quick habituation and high use of a rope bridge by an endangered marsupial, the western ringtail possum

“…In the study area, days with higher minimum temperatures generally experienced higher maximum temperature, which might have placed the possums under heat stress. Several mammalian species have been observed to decrease their food intake and activity under heat stress in order to reduce their heat production (Terrien et al 2011). P. occidentalis may employ similar behavioural coping mechanisms and thus reduce their activity, including bridge crossings, on warmer nights.…”

A Theory of Social Thermoregulation in Human Primates

“…Keeping all this in mind, the most efficient way to conserve energy is by seeking an optimal environment in terms of energy savings before changes in temperature occur, in which the organism can attain "thermoneutrality, " which all depends on an idiosyncratic level of comfort for the animal. In other words, the level of comfort relies on metabolic activity (Terrien et al, 2011), which differs across organisms, across the lifespan, and across social contexts.…”

“…Supporting this idea, vagal tone is associated with social wellbeing and social support seeking (Geisler et al, 2013). for infants. Further, many animals also do so reciprocally, as adult birds and mammals shield each other from harsh climatic environments through huddling (Gilbert et al, 2007;Terrien et al, 2011). We now turn to examples from the animal literature where huddling as a means for social thermoregulation has been detected.…”

Baseline tumor growth and immune control in laboratory mice are significantly influenced by subthermoneutral housing temperature

“…7 C and D) suggesting that tumor growth eventually exhausted the ability of mice to maintain normal body temperature under subthermoneutral conditions. It is well known that when mice are required to increase their metabolic heat production via thermogenesis, they exhibit long-conserved behavioral changes associated with "feeling cold," provoking them to move to warmer ambient temperatures, thus minimizing thermogenesis (3,4,8,22). Because caged mice are unable to carry out this behavioral activity, a thermal preference determination is frequently used to measure the degree of cold stress/heatseeking activity in laboratory mice (6).…”

“…This factor is important because mice have a high surface area to body mass ratio and lose heat rapidly. In nature, mice seek warm environments and build nests to minimize metabolic demands for heat production (3), and thermal preference studies have clearly shown that healthy mice will select an ambient temperature of 30-31°C (termed "thermoneutrality") at which their basal metabolism is sufficient to maintain body temperature (3)(4)(5)(6)(7). However, at subthermoneutral temperatures, mice experience cold stress, which induces a systemic sympathetic response involving adaptive metabolic changes and secretion of catecholamines, particularly norepinephrine (8).…”