Thermoregulation by Mule Deer (Odocoileus hemionus) in Arid Rangelands of Southcentral Washington

We used miniature data loggers implanted in the abdominal cavity to measure core body temperatures at 30·min intervals in eight (three males, five females) adult free-ranging springbok Antidorcas marsupialis in their natural habitat, over a period of 11-13 months. The animals were subjected to a nychthemeral range of air temperature that often exceeded 20°C, with an absolute minimum temperature of -6°C and a maximum of 34°C. Abdominal temperature exhibited a low amplitude (~1.2°C) nychthemeral rhythm, with a temperature peak near sunset and a trough shortly after sunrise. The amplitude of the nychthemeral rhythm of body temperature was not correlated with the 24·h range of air temperature. Although mean 24·h body temperatures were positively correlated with corresponding air temperatures, mean daily body temperature increased, on average, by only 0.02°C per 1°C increase in air temperature, so that it was only ~0.3°C higher in summer than in winter. Mean monthly body temperatures were strongly positively correlated with photoperiod and, in parallel with changes in the time of sunrise, the times at which the minimum and maximum body temperatures occurred were shifted ~1.2·h earlier in summer than in winter. Annual and daily variations in body temperature of springbok, like those of other free-living African ungulates, therefore appear to reflect an endogenous rhythm, entrained by the light:dark cycle, but largely independent of fluctuations in the environmental thermal load. Springbok exhibit remarkable homeothermy and do not employ adaptive heterothermy to survive in their natural environment.

Section: Discussionsupporting

confidence: 80%

Section: Discussioncontrasting

confidence: 65%

A year in the thermal life of a free-ranging herd of springbokAntidorcas marsupialis

Fuller

Kamerman

Maloney

et al. 2005

“…Dawson et al have suggested that the lowering of morning T c in kangaroos might be an energetic adaptation (Dawson et al, 2007). Seasonal changes in mean T c occur in goats (Jessen and Kuhnen, 1996) and Arabian oryx (Hetem et al, 2010); in contrast, previous studies have reported no change in mean T c across seasons in sheep (Bligh et al, 1965) and mule deer (Sargeant et al, 1994). An explanation for these differences might be that energy balance was maintained in sheep and mule deer, but not in goats and Arabian oryx.…”

Section: Discussionmentioning

confidence: 68%

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

Maloney

Fuller

Meyer

et al. 2011

SUMMARYUsing implanted temperature loggers, we measured core body temperature in nine western grey kangaroos every 5min for 24 to 98days in spring and summer. Body temperature was highest at night and decreased rapidly early in the morning, reaching a nadir at 10:00h, after ambient temperature and solar radiation had begun to increase. On hotter days, the minimum morning body temperature was lower than on cooler days, decreasing from a mean of 36.2°C in the spring to 34.0°C in the summer. This effect correlated better with the time of the year than with proximate thermal stressors, suggesting that either season itself or some factor correlated with season, such as food availability, caused the change. Water saving has been proposed as a selective advantage of heterothermy in other large mammals, but in kangaroos the water savings would have been small and not required in a reserve with permanent standing water. We calculate that the lower core temperature could provide energy savings of nearly 7%. It is likely that the heterothermy that we observed on hot days results either from decreased energy intake during the dry season or from a seasonal pattern entrained in the kangaroos that presumably has been selected for because of decreased energy availability during the dry season.

“…Because measurements of Tb have been made in captivity, where opportunities for behavioural thermoregulation by individuals may be limited, the extent to which, and under what circumstances, heterothermy is used by ungulates in their natural environment remains unclear, despite statements to the contrary (Willmer et al, 2000;Randall et al, 2002). Investigations on free-ranging mule deer (Odocoileus hemionus; Sargeant et al, 1994) and black wildebeest (Connochaetes gnou; Jessen et al, 1994), both inhabitants of semi-arid areas, and on springbok (Antidorcas marsupialis; Mitchell et al, 1997) and Cape eland (Fuller et al, 1999), both occurring in arid habitats, did not find that these species routinely employed heterothermy, despite daily variation in air temperature (Ta) of >15°C in some cases. Because Tb of Cape eland was relatively invariant when they were allowed to seek shade, Fuller et al (1999) argued that the heterothermy observed by Taylor and Lyman (1967) was "probably an experimental artefact occurring in animals denied access to behavioural thermoregulation".…”

Section: Heterothermy and The Water Economy Of Free-living Arabian Ormentioning

confidence: 99%

Heterothermy and the water economy of free-living Arabian oryx (Oryx leucoryx)

Ostrowski¹,

Williams

Ismael³

2003

SUMMARY To test the idea that large, free-living, desert ungulates use heterothermy to reduce water loss, we measured core body temperature(Tb) of six free-ranging, adult Arabian oryx (Oryx leucoryx) during 2 years in the arid desert of west-central Saudi Arabia. We report the first case of heterothermy in a free-living ruminant in a desert environment: Tb varied by 4.1±1.7°C day–1 during summer (June to September) and by 1.5±0.6°C day –1 during winter (November to March). Over both seasons, mean Tb was 38.4±1.3°C. During the day in both summer and winter, Tb increased continually, suggesting that oryx store heat instead of dissipating it by evaporation, whereas at night Tb decreased. The minimum Tb was lower in summer (36.5±1.16°C) than in winter (37.5±0.51°C)despite the fact that the temperature gradient between Tband air temperature (Ta) was larger and solar radiation was lower in winter. Throughout the year, daily variation in Tb appeared to reflect thermal load(Ta,max–Ta,min) rather than an endogenous rhythm. Behavioural thermoregulation was used by oryx to cope with thermal stress during summer: animals lay down in shade in the morning shortly before Ta exceeded Tb and remained there until evening when Tb–Tabecame positive. The use of heterothermy by oryx resulted in storage ofandwould672.4 kJ day–1 animal–1258.6 kJ day–1 animal–1in winter, if heat storage is based on calculations involving mean Tb. Todissipaterequirethisheatin summerby evaporation0.28 litres H2O day–1 animal–1and0.11 litres H2O day–1 animal–1 in summer and winter,respectively. Without heat storage in summer, we estimated that oryx would have to increase their water intake by 19%, a requirement that would be difficult to meet in their desert environment. If heat storage was calculated based on the daily change in Tb rather than on heat storage above mean Tb then we estimated that oryx saved 0.538 litres H2O day–1 animal–1during summer.