Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

Abstract

SUMMARYSelective brain cooling is a thermoregulatory effector proposed to conserve body water and, as such, may help artiodactyls cope with aridity. We measured brain and carotid blood temperature, using implanted data loggers, in five Arabian oryx (Oryx leucoryx) in the desert of Saudi Arabia. On average, brain temperature was 0.24±0.05°C lower than carotid blood temperature for four oryx in April. Selective brain cooling was enhanced in our Arabian oryx compared with another species from the same genus (gemsbok Oryx gazella gazella) exposed to similar ambient temperatures but less aridity. Arabian oryx displayed a lower threshold (37.8±0.1°C vs 39.8±0.4°C), a higher frequency (87±6% vs 15±15%) and a higher maximum magnitude (1.2±0.2°C vs 0.5±0.3°C) of selective brain cooling than did gemsbok. The dominant male oryx displayed less selective brain cooling than did any of the other oryx, but selective brain cooling was enhanced in this oryx as conditions became hotter and drier. Enhanced selective brain cooling in Arabian oryx supports the hypothesis that selective brain cooling would bestow survival advantages for artiodactyl species inhabiting hot hyper-arid environments.

Towards a mechanistic understanding of the responses of large terrestrial mammals to heat and aridity associated with climate change

“…In Arabian oryx, the use of selective brain cooling was enhanced in a hot, dry period compared to in a warm, wetter period (Fig. 3) [115]. It also was greater than that in the closely-related gemsbok, which inhabited a grassland habitat with similar environmental temperatures but three times as much rainfall [116], and it was exhibited at a threshold body core temperature lower than that measured in African antelope in more mesic environments [115].…”

“…3) [115]. It also was greater than that in the closely-related gemsbok, which inhabited a grassland habitat with similar environmental temperatures but three times as much rainfall [116], and it was exhibited at a threshold body core temperature lower than that measured in African antelope in more mesic environments [115]. Whether the enhanced selective brain cooling in Arabian oryx compared to that in African antelope has an anatomical or functional basis is not known.…”

“…3 24h patterns of microclimate selection (expressed as the difference between collar miniglobe temperature and weather station miniglobe temperature, n = 2, points below the zero line represent selection of cool microclimates), activity (expressed as a proportion of maximum activity recorded, n = 5), core body temperature (n = 5), and selective brain cooling (n = 1) in Arabian oryx (Oryx leucoryx) in a hot, dry period and a warm, wet period. Data from [91,115,120] able to access microclimate refuges than were Angora goats in an adjacent pristine habitat. As a result, goats in the transformed habitat were more water-dependent and experienced larger increases in body core temperature over the day than did the goats in the pristine habitat [93].…”

“…Despite exhibiting both behavioural and physiological responses to all three stressors (Fig. 3) [90,91,115], the oryx exhibited the largest daily fluctuations (up to 7.7°C) of body temperature ever recorded for a large free-living mammal. Their 24 h maximum body temperatures reached as high as 42.6°C, while in the early morning, when air temperatures were moderate (26°C), body temperature dropped to as low as 34.3°C.…”

Temporal niche switching in Arabian oryx ( Oryx leucoryx ): Seasonal plasticity of 24 h activity patterns in a large desert mammal

“…The Arabian oryx is found primarily within the deserts of the Arabian peninsula and Middle East, this species has been able to successfully survive the extreme conditions of such harsh arid-zones owing to numerous adaptive behaviours (Stanley Price, 1989;Seddon and Ismail, 2002;Ostrowski et al, 2003;Hetem et al, 2012a) common to all species of oryx (Taylor, 1966(Taylor, , 1968(Taylor, , 1969(Taylor, , 1970aTaylor and Lynn, 1972;King et al, 1975;King, 1979;Stanley Price, 1985). Arabian oryx were originally suggested to possibly show altered daily activity patterns between the hotter and cooler months (April -November) of the Saudi Arabian desert (Seddon and Ismail, 2002;Hetem et al, 2012b); however, the A C C E P T E D M A N U S C R I P T 5 winter and early spring months were not investigated (December -March).…”