Living on the edge: Daily, seasonal and annual body temperature patterns of Arabian oryx in Saudi Arabia

Abstract

Heterothermy, the ability to allow body temperature (Tb) to fluctuate, has been proposed as an adaptive mechanism that enables large ungulates to cope with the high environmental temperatures and lack of free water experienced in arid environments. By storing heat during the daytime and dissipating it during the night, arid-adapted ungulates may reduce evaporative water loss and conserve water. Adaptive heterothermy in large ungulates should be particularly pronounced in hot environments with severely limited access to free water. In the current study we investigated the effects of environmental temperature (ambient, Ta and soil, Ts) and water stress on the Tb of wild, free-ranging Arabian oryx (Oryx leucoryx) in two different sites in Saudi Arabia, Mahazat as-Sayd (MS) and Uruq Bani Ma’arid (UBM). Using implanted data loggers wet took continuous Tb readings every 10 minutes for an entire calendar year and determined the Tb amplitude as well as the heterothermy index (HI). Both differed significantly between sites but contrary to our expectations they were greater in MS despite its lower environmental temperatures and higher rainfall. This may be partially attributable to a higher activity in an unfamiliar environment for translocated animals in UBM. As expected Tb amplitude and HI were greatest during summer. Only minor sex differences were apparent that may be attributable to sex-specific investment into reproduction (e.g. male-male competition) during rut. Our results suggest that the degree of heterothermy is not only driven by extrinsic factors (e.g. environmental temperatures and water availability), but may also be affected by intrinsic factors (e.g. sex and/or behaviour).

Diel timing of nest predation changes across breeding season in a subtropical shorebird

“…Second, the ambient and surface temperatures dramatically increase over the breeding season (Figure 1 ) to the point where midday activity of endotherms is close to impossible (Abdu et al., 2018 ; Albright et al., 2017 ; Streicher et al., 2017 ). During such high temperatures, lapwing parents incubate (often rather shade) their eggs continuously to avoid lethal overheating of the embryos (Brown & Downs, 2003 ; Grant, 1982 ).…”

“…Second, we expected nest predation to decrease over the season because some overwintering avian predators migrate out and migrating avian predators pass through the study area early in the lapwing's breeding season (eBird, 2020 ) and because other avian chicks—an alternative prey to red‐wattled lapwing nests—are available later in the breeding season (personal observation). Third, we expected daylight nest predation (if any) to decline over the breeding season, because the presence of migrating avian predators—daylight predators of nests—declines over the breeding season (Table A1 eBird, 2020 ) and because ambient and ground temperatures increase dramatically over the breeding season (Figure 1 ) to the point where midday activity of most endotherm animals is close to impossible (Abdu et al., 2018 ; Albright et al., 2017 ; Streicher et al., 2017 ).…”

Future trends in measuring physiology in free-living animals

“…The majority of physiologging devices to date have therefore been surgically implanted (e.g. [1,7,43,55–60]). Some devices may be mounted externally but are still physically connected to surgically placed indwelling electrodes or cannulas (reviewed in Williams et al .…”

Why implantation of bio‐loggers may improve our understanding of how animals cope within their natural environment

“…For example, Evans and colleagues implanted loggers into the abdominal cavity of brown bears (Ursus arctos) that recorded heart rate and body temperature for up to 1 year, to determine the drivers of hibernation (Evans et al 2016). Similarly, Streicher et al (2017) used implanted loggers in conjunction with a satellite collar to study daily body temperature fluctuations in the Arabian oryx (Oryx leucoryx) as a possible adaptation to life in hot and arid environments.…”