Arabian Oryx (Oryx leucoryx) Respond to Increased Ambient Temperatures with a Seasonal Shift in the Timing of Their Daily Inactivity Patterns

Abstract

The Arabian oryx inhabits an environment where summer ambient temperatures can exceed 40°C for extended periods of time. While the oryx employs a suite of adaptations that aid survival, the effects of this extreme environment on inactivity/sleep, where ambient temperatures often exceed mammalian thermoneutral zones, are unknown.To determine how the oryx manages inactivity/sleep seasonally we used fine and coarsegrain actigraphy, in 16 animals, to reveal when the animals were inactive/sleeping in relation to variations in ambient temperatures and light levels. We demonstrate that during the cooler winter months the oryx is inactive/sleeping during the cooler parts of day (pre-dawn hours), showing a diurnal activity pattern. In contrast, in the summer months, the oryx displayed a crepuscular activity pattern, with the major inactivity/sleep bouts occurring equally during both the coolest part of the night (pre-dawn hours) and the hottest part of the day (afternoon hours). Interestingly, the daily rhythm of the timing of changes in core body temperature did not vary seasonally, although the amplitude did change. The transition from winter diurnal activity to summer crepuscular activity occurred in May, while the reverse occurred in September. By having half of the major summer sleep bouts during the hottest part of the day, the oryx may take advantage of the thermoregulatory physiology of sleep to mitigate increases in body temperature. The seasonal summer desynchronization of circadian entrained daily rhythms (core body temperature and daily activity patterns) is suggestive of temperature acting to mask, or modify, output pathways from the suprachiasmatic nucleus.

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

“…UBM oryx summer activity exhibited more of a crepuscular type phasing in agreement with July activity patterns observed by Davimes et al (2016). Such patterns are typical of most northern free-ranging ungulate species like Spanish ibex (Capra pyrenaica) (Alados, 1986), roe deer (Capreolus capreolus) (Cederlund, 1989), rocky mountain elk (Cervus elaphus) (Green and Bear, 1990) and most caribou (Maier and White, 1998) and reindeer species, Rangifer sp.…”

“…Temporal niche switching was observed between winter-diurnal and summer-crepuscular phasing in relation to seasonal shifts in the light-dark cycle and extreme ambient temperatures. Additional investigation into a free-roaming Arabian oryx living in the Karoo desert of South Africa (semi-arid, fewer climatic extremes than the Arabian Desert) during the summer month of February (Southern Hemisphere) revealed similar nocturnal inactivity to that of the Saudi Arabian winter month of February, indicating a possible masking effect of ambient temperature on inactivity (Davimes et al, 2016). Seasonally, the oryx investigated in Saudi Arabia exhibited no change in the phasing of their body temperature rhythm, only in the amplitude, suggesting a seasonal phase shift in the relationship between body temperature and inactivity patterns.…”

“…Seasonally, the oryx investigated in Saudi Arabia exhibited no change in the phasing of their body temperature rhythm, only in the amplitude, suggesting a seasonal phase shift in the relationship between body temperature and inactivity patterns. Current data on the Arabian oryx indicate a seasonal shift in activity patterns related strongly to extreme ambient temperatures and appears to represent temporal niche switching (Seddon and Ismail, 2002;Hetem et al, 2012b;Davimes et al, 2016); however, no examination of the year-long 24h temporal activity budgets and general activity phasing in relationship to seasonal environmental changes in the Arabian Desert has been conducted thus far.…”

“…The seasonal alteration in daily patterns was further investigated using fine-grain actigraphy, targeting specifically inactivity patterns during the hottest (July) and coldest (February) months in the Arabian Desert (Davimes et al, 2016). Temporal niche switching was observed between winter-diurnal and summer-crepuscular phasing in relation to seasonal shifts in the light-dark cycle and extreme ambient temperatures.…”

Inactivity/sleep in two wild free-roaming African elephant matriarchs – Does large body size make elephants the shortest mammalian sleepers?

“…While this is not always readily achievable, especially for smaller species, it appears that currently this bilateral approach is achievable for larger mammals (e.g. [23]).…”