Examination of head versus body heading may help clarify the extent to which animal movement pathways are structured by environmental cues?

Understanding the processes that determine how animals allocate time to space is a major challenge, although it is acknowledged that summed animal movement pathways over time must define space-time use. The critical question is then, what processes structure these pathways? Following the idea that turns within pathways might be based on environmentally determined decisions, we equipped Arabian oryx with head- and body-mounted tags to determine how they orientated their heads - which we posit is indicative of them assessing the environment - in relation to their movement paths, to investigate the role of environment scanning in path tortuosity. After simulating predators to verify that oryx look directly at objects of interest, we recorded that, during routine movement, > 60% of all turns in the animals' paths, before being executed, were preceded by a change in head heading that was not immediately mirrored by the body heading: The path turn angle (as indicated by the body heading) correlated with a prior change in head heading (with head heading being mirrored by subsequent turns in the path) twenty-one times more than when path turns occurred due to the animals adopting a body heading that went in the opposite direction to the change in head heading. Although we could not determine what the objects of interest were, and therefore the proposed reasons for turning, we suggest that this reflects the use of cephalic senses to detect advantageous environmental features (e.g. food) or to detect detrimental features (e.g. predators). The results of our pilot study suggest how turns might emerge in animal pathways and we propose that examination of points of inflection in highly resolved animal paths could represent decisions in landscapes and their examination could enhance our understanding of how animal pathways are structured.

The hairy lizard: heterothermia affects anaesthetic requirements in the Arabian oryx (Oryx leucoryx).

OBJECTIVE: To study the effect of heterothermia on anaesthetic drug requirements in semi-free ranging Arabian oryx and to assess the temperature quotient (Q10) of oxygen consumption. STUDY DESIGN: Prospective observational study and controlled metabolic experiment. ANIMALS: Sixty-eight anaesthetic events in 59 Arabian oryx from Mahazat As-Sayd protected area, Saudi Arabia METHODS: Anaesthesia was induced by remote injection of 25 mg ketamine, 10 mg midazolam and 0.5 mg medetomidine with a variable amount of etorphine based on a target dosage of 20 µg kg-1 and subjective assessment of body mass. Animals not recumbent within 15 minutes or insufficiently anaesthetized were physically restrained and administered supplementary etorphine intravenously depending on the anaesthetic depth. Body temperature (Tb) was measured rectally immediately upon handling of each animal. From six anaesthetized oryx, expiratory gasses for oxygen analysis and metabolic rate calculation were collected at two Tbs; before and after submersion in ice water for approximately 30 minutes. RESULTS: Forty-two animals (62%) became recumbent with the initial dose, with a mean induction time (± standard deviation) of 9 ± 2 minutes. The remaining animals could be handled but needed 0.3 ± 0.1 mg etorphine intravenously to reach the desired level of anaesthesia. There was a significant positive correlation between Tb and effective etorphine dosage (R2 = 0.48, p < 0.0001). Average Tb of the six animals in which metabolic rate was measured decreased from 40.0 ± 0.5°C immediately after induction to 35.5 ± 0.5°C after cooling. This reduction was associated with a reduction in oxygen uptake from 3.11 ± 0.33 to 2.22 ± 0.29 mL O2 minute-1 kg-1, reflected in Q10 of 2.17 ± 0.14. CONCLUSIONS AND CLINICAL RELEVANCE: Tb significantly affects anaesthetic requirements in Arabian oryx and should be considered when selecting dosages for anaesthetic induction for species showing diurnal heterothermy.

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

To test the idea that large, free-living, desert ungulates use heterothermy to reduce water loss, we measured core body temperature (T(b)) 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: T(b) varied by 4.1+/-1.7 degrees C day(-1) during summer (June to September) and by 1.5+/-0.6 degrees C day (-1) during winter (November to March). Over both seasons, mean T(b) was 38.4+/-1.3 degrees C. During the day in both summer and winter, T(b) increased continually, suggesting that oryx store heat instead of dissipating it by evaporation, whereas at night T(b) decreased. The minimum T(b) was lower in summer (36.5+/-1.16 degrees C) than in winter (37.5+/-0.51 degrees C) despite the fact that the temperature gradient between T(b) and air temperature (T(a)) was larger and solar radiation was lower in winter. Throughout the year, daily variation in T(b) appeared to reflect thermal load (T(a,max)-T(a,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 T(a) exceeded T(b) and remained there until evening when T(b)-T(a) became positive. The use of heterothermy by oryx resulted in storage of 672.4 kJ day(-1) animal(-1) in summer and 258.6 kJ day(-1) animal(-1) in winter, if heat storage is based on calculations involving mean T(b). To dissipate this heat by evaporation would require 0.28 litres H(2)O day(-1) animal(-1) and 0.11 litres H(2)O 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 T(b) rather than on heat storage above mean T(b) then we estimated that oryx saved 0.538 litres H(2)O day(-1) animal(-1) during summer.