Robyn S Hetem

• PhD
• Senior Lecturer at University of Canterbury

Introduction Epidemiological evidence linking heat exposure to adverse maternal and child health outcomes is compelling. However, the biological and social mechanisms underlying these associations remain poorly understood. Understanding the pathways explaining these associations is important given rising global temperatures, and the urgent need for...

Most experts agree that the dominant mechanism through which body temperature is regulated, under a thermal challenge, environmental or metabolic, is negative feedback control. However, some consider negative feedback to be too sluggish to account for the rapid speed of response. The impression of sluggishness is based on an assumption that the bod...

Introduction Epidemiological evidence linking heat exposure to adverse maternal and child health outcomes is compelling. However, the biological and social mechanisms underlying these associations remain poorly understood. Understanding the pathways explaining these associations is important given rising global temperatures, and the urgent need for...

Movement paths are influenced by external factors and depend on an individual's navigation capacity (Where to move?), motion capacity (How to move?) and are ultimately driven by internal physiological state (Why move?). Despite physiology underlying most aspects of this movement ecology framework, the physiology–movement nexus remains understudied...

The thermoregulatory system of homeothermic endotherms operates to attain thermal equilibrium, that is no net loss or gain of heat, where possible, under a thermal challenge, and not to attain a set‐point or any other target body temperature. The concept of a set‐point in homeothermic temperature regulation has been widely misinterpreted, resulting...

Mammals in arid zones have to trade off thermal stress, predation pressure, and time spent foraging in a complex thermal landscape. We quantified the relationship between the environmental heat load and activity of a mammal community in the hot, arid Kalahari Desert. We deployed miniature black globe thermometers within the existing Snapshot Safari...

The physiological performance of a mother during reproduction represents a trade‐off between continued investment in her current offspring, and the mother's own survival and ability to invest in future offspring. Here, we used core body temperature (Tb) patterns to examine the degree to which maternal body temperatures support the infant during per...

Climate change is impacting mammals both directly (for example, through increased heat) and indirectly (for example, through altered food resources). Understanding the physiological and behavioural responses of mammals in already hot and dry environments to fluctuations in the climate and food availability allows for a better understanding of how t...

Reduced energy intake can compromise the ability of a mammal to maintain body temperature within a narrow 24-h range, leading to heterothermy. To investigate the main drivers of heterothermy in a bulk grazer, we compared abdominal temperature, body mass, body condition index, and serum leptin levels in 11 subadult Cape buffalo (Syncerus caffer caff...

Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While African buffalo ( Syncerus caffer ) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle inoculation and co...

Proclaimed in 1907, Etosha National Park in northern Namibia is an iconic dryland system with a rich history of wildlife conservation and research. A recent research symposium on wildlife conservation in the Greater Etosha Landscape (GEL) highlighted increased concern of how intensification of global change will affect wildlife conservation based o...

Many populations experience high seasonal temperatures. Pregnant women are considered vulnerable to extreme heat because ambient heat exposure has been linked to pregnancy complications including preterm birth and low birthweight. The physiological mechanisms that underpin these associations are poorly understood. We reviewed the existing research...

Most primates, including humans, give birth during the inactive phase of the daily cycle. Practical constraints therefore limit our knowledge of the precise timing of nocturnal birth in wild diurnal primates and so limit our understanding of selective pressures and consequences. We measured maternal core body temperature (Tb) across 24 births in a...

Foot-and-mouth disease (FMD) is one of the most important livestock diseases restricting international trade. While it is clear that African buffalo ( Syncerus caffer ) act as the main wildlife reservoir, viral and immune response dynamics during FMD virus acute infection have not been described before in this species. We used experimental needle i...

Significance Using state-of-the-art biologging technology, we document the occurrence of fevers in wild vervet monkeys and demonstrate that fevers coincide with overt sickness behavior. In so doing, we demonstrate a hidden cost of sociality: Febrile animals were twice as likely to receive aggression from their group mates and were six times more li...

Rural farming households in developing countries frequently contend with multiple challenges, including a lack of resources, food insecurity, and poverty. Climate change threatens to compound existing challenges, particularly in such rural subsistence economies with limited adaptive capacity. We aim to establish farmers' perspectives on likely impa...

Links between heat exposure and congenital anomalies have not been explored in detail despite animal data and other strands of evidence that indicate such links are likely. We reviewed articles on heat and congenital anomalies from PubMed and Web of Science, screening 14,880 titles and abstracts in duplicate for articles on environmental heat expos...

Southern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapt...

Mammals in drylands are facing not only increasing heat loads but also reduced water and food availability as a result of climate change. Insufficient water results in suppression of evaporative cooling and therefore increases in body core temperature on hot days, while lack of food reduces the capacity to maintain body core temperature on cold nig...

Nature is experiencing degradation and extinction rates never recorded before in the history of Earth.1,2 Consequently, continuous large-scale monitoring programmes are critical, not only to provide insights into population trends but also to aid in understanding factors associated with altering population dynamics at various temporal and spatial s...

In the face of climate change there is an urgent need to understand how animal performance is affected by environmental conditions. Biophysical models that use principles of heat and mass transfer can be used to explore how an animal's morphology, physiology, and behavior interact with its environment in terms of energy, mass and water balances to...

Objective To assess whether exposure to high temperatures in pregnancy is associated with increased risk for preterm birth, low birth weight, and stillbirth. Design Systematic review and random effects meta-analysis. Data sources Medline and Web of Science searched up to September 2018, updated in August 2019. Eligibility criteria for selecting...

Understanding the physiological processes that underpin primate performance is key if we are to assess how a primate might respond when navigating new and changing environments. Given the connection between a mammal's ability to thermoregulate and the changing demands of its thermal environment, increasing attention is being devoted to the study of...

Understanding the physiological processes that underpin primate performance is key if we are to assess how a primate might respond when navigating new and changing environments. Given the connection between an animal’s ability to thermoregulate and the changing demands of its thermal environment, increasing attention is being devoted to the study o...

Background Exposure to high ambient temperatures during pregnancy may increase the risk of adverse pregnancy outcomes due to physiological and anatomical changes in pregnancy compromising the ability to thermoregulate. Methods A systematic review and meta-analysis of studies that assessed associations between ambient heat, and preterm birth, birth...

Shifting activity to cooler times of day buffers animals from increased heat and aridity under climate change. Conversely, when resources are limited, some nocturnal species become more diurnal, reducing energetic costs of keeping warm at night. Aardvarks (Orycteropus afer) are nocturnal, obligate ant- and termite-eating mammals which may be threat...

• Nearly 90% of the world's large herbivore diversity occurs in Africa, yet there is a striking dearth of information on the movement ecology of these organisms compared to herbivores living in higher latitude ecosystems. • The environmental context for movements of large herbivores in African savanna ecosystems has several distinguishing features....

Climate and land use change modify surface water availability in African savannas. Surface water is a key resource for both wildlife and livestock and its spatial and temporal distribution is important for understanding the composition of large herbivore assemblages in savannas. Yet, the extent to which ungulate species differ in their water requir...

The future of fog‐dependent habitats under climate change is unknown but likely precarious; many have experienced recent declines in fog. Fog‐dependent deserts particularly will be threatened, because, there, fog can be the main water source for biota. We review the interactions between fog and fauna of the Namib Desert, about which there is 50 yr...

We compared body temperature patterns and selective brain cooling (SBC) in eight adult female sheep in an indoor (22–25 °C) and outdoor (mean ~ 21 °C) environment, by measuring brain, carotid arterial, and jugular venous blood temperatures at 5-min intervals using implanted data loggers. To investigate whether ultradian oscillations in brain temper...

Large mammals respond to seasonal changes in temperature and precipitation by behavioural and physiological flexibility. These responses are likely to differ between species with differing water dependencies. We used biologgers to contrast the seasonal differences in activity patterns, microclimate selection, distance to potential water source and...

Objectives: Climate change is having a significant impact on biodiversity and increasing attention is therefore being devoted to identifying the behavioral strategies that a species uses to cope with climatic stress. We explore how wild vervet monkeys (Chlorocebus pygerythrus) respond to heat stress, and how behavioral adaptations are used to regu...

Observations of animal thermoregulatory behavior are labor‐intensive, and human presence may disturb the normal behavior of the animal. Therefore, we investigated whether a remote biologging technique could be used to detect orientation to solar radiation in savanna antelope. We predicted that when a mammal was orientated perpendicular to solar rad...

Domestic species can make the distinction between several human sub-groups, especially between familiar and unfamiliar persons. The Domestication hypothesis assumes that such advanced cognitive skills were driven by domestication itself. However, such capacities have been shown in wild species as well, highlighting the potential role of early exper...

An introduction to the Snapshot Safari - South Africa project.

As one of the few felids that is predominantly diurnal, cheetahs (Acinonyx jubatus Von Schreber, 1775) can be exposed to high heat loads in their natural habitat. Little is known about long‐term patterns of body temperature and activity (including hunting) in cheetahs because long‐term concurrent measurements of body temperature and activity never...

The accuracy of predictive models (also known as mechanistic or causal models) of animal responses to climate change depends on properly incorporating the principles of heat transfer and thermoregulation into those models. Regrettably, proper incorporation of these principles is not always evident. We have revisited the relevant principles of therm...

Knowledge of the thermal ecology of a species can improve model predictions for temperature-induced population collapse, which in light of climate change is increasingly important for species with limited distributions. Here, we use a multi-faceted approach to quantify and integrate the thermal ecology, properties of the thermal habitat, and past a...

Aardvarks (Orycteropus afer) are elusive burrowing mammals, predominantly nocturnal and distributed widely throughout Africa except for arid deserts. Their survival may be threatened by climate change via direct and indirect effects of increasing heat and aridity. To measure their current physiological plasticity, we implanted biologgers into six a...

While most primates are tropical animals, a number of species experience markedly cold winters. In a high latitude arid environment, wild female vervet monkeys (Chlorocebus pygerythrus) that are socially integrated experience reduced cold stress. Here we ask whether sociability is similarly salient for male vervet monkeys, who reside in non-natal g...

Stress-induced hyperthermia following rectal thermometry is reported in normothermic rats, but appears to be muted or even absent in febrile rats. We therefore investigated whether the use of rectal thermometry affects the accuracy of temperature responses recorded in normothermic and febrile rats. Using intra-abdominally implanted temperature-sens...

Some mammals have the ability to lower their hypothalamic temperature below that of carotid arterial blood temperature, a process termed selective brain cooling. Although the requisite anatomical structure that facilitates this physiological process, the carotid rete, is present in members of the Cetartiodactyla, Felidae and Canidae, the carotid re...

It has been proposed that there is a thermal cost of the mane to male lions, potentially leading to increased body surface temperatures (Ts), increased sperm abnormalities, and to lower food intake during hot summer months. To test whether a mane imposes thermal costs on males, we measured core body temperature (Tb) continuously for approximately 1...

In the face of climate change, the life history traits of large terrestrial mammals will prevent them from adapting genetically at a sufficient pace to keep track with changing environments, and habitat fragmentation will preclude them from shifting their distribution range. Predicting how habitat-bound large mammals will respond to environmental c...

The use of selective brain cooling, where warm arterial blood destined for the brain is cooled in the carotid rete via counter-current heat exchange when in close proximity to cooler venous blood, contributes to the conservation of body water. We simultaneously measured carotid blood and hypothalamic temperature in four gemsbok, five red hartebeest...

Individual lizard species may reduce competition within a habitat by diverging along one or more niche dimensions, such as spatial, temporal or dietary dimensions. We compared the morphology, activity patterns, microhabitat characteristics, thermal biology and feeding ecology of two species of diurnally active sympatric insectivorous lizards in the...

Hyperthermia is described as the major cause of morbidity and mortality associated with capture, immobilization and restraint of wild animals. Therefore, accurately determining the core body temperature of wild animals during capture is crucial for monitoring hyperthermia and the efficacy of cooling procedures. We investigated if microchip thermome...

A strong case has been made that the primary function of grooming is hygienic. Nevertheless, its persistence in the absence of hygienic demand, and its obvious tactical importance to members of primate groups, underpins the view that grooming has become uncoupled from its utilitarian objectives and is now principally of social benefit. We identify...

We used stable isotopes of carbon and nitrogen to study the trophic niche of two species of insectivorous lizards, the Husab sand lizard Pedioplanis husabensis and Bradfield's Namib day gecko living sympatrically in the Namib Desert. We measured the δ¹³C and δ¹⁵N ratios in lizard blood tissues with different turnover times (whole blood, red blood c...

The capture of wild animals is a stressful event which may cause a capture-induced hyperthermia, resulting in morbidity or mortality. We investigated whether various cooling techniques were effective at lowering the body temperature of hyperthermic animals. To achieve this, we implanted miniature temperature-sensitive data loggers into the abdomens...

In artiodactyls, arterial blood destined for the brain can be cooled through counter-current heat exchange within the cavernous sinus via a process called selective brain cooling. We test the hypothesis that selective brain cooling, which results in lowered hypothalamic temperature , contributes to water conservation in sheep. Nine Dorper sheep, in...

Background Etorphine, a potent opioid agonist, causes pulmonary hypertension and respiratory depression. Whether etorphine-induced pulmonary hypertension negatively influences pulmonary gas exchange and exacerbates the effects of ventilator depression and the resultant hypoxemia is unknown. To determine if these effects occurred we instrumented twe...

Geckos of the genus Rhoptropus are small diurnal lizards occurring in arid regions of Namibia and Angola, and are not well studied relative to other desert lizards. Rhoptropus afer has a field metabolic rate significantly lower than that of other desert lizards, but comparable studies have not been carried out in any other Rhoptropus species. We ex...

Sociality has been shown to have adaptive value for gregarious species, with more socially integrated animals within groups experiencing higher reproductive success and longevity. The value of social integration is often suggested to derive from an improved ability to deal with social stress within a group; other potential stressors have received l...

Advances in biologging techniques over the past 20 years have allowed for the remote and continuous measurement of body temperatures in free-living mammals. While there is an abundance of literature on heterothermy in small mammals, fewer studies have investigated the daily variability of body core temperature in larger mammals. Here we review meas...

The Husab Sand Lizard (Pedioplanis husabensis Berger-Dell’Mour and Mayer, 1989) is a recently described lacertid lizard endemic to a small region in the central Namib Desert. Although this species is of conservation concern, very little is known about how this lizard functions in its environment. We used the doubly labeled water method to measure t...

Many ungulates, including wildebeest, seek shade and orient their bodies relative to incoming solar radiation in order to reduce environmental heat loads. Blue (Connochaetes taurinus) and black wildebeest (C. gnou), which co-exist artificially in reserves in South Africa, are thought to adopt different thermoregulatory behaviours to mitigate high e...

Most large terrestrial mammals, including the charismatic species so important for ecotourism, do not have the luxury of rapid micro-evolution or sufficient range shifts as strategies for adjusting to climate change. The rate of climate change is too fast for genetic adaptation to occur in mammals with longevities of decades, typical of large mamma...

Abstract We evaluated the effectiveness of a ketamine-medetomidine-midazolam drug combination administered intramuscularly by remote injection followed by isoflurane anesthesia in free-living aardvarks (Orycteropus afer). Seven aardvarks weighing 33-45 kg were immobilized to perform surgical implantation of temperature loggers using 3.8 mg/kg ketam...

We used implanted miniature data loggers to obtain the first measurements of body temperature from a free-ranging anthropoid primate. Vervet monkeys (Chlorocebus pygerythrus) living in a highly seasonal, semi-arid environment maintained a lower mean 24-h body temperature in winter (34.6 ± 0.5 °C) than in summer (36.2 ± 0.1 °C), and demonstrated inc...

Although laboratory studies of large mammals have revealed valuable information on thermoregulation, such studies cannot predict accurately how animals respond in their natural habitats. Through insights obtained on thermoregulatory behavior, body temperature variability, and selective brain cooling in free-living mammals, we show here how we can b...

Hunting cheetah reportedly store metabolic heat during the chase and abandon chases because they overheat. Using biologging to remotely measure the body temperature (every minute) and locomotor activity (every 5 min) of four free-living cheetah, hunting spontaneously, we found that cheetah abandoned hunts, but not because they overheated. Body temp...

Highlights ► Assessment of monthly and hourly activity patterns in wild vervet monkeys. ► Scan sampling and biologging provide comparable measures of monthly activity. ► Scan sampling and biologging provide comparable measures of hourly activity. ► Validation of biologger methods in their measurement of activity.

Heat stress can limit the activity time budget of ungulates due to hyperthermia, which is relevant for African antelopes in ecosystems where temperature routinely increases above 40 °C. Body size influences this thermal sensitivity as large bodied ungulates have a lower surface area to volume ratio than smaller ungulates, and therefore a reduced he...

Selective 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 caro...

Abstract To understand the adaptive capacity of a species in response to rapid habitat destruction and climate change, we investigated variation in body temperature (Tb) of three species of antelope, namely eland, blue wildebeest and impala, using abdominally-implanted temperature data loggers. The study was conducted at two climatically contrastin...

Heterothermy, a variability in body temperature beyond the normal limits of homeothermy, is widely viewed as a key adaptation of arid-adapted ungulates. However, desert ungulates with a small body mass, i.e. a relatively large surface area-to-volume ratio and a small thermal inertia, are theoretically less likely to employ adaptive heterothermy tha...

Body temperature was measured at five different body sites (retroperitoneum, groin, semimembranosus muscle, flank and shoulder) using temperature-sensitive microchips implanted in five female goats, and compared with the core body and rectal temperatures. Body temperature was measured while the goats were kept in different ambient temperatures, wit...

To investigate the role of the angularis oculi vein (AOV) in selective brain cooling (SBC), we measured brain and carotid blood temperatures in six adult female Dorper sheep. Halfway through the study, a section of the AOV, just caudal to its junction with the dorsal nasal vein, was extirpated on both sides. Before and after AOV surgery, the sheep...

Globally, pastoral practices have transformed habitats, which often lead to desertification. With climate change predicted to exacerbate desertification, adaptation provides the best survival strategy for agriculturally important herbivores. We investigated body temperature, water turnover, physical activity and microclimate selection of Angora goa...

The body temperature (T(b)) of Cape ground squirrels (Xerus inauris, Sciuridae) living in their natural environment during winter has not yet been investigated. In this study we measured abdominal T(b) of eight free-ranging Cape ground squirrels over 27 consecutive days during the austral winter. Mean daily T(b) was relatively stable at 37.0 ± 0.2°...

Heterothermy, a variability in body temperature beyond the limits of homeothermy, has been advanced as a key adaptation of Arabian oryx (Oryx leucoryx) to their arid-zone life. We measured body temperature using implanted data loggers, for a 1-year period, in five oryx free-living in the deserts of Saudi Arabia. As predicted for adaptive heterother...

Although many studies have modeled the effects of climate change on future species distributions and extinctions, the theoretical approach most commonly used-climate envelope modeling-typically ignores the potential physiological capacity of animals to respond to climate change. We explore the consequences of the phenotypic plasticity available to...

Respiratory depression is a common side effect when opioids are used to immobilize wildlife. Serotonergic ligands have the potential to reverse opioid-induced respiratory depression. We examined whether any of three serotonergic ligands could reverse this depression in etorphine-immobilized (0.07 mg/kg) impala (Aepyceros melampus). The study took p...