Philip Withers

• The University of Western Australia

Energetics is considered a fundamental ‘currency’ of ecology and the way that metabolic rate (MR)—the rate of energy expenditure on biological processes—scales relative to the size of the organism can be both an adaptive benefit and a constraint in mediating the energetic demands of ecological processes. Since few investigations have examined this...

Acoustic communication occurs in all major groups of terrestrial vertebrates, having evolved independently in early clades of mammals, birds, geckos, crocodilians and frogs, about 100–200 MYA. There is little doubt that acoustic communication was used by ancestral therian mammals, but it is ambiguous whether the reconstruction of the root of the ma...

The storage of seeds in seed banks is a primary strategy for plant conservation world-wide in the face of unprecedented biodiversity loss. For example, the Western Australian Seed Centre is responsible for >16,000 accessions of almost 4,000 wild species, including collections that represent the sole remaining wild populations of a species, or popul...

The collection and storage of wild seeds in seed banks is a primary strategy for conserving plant biodiversity and is a fundamental step in the restoration of degraded landscapes. Given the current demand for wild-sourced seed, effective, economical and efficient storage is of global importance. At Kings Park in Western Australia, we routinely stor...

We explore a recent innovative variation of closed-system respirometry for terrestrial organisms, whereby pO2is repeatedly measured fluorometrically in a constant-volume chamber over multiple time points. We outline a protocol that aligns this technology with the broader literature on aerial respirometry, including the calculations required to accu...

'Insensible' evaporative water loss of mammals has been traditionally viewed as a passive process, but recent studies suggest that insensible water loss is under regulatory control, although the physiological role of this control is unclear. We test the hypothesis that regulation of insensible water loss has a thermoregulatory function by quantifyi...

Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible EWL, reflecting this convergence. We found that bu...

Australian Magpies are widespread passerines found in a broad range of open habitats, but little is known about their physiological mechanisms for energy conservation in the cold. Physiological variables measured using open-flow respirometry demonstrated a typical avian endothermic response to low ambient temperature, with no evidence for energy sa...

Moisture-harvesting lizards, such as the Australian thorny devil Moloch horridus, have remarkable adaptations for inhabiting arid regions. Their microstructured skin surface, with channels in between overlapping scales, enables them to collect water by capillarity and passively transport it to the mouth for ingestion. We characterized this capillar...

Sea turtles found stranded on beaches are often rehabilitated before being released back into the wild. The location and date of release is largely selected on an informal basis, which may not maximize the chance of survival. As oceanic conditions have a large influence on the movements of neonate sea turtles, this study aimed to identify the best...

It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (Pomatostomus superciliosus), which has characteristics related to a high probability of torpor use; it is a sedentary, insectivorous, cooperative breeding...

Moisture-harvesting lizards, such as the Australian thorny devil, Moloch horridus, have the remarkable ability to inhabit arid regions. Special skin structures, comprising a micro-structured surface with capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and transport it to the mouth for in...

The short-beaked echidna (Tachyglossus aculeatus) is a monotreme and therefore provides a unique combination of phylogenetic history, morphological differentiation and ecological specialisation for a mammal. The echidna has a unique appendicular skeleton, a highly specialised myrmecophagous lifestyle and a mode of locomotion that is neither typical...

The early divergence of monotremes and therian mammals has resulted in considerable interest in the comparative physiology of the short-beaked echidna (Tachyglossus aculeatus), the most common and widespread living monotreme. However, there are many and varied interpretations of its physiology, reflecting the many and varied studies, limitations an...

Marsupials have relatively low body temperatures and metabolic rates, and are therefore considered to be maladapted for life in cold habitats such as alpine environments. We compared body temperature, energetics and water loss as a function of ambient temperature for four Antechinus species, two from alpine habitats and two from low altitude habita...

Seasonal acclimatisation of thermal tolerance, evaporative water loss and metabolic rate, along with regulation of the hive environment, are key ways whereby hive-based social insects mediate climatic challenges throughout the year, but the relative importance of these traits remains poorly understood. We examined seasonal variation in metabolic ra...

Thermoregulatory strategies of small, free-living birds are poorly understood, despite being well-studied for equivalently-sized mammals. We measured body and microclimate temperature for three small, sedentary, insectivorous passerines (Western Yellow Robin Eopsaltria griseogularis 18g; Rufous Treecreeper Climacteris rufa 30g; and White-browed Bab...

Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapour deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small...

Rufous Treecreepers (Climacteris rufa) are small (30 g), insectivorous, cooperatively-breeding passerines endemic to southern Australia. In semi-arid Wandoo (Eucalyptus wandoo) woodland they are ground-frequenting and despite below-freezing overnight temperatures in winter, they roost singly in tree hollows. We examine the physiological and behavio...

The mountain pygmy possum (Burramys parvus) is an endangered marsupial restricted to boulder fields in the Australian Alps, where it hibernates under the snow during winter. Understanding its habitat requirements is essential for conservation, so we examine here ecological implications of the thermal consequences of maintaining water balance during...

It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick's law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and...

Abstract Dehydration tolerance of anuran amphibians is directly related to their ability to mobilize lymphatic reserves, with more terrestrial species having more effective lymph mobilization dependent on specialized skeletal muscles acting directly on the lymph sacs and via pulmonary ventilation. Consequently, we tested the hypothesis that pulmona...

We describe how behavioural responses are an important adjunct to physiological responses for two dunnart marsupials that live in arid environments. Behavioural responses of the Stripe-faced Dunnart Sminthopsis macroura and the Ooldea Dunnart S. ooldea differed with acclimation to four ambient temperature (Ta) regimes, 12 h:12 h of 5–15 °C, 12–22 °...

White-browed Babblers (Pomatostomus superciliosus) are socially gregarious, ground-frequenting birds of central and southern Australia. Living in close-knit family groups, they construct domed nests in which they roost communally. In semi-arid Eucalyptus wandoo woodland, free-living babblers implanted with temperature-sensitive radio transmitters m...

The red-tailed phascogale is a small arboreal dasyurid marsupial that inhabits semi-arid to arid regions of Western Australia's wheat belt. Its body mass (34.7 g) is only ∼15% of that predicted based on its phylogenetic position among other dasyuromorphs; we interpret this as an adaptation to its scansorial and semi-arid/arid lifestyle. The standar...

Lymphatic return to the circulation in anurans is dependent upon the interaction of a number of skeletal muscles and lung deflation. We define character states and describe variation of these putative lymphatic skeletal muscles: the M. cutaneus pectoris (CP), M. cutaneus dorsi (CD), M. piriformis (P), M. sphincter ani cloacalis (SAC), and the compl...

Adaptations promoting greater performance in one habitat are thought to reduce performance in others. However, there are many examples of where, despite habitat differences, such predicted differences in performance do not occur. One such example is the relationship between locomotory performance to habitat for varanid lizards. To explain the lack...

The doubly labelled water method ( DLW ) is widely used to measure field metabolic rate ( FMR ), but it has some limitations. Here, we validate an innovative technique for measuring FMR by comparing the turnover of isotopic rubidium ( ⁸⁶ R b k b ) with DLW depletion and the rate of CO 2 production ( ) measured by flow‐through respirometry (FTR) for...

All vertebrate animals share in common the production of lymph through net capillary filtration from their closed circulatory system into their tissues. The balance of forces responsible for net capillary filtration and lymph formation is described by the Starling equation, but additional factors such as vascular and interstitial compliance, which...

Birds live an energetically-expensive lifestyle as they are mostly small, diurnal and use flight. However they are long-lived, dominate most Australian environments and survive successfully in harsh and highly-variable conditions. Despite these contradictions little is known about the mechanisms Australian birds use to cope with these constraints,...

Basking is a behavioural adaptation that reduces thermoregulatory energy expenditure by utilising available solar energy. Basking behaviour is observed across the diversity of Columbiformes, including the naturalised Spotted Dove Streptopelia chinensis in Australia. This study aimed to quantify the energetic savings achieved by basking S. chinensis...

This study investigated the standard metabolic rate (SMR) and evaporative water loss (EWL) responses of three Australian trapdoor-constructing mygalomorph spider species, two undescribed arid-zone species (Aganippe 'Tropicana A' and A. 'Tropicana B') and a mesic-dwelling species (A. rhaphiduca) to acute environmental regimes of temperature and rela...

We examine here evaporative water loss, economy and partitioning at ambient temperatures from 14 to 33°C for the monito del monte (Dromiciops gliroides), a microbiotheriid marsupial found only in temperate rainforests of Chile. The monito's standard evaporative water loss (2.58 mg g(-1) h(-1) at 30°C) was typical for a marsupial of its body mass an...

Metabolic rate and evaporative water loss (EWL) were measured to quantify the thermoregulatory patterns of two dasyurids, the stripe-faced dunnart (Sminthopsis macroura) and the Ooldea dunnart (S. ooldea) during acute exposure to Ta between 10 and 35°C. S. macroura maintained consistent Tb across the Ta range, whereas S. ooldea was more thermolabil...

Stripe-faced dunnarts (Sminthopsis macroura) and Ooldea dunnarts (S. ooldea) were acclimated for 2 weeks to ambient temperature (T(a)) regimes of 12-22°C, 18-28°C and 25-35°C, and then measured for standard, basal (BMR) and maximum (MMR) metabolic rate using flow-through respirometry. Sminthopsis macroura maintained a stable body temperature under...

Temperature profoundly influences physiological responses in animals, primarily due to the effects on biochemical reaction rates. Since physiological responses are often exemplified by their rate dependency (e.g., rate of blood flow, rate of metabolism, rate of heat production, and rate of ion pumping), the study of temperature adaptations has a lo...

We examined the effects of season and captivity on several commonly measured physiological variables (body temperature, metabolic rate, thermal conductance, and evaporative water loss [EWL]) for the numbat (Myrmecobius fasciatus), an endangered myrmecophagous Australian marsupial, because the maintenance of a wild-type physiology may increase the l...

Studies of locomotor performance often link variation in morphology with ecology. While maximum sprint speed is a commonly used performance variable, the absolute limits for this performance trait are not completely understood. Absolute maximal speed has often been shown to increase linearly with body size, but several comparative studies covering...

Temperature profoundly influences physiological responses in animals, primarily due to the effects on biochemical reaction rates. Since physiological responses are often exemplified by their rate dependency (e.g., rate of blood flow, rate of metabolism, rate of heat production, and rate of ion pumping), the study of temperature adaptations has a lo...

Vertical movement of lymph from ventral regions to the dorsally located lymph hearts in anurans is accomplished by specialized skeletal muscles working in concert with lung ventilation. We hypothesize that more terrestrial species with greater lymph mobilization capacities and higher lymph flux rates will have larger lung volumes and higher pulmona...

Geometric scaling predicts that stresses on limb bones and muscles should increase with body size. Mammals counter this size-related increase in stress partially through changes in bone geometry, but largely through changes in posture, with larger species having a more erect stance. However, the ability to counter size-related stresses in this fash...

Physiological studies often involve the repeated measurement of individuals over a range of ordered categorical conditions, for example, varying ambient temperature. We illustrate here the use of a priori contrasts for multivariate repeated-measures ANOVA by analyzing the thermal responses of various physiological variables for a small marsupial, t...

Duration and start time of respirometry experiments have significant effects on the measurement of basal values for several commonly measured physiological variables (metabolic rate, evaporative water loss and body temperature). A longer measurement duration reduced values for all variables for all start times, and this was an effect of reduced ani...

The femoral lymph sac volumes and lymph mobilization capacity were compared in three anuran species that span a range of environments, dehydration tolerance, ability to maintain blood volume with dehydration, and degrees of development of skeletal muscles putatively involved in moving lymph vertically to the posterior lymph hearts. The femoral lymp...

There is a strong correlation between the structure of the mammalian kidney and its urinary concentrating ability. We examine here the kidney of an endangered termitivorous marsupial (Myrmecobius fasciatus) and use the measured kidney morphometrics to calculate maximal urinary concentration. The relative medullary area (1.34) of the kidney of M. fa...

A new method for quantitatively determining lymph flux from various lymphatic sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C(i)V(i)=C(f)V(f) following injection of Evans Blue into specific lymph sacs and measuring its appearance in the venous circulation. The apparent lymph volume was 57 ml kg(-1)....

Giles' planigale (Planigale gilesi) is among the smallest extant marsupials and inhabits deep soil cracks in arid floodplains. We examined whether its physiology shows specific adaptations to its extreme habitat. Metabolic rate, body temperature, evaporative water loss and thermal conductance were measured for eight planigales (average mass 9 g) ex...

Strict criteria have been established for measurement of basal metabolic rate and standard evaporative water loss to ensure that data can be compared intra- and interspecifically. However, data-sampling regimes vary, from essentially continuous sampling to interrupted (switching) systems with data recorded periodically at more widely spaced interva...

Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that standard physiological variables of these quolls are consistent with allometric...

The physiology of the long-furred woolly mouse opossum (Micoureus paraguayanus) conformed to that of other marsupials Body temperature at thermoneutrality (all values reported as mean +/- SE) was 33.3 degrees C +/- 0.3 degrees C and basal metabolic rate was 0.760 +/- 0.074 ml O-2 g(-1) h(-1) Opossums were thermolabile at low ambient temperature (T-...

An extended period of inactivity and reduced metabolic rate of many animals and plants, as well as unicellular organisms, has long been recognized by natural historians, e.g., Aristotle and Pliny. Biologists have studied this phenomenon since the 1550s (Gessner) and 1700s (Van Leeuwenhoek, Buffon). The period of inactivity can be less than a day, a...

The objectives of this study were (1) to measure plasma (Vp), blood (Vb), extracellular (Ve), and interstitial fluid (Vist) volumes using the same techniques; (2) to measure the rate of plasma turnover; and (3) to characterize the three important variables required to interpret transvascular flux at an organismal level (vascular compliance [Cvas],...

We examined the time course for measurement of basal metabolic rate (BMR; measured as O(2) consumption and CO(2) production) and standard evaporative water loss (EWL) for six species of small marsupial to determine the minimum time required to achieve basal/standard values. There was a highly significant effect of measurement duration on measured p...

Abstract Ecomorphological studies often seek to link morphology and performance to relevant ecological characteristics. Varanid lizards are unique in that species can vary in body size by almost four orders of magnitude within a single genus, and a question of considerable interest is whether similar ecomorphological relationships exist when constr...

We present here the first physiological data for the sandhill dunnart (Sminthopsis psammophila), the second largest (35–44 g) sminthopsine dasyurid marsupial, and report torpor for this species. Their thermoneutral body temperature (34.4 °C), thermolability below thermoneutrality (0.062 °C °C− 1), and mild hyperthermia above thermoneutrality (35.5...

In ecomorphological and ecophysiological studies, locomotor performance is often considered to be an intermediate step between the form of an organism and its environment. We examined this premise by measuring morphology, physiology and circular track endurance in the closely related group of Australian varanid lizards. Body size, body mass and rel...

The chuditch is a large carnivorous dasyurid marsupial. Historically it had one of the widest geographical distributions of all marsupials, encompassing much of arid Australia, but it is now restricted to the mesic south-west of Western Australia. It is therefore of interest to determine if its physiology better reflects adaptation to its historica...

The little red kaluta (Dasykaluta rosamondae) is a small, insectivorous-carnivorous dasyurid marsupial found in and spinifex grasslands of northwestern Australia. Kalutas resemble other dasyurids in many aspects of their physiology. Body temperature (T(b); 33.5 degrees C; 1.5 degrees C lower than predicted), wet thermal conductance (1.6 J g(-1) h(-...

We investigated interactions of body mass with geographical location, and five climatic measures for two Australian rodents, the native Australian sandy inland mouse (Pseudomys hermannsburgensis) and the introduced house mouse (Mus domesticus). Correlation and regression analyses identified interactions of body mass with latitude, longitude, averag...

In our earlier analysis of Varanus body shape, size was a dominating factor with some qualitative phylogenetic patterns and grouping of species into ecological categories. With a phylogeny and an improved capacity to account for the effects of size, we have reanalysed our morphometric data for male Australian goannas (Varanus spp.) using an increas...

We present the first complete study of basic laboratory-measured physiological variables (metabolism, thermoregulation, evaporative water loss, and ventilation) for a South American marsupial, the gracile mouse opossum (Gracilinanus agilis). Body temperature (T(b)) was thermolabile below thermoneutrality (T(b) = 33.5 degrees C), but a substantial g...

Dormancy or torpor is a widely-recognized behavioral and physiological state of both animals and plants that generally indicates inactivity and reduced metabolic rate. It can involve very different physiological states in response to a variety of environmental stimuli, including temperature, water, or food. It can last < 1 day, may occur for a few...

To better understand the effects of ambient relative humidity (RH) on physiological variables and the implications of RH-correcting evaporative water loss (EWL) data for marsupials, we examined the effect of RH on EWL, body temperature (Tb), metabolic rate (MR) and thermal conductance (C) of the brushtail possum (Trichosurus vulpecula), a medium-si...

We developed an index to quantify rehabilitation success for terrestrial environments using data on reptile assemblages from five rehabilitated mine site waste dumps and adjacent undisturbed areas. It is based on the multi-metric principles of the index of biotic integrity (IBI). This rehabilitation and degradation index (RDI) is a quantitative mea...

Endurance of juvenile Western Australian varanid lizards was compared with that of conspecific adults. Among adults, endurance generally increased intra-specifically with increasing body size. However, juvenile varanids have a higher than expected endurance. Possible causes for this heightened endurance are discussed, and probably result from a rel...

Metabolic and ventilatory parameters were measured for the smallest and largest Isoodon bandicoots; the arid-adapted Barrow Island golden bandicoot (Isoodon auratus barrowensis) and the tropical northern brown bandicoot (Isoodon macrourus). I. a. barrowensis has a number of physiological characteristics that aid its tolerance of high Ta and surviva...

Bipedal locomotion by lizards has previously been considered to provide a locomotory advantage. We examined this premise for a group of quadrupedal Australian agamid lizards, which vary in the extent to which they will become bipedal. The percentage of strides that each species ran bipedally, recorded using high speed video cameras, was positively...

Seasonal variation in various thermoregulatory, metabolic and ventilatory parameters was examined for southern brown bandicoots (Isoodon obesulus fusciventer) from a Mediterranean climate near Perth, Western Australia. There was significant seasonal variation over the four annual seasons at thermoneutrality (Ta=30 degrees C) in body temperature, ox...

Animal physiology is the study of how animals work and the biological processes essential for animal life, at levels of organisation from membranes to the whole animal. It is closely linked with anatomy and with basic physico-chemical laws that constrain living as well as non-living systems. Despite these constraints, there is a diversity of mechan...

It is well established that forming a cocoon, for frog species capable of doing so, markedly reduces evaporative water loss; however, the capacity of cocooned frogs to maintain hydration during extended estivation is not well understood. The combined effects of long-term estivation and water loss were examined in the cocoon-forming species Cycloran...

Electromyographic (EMG) activity of skeletal muscles that either insert on the skin or are associated with the margins of subcutaneous lymph sacs was monitored for two species of anurans, Chaunus marinus and Lithobates catesbeiana (formerly Bufo marinus and Rana catesbeiana). Our hypothesis was that contraction of these muscles varies the volume, a...

This study compared torpor as a response to food deprivation and low ambient temperature for the introduced house mouse (Mus musculus) and the Australian endemic sandy inland mouse (Pseudomys hermannsburgensis). The house mouse (mass 13.0+/-0.48 g) had a normothermic body temperature of 34.0+/-0.20 degrees C at ambient temperatures from 5 degrees C...

Anurans (frogs and toads) generate lymphatic fluid at 10 times the rate in mammals, largely as a consequence of their very 'leaky' vasculature and high interstitial compliance. Lymph is ultimately pumped into the venous system by paired, dorsally located lymph hearts. At present, it is unclear how lymphatic fluid that accumulates in central body su...

The alleged high net energy cost of running and low net energy cost of walking in humans have played an important role in the interpretation of the evolution of human bipedalism and the biomechanical determinants of the metabolic cost of locomotion. This study re-explores how the net metabolic energy cost of running and walking (J kg(-1) m(-1)) in...

Abstract Environmental impact assessments (EIA) require that the proponent indicates the potential impact that a development will have on the biodiversity of the area. As part of this assessment it is normal practice to inventory the vertebrate species in the area. We show here how species accumulation curves can be used as a tool by environmental...

The diet of Ctenotus xenopleura, a species found in spinifex grasslands in the southern Goldfields of Western Australia, consisted primarily of termites. The high proportion of termites was consistent over different sampling periods, and was higher than observed for most other Ctenotus species. It is not clear whether this high proportion of termit...

Thermoneutral metabolic and ventilatory parameters were measured every 3 months over 2 years for southern brown bandicoots held in captivity, and from a nearby reserve. Captive bandicoots were 130 g (9.9%) heavier than wild bandicoots. Long-term captivity had no effect on body temperature, basal metabolic rate (oxygen consumption), thermal conducta...

To investigate patterns of thermoregulation in free-ranging and captive southern brown bandicoots Isoodon obesulus, we measured abdominal body temperature (Tb) of five free-ranging bandicoots over 42 days using implanted data loggers and Tb of three captive bandicoots over 3 months using implanted temperature-sensitive radio transmitters. Bandicoot...

Burrowed aestivating frogs of the cocoon-forming species Neobatrachus aquilonius and the non-cocooning species Notaden nichollsi were excavated in the Gibson Desert of central Australia. Their hydration state (osmotic pressure of the plasma and urine) was compared to the moisture content and water potential of the surrounding soil. The non-cocoonin...

Many comparative physiological studies aim to determine if a particular species differs from a prediction based on a linear allometric regression for other species. However, the judgment as to whether the species in question conforms to this allometric relationship is often not based on any formal statistical analysis. An appropriate statistical me...

Arenophryne rotunda is a small (2-8 g) terrestrial frog that inhabits the coastal sand dunes of central Western Australia. While sand burrowing is a strategy employed by many frog species inhabiting Australia's semi-arid and arid zones, A. rotunda is unique among burrowing species because it lives independently of free water and can be found noctur...

We analyzed body temperature (T(b)), basal metabolic rate (BMR), wet thermal conductance (C(wet)), and evaporative water loss (EWL) of marsupials by conventional and phylogenetically corrected regression. Allometric effects were substantial for BMR, C(wet), and EWL but not T(b). There was a strong phylogenetic signal for mass and all physiological...

The metabolic, thermoregulatory and ventilatory physiology of western barred bandicoots (Perameles bougainville bougainville), measured in the laboratory during summer and winter at ambient temperatures of 10 and 30°C, is relatively unusual for a peramelid marsupial. It has a low thermoneutral body temperature (33.7 ± 0.2°C), a very high basal meta...

Thermoregulatory, metabolic and ventilatory parameters measured for the Tasmanian eastern barred bandicoot (Perameles gunnii) in thermoneutrality (ambient temperature = 30°C) were: body temperature 35.1°C, basal metabolic rate 0.55 mL O2 g–1 h–1, wet thermal conductance 2.2 mL O2 g–1 h–1 °C–1, dry thermal conductance 1.4 J g–1 h–1 °C–1, ventilatory...

The foraging ecology of many Ctenotus species is considered to be generalised and opportunistic. If their foraging ecology is generalised, we would predict that Ctenotus species in spinifex grasslands of and Australia will (1) feed largely on the most abundant food source, termites and (2) that any differences in diet will largely reflect differenc...