Gordon C. Grigg

University of Queensland | UQ · School of Biological Sciences

The whole‐body (tachymetabolic) endothermy seen in modern birds and mammals is long held to have evolved independently in each group, a reasonable assumption when it was believed that its earliest appearances in birds and mammals arose many millions of years apart. That assumption is consistent with current acceptance that the non‐shivering thermog...

The distribution of the koala (Phascolarctos cinereus) in Queensland is predicted to contract as a result of climate change, driven by the frequency, intensity and duration of heatwaves and drought. However, little is known about the physiological responses of this species to environmental extremes under field conditions. This study aimed to establ...

Large‐bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosy...

The aim of this paper is to highlight long-term (four decades) research and monitoring the populations of the four species of large kangaroos in New South Wales (NSW). Kangaroos are counted by aerial surveys using two types of aircraft: fixed-wing and helicopters. The NSW Commercial Kangaroo Harvest Management Plan 2017-21 states that harvest quota...

During the late 1970s I developed an idea that later became known as 'sheep replacement for rangelands'. It grew from the realisation, gained during hundreds of hours of low flying on kangaroo surveys, that overgrazing by sheep was turning, or had already turned Australia's 'sheep rangelands' into desert. Seeking an economically productive alternat...

Invasive species may have devastating impacts on native biota. Cane toads Rhinella marina continue to invade northern Australia and the consequences for the endemic frogs are unclear. Monitoring frogs in such remote areas is difficult because their activity depends heavily on unpredictable rainfall events. We developed an autonomous acoustic monito...

The koala (Phascolarctos cinereus) is the largest arboreal folivore and is widely distributed across eastern Australia. Koalas appear to be adversely affected by extremely hot and dry environmental conditions and are predicted to experience a distribution contraction under current climate change scenarios. This study measured the body temperature...

Biology and Evolution of Crocodylians is a comprehensive review of current knowledge about the world's largest and most famous living reptiles. Gordon Grigg's authoritative and accessible text and David Kirshner's stunning interpretive artwork and colour photographs combine expertly in this contemporary celebration of crocodiles, alligators, caiman...

Microsatellite markers were used to investigate the mating system of the Estuarine Crocodile (Crocodylus porosus). Three-hundred and eighty-six hatchlings from 13 clutches from a wild Northern Territory population, and 364 hatchlings from 21 clutches from a captive North Queensland population, were sampled. All samples were genotyped across five mi...

We used implanted transmitters to track echidnas and record body temperatures year round. The resultant discovery of hibernation in these non-placental mammals (but not in their close relatives, Platypus), sometimes in quite benign climates, poses questions about the origin of the ability to hibernate and the origin of endothermy itself. To help an...

Data from diverse studies endorse ideas that short term torpor and hibernation are expressions of ancient characters. In evolutionary terms, their basic mechanisms are probably plesiomorphic (= ancestral/primitive) and physiologically similar. This contrasts with the alternate view that they are apomorphic (= derived, specialized), arising independ...

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Management of the commercial harvest of kangaroos relies on quotas set annually as a proportion of regular estimates of population size. Surveys to generate these estimates are expensive and, in the larger states, logistically difficult; a cheaper alternative is desirable. Rainfall is a disappointingly poor predictor of kangaroo rate of increase in...

This paper presents the first data on the diving behaviour of Flatback turtles, Natator depressus, between nesting events. Dive profiles were recorded in turtles from breeding populations at Curtis island in Queensland and at Bare Sand Island in the Northern Territory, using Time-Depth Recorders (TDRs). Both populations displayed dive types typical...

The breeding ecology and phenology of two sympatric stream breeding myobatrachid frogs were studied across a breeding season in a stream at Cunningham's Gap, south-east Queensland. Mixophyes fleayi is listed as endangered and M. fasciolatus is considered not threatened.The two species occur sympatrically and their breeding seasons overlap, but they...

We recorded the calling activity of frogs at a permanent pond 80 km south of Sydney between 1987 and 1989, documenting the calling seasons of five species and relating calling activity (within calling seasons) to temperature, humidity, barometric pressure and rainfall. Three species commenced calling in August/September with Litoria peronli and Upe...

The short-beaked echidna (Tachyglossus aculeatus) is an exceptionally long-living mammal having a maximal lifespan of -50 years. This is about four times that predicted from its body mass and, consequently, its longevity quotient is 4.This longevity quotient is similar to two other exceptionally long-living mammalian species; the naked mole-rat (He...

We measured gas exchange of eggs and mound material as well as gas concentrations at different times during ncubatlon in the mound nests of the salt water crocodile, Crocodylus porosus and the American alligator, Alligator mississippiensis. Oxygen consumption increased gradually during development in both species, peaking well before hatching (at a...

The Pantanal is the world's largest contiguous freshwater wetland spanning Brazil, Bolivia, and Paraguay. It contains the greatest wildlife densities in the Neotropics and was enlisted by all three countries in the Ramsar convention on wetland conservation. The Brazilian government, together the UNESCO's Man and the Biosphere Program, declared a bi...

Provision of artificial waterpoints in Australian rangelands has resulted in an increase in the range and density of kangaroos. At high densities, kangaroos can inhibit vegetation regeneration, particularly in some protected areas where harvesting is prohibited. Fencing off waterpoints has been proposed to limit these impacts. Our aim was to determ...

Evidence is presented which shows that in traversing the heart of the Tuatara, systemic venous blood is selectively distributed to the pulmonary arches. This selective distribution of deoxygenated blood into the pulmonary circuit occurs despite the poorly developed primary ventricular septum and the lack of a secondary septum, and yet it appears to...

In this study of body temperatures (T(b)) in free ranging dromedary camels, we found that bulls in rut start the days cooler. Daily minima during rut averaged 0.6 degrees C lower than at other times (95% CI 0.27-0.94 degrees C) and daily maxima averaged 0.45 degrees C higher (95% CI -0.01 to -0.91 degrees C), increasing the daily T(b) cycle. Knut S...

Relationships between some properties of frog calls and body size are widely recognized. However, generality across call components and diverse faunas, and sources of deviation, remain poorly tested. Using 116 east Australian frog species, we tested the relationship between three call traits and body size, and the effects of taxonomic family and ca...

The echidna Tachyglossus aculeatus is a monotreme mammal from Australia that is exceptionally long-living. Its documented maximum lifespan of 50 years is 3.7 times that predicted from its body mass. Other exceptionally long-living mammals (naked mole-rats and humans) are known to have peroxidation-resistant membrane composition, raising the questio...

We radio-tracked five male and eight female estuarine crocodiles (Crocodylus porosus) in a non-tidal waterhole in Lakefield National Park in northern Queensland during the late dry/mid-wet season (2003–04) and the following dry season (2004). Individual crocodiles occupied larger home ranges (River Channel Areas (RCA) during the late dry/mid-wet se...

In 1935, 101 cane toads, B. marinus, were introduced into north Queensland, Australia in an attempt to control the greyback cane beetle, Dermolepida albohirtum, a pest of sugar cane fields. The cane toad was, however, completely unable to control the beetles and itself became a successful pest. Since their arrival, cane toads have been implicated i...

Oxygen equilibrium curves and other respiratory-related variables were determined on blood from the flatback turtle (Natator depressus) and, for comparison, on some samples from the loggerhead turtle (Caretta caretta). The oxygen carrying capacity of the flatback turtle, 4.9-8.7 mmol l(-1) (n = 49), is at the high end of the range in diving reptile...

Wildlife surveys usually focus on estimating population size, and management actions such as commercial harvesting, culling and poison baiting are referenced commonly to population size alone, without taking into account the way in which those animals are distributed. This paper outlines how point‐based aerial survey data can be converted to contin...

Controlling kangaroo grazing pressure in national parks without harvesting or culling presents a significant challenge. Fencing off waterpoints is often tried or contemplated as a control measure, but its success obviously depends upon the extent to which kangaroos require access to discrete sources of drinking water. To assess the necessity for re...

Crocodilians have a wide distribution, often in remote areas, are cryptic, secretive and are easily disturbed by human presence. Their capacity for large scale movements is poorly known. Here, we report the first study of post-release movement patterns in translocated adult crocodiles, and the first application of satellite telemetry to a crocodili...

Surprisingly little is known about the way chemical secretions modulate behavior in amphibians, and this is particularly so with respect to cane toads. For example, anecdotal observations and some preliminary experimental data suggest that cane toads may deploy sex, alarm or aggregation pheromones. If true, the existence of such ecologically signif...

Short-beaked echidnas have an impressive ability to submerge completely into soil or sand and remain there, cryptic, for long periods. This poses questions about how they manage their respiration, cut off from a free flow of gases. We measured the gradient in oxygen partial pressure (PO2) away from the snouts of buried echidnas and oxygen consumpti...

We investigated the capacity of two reptiles, an agamid lizard Pogona barbata and a chelid turtle Emydura signata, to compensate for the effects of temperature by making changes in their whole blood respiratory properties. This was accomplished by measuring the P50 (at 10, 20 and 30 degrees C), hematocrit (Hct), haemoglobin concentration ([Hb]) and...

Concentrations of ATP and DPG, activities of 10 enzym es and the glycolytic rat es were measured in the erythrocytes of 11 species of marsupials and two speci es of monotremes. Mean DPG concentrations were greater in the erythrocytes of marsupials than those of eutherian mammals. The opposite is true of ATP. Significant findings from the result...

This article argues that a reduction in sheep numbers within the sheep rangelands would lead to an increase in kangaroos, improvement in the vegetation, and a reduction in soil erosion. An increase in the market value of kangaroo products would provide a mechanism for this, by making the replacement of sheep by kangaroos an economically attractive...

1. We analysed time-series data from populations of red kangaroos (Macropus rufus, Desmarest) inhabiting four areas in the pastoral zone of South Australia. We formulated a set of a priori models to disentangle the relative effects of the covariates: rainfall, harvesting, intraspecific competition, and domestic herbivores, on kangaroo population-gr...

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Physiological, anatomical, and developmental features of the crocodilian heart support the paleontological evidence that the ancestors of living crocodilians were active and endothermic, but the lineage reverted to ectothermy when it invaded the aquatic, ambush predator niche. In endotherms, there is a functional nexus between high metabolic rates,...

A study on the biogeography and diversity of bats was carried out on 32 selected sampling sites and published information on the fruit bats in Southeast Asia.

We measured daily changes in plant water content to see if red kangaroos (Macropus rufus), in foraging at night, may gain more water than foraging by day. If so, it could be influential in dictating their time of foraging. The study was stimulated by work in Africa which showed that, by choosing to feed at night, gazelles are able to take advantage...

The routine occurrence of both short-term (daily) and long-term torpor (hibernation) in short-beaked echidnas, but not platypus, raises questions about the third monotreme genus, New Guinea's Zaglossus. We measured body temperatures (T(b)) with implanted data loggers over three and a half years in two captive Zaglossus bartoni at Taronga Zoo, Sydne...

An international workshop on gazelle harvesting and management was held in Ulaanbaatar, Mongolia, in October, 2003. The major output from this workshop was the general agreement that no commercial hunt can be recommended at this time. This is because of the high level of poaching that is appearing to be having a negative impact on gazelle numbers....

This study compared the stress induced in captive estuarine crocodiles, Crocodylus porosus, by two different handling methods: manual restraint (noosing with ropes) and immobilization by electro-stunning. To stun, a short charge (approx. 6 s) at 110 V was delivered to the back of the necks of C. porosus using a custom-built device, which immobilize...

(1) Echidnas occur throughout the hot arid zone of Australia yet laboratory studies have concluded that they are ill equipped physiologically to manage Ta higher than 35°C. (2) Consequently, it is generally assumed that echidnas must rely on behavioural thermoregulation, being nocturnal in hot weather and seeking less extreme microclimates during t...

The effects of moderate and severe hypoxia on air breathing frequency and respiratory properties of the blood of the Queensland (Australian) lungfish Neoceratodus forsteri were measured in fish exposed to these conditions for 14-22 days at 20 degrees C. Haemoglobin oxygen affinity increased after exposure to moderate hypoxia (PW(O(2)) = 60 mmHg), b...

Over the last twenty years, kangaroo harvesting has gained much greater public acceptance and risen in monetary value. However, most landholders still regard kangaroos mainly as pests, and are a long way from making enough money from kangaroos to encourage any shift away from their focus on sheep. Yet kangaroo meat is now sold legally for human con...

Echidnas occur throughout Australia. They exhibit daily fluctuations in body temperature (T-b) and use torpor to various degrees throughout much of their range. Echidnas elsewhere are commonly diurnal except during hot weather. This study used temperature-sensitive radio-transmitters to investigate the activity patterns and temperature relations of...

Laboratory studies and a single field study have shown that heart rate in some reptiles is faster during heating than during cooling at any given body temperature. This phenomenon, which has been shown to reflect changes in peripheral blood flow, is shown here to occur in the lizard Varanus varius (lace monitor) in the wild. On a typical clear day,...

We present some generalizations about the use of radio telemetry in physiological ecology, particularly to monitor body temperature and heart rate, drawn from work on free-ranging camels, echidnas, platypus, Tasmanian devils, quolls, crocodiles, bearded dragon lizards, goannas, freshwater turtles, and Queensland lungfish. We identify some potential...

As part of a radiotelemetric study of echidnas (Tachyglossus aculeatus) in south-east Queensland focusing on thermal relations, we were able to confirm and extend present knowledge of echidna reproduction. Mating was concentrated in July and August, as elsewhere, but we found that echidnas have the ability to conceive successfully a second time wit...

As part of a large-scale monitoring program linked to the management of kangaroos in the South Australian pastoral zone, the western grey kangaroo populations have been surveyed annually with fixed-wing aircraft over the 15-years-period 1978–92. Western grey kangaroos are restricted in their distribution to the southern regions of the pastoral zone...

Most of Australia’s sheep rangelands are enclosed by a dingo-proof fence. Within these rangelands, where dingoes (Canis lupus dingo) are rare, red kangaroos (Macropus rufus) are considered to be food limited because their numbers respond to fluctuations in pasture biomass that are driven by highly variable rainfall. Outside this region, where dingo...

Cane toads have marched their way across the Queensland border and are now quickly spreading into the Northern Territory. The Cane Toad: love it or hate it, you have to admire the biological skills of this invader, to expand its range at such a rate and across such a diversity of habitats. The dry country around the southern Gulf was taken in its s...

Short-beaked echidnas undergo both torpor and hibernation, expressed to different extents in different climates. We propose that when well fed animals hibernate in comparatively mild climates, with food available, they are using the winter cold as a resource and "putting themselves on ice" until the next breeding season. That is, echidnas are hiber...

We mapped the sequence of ventricular depolarization in the crocodile Crocodylus johnstoni. We also attempted to find specialized conduction tissue within the ventricular myocardium. Electrical recordings with miniature multi-point electrodes revealed two strands of rapidly conducting tissue (channels) within the interventricular septum, suggestive...

The discovery that changes in heart rate and blood flow allow some reptiles to heat faster than they cool has become a central paradigm in our understanding of reptilian thermoregulation. However, this hysteresis in heart rate has been demonstrated only in simplistic laboratory heating and cooling trials, leaving its functional significance in free...

Twenty-one surveys have been conducted using a Cessna 182 in the pastoral zone of South Australia, covering the twenty year period 1978 to 1998, flying the same transects and using the same method. Considerable attention has been given to observer training and the turnover rate of observers has been low. The same pilot has flown all surveys. The pa...

The estuary of the Limmen Bight River in Australia's Northern Territory is home to an unusual salt water-adapted population of the Australian `freshwater' crocodile, Crocodylus johnstoni. Crocodiles were captured from tidal reaches of the estuary ranging in salinity from 0.5-240/00 and from several permanent fresh water reaches more or less remote...

Empirical field data describing daily and seasonal cycles in body temperature (Tb) of free-ranging Crocodylus porosus (32-1010 kg) can be predicted by a mathematical analysis. The analysis provides a mechanistic explanation for the decreased amplitude of daily cycles in Tb and the increase in 'average' Tb with increasing mass. Assessments of 'avera...

This paper develops a hierarchical landscape approach for investigating how landscape structure influences the abundance of eastern grey kangaroos, red kangaroos and common wallaroos on properties in a partially-cleared semi-arid woodland of Queensland. This approach is applied to examine the extent to which a mosaic of spatial factors at a hierarc...

We monitored behaviour and environmental and body temperatures (Tb) in summer and winter in 11 salt–water crocodiles (Crocodylus porosus), of body mass 32–1010kg, free–ranging in naturalistic captivity in northern Australia. We found pronounced daily cycle in air and water temperatures in both winter (16–33 °C and 20–31 °C, respectively) and summer...

We recorded physical attributes of sites used for daily shelter or as hibernacula by nine echidnas, Tachyglossus aculeatus, living on a sheep-grazing property in south-eastern Queensland. Home ranges were also determined. For daily shelter sites, echidnas most often used hollow logs and depressions under the roots of fallen trees. Daily shelters we...

The use of line-transect methodology, on foot or from a helicopter, is likely to return the most repeatable, least biased estimates of kangaroo density. However, the associated costs make both methods impractical for broad-scale surveys. For these, a fixed-wing aircraft remains the most cost-effective platform. Limitations of the standard fixed-win...

The broad-snouted caiman Caiman latirostris, of South America mostly frequents freshwater but occurs also in estuaries. Nothing of substance is known of its osmoregulatory physiology but, in the light of accumulating evidence that alligatorids lack specialised adaptations for life in hyperosmotic waters, we anticipated its physiology would be more...

This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994–1995) and autumn (1995). Seasonal patterns of body temperature (T b) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To quantify ther...

Kangaroo harvest quotas for each Australian state have been set mainly as proportions of population estimates derived from aerial surveys. Estimating population size from strip transect counts using fixed wing aircraft has become an established technique, but counts must be adjusted by correction factors to ensure population estimates are both accu...

We measured body temperatures of free-ranging Brisbane River Turtles, Emydura signata with radiotelemetry. These and other species of freshwater turtle are commonly observed "basking" on logs or other elevated sites, a behavior which is usually interpreted as thermoregulatory. However, body temperatures of eight E. signata monitored for more than 1...

We determined diurnal and seasonal patterns of body temperature ( T_b) in Crocodylus johnstoni in the wild by monitoring T_b and behavior of 15 crocodiles, as well as measuring water, air and ground temperatures, and solar radiation. Two fundamentally different diurnal patterns of T_b occurred. One (pattern A) was s...