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, caimans and gharials. This book showcases the skills and capabilities that allow crocodylians to live how and where they do. It covers the biology and ecology of the extant species, conservation issues, crocodylian–human interaction and the evolutionary history of the group, and includes a vast amount of new information; 25 per cent of 1100 cited publications have appeared since 2007. Richly illustrated with more than 500 colour photographs and black and white illustrations, this book will be a benchmark reference work for crocodylian biologists, herpetologists and vertebrate biologists for years to come. Winner of the 2015 Whitley Medal.

Many elements of mammalian and avian thermoregulatory mechanisms are present in reptiles, and the changes involved in the transition to endothermy are more quantitative than qualitative. Drawing on our experience with reptiles and echidnas, we comment on that transition and on current theories about how it occurred. The theories divide into two categories, depending on whether selection pressures operated directly or indirectly on mechanisms producing heat. Both categories of theories focus on explaining the evolution of homeothermic endothermy but ignore heterothermy. However, noting that hibernation and torpor are almost certainly plesiomorphic (=ancestral, primitive), and that heterothermy is very common among endotherms, we propose that homeothermic endothermy evolved via heterothermy, with the earliest protoendotherms being facultatively endothermic and retaining their ectothermic capacity for "constitutional eurythermy." Thus, unlike current models for the evolution of endothermy that assume that hibernation and torpor are specialisations arising from homeothermic ancestry, and therefore irrelevant, we consider that they are central. We note the sophistication of thermoregulatory behavior and control in reptiles, including precise control over conductance, and argue that brooding endothermy seen in some otherwise ectothermic Boidae suggests an incipient capacity for facultative endothermy in reptiles. We suggest that the earliest insulation in protoendotherms may have been internal, arising from redistribution of the fat bodies that are typical of reptiles. We note that short-beaked echidnas provide a useful living model of what an (advanced) protoendotherm may have been like. Echidnas have the advantages of endothermy, including the capacity for homeothermic endothermy during incubation, but are very relaxed in their thermoregulatory precision and minimise energetic costs by using ectothermy facultatively when entering short- or long-term torpor. They also have a substantial layer of internal dorsal insulation. We favor theories about the evolution of endothermy that invoke direct selection for the benefits conferred by warmth, such as expanding daily activity into the night, higher capacities for sustained activity, higher digestion rates, climatic range expansion, and, not unrelated, control over incubation temperature and the benefits for parental care. We present an indicative, stepwise schema in which observed patterns of body temperature are a consequence of selection pressures, the underlying mechanisms, and energy optimization, and in which homeothermy results when it is energetically desirable rather than as the logical endpoint.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. ABSTRACT 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, high blood flow rates, and complete separation of high systemic blood pressure from low pulmonary blood pressure in a four-chambered heart. Ectotherms generally lack all of these characteristics, but crocodilians retain a four-chambered heart. However, crocodilians have a neurally controlled, pulmonary bypass shunt that is functional in diving. Shunting occurs outside of the heart and involves the left aortic arch that originates from the right ventricle, the foramen of Panizza between the left and right aortic arches, and the cog-tooth valve at the base of the pulmonary artery. Developmental studies show that all of these uniquely crocodilian features are secondarily derived, indicating a shift from the complete separation of blood flow of endotherms to the controlled shunting of ectotherms. We present other evidence for endothermy in stem archosaurs and suggest that some dinosaurs may have inherited the trait. The University of Chicago Press

The density of red kangaroos in the sheep country of the north-west corner of New South Wales is much higher now that it was last century. It is also much higher than the present density across the dingo fence in the adjacent cattle country of South Australia and Queensland. The picture is similar for emus. Farther east, about halfway along the New South Wales–Queensland border, no difference in density between the two States could be detected for red kangaroos, grey kangaroos or emus. We examine and discard several hypotheses to account for the density contrasts in the west and the lack of them farther east, deeming it unlikely that the pattern reflects environmental gradients, or differences in plant composition and growth, hunting pressure or availability of water. Instead, we favour this hypothesis: that the past and present patterns of density are attributable directly to predation by dingoes, which can hold kangaroos at very low density in open country if the dingoes have access to an abundant alternative prey.

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 dingoes are common, kangaroo densities are generally substantially lower, suggesting that dingoes are an important limiting factor. However, it is unclear whether dingoes can regulate kangaroo populations. In this study, red kangaroo and emu (Dromaius novaehollandiae) numbers were monitored for varying periods during 1978–92 by aerial survey on both sides of the dingo fence in three areas in the north of the South Australian pastoral zone. Densities of red kangaroos and emus were lower outside the fence, although the disparity varied between areas and over time. The similarity in the environments on both sides of the fence and the marked step in kangaroo density at the fence are consistent with dingoes strongly limiting these prey populations. In the north-east of the pastoral zone, where kangaroo and emu densities are greatest, the contrast in density across the fence was most pronounced. Furthermore, the trends in density over time differed across the fence. Outside the fence, red kangaroos and emus remained at low densities following drought as dingo numbers increased. Inside the fence, red kangaroo and emu populations showed a ‘typical’ post-drought recovery. The data therefore suggest that, in some situations, dingoes may not simply limit red kangaroo and emu populations, but also regulate them. For this to occur, predation rate would need to be density dependent at low prey densities. The availability of alternative prey, and the reduction in the numbers of all prey during drought may provide the mechanism.

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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 crocodilian. Three large male Crocodylus porosus (3.1–4.5 m) were captured in northern Australia and translocated by helicopter for 56, 99 and 411 km of coastline, the last across Cape York Peninsula from the west coast to the east coast. All crocodiles spent time around their release site before returning rapidly and apparently purposefully to their capture locations. The animal that circumnavigated Cape York Peninsula to return to its capture site, travelled more than 400 km in 20 days, which is the longest homeward travel yet reported for a crocodilian. Such impressive homing ability is significant because translocation has sometimes been used to manage potentially dangerous C. porosus close to human settlement. It is clear that large male estuarine crocodiles can exhibit strong site fidelity, have remarkable navigational skills, and may move long distances following a coastline. These long journeys included impressive daily movements of 10–30 km, often consecutively.

Summary. Pressure records from the heart and outflow vessels of the heart of Crocodylus porosus resolve previously conflicting results, showing that left aortic filling via the foramen of Panizza may occur during both cardiac diastole and systole. Filling of the left aorta during diastole, identified by the asynchrony and comparative shape of pressure events in the left and right aortae, is reconciled more easily with the anatomy, which suggests that the foramen would be occluded by opening of the pocket valves at the base of the right aorta during systole. Filling during systole, indicated when pressure traces in the left and right aortae could be superimposed, was associated with lower systemic pressures, which may occur at the end of a voluntary aerobic dive or can be induced by lowering water temperature or during a long forced dive. To explain this flexibility, we propose that the foramen of Panizza is of variable calibre. The presence of a 'right-left' shunt, in which increased right ventricular pressure leads to blood being diverted from the lungs and exiting the right ventricle via the left aorta, was found to be a frequent though not obligate correlate of voluntary aerobic dives. This contrasts with the previous concept of the shunt as a correlate of diving bradycardia. The magnitude of the shunt is difficult to assess but is likely to be relatively small. This information has allowed some new insights into the functional significance of the complex anatomy of the crocodilian heart and major blood vessels.Abbreviations: bpm beats per minute; LAo left aorta (aortic); LV left ventricle (ventricular); PA pulmonary artery; RAo right aorta (aortic); RV right ventricle (ventricular); SC subclavian artery. IntroductionThe anatomical peculiarities of the heart of extant crocodilians have attracted the interest and curiosity of functional morphologists for more than 150 years (Panizza 1833; Fritsch 1869; Sabatier 1873; Greil 1903). Alone among reptiles in having complete separation of left and right ventricles, such as seen in birds and mammals, they also possess two features which are uniquely crocodilian: the left systemic aorta derives not from the left ventricle, but from the right, alongside the main pulmonary arterial trunk, while the foramen of Panizza affords an opportunity for communication between the right and left aortae, at their bases. A detailed review of crocodilian cardiac anatomy in general, and of Crocodylus porosus in particular, was given by Webb (1979). The most recent reviews of functional interpretations of the cardiac anatomy are by White (1976), Johansen (1979Johansen ( , 1985, Johansen and Burggren (1980) and Burggren (1985).Early functional interpretations of the crocodilian cardiovascular anatomy proposed that the left aorta would receive deoxygenated blood (Goodrich 1919) so that the dorsal aorta distal to the confluence of left and right would contain mixed blood. Functional interpretation based on physiological observations has revised substantially that early interpretation. Whit...