Movements of feral camels in central Australia determined by satellite telemetry

Movements of two female one-humped camels in central Australia were tracked using satellite telemetry between March 1986 and July 1987. During that time both animals travelled a minimum distance of over 1000 km within a radius of 125 km for one animal, and 200 km for the other. However, their movements were uite punctuated and both animals spent periods of up to several months in rleatively small areas before moving over longer distances to new areas. Both camels moved at greater rates overnight. An activity index, probably measuring feeding rate, declined during the study period for both animals. Patchy and sporadic rainfall may explain some of these results

Electrical activation of the ventricular myocardium of the crocodile Crocodylus johnstoni: A combined microscopic and electrophysiological study

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 of conductive tissue pathways. From these septal channels, wavefronts of excitation swept around each ventricle. Electrical recordings did not indicate that there was conductive tissue in the wall of either ventricle. Similarly, microscopic studies of the septal channels provided no indication of specialized conductive tissue. We suggest that the channels of early septal depolarization provide the crocodile heart with a high speed depolarization pathway functionally analogous to a rudimentary conductive system

Facultative Aestivation in a Tropical Freshwater Turtle Chelodina rugosa

Abstract-1. Chelodina rugosa dug from aestivation sites at the end of the dry season were immediately alert and well coordinated. 2. Compared with non-aestivating animals, aestivating turtles had 20% higher plasma osmotic pressure and 7% higher sodium. Coupled with a small, but significant weight gain upon return to the water, this suggested the occurrence of minor dehydration in aestivating animals. 3. Plasma lactate levels of aestivating animals were low, averaging 1.99 mmol/1, consistent with aerobic rather than anaerobic metabolism having sustained their long period under ground. 4. No evidence was seen of dramatic physiological specialization. Aestivation in this species is interpreted as a primarily behavioural adaptation, made possible by typically reptilian abilities to tolerate a wide range in plasma electrolytes and to survive long periods without feeding

Osmoregulation of the Cane Toad, Bufo Marinus, in Salt Water

1. Adult cane toads, B. marinus, survived in salinities up to 40% sea-water (SW). 2. Pre-exposure to 30, then 40% SW, increased the survival time of toads in 50% SW. 3. Plasma from toads acclimated to salt water is hyperosmotic to the environment - a result of increased plasma sodium, chloride and urea concentrations. 4. When toads were placed in tap-water and 20% SW, all significant changes to plasma sodium, chloride, urea and osmotic pressure occurred within the first 2 days of exposure. 5. When toads were placed in 30 and 40% SW environments, the increases in plasma sodium and chloride concentrations occurred within the first 2 days of exposure while urea and total osmotic pressure continued to rise until some time between 2 and 7 days exposure

The abundance of kangaroos in suboptimal habitats: wheat, intensive pastoral, and mallee

Densities of red kangaroos Macropus rufus and grey kangaroos M. fuliginosus and M. giganteus in western Victoria and SE South Australia were assessed by aerial survey. Of the total area, 85% had a density of less than one kangaroo per square kilometre, and 32% had a density of less than 0.01 km-2, values considerably lower than those reported for pastoral areas in New South Wales and South Australia. Low densities in settled areas are attributed to intensive agricultural practices, small landholdings and lack of tree cover. Low densities in mallee may be due to the lack of palatable grasses and the absence of permanent watering points

The exceptional longevity of an egg-laying mammal, the short-beaked echidna (Tachyglossus aculeatus) is associated with peroxidation-resistant membrane composition

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 peroxidationresistant membrane composition, raising the question about echidnas. Phospholipids were extracted from skeletal muscle, liver and liver mitochondria of echidnas and fatty acid composition measured. As with other exceptionally long-living mammals, membrane lipids of echidna tissues were found to have a lower content of polyunsaturates and a higher content of monounsaturates than predicted for their body size. The peroxidation index (=peroxidation susceptibility) calculated from this membrane composition was lower-than-expected for their body size, indicating that the cellular membranes of echidnas would be peroxidation-resistant. Additionally when the calculated peroxidation index was plotted against maximum lifespan, the echidna values conformed to the relationship for mammals in general. These findings support the membrane pacemaker theory of aging and emphasise the potential importance of membrane fatty acid composition in aging and in the determination of maximum longevity

How many kangaroos?

Between 1980-1982 much of Australia was surveyed from the air to estimate density and distribution of kangaroos. Numbers were estimated as 8.3 million red kangaroos Macropus rufus, 1.8 million 'western' grey kangaroos M. fuliginosus and 5.0 million eastern grey kangaroos M. giganteus. The unsurveyed eastern highlands probably hold a further 4 million eastern greys, allowing a tentative overall estimate for 1981 of 19 million kangaroos in mainland Australia

Differences in renal-cloacal function between Crocodylus porosus and Alligator mississippiensis have implications for crocodilian evolution

Major electrolytes and nitrogenous excretory products were analysed in the blood plasma, ureteral urine and cloacal urine of juvenile Alligator mississippiensis and Crocodylus porosus in fresh and hypoosmotic salt water (206 mosmol . l). Both species coped well with saline water, showing little (Alligator) or no (Crocodylus) change in plasma composition. Comparisons of renal-cloacal function point to major differences in their osmoregulatory physiology. The cloaca of C. porosus in a very active osmoregulatory organ in salt and fresh water, contributing to water conservation and NaCl excretion through the lingual salt glands. In contrast, the cloaca of Alligator has little impact on the composition of excreted urine. It seems likely that A. mississippiensis is largely constrained to a renal response to osmotic and ionic stress while C. porosus is able to call on a more complex mix of renal response, post-renal modification of urine in the cloaca, and excretion of excess NaCl through the salt glands. The results support the idea that there are deep-seated differences in the osmoregulatory physiology of alligatorids and crocodylids (Eusuchia), an understanding of which should provide valuable insights into their evolution and zoogeography

Kangaroos and climate: an analysis of distribution

Macropus giganteus occupies areas only where rainfall either has little seasonal trend or where rainfall in summer exceeds winter rainfall. M. fuliginosus is found in areas of uniform or winter rainfall. Seasonality of rainfall has little influence on the distribution of M. rufus. Instead, its distribution reflects interaction between mean annual precipitation and mean annual temperatur