Autumnand Winter Research Articles

Distribution and Abundance of Dugongs, Turtles, Dolphins and other Megafauna in Shark Bay, Ningaloo Reef and Exmouth Gulf, Western Australia

Strip-transect aerial surveys of Shark Bay, Ningaloo Reef and Exmouth Gulf were conducted during the winters of 1989 and 1994. These surveys were designed primarily to estimate the abundance and distribution of dugongs, although they also allowed sea turtles and dolphins, and, to a lesser extent, whales, manta rays and whale sharks to be surveyed. Shark Bay contains a large population of dugongs that is of international significance. Estimates of approximately 10000 dugongs resulted from both surveys. The density of dugongs is the highest recorded in Australia and the Middle East, where these surveys have been conducted. Exmouth Gulf and Ningaloo Reef are also important dugong habitats, each supporting in the order of 1000 dugongs. The estimated number of turtles in Shark Bay is comparable to the number in Exmouth Gulf plus Ningaloo Reef (7000–9000). The density of turtles in Ningaloo Reef and, to a lesser extent, Exmouth Gulf is exceptionally high compared with most other areas that have been surveyed by the same technique. Shark Bay supports a substantial population of bottlenose dolphins (2000–3000 minimum estimate). Exmouth Gulf and Ningaloo Reef were not significant habitats for dolphins during the winter surveys. Substantial numbers of whales (primarily humpbacks) and manta rays occur in northern and western Shark Bay in winter. Ningaloo Reef is an important area for whale sharks and manta rays in autumn and winter. The Shark Bay Marine Park excludes much of the winter habitats of the large vertebrate fauna of Shark Bay. In 1989 and 1994, more than half of all the dugongs were seen outside the Marine Park (57·4 and 50·7%, respectively). Approximately one-third to one-half of turtles and dolphins were seen outside the Marine Park (in 1989 and 1994 respectively: turtles, 43 and 27%; dolphins, 47 and 32%). Almost all the whales and most of the manta rays were seen outside the Marine Park. Expansion of the Shark Bay Marine Park, to bring it into alignment with the marine section of the Shark Bay World Heritage Area, would facilitate the appropriate management of these populations. This would also simplify the State– Commonwealth collaboration necessary to meet the obligations of World Heritage listing. The coastal waters of Western Australia north of the surveyed area (over 6000 km of coastline) are relatively poorly known and surveys of their marine megafauna are required for wise planning and management.

Diet of the Long-Nosed Potoroo, Potorous-Tridactylus (Marsupialia, Potoroidae), in Southwestern Victoria

The diet of the long-nosed potoroo, Potorous tridactylus, in south-western Victoria, was investigated by the microscopical identification of faecal remains. P. tridactylus is omnivorous: the main component of the diet was fungi, and other important items included hard-bodied arthropods, vascular plant tissues, seeds and fleshy fruits. There was a seasonal switch in the relative proportions of the main dietary components between the autumn-winter and spring-summer periods of the year. During autumn and winter, the main components were fungi and seeds. In spring and summer, fewer fungi were eaten and the proportions of arthropods, plant tissues, fleshy fruit and flowers in the diet increased. Identification of fungal spores revealed the presence of at least 50 species in the diet, most of which have a hypogeal fruiting habit. Hypogeal fungi form ectotrophic mycorrhizal associations with forest trees and are important in the health and productivity of forests. They lack active mechanisms for spore dispersal and are dependent upon mycophagous animals. The role of mycophagous small mammals, such as P. tridactylus, in the health of forest ecosystems may be more important than previously recognised.

Phenology of Eucalyptus marginata on Sites Infested With Phytophthora cinnamomi

The phenology of Eucalyptus marginata (jarrah) was followed at three sites, Churchmans, Karnet and Ross, in the high rainfall zone of the jarrah forest for a minimum of 3 years. On each site, trees growing in an area infested with the soil-borne, pathogenic fungus Phytophthora cinnamomi (dieback area) were compared with trees of similar diameter in the adjacent, uninfested forest (healthy area). Phenology of jarrah on these dieback sites did not follow a consistent pattern. In the dieback area at Churchmans, the cambium was active more often, and trees had young leaves in their crown more frequently than trees in the healthy area, while at Karnet the reverse occurred. This is consistent with growth measurements. At Ross, in the dieback area, the cambium was active less often but young leaves were seen more frequently than in trees in the healthy area. The trees did not flower every year. At Ross flowering started in early October while at Karnet and Churchmans it started at least 1 month later. New leaves were produced intermittently during autumn and winter while the main leaf flush occurred in spring and summer. Data from all years showed that the leaf flush started earlier at Ross than at Karnet and Churchmans. The cambium was intermittently active throughout the year with most trees growing in late autumn, winter and spring. Observations of stem growth following unseasonable summer rainfall suggest that cambial activity is triggered by high, surface soil moisture, but only if soil aeration is adequate. It is unlikely that timing of the main leaf flush and flowering are determined solely by temperature, soil moisture or photoperiod.

Distribution, Prevalence, and Epidemiology of Bovine Tuberculosis in Brushtail Possums, Trichosurus-Vulpecula, in the Hohonu Range, New-Zealand

Over a 12-month period, 1467 brushtail possums were trapped and then killed or were poisoned along sampling lines on pasture-forest margins and in nearby forest. An additional 334 possums were shot on adjacent farm land. All possums were necropsied, and 141 had macroscopic lesions typical of bovine tuberculosis. Infected possums occurred most commonly in small foci of 2-5 individuals along pasture-forest margins; the furthest from pasture that an infected animal was taken was 4050 m. Lesions occurred in possums of all ages in both sexes, but disease prevalence was highest in immature males and during autumn and winter. Infected possums bred as successfully as non-infected individuals, but were of lighter body weight. Macroscopic lesions occurred in a wide range of visceral and lymph node sites. Lesions were most common in the lungs and axillary nodes, and occasionally formed open sinuses from which infected possums could shed M. bovis readily, and thus were likely to be highly infective. Evidence suggested that disease transmission occurs most frequently on pasture-forest margins, where possum numbers are greatest and possum and cattle mix most freely.

Seasonal Respiration of Transennella tantilla Gould

SYNOPSIS. A population of Transennella tantilla living on an intertidal sandflat became cold-adapted in late autumn. The nature of the adaptation, corresponding with Prosser's pattern IIIA, consists of a clockwise rotation of the respiratory rate-t temperature line and a rarely found intersection with the warm-adapted ratetemperature line within the normal range of habitat temperature. The incomplete temperature-compensation in metabolism puts the species in type 3 of Precht's classification. The seasonal change in the temperature-coefficient of respiration is believed to be induced in autumn andwinter by the characteristic temperature-regime of the tideflat, and in late spring and summer, as the result of the population's growth cycle. This study raises the need for thoroughness in measuring seasonal respiration as a function of size and temperature when investigating the energy flow of populations suspected of seasonal temperature-compensation. A plea is made for physiologists to present their data on respiration in a form more useful to ecologists working on the problems of energetics of a community.