Behaviour, group dynamics, and health of free-ranging eastern grey kangaroos (Macropus giganteus)

Abstract

Eastern grey kangaroos (Macropus giganteus) are one of Australia's most iconic species. An increase in watering sites and urban development have dramatically influenced the species range and abundance. Current knowledge of group structure, dispersal and behaviour of eastern grey kangaroos is limited. Developing a better understanding of these topics is essential in creation of effective management strategies. The following thesis explores multiple aspects of behavioural ecology and health in free ranging eastern grey kangaroos. Motion detecting infra-red camera traps were used to assess activity patterns and social interactions, as well as the suitability of this tool for measuring behaviour in this species. Activity patterns were compared between a modified and natural site. The location of 23 road killed kangaroos was studied to evaluate what influences road mortality. DNA extracted from tissue and blood samples were used to conduct microsatellite analysis and investigate genetic structure of the population. Baseline haematology, blood chemistry, and acute phase protein parameters were examined for eight kangaroos including three adult males, three adult females and two sub-adult males to assess health. The aim of the research was to expand the existing knowledge of the behaviour, social organisation, population dynamics and health of eastern grey kangaroos to assist in developing more informed and effective management strategies for this species. Research was conducted at two sites in NSW, Yarramundi paddocks at the Hawkesbury campus of WSU, Richmond, NSW; an active farmland site fragmented by an urban environment consisting of 308 ha of pasture, grassland, marshes and open woodland, and the Emirates One and Only Wolgan Valley Resort, Newnes, NSW; a largely undeveloped area and conservation reserve at an eco-resort situated on 1619 ha of grasslands, woodland and riparian areas surrounded by the sandstone cliffs of World Heritage listed National Parks. Camera trap data was consistent with activity patterns of eastern grey kangaroos observed on foot in previous studies. The behaviour of kangaroos appeared to be influenced by the presence of cameras, however no kangaroos retreated from cameras and all appeared to become habituated to cameras after eight months. The findings suggest that camera traps are suitable for assessing the diurnal activity of kangaroos, however nocturnal activity appeared to be underrepresented. Observations of unusual fighting behaviour illustrates the potential for camera traps to enable capture of novel observations. Comparison of camera trap data showed that kangaroos at the modified site had a higher density, spent more time in larger groups, and had an earlier peak activity time than those at the natural site. More vigilance (standing still and scanning for threats) and less feeding were observed at the modified site. The higher population density at the modified site is likely to be a result of increased resources and restricted dispersal. The earlier peak activity time observed at the modified site may be in response to artificial lighting. Increased vigilance may be due human presence, and visual barriers in modified landscapes that reduce the line of sight. Reduced feeding time is probably a result of the higher nutritional content of pasture grasses at the modified site. Assessment of factors that influence kangaroo road mortality at the modified site demonstrated that more mortalities occurred during periods of low temperature and low rainfall, and during the waning gibbous phase of the lunar cycle. Periods of low temperature and low rainfall reduce forage quality, causing kangaroos to travel further to find high quality vegetation. High moon illumination provides increased visibility and allows for greater mobility of kangaroos. Significantly more road mortalities occurred a short distance from the end of a section of street lights. Gaps in roadside lighting are likely to reduce motorists' ability to visually detect animals on roads while their eyes adjust to different lighting levels. Investigation of the genetic structure within the population indicated one pair of kangaroos were full siblings, and a high proportion were identified as half siblings. Six positive parentage assignments were detected. The locus used for microsatellite analysis were polymorphic and highly informative for use in the study population. No genetic spatial autocorrelation was detected. Examination of health parameters of free-ranging eastern grey kangaroos found preliminary differences in both the haematological and blood chemistry values of kangaroos of different ages and genders. The kangaroo serumhad a strong antibacterial response to Klebsiella pneumoniae, and moderate responses to Escherichia coli and Staphylococcus aureus. Haptoglobin and serum amyloid A were present in kangaroo serum, but only haptoglobin was elevated in a kangaroo with necrotic wounds. Results confirm that camera traps are suitable for assessing the diurnal activity of eastern grey kangaroos and should be incorporated in into future studies to reduce observer effect and costs, thus enabling effective long term monitoring. The expanded knowledge of the factors found to increase kangaroo road mortality enable more effective road design planning and wildlife management strategies such as targeted wildlife crossing structures and warning signs. Understanding of the genetic structure and dispersal patterns occurring within these free-ranging populations, and their health, will assist in effective population monitoring, which is necessary for the successful management of kangaroo populations in increasingly developed landscapes. Overall, the information gained from this research is essential for developing effective management practices for high density kangaroo populations in developed areas, which is necessary as a result of the increasing development and habitat fragmentation across Australia.

Date of Award	2017
Original language	English