Browsing by Autor "Peter R. Mawson"

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Estimating the age of western grey kangaroos (Macropus fuliginosus ocydromus)
(CSIRO Publishing, 2017) Chris Mayberry; Roberta Bencini; Peter R. Mawson; Shane K. Maloney
Scientific studies and population management may benefit from knowledge of the age structure of a target population. We evaluated traditional and newly developed methods of estimating the age of kangaroos with data from 336 western grey kangaroos (Macropus fuliginosus) culled from a wild population in south-western Australia. We compared their ages based on molar progression with data on head, leg, and foot length, a balanced sum of all three measures, dried eye-lens weight, and molar wear score, and derived formulae to estimate age from each variable. Molar wear score has a linear relationship to molar progression and therefore leads to similar estimations of age, but requires only one complete arcade of molars. Because the relationships between age and the lengths of head, foot and leg are curvilinear, these become less reliable indicators of age with increasing age but the accuracy can be improved by considering a combination of the lengths of head, foot, and leg. Estimation of age from dried lens weight is more accurate than estimation from morphometry. The use of morphometry to estimate the age of kangaroos older than two years is more reliable than previously thought and requisite data can be collected from live animals. Where lethal methods are needed to collect samples, a largely intact skull, a single arcade of molars, or the lens extracted from one eye can reliably be used to estimate age.
Integrating biobanking could produce significant cost benefits and minimise inbreeding for Australian amphibian captive breeding programs
(CSIRO Publishing, 2021) Lachlan G. Howell; Peter R. Mawson; Richard Frankham; John C. Rodger; Rose Upton; Ryan R. Witt; Natalie E. Calatayud; Simon Clulow; John Clulow
Captive breeding is an important tool for amphibian conservation despite high economic costs and deleterious genetic effects of sustained captivity and unavoidably small colony sizes. Integration of biobanking and assisted reproductive technologies (ARTs) could provide solutions to these challenges, but is rarely used due to lack of recognition of the potential benefits and clear policy direction. Here we present compelling genetic and economic arguments to integrate biobanking and ARTs into captive breeding programs using modelled captive populations of two Australian threatened frogs, namely the orange-bellied frog Geocrinia vitellina and the white bellied frog Geocrinia alba . Back-crossing with frozen founder spermatozoa using ARTs every generation minimises rates of inbreeding and provides considerable reductions in colony size and program costs compared with conventional captive management. Biobanking could allow captive institutions to meet or exceed longstanding genetic retention targets (90% of source population heterozygosity over 100 years). We provide a broad policy direction that could make biobanking technology a practical reality across Australia's ex situ management of amphibians in current and future holdings. Incorporating biobanking technology widely across this network could deliver outcomes by maintaining high levels of source population genetic diversity and freeing economic resources to develop ex situ programs for a greater number of threatened amphibian species.
Seasonal anoestrus in western grey kangaroos (Macropus fuliginosus ocydromus) in south-western Australia
(CSIRO Publishing, 2010) Chris Mayberry; Shane K. Maloney; Peter R. Mawson; Roberta Bencini
Public opposition to culling has generated interest in wildlife management through fertility control. Temporary, non-invasive methods of fertility control, such as by xenobiotics, can be best employed with an understanding of the target species’ breeding cycle. We used head length to calculate the conception date of 136 pouch-young of western grey kangaroos (Macropus fuliginosus ocydromus) from four sites around Perth, Western Australia, between May 2006 and October 2008: Thomsons Lake Nature Reserve (n = 80), Harry Waring Marsupial Reserve (n = 11), Melville Glades Golf Club (n = 29), and Marangaroo Golf Course (n = 16). In total, 78% of all pouch-young were conceived in the months of December–February, 11% in November, 6% in March, and less than 2% in each of October, April and May. We examined the ovaries of 134 females culled from Thomsons Lake Nature Reserve during the months of May–July 2006. Only seven ovaries had a follicle of at least 5 mm and none had an active corpus luteum. These data indicate that the breeding activity M. f. ocydromus is restricted almost exclusively to the months of November–February. A practical application of this finding is that temporary fertility controls applied early in October will provide a full year of birth control if they remain active for seven months.