Research Projects | Research Students
Projects
1. Develop remote delivery methods for administration of long-acting contraceptives to marsupials in the field.
Several delivery methods are potentially available; remote delivery using dart guns and large-scale capture of the animals, probably using anaesthetic-laced food for kangaroos and wallabies (Arnold et al. 1986), followed by implanting with the contraceptive. Another possibility for koalas is to use a pole syringe to implant a koala while still in its tree. Suprelorin implants have an advantage when it comes to developing remote delivery as they are significantly smaller than the progestin implants and are readily available as a veterinary product. The use of a dart gun system to administer deslorelin (Suprelorin) implants has already been successfully tested for large African mammals in zoos (Walzer et al. 2004). The challenge now lies in transferring this technology to smaller mammals, such as koalas and kangaroos.
The question whether intramuscular delivery of Suprelorin implants has the same effect as subcutaneous delivery will be tested in captive tammar wallabies. A suitable projectile will be developed and its ballistics tested. The means of delivery may involve dart guns (koalas and kangaroos); pole syringes (koalas) or manual treatment following capture through anaesthetic laced food (kangaroos).
Selected references: tba
2. Evaluate Suprelorin contraceptive implants in large-scale field trials on koalas and macropods.
Two classes of contraceptive agent have shown potential: gonadotrophin releasing hormone (GnRH) superagonists and steroid hormones. The GnRH-based Suprelorin is a commercially available veterinary product while the steroidal progestins Norplant ® and Implanon ® are used for human contraception. Their contraceptive efficiency, possible side effects and cost-effectiveness now need to be investigated further. Finding clear answers to these questions will be a major part of the proposed project.
Field trials will be conducted to evaluate the efficacy of administering fertility control on a large scale. We will also evaluate the possibility that higher dosages of Suprelorin will give longer periods of contraception. These experiments will be habitat and species-specific and will test the contraceptive success rate and duration in a large sample size. The efficiency of remote delivery and delivery following animal capture will be evaluated. The aim is to determine the cost per breeding season to enable comparisons between different fertility control methods. The effects on total population size, social structure, environmental variables (e.g. level of habitat damage) and animal health and behaviour will be assessed as part of a long term study.
3. Investigate the effects of fertility control strategies on the retention of genetic variation.
Fertility control has effects upon genetic variation. Permanent sterilisation leads to a loss of genetic variability within a population. This issue is especially important for some koala populations which have been through severe population bottlenecks, for overabundant island populations, and for some Western Australian species whose numbers are rapidly increasing as a result of the success of the Western Shield program of fox baiting. A second genetic issue concerns animals which fail to be contracepted or which are contracepted for shorter periods than others. The former are expected to be a small minority, but they will make a disproportionate genetic contribution to the next generation. They may have a genetically influenced hormonal status which differs from the rest of the population. Alterations to behaviour, especially reproductive behaviour, are possible.
Accurate estimates of genetic variation will be determined using microsatellite markers for populations lacking basic genetic data (see Cooper references for methods). From these data, and published information on other populations, we will determine the most appropriate fertility control regime to maintain genetic variability. This will balance loss of genetic variation versus the requirement for population control. Population genetics principles imply that it is better to give as many individuals as possible the opportunity to contribute to the next generation at least once (e.g. it is better to let a random 80% of the population breed each season, rather than to irreversibly sterilize 80% of the population). This will be done in conjunction with examination of the populations for phenotypic evidence of inbreeding effects, and we will assess these against the data which exist on founder numbers for each population.
Selected references: tba
Research Students
Kris Carlyon
Department of Biological, Earth and Environmental Sciences,
University of New South Wales
Kris Carlyon investigates the efficacy of using deslorelin implants as a management tool to control the reproductive recruitment rate of large free-ranging koala ( Phascolarctos cinereus ) populations on South Australia 's Kangaroo Island . Concentrating on areas of high management concern, he is also examining koala browse pressure on local eucalypt food trees and vegetation recovery following koala management.
Kris Carlyon is supervised by Professor Des Cooper (UNSW), Dr Cathy Herbert (UNSW), Dr Kath Handasyde (UoM) and Dr Desley Whisson (DEH). He works in close collaboration with industry partner the Department for Environment and Heritage, South Australia.
Andrew Greenfield
Department of Zoology
The University of Melbourne, Victoria
Andrew Greenfield investigates the contraceptive effect of deslorelin implants in free-ranging koalas in a Chlamydia-infected population ( Raymond Island ) and a Chlamydia-free population ( French Island ). He also assists in the development of a remote delivery system for these implants in koalas to enable efficient delivery of contraceptives for future management programs targeting control of overabundant koala populations in
south-eastern Australia .
Andrew Greenfield is supervised by Professor Marilyn Renfree, Dr Kath Handasyde and Associate Professor Geoff Shaw, and works in close collaboration with the industry partners from the Department of Sustainability and Environment, Victoria , and Parks Victoria.
Emily Miller
Department of Biological, Earth and Environmental Sciences,
The University of New South Wales
(link to newspaper article soon to come)
The evolution of sexually selected traits is driven by contests over mating opportunities. In polygynous species, males often have specialised sexually selected traits such as larger body size, elaborate ornaments or weaponry. Generally the winners of male-male contests are thought to be of superior quality and that it would be in the interest of females' to mate with these males. The overall aim of Emily Miller's research project is to understand how particular traits contribute to variance in male reproductive success in marsupials.
This project will investigate the genetic mating system of the Eastern and Western Grey kangaroos in both captive and semi-free-ranging populations. It will involve assessing what/how morphological and genetic traits influence male reproductive success. This includes the collection of morphological data, paternity analysis and testing the effects of genetic compatibility and heterozygosity on mating preferences with the focus on the major histo-compatibility complex.
Nicole Willers
School of Animal Biology,
The University of Western Australia, Perth
Nicole Willers is supervised by Dr Roberta Bencini (UWA), Dr Mark Garkaklis (DEC), Dr Peter Mawson (DEC) and Dr Keith Morris (DEC).
Nicole Willers studies the fertility control of quokkas ( Setonix brachyurus ). The quokka, while overabundant on Rottnest, is listed as threatened species under State and Federal legislation. Being also an iconic animal, culling on Rottnest cannot be contemplated by the authorities. Nicole will study the effect of the deslorelin implants on a captive colony of quokkas. Her study of the captive animals will include implanting lactating females to verify that the implant does not affect the survival of the young or the composition of the milk. On Rottnest we are planning to implant females at West End as it is a peninsula and we expect minimum movement between West End and the rest of the island. We also want to implant females on the main settlement at Thompson Bay as these animals tend to scavenge around the cottages and the population is quite dense.
Nicole Willers is supervised by Dr Roberta Bencini (UWA), Dr Peter Mawson (CALM) and Dr Keith Morris (CALM).
Chris Mayberry
School of Animal Biology,
The University of Western Australia, Perth
Chris Mayberry is supervised by Dr Roberta Bencini (UWA), Dr Shane Maloney (UWA Physiology), Dr Peter Mawson (DEC) and Keith Morris (DEC).
Chris Mayberry studies fertility control of Western grey kangaroos ( Macropus fuliginosus ) both in a semi captive situation where animals can be easily captured, implanted and monitored, as well as some selected problem populations that inhabit some of the metropolitan golf courses.
Chris Mayberry is supervised by Dr Roberta Bencini (UWA), Dr Shane Maloney (UWA Physiology), Dr Peter Mawson (CALM) and Keith Morris (CALM).
Cheryl Hetherington
School of Animal Biology,
The University of Western Australia, Perth
Cheryl Hetherington is using the deslorelin implant to study its applicability to control a problem population of possums ( Trichosurus vulpecula ) at the Perth Zoological Gardens.
Cheryl Hetherington is supervised by Dr Roberta Bencini (UWA)
Content Last Modified: Thursday, 9th November 2006.
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October 2006
In the press:
Australian scientists
to try contraceptive
darts on koalas.
For more info, click here.