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The management of overabundant marsupial populations in Australia presents wildlife managers with numerous challenges. The prevailing socio-political climate is such that lethal control techniques are often deemed unacceptable for these populations, particularly in the case of Koalas Phascolarctos cinereus. Fertility control has been heralded as a future panacea for these problems, but after a decade of investigations, where are we? Large sterilisation programs have been the cornerstone of many koala management programs in Southern Australia to date, but evaluation of these programs has been limited. Advances have been made in the development of protocols for the treatment of individual animals with progestin and gonadotrophin-releasing hormone (GnRH) agonist contraceptive implants or via surgical sterilisation, but their large-scale effectiveness has not yet been clearly demonstrated. This paper reviews the literature on overabundant marsupial populations, with specific reference to management issues related to overabundant koala and macropod populations. The emerging fertility control technologies, in the form of long-acting contraceptive implants, are discussed along with details of ongoing trials designed to evaluate their effectiveness. This information is used to determine recommendations for developing and implementing management plans for overabundant marsupial populations.

Adderton Herbert, C. 2004. Long-acting contraceptives: a new tool to manage overabundant kangaroo populations in nature reserves and urban areas. Australian Mammalogy, 26: 67-74.
ANZECC 1998 National Koala Conservation Strategy, Environment Australia, Canberra.
Bomford, M. 1990 A role for fertility control in wildlife management? Bureau Rural Resources Bulletin No. 7, Department of Primary Industries, Canberra.
Coulson, G. 1998. Management of overabundant macropods - are there conservation benefits? Pp. 37-48 in: Managing Marsupial Abundance for Conservation Benefits, edited by A. Austin. Cooperative Research Centre for the Conservation and Management of Marsupials, Sydney, Australia.
DSE 2004 Victoria's Koala Management Strategy, Department of Sustainability and Environment.
Duka, T. and Masters, P. 2005. Confronting a tough issue: Fertility control and translocation for over-abundant koalas on Kangaroo Island, South Australia. Ecological Management and Restoration, 6: 172-181.
Eldridge, M.D., Kinnear, J.E., Zenger, K.R., McKenzie, L.S. and Spencer, P.B. 2004. Genetic diversity in remnant mainland and “pristine” island populations of three endemic Australian macropodids (Marsupialia): Macropus eugenii, Lagorchestes hirsutus and Petrogale lateralis. Conservation Genetics, 5: 325-338.
Fraser, H.M. 1993. GnRH analogues for contraception. British Medical Bulletin, 49: 62-72.
Gordon, G. and Hrdina, F. 2005. Koala and possum populations in Queensland during the harvest period, 1906-1936. Australian Zoologist, 33: 69-99.
Herbert, C.A. 2002 Contraception of marsupials using slow release implants containing the GnRH agonist deslorelin. Ph.D. Thesis, Macquarie University, Sydney.
Herbert, C.A., Trigg, T.E. and Cooper, D.W. 2004. Effect of deslorelin implants on follicular development, parturition and post-partum oestrus in the tammar wallaby ( Macropus eugenii). Reproduction, 127: 265-273.
Herbert, C.A., Trigg, T.E. and Cooper, D.W. 2006. Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin. 1. Effects on reproduction. Wildlife Research, 33(1): 41-46.
Herbert, C.A., Trigg, T.E., Renfree, M.B., Shaw, G., Eckery, D.C. and Cooper, D.W. 2005. Long-term effects of deslorelin implants on reproductive success and plasma progesterone and LH concentrations in the female tammar wallaby. Reproduction, 129: 361-9.
Hrdina, F. and Gordon, G. 2004. The koala and possum trade in Queensland, 1906-1936. Australian Zoologist, 32: 543-585.
Hundloe, T. and Hamilton, C. 1997 Koalas and Tourism: an economic evaluation, The Australian Institute, Canberra.
IUCN 2004. IUCN Red List of Threatened Species, www.iucnredlist.org. Downloaded on 23 January 2006.
Jurskis, V. and Turner, J. 2002. Eucalypt dieback in eastern Australia: a simple model. Australian Forestry, 65: 81-92.
Kinnear, J.E., Onus, M.L. and Sumner, N.R. 1998. Fox control and rock wallaby population dynamics. II, an update. Wildlife Research, 25: 81-88.
Masters, P., Duka, T., Berris, S. and Moss, G. 2004. Koalas on Kangaroo Island: from introduction to pest status in less than a century. Wildlife Research, 31: 267-272.
Mawson, P.R. 2004. Translocations and fauna reconstruction sites: Western Shield review - February 2003. Conservation Science W. Aust., 5: 108-121.
Maxwell, S., Burbidge, A.A. and Morris, K. 1996 Action Plan for Australian Marsupials and Monotremes, IUCN/SSC Australasian Marsupial and Monotreme Specialist Group. Endangered Species Program, Environment Australia, Canberra, ACT.
Melzer, A., Carrick, F., Menkhorst, P., Lunney, D. and St John, B. 2000. Overview, critical assessment, and conservation implications of koala distribution and abundance. Conservation Biology, 14: 619-628.
Menkhorst, P., Middleton, D. and Walters, B. 1998. Managing over-abundant koalas ( Phascolarctos cinereus) in Victoria: A brief history of some potential new directions. Pp. 19-29 in: Managing marsupial abundance for conservation benefits, edited by A. Austin. CRC for Conservation and Management of Marsupials, Sydney.
Middleton, D.R., Walters, B., Menkhorst, P. and Wright, P. 2003. Fertility control in the koala, Phascolarctos cinereus: the impact of slow-release implants containing levonorgestrel or oestradiol on the production of pouch young. Wildlife Research, 30: 207-212.
Mitchell, P.J., Bilney, R. and Martin, R.W. 1988. Population structure and reproductive status of koalas on Raymond Island, Victoria. Australian Wildlife Research, 15: 511-514.
Munson, L., Moresco, A. and Calle, P.P. 2005. Adverse effects of contraceptives. Pp 66-82 in Wildlife Contraception: Issues, methods, and applications, edited by C.S. Asa and I.J. Porton, Zoo and Aquarium Biology and Conservation Series. The John Hopkins University Press, Baltimore.
Nave, C.D., Coulson, G., Poiani, A., Shaw, G. and Renfree, M.B. 2002a. Fertility control in the eastern grey kangaroo using levonorgestrel implants. Journal of Wildlife Management, 66: 470-477.
Nave, C.D., Coulson, G., Short, R.V., Poiani, A., Shaw, G. and Renfree, M.B. 2002b. Long-term fertility control in the kangaroo and wallaby using levonorgestrel implants. Reproduction Supplement, 60: 71-80.
Nave, C.D., Shaw, G., Short, R.V. and Renfree, M.B. 2000. Contraceptive effects of levonorgestrel implants in a marsupial. Reproduction, Fertility and Development, 12: 81-86.
Orell, P. 2004. Fauna monitoring and staff training: Western Shield review - February 2003. Conservation Science W. Aust., 5: 51-95.
Parks Victoria 2003 Koala Relocation at Snake Island Continues, Parks Victoria Information Sheet. <http://www.parkweb.vic.gov.au/resources/mresources/conservation/kinfo_snake.pdf> (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Parks Victoria 2004 Koala Management Mt Eccles National Park, Parks Victoria Information Sheet. http://www.parkweb.vic.gov.au/resources/05_1211.pdf (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Parks Victoria 2005. Koala Management and Fertility Control Spring 2005, Parks Victoria web site http://www.parkweb.vic.gov.au/1process_content.cfm?section=89&page=25 (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Poiani, A., Coulson, G., Salamon, D., Holland, S. and Nave, C.D. 2002. Fertility control of Eastern grey kangaroos: Do levonorgestrel implants affect behavior? Journal of Wildlife Management, 66: 59-66.
Possingham, H., Jarman, P. and Kearns, A. 2004. Independent review of Western Shield. Conservation Science W. Aust., 5: 2-18.
Rottnest Island Authority 2003 Rottnest Island Management Plan 2003-2008, Rottnest Island Authority, Government of Western Australia.
Segal, S.J., Alvarez-Sanchez, F., Brache, V., Faundes, A., Vilja, P. and Tuohimaa, P. 1991. Norplant implants: the mechanism of contraceptive action. Fertility and Sterility, 56: 273-7.
Strahan, R. and Martin, R. 1982. The Koala: Little fact, much emotion. Pp. 147-155 in Species at Risk: Research in Australia, edited by R.H. Groves and W.D.L. Ride. Australian Academy of Science, Canberra, ACT.
Turner, M. 2004. KI Koalas: the cute and cuddly factor obstructing genuine conservation. Eco Voice, June: 2
TSSC 2006. Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (the Committee) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Accessed from http://www.deh.gov.au/biodiversity/threatened/species/pubs/koala.pdf (Unsuccessful threatened species list nomination) on 24 July 2006.
Tyndale-Biscoe, H. 1995. Vermin and viruses - Risks and benefits of viral-vectored immunosterilisation. Search, 26: 239-244.
Woodward, R., Herberstein, M. and Herbert, C.A. 2006. Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin. 2. Effects on behaviour. Wildlife Research, 33(1): 47-55.
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References

Adderton Herbert, C. 2004. Long-acting contraceptives: a new tool to manage overabundant kangaroo populations in nature reserves and urban areas. Australian Mammalogy, 26: 67-74.
ANZECC 1998 National Koala Conservation Strategy, Environment Australia, Canberra.
Bomford, M. 1990 A role for fertility control in wildlife management? Bureau Rural Resources Bulletin No. 7, Department of Primary Industries, Canberra.
Coulson, G. 1998. Management of overabundant macropods - are there conservation benefits? Pp. 37-48 in: Managing Marsupial Abundance for Conservation Benefits, edited by A. Austin. Cooperative Research Centre for the Conservation and Management of Marsupials, Sydney, Australia.
DSE 2004 Victoria's Koala Management Strategy, Department of Sustainability and Environment.
Duka, T. and Masters, P. 2005. Confronting a tough issue: Fertility control and translocation for over-abundant koalas on Kangaroo Island, South Australia. Ecological Management and Restoration, 6: 172-181.
Eldridge, M.D., Kinnear, J.E., Zenger, K.R., McKenzie, L.S. and Spencer, P.B. 2004. Genetic diversity in remnant mainland and “pristine” island populations of three endemic Australian macropodids (Marsupialia): Macropus eugenii, Lagorchestes hirsutus and Petrogale lateralis. Conservation Genetics, 5: 325-338.
Fraser, H.M. 1993. GnRH analogues for contraception. British Medical Bulletin, 49: 62-72.
Gordon, G. and Hrdina, F. 2005. Koala and possum populations in Queensland during the harvest period, 1906-1936. Australian Zoologist, 33: 69-99.
Herbert, C.A. 2002 Contraception of marsupials using slow release implants containing the GnRH agonist deslorelin. Ph.D. Thesis, Macquarie University, Sydney.
Herbert, C.A., Trigg, T.E. and Cooper, D.W. 2004. Effect of deslorelin implants on follicular development, parturition and post-partum oestrus in the tammar wallaby ( Macropus eugenii). Reproduction, 127: 265-273.
Herbert, C.A., Trigg, T.E. and Cooper, D.W. 2006. Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin. 1. Effects on reproduction. Wildlife Research, 33(1): 41-46.
Herbert, C.A., Trigg, T.E., Renfree, M.B., Shaw, G., Eckery, D.C. and Cooper, D.W. 2005. Long-term effects of deslorelin implants on reproductive success and plasma progesterone and LH concentrations in the female tammar wallaby. Reproduction, 129: 361-9.
Hrdina, F. and Gordon, G. 2004. The koala and possum trade in Queensland, 1906-1936. Australian Zoologist, 32: 543-585.
Hundloe, T. and Hamilton, C. 1997 Koalas and Tourism: an economic evaluation, The Australian Institute, Canberra.
IUCN 2004. IUCN Red List of Threatened Species, www.iucnredlist.org. Downloaded on 23 January 2006.
Jurskis, V. and Turner, J. 2002. Eucalypt dieback in eastern Australia: a simple model. Australian Forestry, 65: 81-92.
Kinnear, J.E., Onus, M.L. and Sumner, N.R. 1998. Fox control and rock wallaby population dynamics. II, an update. Wildlife Research, 25: 81-88.
Masters, P., Duka, T., Berris, S. and Moss, G. 2004. Koalas on Kangaroo Island: from introduction to pest status in less than a century. Wildlife Research, 31: 267-272.
Mawson, P.R. 2004. Translocations and fauna reconstruction sites: Western Shield review - February 2003. Conservation Science W. Aust., 5: 108-121.
Maxwell, S., Burbidge, A.A. and Morris, K. 1996 Action Plan for Australian Marsupials and Monotremes, IUCN/SSC Australasian Marsupial and Monotreme Specialist Group. Endangered Species Program, Environment Australia, Canberra, ACT.
Melzer, A., Carrick, F., Menkhorst, P., Lunney, D. and St John, B. 2000. Overview, critical assessment, and conservation implications of koala distribution and abundance. Conservation Biology, 14: 619-628.
Menkhorst, P., Middleton, D. and Walters, B. 1998. Managing over-abundant koalas ( Phascolarctos cinereus) in Victoria: A brief history of some potential new directions. Pp. 19-29 in: Managing marsupial abundance for conservation benefits, edited by A. Austin. CRC for Conservation and Management of Marsupials, Sydney.
Middleton, D.R., Walters, B., Menkhorst, P. and Wright, P. 2003. Fertility control in the koala, Phascolarctos cinereus: the impact of slow-release implants containing levonorgestrel or oestradiol on the production of pouch young. Wildlife Research, 30: 207-212.
Mitchell, P.J., Bilney, R. and Martin, R.W. 1988. Population structure and reproductive status of koalas on Raymond Island, Victoria. Australian Wildlife Research, 15: 511-514.
Munson, L., Moresco, A. and Calle, P.P. 2005. Adverse effects of contraceptives. Pp 66-82 in Wildlife Contraception: Issues, methods, and applications, edited by C.S. Asa and I.J. Porton, Zoo and Aquarium Biology and Conservation Series. The John Hopkins University Press, Baltimore.
Nave, C.D., Coulson, G., Poiani, A., Shaw, G. and Renfree, M.B. 2002a. Fertility control in the eastern grey kangaroo using levonorgestrel implants. Journal of Wildlife Management, 66: 470-477.
Nave, C.D., Coulson, G., Short, R.V., Poiani, A., Shaw, G. and Renfree, M.B. 2002b. Long-term fertility control in the kangaroo and wallaby using levonorgestrel implants. Reproduction Supplement, 60: 71-80.
Nave, C.D., Shaw, G., Short, R.V. and Renfree, M.B. 2000. Contraceptive effects of levonorgestrel implants in a marsupial. Reproduction, Fertility and Development, 12: 81-86.
Orell, P. 2004. Fauna monitoring and staff training: Western Shield review - February 2003. Conservation Science W. Aust., 5: 51-95.
Parks Victoria 2003 Koala Relocation at Snake Island Continues, Parks Victoria Information Sheet. <http://www.parkweb.vic.gov.au/resources/mresources/conservation/kinfo_snake.pdf> (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Parks Victoria 2004 Koala Management Mt Eccles National Park, Parks Victoria Information Sheet. http://www.parkweb.vic.gov.au/resources/05_1211.pdf (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Parks Victoria 2005. Koala Management and Fertility Control Spring 2005, Parks Victoria web site http://www.parkweb.vic.gov.au/1process_content.cfm?section=89&page=25 (Conservation/Koala Management and Fertility Control). Downloaded 23 January 2006.
Poiani, A., Coulson, G., Salamon, D., Holland, S. and Nave, C.D. 2002. Fertility control of Eastern grey kangaroos: Do levonorgestrel implants affect behavior? Journal of Wildlife Management, 66: 59-66.
Possingham, H., Jarman, P. and Kearns, A. 2004. Independent review of Western Shield. Conservation Science W. Aust., 5: 2-18.
Rottnest Island Authority 2003 Rottnest Island Management Plan 2003-2008, Rottnest Island Authority, Government of Western Australia.
Segal, S.J., Alvarez-Sanchez, F., Brache, V., Faundes, A., Vilja, P. and Tuohimaa, P. 1991. Norplant implants: the mechanism of contraceptive action. Fertility and Sterility, 56: 273-7.
Strahan, R. and Martin, R. 1982. The Koala: Little fact, much emotion. Pp. 147-155 in Species at Risk: Research in Australia, edited by R.H. Groves and W.D.L. Ride. Australian Academy of Science, Canberra, ACT.
Turner, M. 2004. KI Koalas: the cute and cuddly factor obstructing genuine conservation. Eco Voice, June: 2
TSSC 2006. Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (the Committee) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Accessed from http://www.deh.gov.au/biodiversity/threatened/species/pubs/koala.pdf (Unsuccessful threatened species list nomination) on 24 July 2006.
Tyndale-Biscoe, H. 1995. Vermin and viruses - Risks and benefits of viral-vectored immunosterilisation. Search, 26: 239-244.
Woodward, R., Herberstein, M. and Herbert, C.A. 2006. Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin. 2. Effects on behaviour. Wildlife Research, 33(1): 47-55.
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