Biology Bytes Vol 1 No 3, May 1998
"Wildlife forensics"

New Zealand's pests 
are 
Australia's treasures

A South Australian wallaby subspecies, considered extinct for nearly a century, has been "rediscovered" in New Zealand by researchers from the Co-operative Research Centre (CRC) for Conservation and Management of Marsupials, at Macquarie University.

DNA sampling has established that an introduced colony of tammar wallabies living on Kawau Island, 55 kilometres north-east of Auckland, is almost certainly comprised of the descendants of a wallaby subspecies that vanished from mainland South Australia in the early 1900s.


"The Kawau Is. tammar wallaby might LOOK the same as the many in Australian wildlife parks and on Kangaroo Is., but wait until you see its DNA!"

Prior to the turn of the century, there were at least two morphologically-distinct subspecies of tammar wallaby living in South Australia. There ís only one left, living on Kangaroo Island and two other islands where the Kangaroo Island wallabies were introduced. Sampling by researchers at the CRC has established that there is only a 3% chance that the Kawau colony was founded from Kangaroo Island. This finding means that this New Zealand population is very precious because it represents genetic stock that no longer exists in Australia.

The Kawau Island wallabies (known there as damas) were shipped to New Zealand in the late 1800s by New Zealand's then-governor, Sir George Grey, who took the post immediately after his governorship of South Australia. Grey bought the 2000 hectare island in 1862 and stocked it with reminders of his postings in Australia and South Africa, including zebra, antelope and kookaburras, as well as tammar, parma, and brush-tailed rock-wallabies. The wallabies flourished to such an extent that in the 1950s-60s they overran attempts to establish farms on the island.

There now may be more than 2000 tammar wallabies on Kawau Island. They are progressively destroying the native vegetation through over-grazing (they climb to reach foliage) and digging nests among tree roots. Island residents occasionally cull the wallabies and the marsupials are regularly exported to zoos and fauna parks in 15 countries. Despite this, the subspecies has been believed to have been extinct for nearly a century.

"The microsatellite DNA profiles of Kawau Is. wallabies are sufficiently different from surviving Australian populations, that they must be descended from one which is now extinct"

The wallaby's resurrection from extinction came about when DNA techniques applied to skin samples were used to unravel the population's genetic history. Comparison of the DNA of animals from Kawau and Kangaroo islands effectively eliminated Kangaroo Island as the source of the Kawau population. This suggested that the Kawau wallabies were introduced from mainland South Australia or one of the small islands that also once harboured tammars. In either case, they are unique. National Parks and Wildlife South Australia is excited at the prospect that the tammar wallabies on Kawau Island may be the descendants of the now-extinct mainland subspecies. They may have discussions with the New Zealand Government regarding the wallabies future in New Zealand with a view to reintroducing them back to South Australia. Such a process would be complex, requiring the establishment of a captive breeding colony, and selection of large areas of habitat free of introduced predators. A future project may aim to more accurately pin-point the origins of the Kawau Island tammar colony. Around the turn of the century, tammars were so numerous on the South Australian mainland that landholders held regular culling drives. By 1925, the first handbook on the State's mammals was lamenting the mainland subspecies' probable extinction. The population's demise was unexpectedly swift and zoologists failed to make comprehensive collections. Today the "extinct" population is represented in Australia by just two specimens held in the Museum of South Australia, one from Hartley, south-east of Adelaide and the other from the Eyre Peninsula.

Similarity of the DNA from the museum specimens to that of the Kawau animals would establish their ancestry, but a discrepancy would raise more questions, the answers to which might lie locked away in 19th Century collections of overseas museums.

The two other wallaby species residing on Kawau Island, the parma and the brush-tailed rock wallaby, are also potentially valuable conservation resources, as their Australian counterparts have suffered severe population declines in recent years. Similar analyses to those applied to the tammar wallaby may also find that the ancestors of the Kawau parma and brush-tailed rock-wallabies have also vanished from Australia.

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Staff working on this research