ZooNooz Article - DECEMBER 2008

Rats in the ranks

Story by David Blisset Photographs Mel Hall,
Hans and Judy Best, Courtesy of Australian Museum

Black Rat

There would be little argument that Taronga Zoo is a stunningly beautiful place. Not only are the views among the best in Sydney, but the zoo grounds are surrounded by hectares of precious native bushland. In recent times, there has been some great work, both by zoo staff and the community, regenerating these areas, and much of the native vegetation has been returned to pre-colonial conditions.

However, when you look more closely, the environment around Taronga is not as healthy as it might seem. Many animal species once native to the region are no longer in residence. Ecologically, there is still much to be done. Now a unique study is looking at how Taronga's bushy backyard can truly be brought back to life.

Gráinne

Dr Gráinne Cleary is a terrestrial ecologist at Taronga Zoo who is carrying out a study with Professor Chris Dickman (USyd) and Dr Peter Banks (UNSW) that will combine animal reintroduction and habitat restoration. They aim to test if a species once common in the Mosman area can be reintroduced as a long-term biological control agent. And this animal's ability to keep out introduced pests just might help increase the biodiversity of the area's ecosystem. So, which species has been selected for this pioneering work? Would you believe ... a humble native rat!

Like much of urban Sydney, the zoo grounds and the surrounding bush are home to established populations of feral Black Rats - an animal with which most of us are familiar. When most people think of rats, they think of dirty animals that invade our homes and carry disease. It's the European Black Rat which earned the family this bad reputation. Scientists believe that these rats came to Australia on the same ships that brought the first Europeans. They've been with us ever since and are now among the most successful feral animals in the country. The rats' success, though, has come at a cost. Not only do Black Rats transmit disease, affecting both humans and other animals, they also damage the bushland ecosystem by preying on other animals and destroying native plants. Millions of dollars are spent every year trying to eradicate these pests, but in spite of the occasional success, the Black Rat remains as common as ever. Our researchers believe they have found an ally in the fight against these invaders.

Bush Rat

The native Bush Rat looks similar to its European relative, but there are a couple of physical differences: Black Rats have a tail longer than the body, while Bush Rats have a shorter tail and their ears are rounded.

Native rodents like the Bush Rat are part of the natural ecology of the Sydney region. But there is another quality that makes these little locals so important to Gráinne, Peter and Chris's work. Recent research carried out by Peter and Chris has found that established populations of Bush Rats will drive feral rats away! Under their guidance, Gráinne hopes to expand on this research and reintroduce Bush Rats back into the area around the zoo. Even more exciting is the possibility that Bush Rats will not only keep out feral rats, but also encourage other native fauna and flora to return. Native species, which suffer predation from Black Rats, could become re-established and successfully multiply. Further down the line, Gráinne believes we will see the return of other native animals, such as the antechinus and bandicoot, through further reintroduction into the area.

The challenge is how to re-establish such a colony of Bush Rats in the bush around Taronga. This is where Zoo Friends come in.

Using funds raised by Zoo Friends Volunteers, an enclosure is being built and Gráinne, Peter and Chris are conducting a pilot study which they hope will secure a government research grant. The aim of this study is to show that Bush Rats and Black Rats won't stay in the same area. Once the Bush Rat colony is established, Black Rats will be introduced and the scientists will see if, as they believe will be the case, the ferals are driven out of the natives' territory.

The implications of the study are significant. The goal is for the local bushland reserves to be returned to their pre-colonial ecology. If successful, the same technique could then be applied to other urban bushland areas. Even the zoo itself could benefit. If the number of Black Rats in neighbouring bush can be significantly reduced, the population within the zoo grounds may also decrease.

Though this study is only in its early stages, the possibilities are very exciting. It is work which the three scientists are passionate about and which provides an opportunity to right some past ecological wrongs. Gráinne, Chris and Peter are extremely grateful to the zoo's volunteers. By taking people on guided tours through the zoo, the volunteers have raised over $10,000 to donate towards this project.

Not only has it made this pilot study possible, but it has also opened the door for ground-breaking research into the regeneration of the Sydney bushland ecosystem.

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