Australia’s new rabbit database
AUSTRALIAN SCIENTISTS have released an opensource database in the battle against the country’s most invasive species – the European rabbit (Oryctolagus cuniculus).
Such high-tech tools have been widely used in oceanography and taxonomy, but with advances in computing, ecologists also are generating and sharing immense volumes of data. Welcome to the world of “big ecology”.
The Australian National Rabbit Database is, in fact, one of the largest datasets in the world on an invasive species. Created by a team of researchers from around the country led by Emilie Roy-Dufresne from the University of Adelaide, it brings together more than 50 years of survey data and will allow nationwide studies of rabbit ecology for the first time.
It’s the latest weapon in what has been a long and involved battle with the bunny.
RISE OF THE RABBIT
All of the world’s domestic rabbit breeds can trace their lineage back to the European rabbit.
Ironically, while they are formidable pests in many of the countries into which they have been introduced – Australia, New Zealand, the US, England and Russia among them – they are in decline in their native habitat of southern France and northern Africa, to the extent that they are listed as Near Threatened by the International Union for Conservation of Nature.
The rabbit’s story in Australia began with the First Fleet: several domestic rabbits were on board as food for the crew and convicts. Numerous subsequent introductions failed to establish wild populations, however.
In 1859, Thomas Austin, a wealthy Victorian landholder, released 13 rabbits on his estate in Barwon Park, near Geelong. He had the wild rabbits collected and sent to him by a relative in England to establish a population for hunting. Within six years, he had more than 14,000. The conditions for these first rabbits were ideal, with abundant native plant food, marsupial burrows to shelter in, and an absence of predators.
These conditions, combined with their famed ability to “breed like rabbits”, meant that just 70 years after the Geelong release, rabbits occupied two-thirds of the continent – the fastest rate of colonisation by any mammal anywhere in the world.
In the following years, a series of rabbit plagues ravaged the country. In desperation, farmers and government teams shot millions of them, bulldozed their burrows, and erected hundreds of thousands of kilometres of rabbit-proof fences. Despite this, many farms were simply abandoned.
By 1950 it was estimated there were over 600 million rabbits successfully competing with domestic animals and wildlife for food and shelter.
THE ARMS RACE
It was also in 1950 that the CSIR (later the CSIRO) decided to try to do something to stem the tide, successfully releasing the Myxoma virus, which causes myxomatosis. It was the first successful biological control of a mammal anywhere in the world, with an initial mortality rate of 99% in some areas. The rabbit population fell to very low levels.
By the late 1950s, host-pathogen co-evolution led to a less severe form of the disease, and rabbit numbers increased again, although not to pre-1950 levels.
Things were relatively quiet until 1991, when a new rabbit disease – a calicivirus called Rabbit Haemorrhagic Disease Virus (RHDV) – was brought to Australia for trials.
Four years later, “calici virus” as it was known, was accidentally released from a laboratory. The rabbit population initially was hit hard but, as with Myxoma, they developed resistance over time, meaning new strains have to be developed and released to keep pace with their resistance.
Nonetheless, it is estimated that the calici virus has saved Australia’s livestock industry $350 million a year since its release, and thanks to such biological controls we no longer have to contend with rabbit plagues.
But constant active management is still required, because rabbits remain Australia’s most costly vertebrate pest when their combined impact on agricultural and environmental assets is taken into account.
Bunnies are a disaster for biodiversity; they suppress the regeneration of native vegetation, compete with native animals for food and habitat, and support inflated populations of two major invasive predators – foxes and cats.
THE NATIONAL DATABASE
Governments, community groups and landholders have invested heavily in rabbit control, and the achievements of the scientific community have been significant. However, the systematic analysis of the ecological processes driving the rise and fall of rabbit populations on a national level was not possible until the release of the new, standardised database.
To compile it, Roy-Dufresne and her team collated information from more than 120 individual studies. The data included rabbit occurrence (689,265 records) and abundance (51,241 records).
Being such a tight-knit community, rabbit researchers from around Australia soon heard about the project and were eager to contribute.
“The real surprise for us was how many datasets we were able to collate. We knew that there were many studies that had been submitted in Australia in the last 50 years but being able to obtain and use the raw data of most of these was particularly surprising”, says Roy-Dufresne. A standardised dataset means that you have consistent information, allowing scientists to compare apples with apples and oranges with oranges.
“When developing more complex models, if the data is not standardised in terms of effort and information provided, the analyses get complicated, uncertainties arise, and errors can easily be made. It is important to have consistent information across all the studies”.
Each study was analysed, after first being transcribed from paper or downloaded from old formats such as floppy disc. Care was taken to remove any possible inconsistencies that result from multiple monitoring and reporting methods used for data collection – including scientific reports, landholder logs and citizen science data.
“We were really trying to find a balance between the minimum information we wished to collate but also had to try to avoid having big gaps,” Roy-Dufresne says.
The survey data was combined with high resolution weather climate and environmental information, as well as assessment of the data quality. The data will allow researchers to identify the drivers of rabbit population dynamics, teasing out patterns in the rabbits’ life history traits – most importantly, what determines population growth.
Roy-Dufresne says that as rabbits are an invasive species in other parts of the world, the dataset has potential beyond Australia and may be used for general analysis and testing on theories of invasive species ecology; for example, how climate can influence the reproductive biology of an invasive species.
Closer to home, she is using the database for her PhD, part of which demonstrates the important role that citizen science data can play in such a large country as Australia.
She uses the suite of environmental information to test models of the limits of rabbit distribution in Australia and has found that in arid areas, close access to permanent water and reduced clay soil composition are the major factors influencing the probability of occurrence of rabbits.
The database is freely available to researchers via a data paper published on the open-source journal Ecology, which is produced by the Ecological Society of America. Roy-Dufresne and her team at the University of Adelaide also provide a step-by-step tutorial on how to extract the information.
TANYA LOOS is an ecologist and science writer based in regional Victoria, Australia.