The Kritic

Gould’s goanna

Gould’s goanna is commonly eaten in Indigenous communities, but can contain high levels of rat poison.Source: Robert A. Davis, Author

Introduced rats and mice have probably troubled most of us at some time in our lives. These pesky invasive rodents are found around the world. We usually target them with toxic baits to stop them spreading disease and causing environmental or commercial damage.

In some instances rat baits are useful. They can protect crops, reduce the spread of disease, keep the contents of your pantry from disappearing, or even protect endangered wildlife on islands where rats have invaded.

These baits are freely available to homeowners and are used liberally by pest controllers. However, they have potentially deadly consequences for native predatory animals that eat poisoned rats and mice.

Our new research shows that this secondary poisoning may be worsened in Australia by reptiles, which are extremely effective at spreading these poisons up the food chain – a process that may even have consequences for human health.

While little is known about how well reptiles tolerate rodent baits, several studies have suggested that at least some reptiles are extremely resistant. In a toxicity study using one lizard species, all of the test subjects survived an incredibly high dose of the strongest poison on the market – over 4,000 times the poison per body weight needed to kill most rats.

This is probably good news for the lizards, but eating poison-supercharged reptiles may be a serious concern for their predators – and for us.

Humans eat lizards too

During a rat eradication program in the Montebello Islands, one goanna species was seen eating poisoned rats – without apparent ill effect – to the point that the green dye used in the bait was visible in their droppings. Unfortunately, this species of goanna is an important traditional food in Indigenous communities throughout Australia. To make matters worse, these poisons usually build up in commonly eaten parts of the goannas, like fat and liver tissue.

The risks associated with sublethal human exposure to rodent baits are not well known. However, recent studies in some wildlife species show that even mild chronic exposure to the longer-lasting poisons can lead to dangerous changes in the immune system.

With so many unknowns in a potentially dangerous situation, more research is urgently needed. We need to know how often and how severely the reptiles that humans eat are exposed to poison. Otherwise, some Indigenous people may have to choose between losing traditional hunting practices and risking exposure to rat poison.

Poison in the food web

In our research, we reviewed all published examples of wildlife deaths from exposure to rat bait. We found that rat poison has killed members of at least 32 native wildlife species in Australia. There are probably many more; only a few studies have looked at this problem in Australia, compared with other parts of the world.

We found that a small species of owl called the Southern Boobook is exposed to rat poison frequently, and sometimes lethally, in developed areas of Western Australia. Scavengers and prolific predators of rodents are likely to be even worse off – and these predators include a variety of threatened or endangered species such as Masked Owls, Tasmanian Devils and various species of quolls.

Most deaths will occur far from the original bait, as the poison travels through other species in the food web to reach its final destination. Without a better understanding of how baits affect Australian predators, we are unlikely to appreciate the scale of this invisible threat.

At present, powerful rat poisons are available at most supermarkets and hardware stores. The Australian Pesticides and Veterinary Medicines Authority is now reviewing how these are regulated because of concerns about human health and impacts on wildlife populations.

Other countries like the United States and Canada have already restricted the stronger poisons to licensed pest controllers. They have banned outdoor use and require lockable bait boxes to keep children and pets away from baits.

These steps might not be enough to overcome Australia’s unique risks, but allowing the current situation to continue is guaranteed to result in more poisonings of wildlife – and possibly unseen and unstudied effects on humans too.

This article was originally published at The Conversation.
By Michael Lohr, PhD Student – Wildlife Ecology, Edith Cowan University and Robert Davis Senior Lecturer in Vertebrate Biology, Edith Cowan University
Read the original article.

Kangaroo Island Dunnart

Kangaroo Island Dunnart*Source: Jody Gates

MEDIA RELEASE

4 May 2018

Without monitoring, threatened species could slide toward extinction without it being noticed. Good monitoring helps us understand how species are faring, where and when to act and if management investments are working.

*Monitoring is helping conservation managers identify the last remaining areas with Kangaroo Island Dunnarts, which will enable them to better direct conservation investments. Photo: Jody Gates

Given the vital importance of monitoring in the fight against extinctions, the Threatened Species Recovery Hub of the Australian Government’s National Environmental Science Program has released a national assessment of Australia’s monitoring – by state and territory governments, not-for-profits, consultants, indigenous groups, the Commonwealth and the community.

Project leader Dr Sarah Legge said the results were poor for most groups, but monitoring for threatened birds was relatively better, thanks to a large and enthusiastic volunteer base, co-ordinated by organisations like Birdlife. In contrast, she said half of all threatened fish receive no monitoring and monitoring of threatened reptiles was little better.

“Overall, over a third of Australia’s threatened animals received no monitoring at all, and where monitoring does exist, it is often inadequate,” said Dr Legge from the Australian National University.
“This puts these species at risk. By the time we realise we have a problem it may be too late to act.”

“Many people do not appreciate how vital monitoring is for all aspects of managing threatened biodiversity.”

The monitoring activities for threatened species were assessed against a framework of nine key principles which was developed by Professor John Woinarski and colleagues.

“To be effective monitoring needs to sample across the whole area where a species occurs, and to happen often enough and for long enough to pick up changes,” said Prof Woinarski from Charles Darwin University.

“We have developed this framework to give monitoring the profile it merits and to improve the standard of monitoring for Australia’s threatened biodiversity.

“Without monitoring we have no idea if populations are going up or down, or what’s driving any changes. We also won’t know if the conservation actions we are investing in are working or need to be adapted.”

Threatened Species Recovery Hub

Threatened Species Recovery HubSource: Supplied

The framework and national assessment have been published in a new book, Monitoring Threatened Species and Ecological Communities (CSIRO Publishing). The book also gathers insights and case studies from 70 of the most experienced managers and scientists involved with threatened species monitoring in Australia.

In response to the national assessments Professor Brendan Wintle, the Director of the Threatened Species Recovery Hub has called for a national effort to improve the state of Australia’s threatened species monitoring.

“Good information is crucial in the fight against extinctions. Without good monitoring we are flying blind and could waste precious scarce resources,’ said Prof Wintle from the University of Melbourne.

“Many species occur across multiple states and territories, and the monitoring data that exists are currently scattered across many different agencies and research groups.

“Australia needs investment and co-ordination to manage, store, analyse and report on monitoring data.

“Monitoring should involve the public and the results should be available to the public. Much of conservation spending is taxpayer funded. People need to know what they are getting for that.”

The Threatened Species Recovery Hub is a partnership of ten Australian Universities and the Australian Wildlife Conservancy to undertake research to recover threatened species. It receives funding from the Australian Government’s National Environmental Science Program.

Media inquiries:
Jaana Dielenberg, TSR Hub Science Communication Manager, 0413 585 709 j.dielenberg@uq.edu.au