The Times Australia
The Times World News

.
The Times Real Estate

.

We found pesticides in a third of Australian frogs we tested. Did these cause mass deaths?

  • Written by Jodi Rowley, Curator, Amphibian & Reptile Conservation Biology, Australian Museum, UNSW Sydney
We found pesticides in a third of Australian frogs we tested. Did these cause mass deaths?

In winter 2021, Australia’s frogs started dropping dead. People began posting images of dead frogs on social media. Unable to travel to investigate the deaths ourselves because of COVID lockdowns, we asked the public[1] to report to us any sick or dead frogs.

Within 24 hours we received 160 reports of sick and dying frogs, sometimes in their dozens, from across the country. That winter, we received more than 1,600 reports of more than 40 frog species.

A dying green tree frog next to a wall
The numbers of dead and dying frogs alarmed the public. Chris Exton, Author provided (no reuse)

We needed help to investigate these deaths. We asked people across New South Wales to collect any dead frogs and store them frozen until travel restrictions eased and we could pick them up for testing. Hundreds of people stepped up to assist.

What could be causing these deaths? Aside from the obvious suspect, disease, many people wondered about pesticides and other chemicals. One email we received pondered:

Maybe a lot of these Green Frogs that are turning up dead have in fact died from chemicals.

Another asked:

Is there any relationship between chemicals being used to control the current mice plague in Eastern Australia and effects on frogs?

In our newly published research[2], we detected pesticides in more than one in three frogs we tested. We found a rodenticide in one in six frogs.

Pesticides have been shown to be a major cause of worldwide declines in amphibians, including frogs and toads. In the case of the mass deaths in Australia, we don’t believe pesticides were the main cause, for reasons we’ll explain.

Read more: Dead, shrivelled frogs are unexpectedly turning up across eastern Australia. We need your help to find out why[3]

What did the research find?

As soon as travel restrictions eased, we drove around the state with a portable freezer collecting these dead frogs. We began investigating the role of disease, pesticides and other potential factors in this awful event.

We tested liver samples of 77 frogs of six species from across New South Wales for more than 600 different pesticides. We detected at least one pesticide in 36% of these frogs.

Our most significant discovery was the rodenticide Brodifacoum[4] in 17% of the frogs. This is the first report of rodenticides – chemicals meant to poison only rodents – in wild frogs.

We found it in four species: the eastern banjo frog (Limnodynastes dumerilii), green tree frog (Litoria caerulea), Peron’s tree frog (Litoria peronii) and the introduced cane toad (Rhinella marina).

A head-one view of an eastern banjo frog The eastern banjo frog (Limnodynastes dumerilii) was one of the species in which rodenticide was detected. Jodi Rowley, CC BY-NC-ND[5]

How did these poisons get into frogs?

How were frogs exposed to a rodenticide? And what harm is it likely to be causing? Unfortunately, we don’t know.

Until now, frogs weren’t known to be exposed to rodenticides. They now join the list of non-rodent animals shown to be exposed – invertebrates, birds[6], small mammals, reptiles and even fish.

It’s possible large frogs are eating rodents that have eaten a bait. Or frogs could be eating contaminated invertebrates or coming into contact with bait stations or contaminated water. Whatever the impact, and the route, our findings show we may need to think about how we use rodenticides.

A cane toad on leaf litter Large species like the cane toad (Rhinella marina) could eat rodents that have ingested baits. Jodi Rowley, CC BY-NC-ND[7]

Two pesticides detected in frogs were organochlorine compounds[8] dieldrin and heptachlor. A third, DDE, is a breakdown product of the notorious organochlorine, DDT[9].

These pesticides have been banned in Australia for decades, so how did they get into the frogs? Unfortunately, these legacy pesticides are very stable chemicals and take a long time to break down. They usually bind to organic material such as soils and sediments and can wash into waterways after rain.

As a result, these pesticides can accumulate in plants and animals. It’s why they have been banned around the world.

We also found the herbicide MCPA and fipronil sulfone, a breakdown product of the insecticide fipronil[10]. Fipronil is registered for use in agriculture, home veterinary products (for flea and tick control) and around the house for control of termites, cockroaches and ants. MCPA has both agricultural and household uses, including lawn treatments.

A graphic showing the types of pesticides detected in frogs and the percentages of tested frogs in which each chemical was detected
Pesticides detected in frogs and the percentages of tested frogs in which each chemical was detected. Jodi Rowley, CC BY-NC-ND[11]

What are the impacts on frogs?

There’s very little research on the impact of pesticides on frogs in general, particularly adult frogs and particularly in Australia.

However, from research overseas, we know pesticides could kill frogs[12], or cause sub-lethal impacts[13] such as suppressing the immune system or malformations, or changes in growth, development and reproduction. Pesticides are considered a threat to almost 700 amphibian species[14].

Unfortunately for them, frogs do have characteristics that make them highly likely to come into contact with pesticides.

Most frog species spend time in both freshwater systems, such as wetlands, ponds and streams (particularly at the egg and tadpole stage), and on the land. This increases their opportunities for exposure.

Second, frogs have highly permeable skin, which is likely a major route for pesticides to enter the body. Frogs obtain water through their skin – you’ll never see a frog drinking – and also breathe through their skin[15].

A tree frog sits on a branch Peron’s tree frog (Litoria peronii) is one of the common species in which pesticides were detected. Jodi Rowley, CC BY-NC-ND[16]

Our findings are a reminder that frogs are sensitive indicators of environmental health. Their recognition as bioindicators, or “canaries in the coalmine”, is warranted.

Frogs and other amphibians are the most threatened group of vertebrates on the planet. More research is needed to determine just how our use of pesticides is contributing to ongoing population declines in frogs.

So, were pesticides the major driver of the mass frog deaths in 2021? We don’t believe so.

We didn’t detect pesticides in most frogs and the five pesticides detected were not consistently found across all samples. It’s certainly possible they contributed to this event, along with other factors such as disease and climatic conditions, but it’s not the smoking gun.

Our investigation, with the help of the public, is ongoing.

Chris Doyle, from the NSW Department of Climate Change, Energy, the Environment and Water, contributed to this article.

References

  1. ^ asked the public (theconversation.com)
  2. ^ newly published research (www.sciencedirect.com)
  3. ^ Dead, shrivelled frogs are unexpectedly turning up across eastern Australia. We need your help to find out why (theconversation.com)
  4. ^ Brodifacoum (www.sciencedirect.com)
  5. ^ CC BY-NC-ND (creativecommons.org)
  6. ^ birds (theconversation.com)
  7. ^ CC BY-NC-ND (creativecommons.org)
  8. ^ organochlorine compounds (www.dcceew.gov.au)
  9. ^ DDT (www.uwa.edu.au)
  10. ^ fipronil (npic.orst.edu)
  11. ^ CC BY-NC-ND (creativecommons.org)
  12. ^ could kill frogs (setac.onlinelibrary.wiley.com)
  13. ^ or cause sub-lethal impacts (www.sciencedirect.com)
  14. ^ almost 700 amphibian species (www.iucnredlist.org)
  15. ^ breathe through their skin (www.brown.edu)
  16. ^ CC BY-NC-ND (creativecommons.org)

Read more https://theconversation.com/we-found-pesticides-in-a-third-of-australian-frogs-we-tested-did-these-cause-mass-deaths-228194

The Times Features

Understanding the Dangers of Ignoring a Gas Leak

Gas leaks are silent threats lurking within both homes and workplaces. A gas leak occurs when natural gas or any other gaseous substance escapes from a pipeline or containment. T...

Can You Sell Your House Privately in Queensland? Here’s How

Selling a house privately in Queensland is entirely possible and can be a cost-effective alternative to using a real estate agent. While agents provide valuable expertise, their co...

Itinerary to Maximize Your Two-Week Adventure in Vietnam and Cambodia

Two weeks may not seem like much, but it’s just the right time for travelers to explore the best of Vietnam and Cambodia. From the bustling streets of Hanoi to the magnificent te...

How to Protect Your Garden Trees from Wind Damage in Australia

In Australia's expansive landscape, garden trees hold noteworthy significance. They not only enhance the aesthetic appeal of our homes but also play an integral role in the local...

Brisbane Homeowners Warned: Non-Compliant Flexible Hoses Pose High Flood Risk

As a homeowner in Brisbane, when you think of the potential for flood damage to your home, you probably think of weather events. But you should know that there may be a tickin...

Argan Oil-Infused Moroccanoil Shampoo: Nourish and Revitalize Your Hair

Are you ready to transform your hair from dull and lifeless to vibrant and full of life? Look no further than the luxurious embrace of Argan Oil-Infused Moroccanoil Shampoo! In a...

Times Magazine

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

How AI-Driven SEO Enhancements Can Improve Headless CMS Content Visibility

Whereas SEO (search engine optimization) is critical in the digital landscape for making connections to content, much of it is still done manually keyword research, metatags, final tweaks at publication requiring a human element that takes extensiv...

Crypto Expert John Fenga Reveals How Blockchain is Revolutionising Charity

One of the most persistent challenges in the charity sector is trust. Donors often wonder whether their contributions are being used effectively or if overhead costs consume a significant portion. Traditional fundraising methods can be opaque, with...

Navigating Parenting Arrangements in Australia: A Legal Guide for Parents

Understanding Parenting Arrangements in Australia. Child custody disputes are often one of the most emotionally charged aspects of separation or divorce. Parents naturally want what is best for their children, but the legal process of determining ...

Blocky Adventures: A Minecraft Movie Celebration for Your Wrist

The Minecraft movie is almost here—and it’s time to get excited! With the film set to hit theaters on April 4, 2025, fans have a brand-new reason to celebrate. To honor the upcoming blockbuster, watchfaces.co has released a special Minecraft-inspir...

The Ultimate Guide to Apple Watch Faces & Trending Wallpapers

In today’s digital world, personalization is everything. Your smartwatch isn’t just a timepiece—it’s an extension of your style. Thanks to innovative third-party developers, customizing your Apple Watch has reached new heights with stunning designs...

LayBy Shopping