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

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"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 ...

LayBy Shopping