Cane toads teach other animals to avoid their poison

Cane toads hopped onto the Australian scene in the 1930s, promising to fix a beetle problem for sugarcane farmers. The catch? These toads have poison glands that make them deadly snacks for unsuspecting predators. Young cane toads, it turns out, can teach native animal species to avoid the fatal mistake of consuming them.

The problem with cane toads

If you’re a big predator in Australia, cane toads are bad news. Apex predators like goannas (large monitor lizards), crocodiles, and some snakes love a juicy toad snack.

The problem is that cane toads are walking poison sacs. If an animal tries to eat a full-grown cane toad, they don’t just get a tummy ache – the poison can very quickly kill them.

When hungry predators vanish, the consequences are disastrous for the entire ecosystem. With no predators to keep them in check, smaller animals like snakes and other lizards multiply, putting pressure on the smaller frogs and insects they prey upon. It’s a domino effect that can throw the delicate balance of nature completely out of whack.

Young cane toads teach goannas

Dr. Georgia Ward-Fear, a wildlife biologist at Macquarie University, has spent years researching cane toads and the devastation they cause. Her studies uncovered an intriguing possibility: young cane toads could help goannas learn a vital survival lesson.

Young cane toads possess less potent poison in their glands than adult toads. If a goanna eats a young toad, the poison will make it sick, but won’t be fatal. This negative experience teaches the goanna to avoid cane toads in the future.

Dr. Ward-Fear describes this as “ecological immunization,” as it provides the goannas with a form of resistance against the cane toad’s deadly poison.

Unleashing the teacher toads

This fascinating discovery got Dr. Ward-Fear thinking – could she use this immunization to save goanna populations on a bigger scale? And so began a remarkable project.

Teaming up with Professor Rick Shine, an evolutionary biologist, and many other organizations, they formed the Cane Toad Coalition. Together, they set out to test her theory in the Kimberley region of Western Australia, right at the frontline of the cane toad invasion.

The plan involved releasing hundreds of “taster toads” – tiny baby cane toads – just before the big, poisonous adult toads arrived in an area. It was like setting up a mini-classroom for the local goannas.

Did it work?

The results of this strategy were striking. In locations where researchers released the young teacher cane toads, ahead of the invasive cane toad front, goanna populations remained stable or even increased.

This is a significant finding, especially when compared to areas without this intervention. In those areas, goanna populations experienced devastating declines of up to 94% after the arrival of the highly poisonous adult cane toads.

Study significance

This study tracked Australia’s biggest cane toad defense project so far. It could be beneficial for the following:

• Protecting a vital link in the food web: Goannas, as apex predators, play a crucial role in maintaining balanced ecosystems. They help regulate the populations of smaller animals, preventing any single species from becoming too numerous. Their disappearance can destabilize the entire food web.
  
• Long-term benefits: The initial “toad training” may have lasting effects. When trained goannas reproduce, their offspring may instinctively avoid cane toads, inheriting this survival advantage.
  
• Beyond just goannas: The success of this technique offers hope for protecting other native Australian predators vulnerable to cane toad poison. It could be adapted to help other species learn to avoid these toxic invaders.
  
• A shift in conservation strategy: This project highlights a new approach in conservation. Instead of solely focusing on eradicating invasive species (which is often incredibly difficult or impossible), the emphasis shifts to helping native wildlife adapt and survive alongside the invaders.

Limitations and future directions

It’s impossible to send “teacher toads” everywhere across the Australian tropics. However, this technique could save populations of goannas in key areas, allowing them to survive and hopefully repopulate areas where they’ve been wiped out.

Dr. Ward-Fear’s research is changing how we think about conservation. Clever behavioral training could be a vital tool in protecting wildlife from invasive species the world over. Who knew these toxic toads could teach us such a valuable lesson?

More about cane toads beyond teaching

Cane toads’ impact extends beyond direct poisoning of native predators; they also compete with local species for food and habitat, exacerbating their invasive threat.

They are omnivorous and consume a wide range of foods – from insects and small animals to pet food left outside – often outcompeting native species for these resources. This competition for food can lead to a decrease in the populations of native species that rely on the same food sources.

Cane toads and humans

Another less discussed aspect is their effect on human activities. Cane toads have been known to cause power outages by short-circuiting electrical equipment, including substations and domestic air conditioners, when they seek warmth.

Their prolific numbers and willingness to inhabit human-modified landscapes mean they can also become a nuisance in residential areas, impacting gardens and local fauna.

Cane toads and disease

The toads’ ability to spread diseases to native amphibians and other species adds another layer of complexity to their impact. Cane toads carry and transmit diseases such as chytridiomycosis, which affects native amphibian populations, further endangering them.

Efforts to control cane toad populations have included physical removal, traps, and the exploration of biological control methods, though finding an effective and ecologically safe solution has proven challenging.

The adaptability of cane toads, combined with Australia’s vast and varied landscapes, makes their management a significant conservation challenge.

The study is published in the journal Conservation Letters.

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