MOSSMAN, QUEENSLAND, AUSTRALIA -FEBRUARY 11:  A cane toad in Mossman, Queensland, Australia, on February 11, 2005. The cane toad is an introduced species. The toad's poison back is killing off many indigenous Australian species of birds and marsupials - and even family pets. (Photo by Melanie Stetson Freeman/The Christian Science Monitor via Getty Images)
MOSSMAN, QUEENSLAND, AUSTRALIA -FEBRUARY 11: A cane toad in Mossman, Queensland, Australia, on February 11, 2005. The cane toad is an introduced species. The toad's poison back is killing off many indigenous Australian species of birds and marsupials - and even family pets. (Photo by Melanie Stetson Freeman/The Christian Science Monitor via Getty Images)

Imported pest getting stronger, faster

The pesky cane toad that was introduced to try and "control" a native insect but has instead altered the balance of Australia's ecology is getting faster and stronger as it continues to spread across the country.

That's the finding of new research from Australian academics who analysed the cane toads spreading across northern Australia and compared them to ones in north Queensland, where they were first introduced in 1935.

A bunch of cane toads in a bin, where some might argue they belong.
A bunch of cane toads in a bin, where some might argue they belong.


The team found that "locomotor performance" - how the toads move - varied by geography, and the closer toads were to the "invasion front" the quicker they moved, supporting a theory the toad's invasion has generated rapid evolutionary shifts for the animal.

The fact that cane toads have only existed in Australia for 85 years provided a unique opportunity to the researchers to observe rapid evolution.

Normally scientists are comparing traits in animals that may have been separated for centuries or even millennia, and they can be trying to compare hard to quantify traits like brain cognition.

Cane toads in north Queensland and ones in places like the Northern Territory and WA haven't been separated that long, and the traits examined in the study - things like how far they can hop and how long their legs are - can be easily measured.

 

The researchers raised toads from different populations in a "common garden", which allowed them to observe that some of the traits helping the toads to continue their invasion of Australia are being passed down through generations.

Similar findings were made on toads from populations in the wild.

The WA toads were bigger, with longer legs and larger heads. They also had bigger rear feet and smaller front feet.

The study used 163 toads from El Questro, Oombulgurri, Purnululu and Wyndham in Western Australia, where the toads were first detected in 2009.

A now famous image of cane toads riding an olive python in Western Australia. The researchers did not investigate whether the toads spread across the country by riding on the backs of other animals. Picture: Paul Mock
A now famous image of cane toads riding an olive python in Western Australia. The researchers did not investigate whether the toads spread across the country by riding on the backs of other animals. Picture: Paul Mock


It compared them to 148 toads from Innisfail, Townsville and Tully, where populations have existed for more than eight decades.

In a series of tests, researchers made the toads jump while high-speed cameras recorded their performance.

They also set up a dedicated "raceway" to pit the toads against each other.

The wild-caught WA toads could reach higher speeds on their hops.

In the common garden, the offspring of the Queensland toads also exhibited "flatter take off angles and achieved lower heights".

Previous research has found the cane toads native to South America more closely resemble the ones introduced in Queensland than the ones that have made it to WA.

Shorter front limbs make it easier for toads to mate.
Shorter front limbs make it easier for toads to mate.

The researchers noted male Qld toads are typically faster and have longer legs, but the toads who spread across Australia couldn't move faster than the females or they would outrun them and have no way of breeding.

They also noted a "strong sexual selection" for shorter front limbs, because they allow the male toads to cling more tightly to the female toads "for success in sexual struggles".

The research was conducted by academics from The University of Sydney, The Australian National University, Macquarie University.

Their findings are published in The Proceedings of the Royal Society Biological Sciences journal.

Originally published as Imported pest getting stronger, faster



Foul-mouthed tirade lands man in court

Premium Content Foul-mouthed tirade lands man in court

Christopher Michael Currie was found on Goondoon St, mouthing off at someone...

How does Gladstone’s 2020 rainfall compare?

Premium Content How does Gladstone’s 2020 rainfall compare?

The predicted La Nina climate pattern could bring higher volumes of above average...

Gladstone Council records $2.7m operating deficit

Premium Content Gladstone Council records $2.7m operating deficit

The result was a stark contrast to the previous financial year which yielded a...