Toxic Toads Leap Straight to Invade New Grounds Faster

If an officer were to give most toads a sobriety test, they would horribly fail at walking er... hopping the line. But researchers have found that initial waves of invasive toads in Australia would pass in leaps and bounds, wandering in remarkably straight lines to cover more ground and invade faster.

Rick Shine from the University of Sydney says that most toads don't hop straight. Instead, to get from one place or another faster, they have to hop more frequently, or travel further with each leap.

However, that can be exhausting, and they seem to be ignoring a very simple rule.

"The best way to cover more distance with a given amount of time and effort is to go in a straight line," Shine recently told New Scientist.

That might be why Cane toads in Australia were jumping in much straighter paths when their invasion of the continent began to accelerate, according to a new study published in the journal Proceedings of the Royal Society B.

Shine and his colleagues reportedly looked over a decade of tracked Cane toad movement along Australia's north coast, since they were first introduced to Queensland to help control insect populations. Like the American bullfrog in US waters, the toad has proven too hearty and ravenous, out-eating and out-breeding other native amphibians. It's also toxic to many predators.

Interestingly, the vanguard invaders seemed to be traveling in straight lines day after day. They covered more ground this way, making for a very aggressive invasion. As the invasion has slowed down, however, the toads' aim seems to have shifted, and it is more apparent that they are hopping in less directional paths.

In a breeding and field experiment of 129 toad offspring, the researchers found that hopping in straight lines is a genetic trait, inheritable from straight-hopping parents. Parents at the front of the invasion would continue to breed straight-line hoppers that would trail-blaze ahead. In the back of the invasion, frogs more likely to wander in more random directions would then help fill out and populate what has been claimed.

Still, the authors are quick to point out that a specific gene has not been identified, and this has so far only been seen in one species of invaders. More work will be needed to confirm their theories.