Hello and welcome to your Daily Fun Fact From Flora ,

Today we are going to have a look at the effect that us lovely humans are having on the natural world and some of the ways that we have changed the course of evolution without meaning to.

Cane toads were introduced in Australia to try and counteract the cane beetles that were munching through all of Australia’s fabulous sugarcane. It had turned out pretty well in Puerto Rico so they took 102 cane toads from Hawaii and introduced them into cane fields.

There are now over 200 million of them.

Whoopsies.

Now these cane toads are extremely poisonous , which was one of the reasons why they were so successful at spreading. Nothing had evolved resistance to eat them.

This has had some pretty interesting effects in driving evolution other species around them. Especially in a couple of species of Australian black snake ( Pseudechis porphyriacus and Dendrelaphis punctulatus if you’re feeling fancy).

Now it’s not what you think — the snakes are not gaining resistance to the cane toad’s toxins. Oh no. Instead they are showing a remarkably rapid increase in body size (now that’s a mood) accompanied by a decrease in relative head size.

What is going on here?

This change was seen in fewer than 23 snake generations and for evolution that is RAPID so it must be some quite strong selective pressures that the snakes are experiencing.

Now these cane toads, as I mentioned, are VERY toxic and so a mature can toad will likely kill any snake that tries to eat one. A juvenile might not kill them, but it isn’t going to be pleasant.

Interestingly, these snakes are known as gape-limited predators which literally means they will only not eat things because they are simply too big to fit in their mouths.

Therefore, the smaller their heads are, the less likely they are to eat a toad that is big enough to kill them.

And on top of THAT a bigger body size helps too, as it takes a larger amount of toxin to kill a larger snake.

I love this weird reverse evolution of not evolving to be able to cope with eating the poisonous thing but instead evolving a body that doesn’t fit the poisonous thing inside.

And the scientists involved compared these snakes to another two species that were not exposed to toads ( Hemiaspis signata and Tropidonophis mairii ) and they showed NO TRENDS in either of the traits.

This makes us pretty darn sure that the changes we are seeing in those other snakes are a form of adaptation to the toxic cane toads.

Pretty neat, eh?

If you"d like to learn more here’s a highly scientific and informative film you can watch

Thank goodness they included that warning at the bottom. If you can’t read it, it says WARNING: LICKING THIS TOAD CAN BE HAZARDOUS TO YOUR HEALTH.

Wow. What scientific content.

Lots of love,

Flora