The Ant and the Toad
Our story begins with a beetle. We’ll call him Lachlan*. Lachlan was a cane beetle who lived in Australia’s sugar cane fields with all his cane beetle friends. They were happy beetles, eating the leaves of the sugar cane plants while their babies ate the sugar cane roots. But all this munching pissed the sugar cane farmers off. They had to get rid of Lachlan and his hooligan buddies, but how? They couldn’t crush them—Lachlan and the other adults had heavy armor and the larvae hid underground. They couldn’t poison them because pesticides that would kill the cane beetles would also kill the helpful insects.
The farmers needed a secret weapon…something the cane beetles had never seen before…a fierce insect-eating predator that may** have contributed to the dramatic decline of white grubs in Puerto Rican sugar cane fields. They needed the cane toad (or so they thought).
Cane toads are native to South America, but have been introduced to most Caribbean and Pacific islands. The toads, which defend themselves by excreting a poison that targets the heart of their attackers, are known for eating everything that moves and some things (like garbage and dog food) that don’t. The 102 cane toads that arrived in Queensland, Australia in 1935 certainly ate. They ate and ate and ate. But they didn’t eat the cane beetles because they couldn’t jump high enough to reach the beetles on the top of the sugar cane stalks.
The toads’ pathetic jumping abilities screwed the farmers, but didn’t seem to phase the toads. In fact, the toads flourished in their new home. Their population grew and grew (to an estimated 200 million today) and the toads moved inland, eating everything they could along the way. Of course, the eight-inch toad couldn’t eat every critter it encountered. Some animals—snakes, raptors, freshwater crocodiles, lizards and northern quolls—thought they could eat the little toad. They were wrong. The little toad poisoned the big bad predators, killing more than 75% of the freshwater crocodiles in one region.
While the cane beetles happily munched on sugar cane and the cane toads happily conquered tropical Australia, another species was happily dispersing bellyache bush seeds throughout the northern rangelands. Meet the meat ant, an Australian native that, in the grand scheme of freaky things that ants do, isn’t all that exciting. Meat ants live in underground colonies of up to 64,000 workers. They scavenge for dead invertebrates and, like yellow crazy ants, have mutualistic relationships with some caterpillars and butterflies. Farmers often use meat ants to clean carcasses, hence the name.
Until recently, the most exciting meat ant-related news was the proposed erection of a giant meat ant statue. But then scientists from the University of Sidney decided to try a little experiment. They placed cat food along the edges of ponds where female cane toads were laying eggs (with up to 30,000 eggs per clutch). The cat food attracted meat ants. Then, when the baby toads (“toadlets”) emerged from the ponds, the meat ants swarmed them. The researchers report that 98% of the emerging toadlets were attacked by meat ants in two minutes or less and 80% of the toadlets that escaped immediate death-by-meat-ant died from ant-inflicted injuries within 24 hours.
How do the itty bitty ants kill the big bad toads? First of all, the toadlets aren’t big. They’re only about one centimeter long. And secondly, the toadlets are slow. When attacked, they freeze instead of running away. Still, don’t the toadlets have poison to fend off attacks from vicious creatures like meat ants? Yes, but the heart-attacking toxin doesn’t phase the ants, probably because ants lack a central heart.
Meat ants probably won’t save Australia from cane toads. It would take a lot of meat ants to kill all the cane toads…and remember the last time the Australians tried to use one animal to control the population of another animal? That’s how they got into this mess.
*According to yeahbaby.com, Lachlan is the second most popular boy’s name in Australia.
**The white grub decline also happens to correspond with years of record-high rainfall.