Antlions & helmeted basilisks

Spend a moment visualising your most active days and your laziest days. On active days, you might visit the gym, trek the Himalaya or run a marathon. On lazy days, perhaps, you would walk from your bed to the fridge and back. Some animals live in a state of perpetual activity like you on your active days — imagine a constantly buzzing bee or a hummingbird flitting from flower to flower. Today, however, we are taking a break from these exhausting creatures to talk instead about those that behave like you on your laziest days.

One of my favourite animals, the antlion larva, perfectly illustrates such a sedentary lifestyle. Have you ever noticed small, conical pits in the ground, often in sandy soil along walls, sheltered by trees or eaves? These pits have been dug by antlion larvae, who wait patiently at the bottom for their food — ants and other insects — to fall in. When an ant falls into the pit, all hell breaks loose. The antlion jerks its head violently to spray sand in the direction of the unsuspecting ant, which loses its balance and careens into the gigantic jaws of the antlion below. After grasping the ant firmly, the antlion injects it with digestive juices and retires below the sand to eat it at its own leisure, returning to its placid existence.

This mode of hunting is aptly called extreme sit-and-wait predation. Another fascinating sit-and-wait predator is the Central and South American helmeted basilisk lizard. Like antlions, these lizards are most active when catching food. When a helmeted basilisk spots an insect it wants to eat, it dashes off the tree it’s been sitting on and sprints on its hind legs across the forest floor to catch the insect. But most of the time, this lizard sits very, very still. So still, in fact, that not one but three different types of creatures — nine species of algae, a tiny plant called a liverwort, and a slime mould — can grow on the body of the helmeted basilisk! This association is a win-win situation for everyone involved. By growing on the lizard’s body, these green creatures help the lizard camouflage against tree trunks in the its periods of immobility, but the creatures benefit by being dispersed to new environments when the lizard runs across the jungle.

In thinking about how infrequently antlions and helmeted basilisks move, and therefore how infrequently they eat, I’ve always wondered whether they get hungry. It appears that both animals have found ways of dealing with this problem. Antlions cope with the uncertainty of catching prey not only by eating whatever they can catch, but also by not eating very often — they can survive for several months without food, because they burn their energy reserves more slowly than most other cold-blooded creatures. In contrast, helmeted basilisks are very picky eaters. They only decide to move when they can catch a very large insect, an insect big enough to satisfy the lizard’s appetite for over a day.

Nature documentaries have us believe that the animal world is always filled with motion and excitement, but this is definitely not the case. That antlions and helmeted basilisks exist today, in the same ecosystems as bees and hummingbirds, is proof that a sedentary lifestyle can be just as successful as an active one.

This is a monthly series on animals you may have never met, but must (at least, on page).

Ambika Kamath: Studies organismicevolutionary biology at Harvard University

COMMENT NOW