Move and Sense

Part of the Life at the Limits exhibition.

Whether they’re foraging for food, evading a predator, or just heading home to nest, nearly all animals move at some point in their lives. And for most organisms—other than plants—this task takes more energy than anything else they do. Creatures that waste energy are very likely doomed, so it’s no surprise that evolution has produced some amazingly efficient methods of locomotion.

Just being able to move isn’t enough, though. Animals also need to be able to get a sense of where they’re going—though that doesn’t always mean seeing. We can’t know exactly what the world looks like through another set of eyes (or antennae), but we do know that other species have sensory experiences very different from ours. Some animals have sensory abilities that go far beyond the powers of humans—sophisticated systems used to navigate, communicate, and find food and shelter.

Swimming with the Jet Set

Jet propulsion seems very modern, but it’s actually ancient. Long before there were dinosaurs, creatures like the nautilus used exactly that method to navigate the ancient seas, and its modern descendants still do. To produce a jet of water that will propel it backwards, one set of muscles draws water into the internal space called the mantle cavity, and another set shoots the water out through a tube called a siphon. These jets don’t move the nautilus along very fast, but moving this way doesn’t require much energy.

Chambered Nautilus
Chambered nautiluses are sometimes called living fossils because they so closely resemble ancient cephalopods like ammonites. 
Image courtesy of T.B. Smith 

 Sensing the Body Electric

Some predators have the uncanny ability to locate prey without seeing, hearing or smelling it. The sawfish, for instance, hunts with peculiar hardware at the front of its head. It’s distinctive snout, which looks like the business end of a chain saw, does more than just cut. Its surface is speckled with electrosensory pores, which detect weak electric fields produced by prey animals. In the murky lagoons and rivers where sawfishes swim, this built-in voltage meter can reveal food that is impossible to see.

Sawfish Saw
The distinctive nose of the sawfish is dotted with pores that can sense electrical fields.
©AMNH/R. Mickens 

On the Lookout

Scallops are built like clams and mussels, with shapely shells, soft, headless bodies and simple brains. Shellfish like these may not seem alert. But scallops see in all directions. Their mantle—the thin body part that secretes the shell—is fringed with up to 100 miniature eyes, each with its own tiny retina and lens. Scallops live on the seafloor, rather than buried in sand or attached to rocks. When their shells are open, they can monitor their surroundings at all times. 

Scallop L@L
The tiny blue spots are the eyes of this Atlantic Bay Scallop. 
Wikimedia/Rachael Norris and Marina Freudzon

Midair Marauders

Dragonflies are among the world’s fastest insects, achieving speeds up to 30 miles (50 kilometers) an hour. These four-winged insects, can fly backwards or upside down, hover for a minute at a time, and have amazing vision. These traits make dragonflies deadly predators that capture prey they attack in mid-air an astounding 95 percent of the time.

Dragonflies have amazing flight capabilities, like the ability to hover in midair and turn on a dime.
Wikimedia/R. A. Nonenmacher 

Visitors to Life at the Limits will get to see live nautiluses in action at the exhibit, and learn about ongoing conservation efforts to ensure these animals, valued for their beautiful shells, do not become endangered.