Leopard sharks have a reputation for being docile toward people, says Manny Ezcurra, who has handled the Aquarium's leopard sharks since 1996. "But they're not so docile toward invertebrates and small fishes. We have to be careful about who we put in the exhibit with them," he says.

Manny rotates his leopard sharks among several exhibits as the animals grow up. He has to make sure the leopards don't tempt hungry sevengill sharks, larger relatives that are also on display at the Aquarium. So he keeps small leopard sharks in the Slough exhibit. As they grow, they move up to the wave pool of the Aviary exhibit, then into the Kelp Forest. Finally, when they're near full size, they go into the Deep Reef exhibit with the big fish.

When they're first brought in to the Aquarium, wild leopard sharks do require a little care. Often they have parasites called copepods living on their skin — a problem that's common in many sharks. "But leopards are fairly clean compared to other sharks," Manny says. "You can just pluck them right off." After the sharks have been in captivity for a while they get used to food like squid, fish and prawns, often handed to them by divers. "They'll even swim up to the sevengills and take the food away from them — you'd never see that in the wild," Manny says.

Out in the bays and estuaries, squid and prawns make up only a small part of a leopard shark's diet, but Manny can't provide his charges with too many of their staple foods, such as shore crabs and fat innkeeper worms. "We buy food according to the Seafood Watch card," Manny says. "And there doesn't seem to be too many markets selling fat innkeeper worms."

The leopard shark lives in shallow waters of bays and estuaries and occasionally patrols the kelp forest, usually staying near the bottom. It’s rarely found in water more than 65 feet deep (19.8 m), although some have strayed as deep as 300 feet (91.4 m). At the other extreme, a leopard shark will often follow the high tide to feed while cruising shallow mudflats, then move back out again as the water recedes. 

Shark pups

A baby shark is called a pup. Unlike most fish, which lay eggs, a mother leopard shark keeps her eggs inside her body until they hatch. After 10 to 12 months, she gives birth to a litter of 7 to 36 pups, each about 7 inches (17.8 cm) long. 

Keeping the eggs safe inside her is a good way to make sure they all hatch. But it's also a reason the leopard shark has so few young — at least compared to the thousands of eggs many other fish lay. A female leopard shark is usually about 10 years old when she has her first litter. After that, a female will generally mate every year. 

Swim or sink

The leopard shark is at home on the seafloor, just a foot or so above the sand. This is because it, like all sharks, lacks the swim bladders that other fish use to fine-tune their buoyancy. Instead, a leopard shark stores oil in its enormous liver. All that oil helps to counterbalance the shark's weight, but it usually remains slightly less buoyant than the water around it, so the shark tends to sink whenever it’s not swimming. 

Bottom feeders

A leopard shark is made to feed on the seafloor. Its mouth is on the flat underside of its head and opens downward. Skimming above the sandy surface, juvenile leopard sharks pluck up crabs, clam siphons, fish eggs and the burrowing, hot dog-shaped fat innkeeper worm. 

As a leopard shark gets older, it starts eating more fish and fewer crabs. The leopard shark has been found with smoothhound sharks, bat rays and even octopuses in its stomach. 

Shovel for your supper

How does a leopard shark get buried prey? Divers have seen a shark swimming stealthily just above the sand, looking for the fleshy siphon of a clam sticking two or three inches above the bottom. If the shark is quick enough, it can grab the siphon in its teeth and yank it out of the sand, occasionally getting the whole clam in the process. 

Other times the clam senses the predator and yanks its siphon back to safety. In this case — as well as when the shark goes after innkeeper worms — the shark shovels its nose into the sand. With a mighty twist of its body, the shark unearths a pile of sand and, if it's lucky, gets a clam or worm for its trouble.

The leopard shark lives close to shore and has firm, light meat that tastes good, so it’s popular with anglers and spearfishers. Although the International Union for Conservation of Nature classifies this shark as a species of "least concern," studies indicate that populations could be vulnerable to overfishing. One reason for this is because the leopard shark takes a long time to grow to maturity — about a decade. 

Setting a size limit for "keepers" helps. Right now a leopard shark must be 36 inches (91 cm) long for anglers to keep it. Because of its looks, the leopard shark is also a popular aquarium fish — just remember that fish below this size limit are illegal if they came from California waters.

Polluted water can pollute fish

In 1975, scientists dissected five leopard sharks caught in San Francisco Bay to see what they ate. On a hunch, they also had the fishes' livers analyzed. In all five they found high levels of mercury, a toxic element. In 1997, another study investigated pollutants in a variety of fish from San Francisco Bay, including eight leopard sharks. All eight had levels of mercury in their tissues that were over the accepted safe limit for humans. 

Mercury is an industrial pollutant that gets into coastal waters through rain and runoff. Because the leopard shark spends so much time feeding in sand and mud, it likely gets exposed to more pollutants than other fish. The leopard shark also lives a long time, giving mercury levels longer to accumulate. We don't yet know whether such high mercury levels harm the leopard shark. But evidence suggests it could be a bad idea for people to eat them — at least ones caught in San Francisco Bay.