Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name.

Large schools of leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs.

The International Union for Conservation of Nature has assessed this species as of Least Concern, while noting that local stocks may easily become overfished because of the shark's slow growth and limited migratory habits.

[4] Despite M. felis being the senior synonym, an error in recording the dates of publication resulted in the widespread use of T. semifasciata as the leopard shark's scientific name.

[4] The specific epithet semifasciata comes from the Latin words semi ("half") and fasciatus ("banded"), describing this shark's dorsal pattern of saddle-like markings.

[3] A 2006 phylogenetic analysis by J. Andrés López and colleagues, based on protein-coding genes, revealed that Triakis and Cazon are in fact not closely related, and additionally that the leopard shark may be the most basal member of its family.

It favors muddy or sandy flats within enclosed bays and estuaries, and may also be encountered near kelp beds and rocky reefs, or along the open coast.

A study in Tomales Bay in northern California determined that they depart when the water temperature drops below 10–12 °C (50–54 °F); one tagged shark was found to have swum some 140 km (87 mi) south.

[3][12] In Tomales Bay (among other similar regions), the leopard shark follows the tide onto mudflats to forage for food, retreating just fast enough to prevent being stranded or trapped as the water recedes.

[13] At Santa Catalina Island, resident sharks spend the day together in the shallows and at night, they disperse into deeper water, up to 10 km (6.2 mi) away.

[12] From birth, leopard sharks form large schools, generally segregated by age and sex; these groups may intermingle with grey or brown smoothhounds (Mustelus californicus and M. henlei) and spiny dogfish (Squalus acanthias).

As these females follow the warmest patches of water (allowing them to raise their internal body temperatures by up to 3 °C (37 °F), they are speculated to be taking advantage of the heat to speed their own growth and that of their gestating young.

[14] Compared to the related grey and brown smoothhounds that share its range, the leopard shark has smaller and more numerous red blood cells, allowing it to process oxygen more efficiently.

[18] Known parasites of this species include the tapeworms Phyllobothrium riseri, Lacistorhynchus dollfusi and Paraorygmatobothrium barber,[19][20][21] as well as the copepods Echthrogaleus eoleoptratus and Achtheinus oblongatus.

[22][23] The diet of the leopard shark consists of small benthic and littoral animals, most significantly crabs (Cancridae, Grapsidae, and Hippoidea), shrimp, bony fish (including anchovies, herring, topsmelt, croakers, surfperch, gobies, rockfish, sculpins, flatfish, and midshipmen), fish eggs, clams, and the echiurid fat innkeeper worm (Urechis caupo).

This opportunistic hunter has also been known to eat ghost shrimp, polychaete worms, and the young of smoothhounds, shovelnose guitarfish (Rhinobatos productus), and bat rays (Myliobatis californicus).

[3] The leopard shark captures prey by expanding its buccal cavity to create a suction force, which is facilitated by its labial cartilages swinging forward to form the mouth into a tube.

Young sharks feed mostly on crabs and transition to clam siphons, fish eggs, and innkeeper worms once they reach 70–80 cm (2.3–2.6 ft) long.

[7][26] Multiple males may father a litter from a single mother[28] In Humboldt and San Francisco Bays, females drop their pups in beds of eelgrass that provide both shelter and food.

[5] Individuals of the same age can vary significantly in size and large sharks are especially slow-growing: one specimen was documented to have gained only 4 cm (1.6 in) in length over 12 years.

[5] However, leopard sharks living alongside human development may accumulate pollutants such as mercury, pesticides, and polychlorinated biphenyls (PCBs) within their bodies, and the California Department of Fish and Wildlife warns against eating them regularly.

[10][15] The leopard shark is prized by the aquarium trade for its attractive appearance and hardiness; this led to many newborn pups being captured with hook-and-line off southern California in the late 1980s and early 1990s.

In addition, Californian restrictions on the use of certain types of fishing gear in near-shore waters confer good protection to this shark's core population.