The California spiny lobster is a spiny lobster, one of several groups of reptant decapods. They may be found from the southern tip of the Baja California Peninsula to Monterey Bay, California. They are generally found at very shallow depths near the coastline or near offshore islands. They migrate in order to mate and to give birth to their young. During the spring, California spiny lobster travel to shallow waters and then move to deeper waters in the fall. In December, they often move offshore to waters as deep as 110 feet. By late January, the lobsters generally move back up to depths between 15 and 45 feet of water.

The California spiny lobster is generally nocturnal; during the daytime, these spiny lobsters can be found in small holes and cracks, or hidden in grass with other lobsters, but at night, they tend to hunt singly. Spiny lobsters are scavengers that mainly eat sessile or slow-moving animals, such as snails, sea urchins, clams, sponges, kelp, worms, mussels, scallops, barnacles, and fish. California spiny lobsters are a vital part of the California coast habitat because they keep the purple and red sea urchin population under control. The jaws of the California spiny lobster are extremely strong, and they are capable of crushing shells and bones of other animals.

One of the most noticeable features of the spiny lobster is the two large antennae. The antennae are longer than the body, and they are used to sense any movement in front of them. Spiny lobsters also have smaller antennae called antennules , which are used to sense food and predators.

Predators of the California spiny lobster include giant sea bass, kelp bass , California sheephead , California scorpionfish , rockfishes, octopus, California moray eels, sea otters, cabezon , horn sharks , leopard sharks, other lobsters, and humans.

Although they lack the large chelae of true lobsters, one protection that these spiny lobsters have is the abundance of spines on their backs. The two largest spines located over their eyes are known colloquially as the horns. In the event of danger, the tail fan is used to propel the animal backwards (the "caridoid escape reaction").

Mating takes places between January and April, with the ventral sides of the male and female animal against each other, during which a sperm packet is transferred from the male to the female. When the female spiny lobster is ready, she will scratch open the sperm packet with specialized claws while simultaneously releasing her eggs. Once the sperm have fertilized the eggs, they will stick to the pleopods (swimmerets) and stay there until hatched. A newly matured female will produce about 100,000 eggs while an older and larger female will make nearly 1,000,000. When the female spiny lobster is ready to release the fertilized eggs she goes to shallower, warmer water, usually in May or June. The eggs are bright red when first fertilized, but become dark brown after about ten weeks.

The eggs hatch into Phyllosoma larvae, which look quite unlike the adult, and are free-floating creatures with very little mobility or defence. After about six to nine months, when the larva has molted 12 times, it will reach the puerulus (from the Latin meaning child) stage. This looks like a small lobster with very large antennae. The puerulus moves very close to shore where it molts into a juvenile spiny lobster.

Back in the days before divers went down to pick them by hand, spiny lobsters often grew to be 150 years old and over three feet long. These giant spiny lobsters were too big to fit into any traps, and had very few predators. Most spiny lobsters now grow to the age of five to seven years before being caught.