Triakis semifasciata, commonly known as the leopard shark, is primarily found in the near-coastal regions in the Pacific Ocean from Oregon down the California coast to Mazatlan, México. During the spring and summer months leopard sharks can be found in the waters around Oregon and California. When the water begins to get colder, around 10 to 12 degrees Celsius, they migrate to the warmer waters of coastal Mexico. (Farrer, 2009; Hopkins and Cech, 2003; Lewallen, et al., 2007; Nosal, et al., 2012; Smith, 2001; Smith, 2007)
The temperate shallow bays and estuaries of coastal California provide the ideal habitat for leopard sharks, with temperatures of 13 to 16 degrees Celsius. Leopard sharks use the rise and fall of tidal waves to get in and out of bays and estuaries. The sand and mud in these estuarine habitats offer them a place to reproduce and a steady supply of food. They are found closest to the bottom of estuarine habitats at a typical depth of between 4 and 20 meters, but up to 91 meters has been observed. Movement patterns have been tracked and demonstrate that leopard sharks venture out into the open ocean and do not strictly stay in the bays and estuaries. (Cech, et al., 2000; Farrer, 2009; Hopkins and Cech, 2003; Nosal, et al., 2012; Smith, 2001; Smith, 2007)
The most distinct features of leopard sharks are the dark patches found all over the dorsal side of the body on a bronze or silver backdrop. The belly is often white and lighter than the dorsal side. Leopard sharks have flattened heads with short, rounded snouts. The average length of a leopard shark is between 1.2 and 1.5 meters, although some females can reach 1.9 meters long. Leopard sharks have slender but stout bodies, making it easy for them to maneuver. They have two dorsal fins that are about the same size. The first dorsal fin is situated at the midpoint of the body and the second dorsal fin is located closer to the anal fin. Leopard sharks have large eyes that are oval and they have a protective layer known as a nictitating membrane. The jaw is lined with smooth teeth that overlap, creating a ridge-like surface that helps with eating crushing invertebrate and crustacean prey. (Farrer, 2009; Nosal, et al., 2012)
Female leopard sharks carry and nourish fertilized embryos until they hatch. Females give live birth to as many as 37 pups a season between the months of March and July. These pups, which range from 20.3 to 24.4 cm, are left in shallower water, where the abundance of food is higher and the risk of predation is lower. The rate of growth for leopard sharks is relatively slow. Males grow at a rate of 2.0 cm a year and reach maturity between 0.7 to 1.2 meters at approximately 7 to 13 years old. Females grow at a rate of 2.3 cm a year and reach maturity between 0.7 to 1.3 meters, or at 10 to 15 years old. (Farrer, 2009; Hopkins and Cech, 2003; Smith, 2001; Smith, 2007)
There is little known about how leopard sharks mate. There was a sighting by a researcher that noted one male was mating with many females within an aggregation. This mating was observed in August of 2003 in shallow water (0.3 to 3 m). (Farrer, 2009; Smith, 2001; Smith, 2007)
Male leopard sharks reach reproductive maturity between 7 to 13 years old. Female leopard sharks reach maturity from 10 to 15 years old. Female leopard sharks give birth to 4 to 37 (average of 20) live pups, depending on the size of the female. After a gestation period of 10 to 12 months, the pups are born between April and July. Leopard shark pups are left to fend for themselves after birth. Shortly after females give birth, mating occurs. (Lewallen, et al., 2007; Smith, 2001; Smith, 2007)
Leopard sharks give birth to live young. After the pups are born, they are immediately independent. Female leopard sharks give birth to their young in shallow, productive areas, giving the pups a better chance at not being preyed on by other species and of finding appropriate prey. (Carlisle and Starr, 2009; Farrer, 2009; Hopkins and Cech, 2003; Knip, et al., 2010; Smith, 2001; Smith, 2007; Tester, 1963)
The average lifespan for a leopard shark in the wild is 18 to 24 years. Males average 24 years and females average 20 years. The lifespan for a leopard shark in captivity is 22 to 26 years. (Farrer, 2009; Smith, 2001; Smith, 2007)
Leopard sharks travel in schools that are segregated by size and gender. Smaller male leopard sharks travel with other small male leopard sharks; juveniles have also been spotted in schools together. Leopard sharks travel with other elasmobranchs, such as bat rays (Myliobatis californica) and smoothhound sharks (Mustelus). These schools of sharks have been tracked by researchers, who found that some leopard sharks are residents in particular areas and others roam throughout coastal regions. Warm coastal waters increase the speed of digestion and accelerate gestation in leopard sharks. A winter 2013 sighting of hundreds of female leopard sharks off the coast of La Jolla, California caused a stir in the region. Local scientists who study sharks reported that approximately 95% of the leopard sharks in this area, termed La Jolla Shores, spend 6 months of their pregnancy in these warm, calm waters. They spend the days near the surface (warmer waters) and the nights at greater depths (greater abundance of food). Males did not congregate in this area, instead they inhabited kelp-rich waters about 16 km north of the aggregations of females. (Ash, 2013; Hight and Lowe, 2007; Hopkins and Cech, 2003; Smith, 2001; Smith, 2007)
Leopard sharks travel up to 2 km to find food. They are not known to defend territories. Some remain in particular areas, other individuals appear to be nomadic. (Farrer, 2009; Hopkins and Cech, 2003; Lewallen, et al., 2007; Nosal, et al., 2012; Smith, 2001; Smith, 2007)
Leopard sharks use their eyesight and sense of smell to navigate through their environment, catch prey, and actively use the dark to advantage. Like other sharks, their eyes contain rods, cones, and horizontal cells. The concentration of rods outweighs the number of cones. The rods permit short wavelengths to penetrate the retinas, allowing them to see in dimmer light. This adaptation in their eyes support their nocturnal lifestyle and ability to navigate deep waters. Leopard sharks also use their sense of smell via the flow of water over their nares. For example, fish give off an odor when they get excited, which leopard sharks detect via chemical receptors in their nares. Female leopard sharks releases a sex pheromone that can be detected by male leopard sharks. This sex pheromone indicates that the female leopard shark is ready to mate. (Carlisle and Smith, 2009; Carlisle and Starr, 2009; Schluessel, et al., 2009; Tacutu, et al., 2013)
Leopard sharks use suction to grab their prey; they then clench their jaw down and capture the prey between their teeth. Leopard sharks have rows of teeth, but the first row is the only row that stands upright. They rip apart their prey into smaller bites and swallow them whole. Leopard sharks are opportunistic carnivores. Studies have shown that the larger the leopard shark, the more likely it will prey on fish, like herring (Clupea), topsmelt (Atherinops affinis), croakers (Sciaenidae), and surfperches (Embiotocidae). They are also known to eat fish eggs and the young of other sharks. Smaller leopard sharks and juveniles eat mainly benthic prey, like crabs (Brachyura), ghost shrimp (Thalassinidea), clams (Veneridae), and worms. Many researchers have found bite marks from the fat innkeeper worm (Urechis caupo) along the mouth and jaws of captured leopard sharks. Fat innkeeper worms have been found in abundance in the stomachs of leopard sharks. (Hopkins and Cech, 2003; Smith, 2001; Smith, 2007)
Leopard sharks are preyed on by white sharks (Carcharodon carcharias), sevengill sharks (Notorynchus cepedianus), along with other, larger shark species. They live in shallow water with low visibility and their cryptic coloration may help protect them from some predators. (Smith, 2001; Smith, 2007)
Leopard sharks are key predators in their ecosystems. They are only hunted by bigger sharks and humans (Homo sapiens). Two cestode species, Lacistorhynchus dollfusi and Lacistorhynchus tenuis, have been found in the spiral valves and rectal glands of the leopard shark. High levels of infestation seem to decrease the lifespan of the infected shark. (Carlisle and Starr, 2009; Hopkins and Cech, 2003; Sakanari and Moser, 1985; Sakanari and Moser, 1989)
Leopard sharks have distinctive features and their lifespan is long. Because of these characteristics, thes sharks often are targets for aquariums. Many places along the Pacific bay offer tourists a chance to swim with leopard sharks, because they tend to be timid. Recreational fishermen often capture leopard sharks in their nets, or on their lines, and sell them to aquatic collectors for their hardiness; they are highly prized for personal aquariums. Fisheries also capture leopard sharks and sell them for food. Collecting leopard sharks was made illegal in 1994 but fisheries capture them in their nets and sell them on the black market. (Farrer, 2009; Hopkins and Cech, 2003; Smith, 2007)
Leopard sharks are predators, but are not large or aggressive. There has been only one recorded account of a leopard shark attack on a human. In the 1950’s a spear fisher caught a fish and the smell of its blood attracted the leopard shark. There was no significant injury to the human. (Farrer, 2009; Smith, 2001; Smith, 2007)
The IUCN status for leopard sharks is Least Concern. Their numbers have been stabilized by the conservation acts enforced by the state of California. Habitat loss affects leopard sharks, which depend upon bays and estuaries for breeding and nursing. These habitats have been degraded by agriculture, development, and pollution. The biggest current issue for leopard sharks is over-exploitation by fishing. To address this problem, gillnets have been prohibited along the California coast in water that is shallower than 110 m. The type of fishing gear for coastal fishing has also been restricted by the state of California. Commercial harvesting and aquatic trade, has been limited to a minimum size of 46 cm for sharks and rays. For recreational fishermen, they are limited to a maximum number of three sharks longer then 91 cm. Due to the small geographic range, low genetic exchange, slow growth, delayed maturity, and long gestation period, leopard sharks are deemed vulnerable by some researchers. (Smith, 2001; Smith, 2007; Tacutu, et al., 2013)
Research on the DNA of leopard sharks define 7 distinct populations that are separated geographically. Leopard sharks that are mainly found in the waters off of the Mexican coast have little genetic difference with those that are found off the coast of California. Other aggregations off the coast of California have more genetic information in common with each other. The isolated aggregation of leopard sharks that is found in Humboldt Bay have some unique genetic characteristics. (Lewallen, et al., 2007)
Caitlyn Long (author), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
generally wanders from place to place, usually within a well-defined range.
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats fish
having more than one female as a mate at one time
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
uses sight to communicate
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