Sea Wonder: Tiger Shark
Named for their distinct coloration — dark grey stripes on their bodies and a white underside — tiger sharks (Galeocerdo cuvier) are one of the world’s largest predatory sharks. Tiger sharks can weigh upwards of 1,400 pounds and their average length is between 10 and 14 feet with the longest tiger shark being as long as 18 feet, which puts them at a rank of the fourth largest shark on the planet and in second behind the Great White Sharks, the largest predatory shark in the ocean. These sharks are sexually dimorphic — meaning one sex is noticably larger than the other – with females generally larger than their male counterparts.
Tiger sharks are countershaded, meaning their backs are darker than their bellies, an adaptation that helps them blend into the aquatic environment and go unnoticed by their prey. Their backs are typically grey with dark grey stripes running vertically down the length of their bodies, though these stripes fade as the sharks age. In their mouths are multiple rows of large, serrated teeth used for catching, tearing, and crushing their prey.
Diet & Habitat
Tiger sharks are omnivores and voracious predators; they will eat anything in their paths, favoring whatever is easiest to catch. They are typically slow moving animals, but use ambush predation – quick bursts of speed used to grab the prey they are stalking – as their primary hunting strategy. To find food, they rely both on chemoreception similar to our sense of smell and electroreception, which is the use of electromagnetic fields naturally produced by moving animals. Studies of tiger shark stomach contents have revealed everything from stingrays to sea snakes and from license plates to different kinds of trash.
Younger tiger sharks will eat softer, easier to catch foods like small fish, jellies, and mollusks (including squids). Adults will feed on more difficult to find and catch prey like larger fish, crustaceans, sea turtles, and marine mammals. In fact, some tiger sharks migrate to the Hawaiian islands in the late spring to prey on seabirds like albatrosses.
Tiger sharks live near coastlines in tropical and subtropical waters all over the world. In the National Marine Sanctuary System, we see them in or near almost all of the oceanic sanctuaries, such as Flower Garden Banks and Hawaiian Island Humpback Whale National Marine Sanctuaries, but none of the freshwater ones. During the day they occupy deeper waters offshore and venture nearshore at night to feed.
Tiger shark pups are born after a gestation period of 12 to 16 months. After fertilization, females incubate her eggs internally, where they hatch before being born. A single female can give birth to as many as 82 pups in a single pregnancy! The pups are between two and three feet long at birth and double in length in their first year of life. After that first year, their growth rate slows but doesn’t stop until sexual maturity, which occurs between seven and 10 years old. We don’t know the maximum age of these sharks, but the oldest recorded one lived to be approximately 12 years old.
Tiger sharks are generally solitary animals, taking care of themselves from the moment they are born, though multiple individuals may gather in the same habitat range due to food availability or other environmental factors. Breeding season occurs in the warmer summer months, which depend on the hemisphere in which a population of tiger sharks lives. Fertilization occurs internally and both males and females can have multiple partners in a given season. Females usually give birth every three years or so.
Threats & Conservation
Tiger sharks don’t have many natural predators beyond the occasional killer whale, though human activities pose risks to the health of their populations around the world.
Tiger sharks are a desirable species of shark to hunt because of their proximity to shore, and are fished for their fins, meat, and liver oil, which is high in vitamin A and can be used to make nutritional supplements. In the United States, tiger sharks are the third most commonly caught species of large coastal sharks and are highly sought after big game fish in recreational fishing activities. Bycatch is also a problem for tiger sharks throughout the global ocean, especially when they attempt to feed on fish that are trapped in nets or other gear.
In addition to fishing pressures, tiger sharks face challenges spanning ingestion of marine debris, loss of food sources due to climate change, ocean acidification, and overfishing, and are vulnerable to environmental changes like ocean deoxygenation caused by land-based fertilizers that make their way to the ocean via runoff and fuel rapid algae growth.
The International Union for Conservation of Nature (IUCN) lists tiger sharks as near threatened.