What You're Looking at When You See a Frilled Shark
The frilled shark is a deep-sea predator that looks like something from a different era—because it essentially is. This creature has remained virtually unchanged for millions of years, making it one of the ocean's living fossils. It grows to about 4 to 5 feet long, though some specimens reach 6 feet, with a body shaped like an eel and a head that seems disproportionately large. The most distinctive feature is its mouth: lined with 300 needle-like teeth arranged in 25 rows, it opens vertically rather than horizontally, designed to engulf prey whole.
The frilled shark's name comes from the gill slits along its sides, which form a frilled appearance. Its coloring is typically dark gray or brown, which serves as camouflage in the lightless depths where it hunts. Unlike most sharks, the frilled shark is ovoviviparous—meaning eggs hatch inside the mother and pups are born live—and it has an unusually long gestation period of up to three and a half years, the longest known in any shark species.
Key Takeaways
- Frilled sharks live at depths of 2,000 to 4,000 feet where they hunt squid, fish, and other sharks in near-total darkness.
- They are rarely encountered alive because they inhabit the deep ocean far from commercial fishing grounds and human observation.
- The species has remained virtually unchanged for 80 million years, making it a window into prehistoric shark evolution.
- Most specimens documented by humans are either dead specimens caught accidentally in deep-sea fishing nets or washed ashore in unusual circumstances.
Where Frilled Sharks Live and How Deep They Go
Frilled sharks inhabit the continental slopes and deep ocean basins of the Atlantic, Pacific, and Indian Oceans. They are found at depths ranging from 2,000 to 4,000 feet, though they occasionally venture shallower or deeper depending on prey availability and water temperature. The species prefers cold water and is most commonly documented off the coasts of Japan, Portugal, and southern Africa, though this likely reflects where deep-sea research and fishing occur rather than where the sharks are most abundant.
The environment at these depths is almost completely dark, with water temperatures hovering just above freezing. Frilled sharks have adapted to this world with large eyes positioned on the sides of their head, giving them a wide field of view to detect the faint bioluminescence of prey. They move slowly through the water column, conserving energy in an environment where food is scarce and encounters with other animals are rare.
What Frilled Sharks Eat and How They Hunt
The frilled shark is an ambush predator that feeds primarily on deep-sea squid, though it also hunts fish and smaller sharks. Its hunting strategy relies on stealth and patience rather than speed. The shark drifts through the water, waiting for prey to come within striking distance, then uses its highly flexible jaw to snap upward and engulf the target whole. The 300 teeth are not designed for cutting or chewing—they are positioned to grip and hold prey that might otherwise escape.
Stomach contents from specimens caught in fishing nets reveal that frilled sharks are opportunistic feeders, taking whatever prey they encounter. This flexibility is likely essential for survival in an environment where meals are unpredictable. The shark's slow metabolism and low activity level mean it does not need to eat frequently, an adaptation that helps it survive in a food-scarce habitat.
Why Frilled Sharks Are So Rarely Seen Alive
Most human encounters with frilled sharks are accidental. The species is occasionally caught in deep-sea fishing nets targeting other species, and specimens sometimes wash ashore after dying at depth. Live frilled sharks are almost never observed because they inhabit depths far below where recreational diving or most research submersibles operate. The few documented instances of live specimens being brought to the surface have occurred when deep-sea fishing vessels operating off Japan or Portugal hauled them up in nets.
When a frilled shark does surface, it typically does not survive long. The dramatic change in pressure and temperature causes rapid stress and organ failure. Most specimens documented by marine biologists are either dead when recovered or die within hours of capture. This makes studying the species difficult and means much of what we know comes from examining dead specimens and analyzing stomach contents.
Reproduction and Life Cycle
The frilled shark's reproductive cycle is among the slowest in the shark world. Females are ovoviviparous, meaning they carry developing pups inside their body until they are ready to be born. The gestation period lasts approximately three and a half years—longer than any other known shark species. A single litter typically contains between 2 and 12 pups, each born at around 12 inches long.
This extremely slow reproduction rate means the population cannot recover quickly from overfishing or other population pressures. If frilled sharks are caught in fishing nets at rates higher than they can reproduce, the population will decline. The species' deep-sea habitat provides some protection from commercial fishing, but deep-sea trawling operations do occasionally catch them as bycatch.
Evolutionary Significance and Scientific Interest
The frilled shark is a "living fossil" in the truest sense. Its body plan has remained essentially unchanged for approximately 80 million years, making it a direct link to the sharks that swam alongside dinosaurs. Scientists study frilled sharks to understand how ancient sharks were built and how they hunted. The species represents an evolutionary strategy that has proven successful enough to persist through multiple mass extinctions and dramatic changes in ocean chemistry and temperature.
The frilled shark's primitive features—including its simple tooth structure, flexible jaw, and slow metabolism—suggest what early sharks may have been like. By studying this species, marine biologists gain insight into shark evolution and the adaptations that allowed sharks to dominate ocean ecosystems for over 400 million years. Every specimen recovered provides new data about deep-sea ecology and the limits of animal adaptation.
Conservation Status and Fishing Pressure
The frilled shark is not currently listed as endangered, but this reflects a lack of data rather than a healthy population. The species is caught occasionally in deep-sea fishing nets, particularly those targeting other species like grenadiers and rattails. Because frilled sharks reproduce so slowly and live in remote depths, even modest levels of bycatch could have significant population effects over time.
Most deep-sea fishing operations do not specifically target frilled sharks, and the species' remote habitat provides some natural protection. However, as deep-sea fishing expands into new areas and deeper waters, the risk of increased bycatch grows. The International Union for the Conservation of Nature (IUCN) has not formally assessed the species' conservation status, meaning there is no official population estimate or trend data available.
Frequently Asked Questions
Is the frilled shark dangerous to humans?
No. Frilled sharks live at depths where humans cannot survive without specialized equipment, and they are not aggressive toward humans. There are no documented attacks on people. The species is so rarely encountered alive that the question is largely theoretical.
How long do frilled sharks live?
The lifespan is unknown because no frilled shark has been kept alive in captivity long enough to determine natural lifespan. Based on their slow metabolism and deep-sea habitat, scientists estimate they may live several decades, but this is speculation rather than confirmed data.
Can frilled sharks survive in aquariums?
No. The extreme pressure and temperature changes required to bring a frilled shark to the surface cause fatal stress. Even if one survived the journey, maintaining the precise cold temperatures and pressure of the deep ocean would be technically impossible in any existing aquarium facility.
Why do frilled sharks have so many teeth?
The 300 teeth are arranged in rows that work together to grip and hold prey that might otherwise escape. In the dark depths where the frilled shark hunts, prey is unpredictable and often struggles violently. The multiple rows of teeth ensure a secure grip on slippery squid and fish.
Are frilled sharks related to other deep-sea sharks?
Yes, but distantly. The frilled shark belongs to its own family, Chlamydoselachus, which diverged from other shark lineages millions of years ago. Other deep-sea sharks like sixgill sharks and goblin sharks are more closely related to modern sharks than the frilled shark is.