# Hammerhead Shark (*Sphyrnidae*)

> Hammerhead sharks are a family of coastal and open-ocean sharks (Sphyrnidae) instantly recognised by the flattened, hammer-shaped head, or cephalofoil, that spreads their eyes and sensory organs wide apart. Species range from under a metre to more than 6 m long, with large individuals weighing around 230 kg. They swim through warm seas worldwide, hunting fish, squid and rays, and can live 20 to 30 years or more. The great hammerhead is listed as Critically Endangered.

- **Category:** Fish
- **Conservation status (IUCN):** Critically Endangered
- **Range:** Warm coastal and open waters worldwide, in temperate and tropical seas of all major oceans.
- **Canonical page:** https://globalanimalguide.org/animals/hammerhead-shark/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Chondrichthyes
- **Order:** Carcharhiniformes
- **Family:** Sphyrnidae
- **Genus:** Sphyrna

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Sphyrnidae (family) |
| Diet | Carnivore |
| Habitat | Warm coastal and open oceans worldwide |
| Lifespan | 20–30 years or more |
| Length | 0.9 m to over 6 m by species |
| Top speed | Around 40 km/h (25 mph) in bursts |
| Conservation status | Critically Endangered (great hammerhead) |

## The hammer-shaped head

The wide, flattened head that gives these sharks their name is called a cephalofoil, and it is more than an odd silhouette. Spacing the eyes far apart gives the shark a broader field of vision, while the underside is packed with electroreceptors called ampullae of Lorenzini that detect the faint electrical signals of buried prey. Sweeping the head from side to side lets a hammerhead scan the seabed like a metal detector. The shape also acts as a hydrofoil, helping the shark bank and turn sharply as it swims.

## Hunting and diet

Hammerheads are carnivores that feed on bony fish, squid, octopus, crustaceans and other sharks, but they are best known for hunting stingrays. A hammerhead will pin a ray to the seabed with the edge of its head, then pivot to take bites from the disc. Many individuals seem largely unbothered by the venomous barbs of their prey, and rays recovered from their stomachs are sometimes studded with spines. Larger species hunt alone, cruising close to the bottom where their electrical sense works best.

## Size and species

The family Sphyrnidae contains around nine species, and they vary enormously in size. The small bonnethead reaches under a metre, while the great hammerhead can exceed 6 m and weigh in the region of 230 kg, making it one of the largest predatory sharks. The scalloped and smooth hammerheads fall between these extremes. Despite their formidable appearance, hammerheads pose little danger to people, and unprovoked bites are very rare.

## Where they live

Hammerheads swim through warm temperate and tropical waters around the world, along coastlines, over continental shelves and out into the open ocean. They are found from shallow lagoons and coral reefs to depths of several hundred metres. Some species, notably the scalloped hammerhead, gather in large schools around seamounts and offshore islands, particularly by day. These aggregations can number in the hundreds and are a famous sight for divers.

## Reproduction

Hammerheads give birth to live young rather than laying eggs, nourishing the developing pups through a placenta-like connection inside the mother. Litters range from around a dozen to more than 40 pups depending on the species. The newborns are miniature versions of the adults, with heads that are more rounded at birth and flatten as they grow. Coastal nursery areas in shallow water shelter the young from larger predators during their vulnerable first months.

## Why the great hammerhead is Critically Endangered

The great hammerhead is listed as Critically Endangered by the IUCN, and several other hammerhead species are also threatened. Their large fins are highly valued in the shark-fin trade, and the sharks are frequently caught both deliberately and as bycatch in commercial fisheries. Hammerheads are especially vulnerable because they are slow to mature and produce relatively few young. They also suffer very high stress levels when hooked, so many die even when released.

## Frequently asked questions

### Why do hammerhead sharks have such strange heads?

The wide, flattened head, called a cephalofoil, spreads the eyes and electrical sensors far apart. This gives the shark a wider field of vision and a better ability to detect prey hidden in the sand. The shape also helps the shark turn quickly as it swims.

### Are hammerhead sharks dangerous to humans?

Hammerheads look intimidating but rarely pose a threat to people. Unprovoked bites are extremely uncommon, and most encounters involve the shark simply swimming away. Only the largest species could realistically injure a swimmer, and they show little interest in humans.

### How big do hammerhead sharks get?

Size varies greatly by species. The small bonnethead stays under a metre, while the great hammerhead can exceed 6 m and weigh around 230 kg. This makes the great hammerhead one of the largest predatory sharks in the ocean.

### What do hammerhead sharks eat?

Hammerheads are carnivores that eat fish, squid, octopus, crustaceans and other sharks. They are particularly known for hunting stingrays, which they pin to the seabed with their broad heads. They often appear immune to the rays' venomous barbs.

### How long do hammerhead sharks live?

Hammerheads are long-lived sharks, typically reaching 20 to 30 years and sometimes more. Their slow growth and late maturity are part of why overfishing has hit their populations so hard, as they cannot replace their numbers quickly.

### Why are hammerhead sharks endangered?

The great hammerhead is Critically Endangered, mainly because of the shark-fin trade and heavy accidental capture in fisheries. Hammerheads mature slowly and have small litters, so populations recover slowly. They also die easily from the stress of being hooked, even when released.

## Sources

- Rigby, C. L. et al. (2019). Sphyrna mokarran. IUCN Red List of Threatened Species.
- Compagno, L. J. V. (2001). Sharks of the World. FAO Species Catalogue for Fishery Purposes.
- [Froese, R. & Pauly, D. (eds.). FishBase — Sphyrna.](https://www.fishbase.se/)

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Source: Global Animal Guide (https://globalanimalguide.org/animals/hammerhead-shark/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.