Hourglass dolphin

The hourglass dolphin (Cephalorhynchus cruciger) is a small dolphin that lives in the cold waters far from shore around Antarctica and nearby islands. These dolphins are often spotted from ships traveling through the Drake Passage, but they can be found all around the southern part of the world.

Scientists first described this dolphin as a new species in 1824. Two explorers, Jean René Constant Quoy and Joseph Paul Gaimard, used a drawing made during a trip in the South Pacific in 1820 to identify it. It is special because it was the only dolphin kind ever officially named just from drawings and stories, not from a real animal specimen.

Description

The hourglass dolphin has a black back and a white belly, with white patches on the sides that sometimes have dark grey areas. These patches and a thin white strip between them create an shape that looks like an hourglass, which is how the dolphin got its name. The scientific name cruciger refers to a black area that looks a bit like a cross from above.

In the waters where it lives, this dolphin is easy to recognize. It is often confused only with the southern right whale dolphin, but the hourglass dolphin has a tall, curved dorsal fin, while the southern right whale dolphin does not have one at all. This makes it very unlikely for the two to be mistaken for each other.

An adult male hourglass dolphin is about 1.8 meters long and weighs over 90 kilograms. Juvenile females are a bit smaller, ranging from 1.6 to 1.8 meters. Even though they are small, these dolphins are very fast and agile. Females are thought to carry their babies for about 12.9 months and give birth between mid to late July through October.

An hourglass dolphin has between 26 to 34 teeth in the top jaw and 27 to 35 teeth in the bottom jaw. Like all dolphins, they use echolocation to find their food. However, there have been no confirmed sightings of very young dolphins, so details about their color, size, and what they eat are still unknown.

Geographic range and distribution

The hourglass dolphin lives in a wide area around Antarctica, from near the Antarctic pack ice to about 45 degrees south. People have most often seen these dolphins in the Southern Ocean, especially near the south of New Zealand, around the South Shetland Islands, and off Tierra del Fuego, Argentina. They have also been spotted as far north as 36 degrees south in the South Atlantic and 33 degrees south near Valparaíso, Chile.

Habitat

The hourglass dolphin is a dolphin that lives only in Antarctic waters. It likes cold water and is usually found near the surface where the temperature is between -0.3°C and 7°C. The warmest water these dolphins have been seen in was 14°C.

These dolphins move to follow the seasons. In the summer, they travel farther south, and in the winter, they move farther north.

Behavior

Hourglass dolphins are often seen in small groups of up to 10 to 15 individuals, but sometimes groups as large as 100 have been observed. They share areas where they find food with other sea animals such as pilot whales, minke whales, and southern right whale dolphins. They are often seen riding the waves created by ships and large whales like fin whales. Scientists have also seen them with southern bottlenose whales, orcas, and Arnoux's beaked whales.

Studies of the few hourglass dolphins that have been examined show they eat mantis shrimp, polychaete worms, and various types of squid and small fish. Scientists believe these dolphins live about as long as Atlantic white-sided dolphin and Pacific white-sided dolphin dolphins, which is around 27 to 46 years.

Taxonomy

The hourglass dolphin was first named Delphinus cruciger by scientists Quoy and Gaimard in 1824 after they saw one in 1820. Over time, scientists used many different names for this dolphin. In 2025, after studying the dolphin's genes, scientists decided it belonged to the genus Cephalorhynchus, which also includes Hector's dolphin.

Quoy Gaimard Lagenorhynchus Cephalorhynchus Sagmatias Hector's dolphin

Population status

Scientists counted these dolphins in surveys during 1976–77 and 1987–88. They estimated there were about 144,300 hourglass dolphins, based on sightings in January 1977 and January 1988 in northern Antarctic waters. Though their numbers have gone down a little since 1988, these dolphins are not considered endangered.

Conservation status

The hourglass dolphin is protected by an agreement called the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region, which helps keep their homes safe [Pacific Cetaceans MOU]. They are also listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning trade of these animals is controlled.

Even though scientists haven’t studied them a lot, there are no big dangers known for hourglass dolphins. Because of this, they are considered to be in the safest group on the IUCN Red List, called Least Concern.