Hourglass Dolphin Facts

Scientific Name: Lagenorhynchus cruciger

Hourglass dolphins
Hourglass dolphins.

Richard McManus / Getty Images

Hourglass dolphins are part of class Mammalia and are found throughout the cold Antarctic waters, though they have been spotted as far north as the coasts of Chile. Their generic name, Lagenorhynchus, is derived from the Latin word for “flagon nosed” because animals in this genus have stubby rostrums. Their Latin name cruciger means “cross-bearing” for the hourglass pattern on their backs. Hourglass dolphins are known for their unique black and white pattern and are the only species of dolphin with dorsal fins found below the Antarctic convergence point.

Fast Facts

  • Scientific Name: Lagenorhynchus cruciger
  • Common Names: Hourglass dolphin
  • Basic Animal Group: Mammal
  • Size: Up to 6 feet long
  • Weight: Up to 265 pounds
  • Life Span: Unknown
  • Diet: Fish, squid, crustaceans
  • Habitat: Antarctic and sub-Antarctic ocean waters
  • Population: Estimated 145,000
  • Conservation Status: Least Concern
  • Fun Fact: These mammals are found in waters ranging from 32 to 55 degrees Fahrenheit.

Description

Hourglass dolphin
Hourglass dolphin illustration. Dorling Kindersley / Getty Images

These creatures’ bodies are mostly black with one patch of white that stretches from the beak to the dorsal fin and another that starts at the dorsal fin and connects at the tail. This pattern of white on their bodies creates an hourglass shape, earning them the name of hourglass dolphins. Their bodies are short and stocky, and their dorsal fins are broad at the base and hooked on the top. Adult males have been spotted with “swept-back” dorsal fins. Additionally, they have conical teeth, with 26 to 34 teeth in the upper jaw and 27 to 35 in the lower jaw.

Habitat and Distribution

Range of the Hourglass Dolphin
Range of the Hourglass Dolphin. Wikimedia Commons / Creative Commons Attribution-Share Alike 3.0 Unported / 

These dolphins live in the Antarctic and sub-Antarctic waters. They are the only dolphin species with a dorsal fin that lives below the Antarctic convergence point. They are thought to have north-south migration patterns following the West Wind drift, living in the southern cool waters in the summer and moving north in the winter months. The farthest extent of their northern migration is currently unknown.

Diet and Behavior

Due to their cold and remote habitat along with their natural timidity, direct observation of the diet, habits and behaviors of the hourglass dolphin can be quite difficult. This limits the amount of information that scientists know about them. What scientists do know has come from limited studies of a small number of hourglass dolphins.

Not much is known about the hourglass dolphin's diet, but they have been spotted eating crustaceans like shrimp, squid, and small fish. They have also been seen feeding among plankton blooms. Because these creatures feed near the surface, they also attract seabird congregations, which allows researchers to find and observe these creatures.

Hourglass dolphins are social creatures and commonly travel in groups of around 10 individuals, but can be found in groups as large as 100 individuals. They spend most of their time in deep waters but can be found closer to land in shallow bays and islands. They feed among other cetaceans, such as pilot and minke whales. Scientists have also spotted them traveling with pilot and minke whales, as well as right whale dolphins and killer whales.

Hourglass dolphins can reach speeds of up to 14 mph, often making a lot of spray as they surface to breathe. They love to play in the waves generated by larger animals and also enjoy riding in the waves created by boats. They are thought to migrate via the West Wind Drift to warmer waters during the winter months.

Reproduction and Offspring

Hourglass Dolphins in Drake Passage
Hourglass dolphins in Drake Passage. Wikimedia Commons / Attribution-Share Alike 3.0 Unported / Lomvi2

Not much is known about the mating behavior of the animals. Males and females reaching sexual maturity or attaining sexual maturity are 70 inches and 73 inches respectively, but their ages of sexual maturity are not known. The average gestation period for females is around 12 months.

Based on the behavior of other species in the genus, hourglass females are thought to only give birth in the winter months from August to October, averaging just one calf per birth. The calf is as small as 35 inches at birth. These young are able to swim with their mothers at birth and are nursed by her for 12 to 18 months before being weaned off her milk.

Conservation Status

Hourglass dolphins are designated as Least Concern by the International Union for Conservation of Nature (IUCN). Population trends are relatively unknown and there are currently no identified threats. Scientists speculate that this is because these creatures live so far away from human society. However, scientists are concerned that global warming could raise sea temperatures and disrupt their migration patterns.

Sources

  • Braulik, G. "Hourglass Dolphin". IUCN Red List Of Threatened Species, 2018, https://www.iucnredlist.org/species/11144/50361701#population.
  • Callahan, Christopher. "Lagenorhynchus Cruciger (Hourglass Dolphin)". Animal Diversity Web, 2003, https://animaldiversity.org/accounts/Lagenorhynchus_cruciger/.
  • "Hourglass Dolphin". Oceana, https://oceana.org/marine-life/marine-mammals/hourglass-dolphin.
  • "Hourglass Dolphins". Marinebio Conservation Society.Org, https://marinebio.org/species/hourglass-dolphins/lagenorhynchus-cruciger/.
  • "Hourglass Dolphin". Whale & Dolphin Conservation USA, https://us.whales.org/whales-dolphins/species-guide/hourglass-dolphin/.