Lagenorhynchus cruciger, Hourglass Dolphin [+]

Kingdom Animalia Phylum Chordata Class Mammalia Order Cetacea Family Delphinidae Genus Lagenorhynchus species: Lagenorhynchus cruciger [+ITIS +WoRMS]

← Previous Photo | Next Photo →

Description & Behavior

The hourglass dolphin, Lagenorhynchus cruciger (Quoy and Gaimard, 1824), is a small cetacean with a stocky body and a characteristic black and white color pattern resembling an hourglass, hence the common name. These markings vary greatly among individuals. The hourglass dolphin, based on the few records that exist for this species, reaches an average of 1.57 m in length in females, 1.75 m in males. Weight data is also scarce for this species, however the few weighed were between 74-94 kg. They are mostly black in color with 2 white patches. The first patch begins behind the beak, extends over the eyes, widens to the hourglass shape, then tapers at the dorsal fin. The second patch begins mid-flank at the dorsal fin, widens toward the posterior end, and tapers at the tailstock. The ventral surface is mostly white. Hourglass dolphins have conical teeth, 26-34 teeth in the upper jaw and 27-35 teeth in the lower jaw. This species is the only small cetacean with a dorsal fin found below the Antarctic convergence making them easily distinguishable from other dolphin species. Above the convergence, they may be confused with dusky dolphins and Peale's dolphins.

The hourglass dolphin is a gregarious species that forms schools of 1-100 animals. The average school size is 7 individuals. In studies of the social habits of hourglass dolphins, only 3 calves were identified out of a group of 1,634 individuals. This may be due to a winter birthing season when the weather prevents studies from being conducted or due to females protecting their calves by avoiding research vessels. Hourglass dolphins have been observed associating with fin whales, sei whales, minke whales, Arnoux's beaked whales, southern bottlenose whales, long-finned pilot whales, orca (killer whales), southern right whale dolphins, and there is one sighting of an hourglass dolphin traveling near southern right whales. Lagenorhynchus cruciger has also been observed playing around large whales and appear to enjoy bow riding the waves of these much larger animals. In terms of human interaction, hourglass dolphins enjoy bow riding and traveling with large marine vessels as well.

The lifespan of hourglass dolphins is not known, but is likely similar to other members of its genus such as the Atlantic white-sided dolphin, which lives up to 27 years and the Pacific white-sided dolphin, which lives up to 46 years.

World Range & Habitat

The hourglass dolphin, Lagenorhynchus cruciger, is found throughout the cold open waters of the Southern Ocean between 43°-67°S and are widely distributed throughout their range. They're found in waters ranging between -0.3-7°C, although they prefer colder surface temperatures and are most commonly found in waters between 0.1-0.3°C. The warmest recorded surface temperature associated with this species was 13.4°C. It is thought that the hourglass dolphin follows cold-water currents such as the West Wind Drift. In the summer months they are more common in cooler southern waters and in winter they appear to move further north. The farthest northern sighting of the hourglass dolphin was near Chile 33°40'S.

» GBIF occurrence data in Google Earth [Tips] | Ocean Biogeographic Information System (OBIS) (World Distribution) [about]

Feeding Behavior (Ecology)

The hourglass dolphin, Lagenorhynchus cruciger, feeds primarily on fish, squid, and crustaceans. They have been observed feeding in large groups near the surface, which attracts sea birds and helps research vessels find groups of hourglass dolphins.

Life History

Based on limited data, female hourglass dolphins, Lagenorhynchus cruciger, are thought to reach sexual maturity at a little over 1.83 m in length, 2 males measuring 1.74 m and 1.87 m were sexually mature. No data are available on the reproductive habits of the hourglass dolphin, however other female members of the genus Lagenorhynchus, such as Lagenorhynchus obscurus give birth every 28.7 months to calves measuring 0.90-1.25 m in length, have a gestation period of about 12.9 months, and give birth between August-October. Lagenorhynchus obscurus calves are nursed for about 12 months, Lagenorhynchus acutus for about 18 months.

Conservation Status/Additional Comments

The population of hourglass dolphins, Lagenorhynchus cruciger, is >140,000. This species is not listed threatened or endangered. They are not hunted commercially and conflicts with fisheries such as entanglement and being caught as bycatch do not pose a great threat due to the remote habitat. There have, however, been reports of entanglement and stranded individuals were found with net scars.