Hourglass Dolphin

Topics: Temperature, Dolphin, Thermodynamics Pages: 2 (384 words) Published: March 3, 2013
Name: Hourglass Dolphin
Location: They live in the Antarctic but they go as far as New Zealand. Description: The hourglass dolphin is most easily recognized by its unique white "hourglass" marking against a largely black body. Its underside is also white, though both sides of the fluke are black. The two white patches that make up the hourglass shape are often connected by points or at least a thin white line, though in some individuals the two white patches do not touch. The dorsal fin is easily notable and concave, though in some individuals it becomes sharply hooked backwards. Pectoral flippers may also have a definite "elbow" and curve back sharply on their leading edge.

Diet & Behaviour: Stomach contents of stranded hourglass dolphins have revealed that they feed on small fish, crustaceans, and squid. Usually found in groups of 7-10, these dolphins are not at all shy when encountered and often bow ride, even approaching slower moving vessels. Sometimes they'll spin while riding the waves. When they bow ride, they swim in long low leaps and may resemble a porpoising penguin. They may also create a "rooster tail" of spray when surfacing to breathe at high speeds.

Habitat: The hourglass dolphins 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.

Place in food chain:

Life Expectancy: Since the hourglass dolphins are rarely seen...
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