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Background Information
The sperm whale (Physeter macrocephalus) was originally named because the contents of the spermaceti organ were mistaken for semen. Although it is actually oil and not sperm, the name is still used today. The largest of the toothed whales (Odontocete), the sperm whale can be easily identified by its square-like head which is massive in proportion to its body and contains the largest brain on Earth (Whitehead, 2003). Sperm whales are generally grayish or brownish and covered in a somewhat wrinkled skin with many scratches and scars. Their underside and areas near the mouth and genitals are light gray to white (Sperm Whale, 2005, April 4). They are sexually dimorphic with males averaging 15 meters and 45 tons and females only 11 meters and 20 tons (Martin and Reeves, 2002). Flukes can be as wide as 16 feet. They have one blowhole on the left side at the front of the head (Sperm Whale, 2005, April 4). Sperm whales live in all of the oceans of the world with the exception of the coldest extremes (Minasian et al, 1984). They are known to dive to depths of 3,000 feet and can last about an hour without surfacing (Sperm Whale, 2005, April 4). The average lifespan is 70 years (Minasian et al, 1984).
Unfortunately, because sperm whales live in the vast ocean and spend much of their time at great depths, many facts about this animal are unknown. According to Hal Whitehead (2003) “human eyes and artificial sensors have so far given us little more than a glimpse, and not a very systematic glimpse, of the second-to-second details of the animals’ social lives.”
Photo courtesy Ken Balcomb-Center for Whale Research
Threats
Their only natural predator is the killer whale, although they are occasionally attacked by pilot and false killer whales. Sadly, their main predator is humans, who have been hunting them since about 1712 (Whitehead, 2003). Whaling, especially from the Japanese, is still the clearest threat. Whaling is hard to control and although Japanese whalers only killed 13 sperm whales in 2000 and 2001, they hope to continue to actively hunt and increase the number of whales they bring in (Whitehead, 2003). Noise pollution is a threat to sperm whales because they are dependent on sound for so many aspects of survival, most importantly locating their prey. Whales have been known to become silent, stop foraging, and eventually starve probably as a result of shipping, seismic exploration, drilling, and sonar (Weilgard and Whitehead, 2001). They can also be killed by colliding with ships, swallowing plastic debris, getting caught in fishing gear, and ingesting toxic chemicals (Whitehead, 2003).