Threats to Sperm Whales Continue
Losses From Whaling, Net Entanglement, Ship Strikes and Ocean Noise
Mar 26, 2008
The sperm whale (Physeter macrocephalus), made famous by the attack on the whaling ship Essex, which was fictionalized by Herman Melville in Moby Dick, is still struggling to survive. The whales are subject to pollution, being hit by ships and entanglement in fishing gear. With their dependence on sound for feeding, sperm whales are particularly sensitive to ocean noise issues, leading to endangered status for some populations.
Sperm Whales and the Whaling Industry
Between 1800 and 1987 over 400,000 sperm whales were taken by the whale hunt. In 1987 the International Whaling Commission's moratorium on whaling ended this slaughter. But this long-lived, slow reproducing whale has been particularly slow to recover.
It is speculated that the taking of large numbers of adult male sperm whales for ambergris and spermaceti may have had a significant impact on this species. At the same time the taking of adult females may have affected the whales' complex social structure, resulting in lower overall survival.
Japanese "scientific whaling" for sperm whales was initiated in 2000 despite the slow recovery of the species from earlier whaling activities. The few animals taken in traditional Indonesian hand harpooning likely do not heavily impact the species' overall population; however there is some evidence that illegal sperm whale hunting is still occurring in other areas.
Predators and Pollution
The sperm whale, although subject to some predation would not likely be threatened without human created problems. Orca, or killer whales, and large sharks are known to prey on sperm whales. Pilot whales have been known to harass them but it is not clear whether they are a real threat to the species.
Ocean pollution from PCBs, PBDEs, Polycyclic Aromatic Hydrocarbons (PAHs), and other stable pollutants may be affecting the health and behavior of sperm whales but further data is needed on this.
Ship Strikes, Net Entanglement and Ocean Noise
Sperm whales are vulnerable to being hit by large ocean vessels. They tend to spend time resting on the surface and can be difficult to see from the bridge of a ship. Ghost nets, walls of fishing gear torn from factory trawlers, entangle sperm whales. These two dangers seem to be a particular problem in the Mediterranean but that may be a reflection of the size of the sea which results in whales washing ashore or being easily spotted. A sperm whale similarly affected in the open ocean might be scavenged by other wildlife and disappear without being found.
The problem of ocean noise is compounded for the sperm whale. It uses sound to capture its prey, the giant squid. Interference from sonar testing and other underwater noise may reduce their ability to feed. So, although sperm whale numbers are reasonable worldwide, it will be important to reduce human impact on their ocean environment if the species is to recover.
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