Whalebones show damage from diving.

Long-lived sperm whales typically develop bone damage resembling that observed in human divers who surface too quickly or dive too frequently, new research indicates. Marine mammals that dive throughout their lives hadn't been known to be susceptible to such a hazard.

Biologists Michael J. Moore and Greg A. Early of the Woods Hole Oceanographic Institute in Massachusetts made their discovery when they examined the museumhoused skeletal remains of 16 sperm whales.

In people, pitting of bones is often a sign of decompression sickness, which scuba divers can develop after experiencing pressure changes that cause bubbles of gas to form in the body. In mild cases, the condition can cause internal damage without producing symptoms. Extremely abrupt decompression can be fatal.

In their study, Moore and Early found extensive bone pitting in the largest and presumably oldest whales, and only calves were flee of the damage. This suggests that the animals accumulate decompression-related bone damage gradually as they live out their lives, the scientists suggest in the Dec. 24, 2004, Science.

Because whales appear to be vulnerable to decompression sickness, any influence that causes them to surface suddenly could cause lethal harm, Moore speculates.

Some past research suggests that the U.S. Navy's use of some forms of sonar has caused the deaths of marine mammals by prompting the animals to surface.--B.H.