Scientists find marine mammals can suffer ‘the bends’

The bends is cause by nitrogen bubbles forming in the blood (Picture by Whit Welles)

WHALES and seals could suffer from the same sickness experienced by human divers, new research shows.

Scientists at the University of St Andrews have found evidence that marine mammals can suffer from ‘the bends’.

Until now, it has not been known whether sea mammals could suffer from the disorientating sickness, which can cause everything from skin rashes to death in extreme cases in humans.

The new study published today reviews evidence of bubble formation in the bodies of whales and seals that suggests the potential for decompression sickness, caused by the pressure experienced during deep sea diving.

The research also suggests that excessive human noise, such as exposure to military sonar, might cause disorientation in marine mammals, leading to them losing their natural defences and to succumb to the bends rather than avoid them.

Lead researcher Dr Sascha Hooker of the University of St Andrews said: “Decompression sickness, commonly known as ‘the bends’ is a serious problem for human divers, but the jury has been out as to whether marine mammals could get the bends or if it would be as serious for them.

“Unfortunately the technology doesn’t yet exist to measure what is going on physiologically inside a free-living whale during its descent to depths of over 1000 metres.

“However, our review of recent work on marine mammal diving physiology leads us to the conclusion that they could suffer from the bends in the same way that humans do.”


The clue to ‘the bends’ taking hold is the appearance of bubbles in the bodies of marine mammals.  Bubbles are caused by pressure-induced increases in nitrogen levels in the blood and body tissues, followed by depressurisation that causes nitrogen to come out as bubbles.

The research involved a team of experts from diverse fields including human diving medics, veterinary pathologists and experts in comparative animal anatomy, physiology, ecology and behaviour.

Dr Hooker added: “Our findings change the way we think about how marine mammals manage the problems of pressure when deep sea diving. The textbooks tell us that seals and whales can tolerate deep dives and rapid ascent without developing the nitrogen load that might lead to the bends.  We suggest that this is not the case for all species, and that they may balance their management of nitrogen against other physiological requirements, such as the need for oxygen or the need for circulation to keep warm.

“One concern is that these naturally evolving mechanisms may be stretched by human pressures.  An apparent threat to these animals, such as sudden high-levels of noise, could cause them to react; altering their dive trajectory or eliciting a fight-or-flight response – that causes them to exceed their normal coping mechanisms for the prevention of the bends.

“While the bends is rare under normal circumstances, excessive human noise or disturbance may cause a marine mammal to change its diving behaviour in ways that result in serious illness or injury.”


The research is published in Proceedings of the Royal Society B.