11 July 2009

Sonar gives whales the bends

ResearchBlogging.orgThe New York Times Magazine has a cover article on human-whale interactions, with special attention to whales' cognitive, communicative, and social abilities. It's pretty neat stuff, and I started reading it with the intention of posting something about it with a title along the lines of "So long, and thanks for all the fish." But, rather than all the whales-as-fellow-sentients stuff, this early aside about the effects of navigational sonar on whales is what actually caught my attention:
The results of the examinations performed on the [beached] Canary Islands whales, however, added a whole other, darker dimension to the whale-stranding mystery. In addition to bleeding around the whales’ brains and ears, scientists found lesions in their livers, lungs and kidneys, as well as nitrogen bubbles in their organs and tissue, all classic symptoms of a sickness that scientists had naturally assumed whales would be immune to: the bends.

A beached Cuvier's beaked whale.
Photo by fiat luxe.
That's right -- the bends. As in the harmful effects of a rapid decrease in atmospheric pressure associated with rising too rapidly from deep water to the surface, which can cause gasses dissolved in the bloodstream to come out of solution and form bubbles. Human divers take precautions to avoid "decompression sickness," but it's surprising to find that mammals who spend their lives underwater should run the same risk. The idea is that navigational sonar is so irritating or disorienting that it drives whales to the surface faster than is safe, and often kills them.

Naturally, I went to Google Scholar: although the original report of "gas-bubble lesions" in beached whales [$-a] generated some controversy [PDF] at first, the most recent review I could find seems to accept the diagnosis [PDF]:
Although no potential mechanisms can be eliminated at this stage, we highlight gas bubble formation mediated through a behavioural response as plausible and in need of intensive study.
The review cites a number of documented whale strandings closely associated with offshore naval maneuvers, and calls for, among other things, re-evaluating past records of strandings with an eye to whether sonar use may have been involved.

This, of course, is what prompted conservation groups to sue the U.S. Navy for investigation of the environmental impact of navigational sonar; the Supreme Court eventually ruled, regrettably, that the Navy's need for sonar use in training exercises trumps the requirements of federal environmental law. I'd followed the story when it originally unfolded, but never really understood exactly how whales were hurt by sonar -- I think I assumed they were just sort of driven onto beaches. So, my totally non-marine biologist, non-mammalogist reaction: wow. And, ugh.


Cox, T.M., T.J. Ragen, A.J. Read, E. Vos, R.W. Baird, K. Balcomb, J. Barlow, J. Caldwell, T. Cranford, & L. Crum (2005). Understanding the impacts of anthropogenic sound on beaked whales. J. Cetacean Res., 7 (3), 177-87

Jepson, P., Arbelo, M., Deaville, R., Patterson, I., Castro, P., Baker, J., Degollada, E., Ross, H., Herráez, P., Pocknell, A., Rodríguez, F., Howie, F., Espinosa, A., Reid, R., Jaber, J., Martin, V., Cunningham, A., & Fernández, A. (2003). Gas-bubble lesions in stranded cetaceans Nature, 425 (6958), 575-576 DOI: 10.1038/425575a

Piantadosi, C., & Thalmann, E. (2004). Pathology: Whales, sonar and decompression sickness Nature, 428 (6984) DOI: 10.1038/nature02527a

1 comment:

  1. This is very sad to hear about; but then there's little our species does technologically that doesn't deleteriously affect some other species somewhere, somehow.