Research Projects

Popups in the deep ocean: a new way to study whales

Whales of the deep ocean are not easy to study. They live far from shore and spend most of their lives deep under water. A great way around these problems is to use popup hydrophones.  These devices sit on the bottom of the ocean, recording sounds of the whales as well as the sounds of human activities.  On command, they popup to the surface and float. On one hand we can then learn when whales were near the popups and what they were doing, as whale sounds vary with their behaviour. On the other hand how affected they are by noise from ships or seismic operations?

We dropped popups in two locations and put them deeper, and left them longer, than anyone had before.
The Gully is a huge underwater canyon 200 kilometres off the coast of Nova Scotia.  It is the primary home of a small population of northern bottlenose whales (Hyperoodon ampullatus).  For twenty years we have studied them in a sailing boat during the summer months.  But what happens during the rest of the year, where are the whales when they are not in Gully? The sounds recorded from popups placed 1,000 metres down in the Gully, as well as in nearby, smaller, canyons, and left there for months, are giving us answers.

The other popup drop is on Kelvin Seamount even further from the west coast of North America.  The seamount is an underwater extinct volcano rising to about 1,000 metres beneath the surface. Seemingly, the surrounding Sargasso Sea has little life except floating sargassum weed.  Yet in this apparently unproductive environment we find the highest density of sperm whales (Physeter macrocephalos) recorded anywhere in the world.  Why?  Sounds from the Kelvin popups are giving us detailed long term information about this mystery.

Whales were heard frequently from the popups in both locations.  On Kelvin Seamount, the proportion of 2-minute sound segments containing sperm whales varied between 46% in spring and 16% in winter, and increased as the waters became more productive, although with a lag of one month.  It seems that the productivity in the area, while not very high, is sufficient to drive an ecosystem that supports the whales.  In the Gully, bottlenose whales were heard on 97% of 10-minute recording segments in winter, and 93% in summer, and also in two nearby canyons where we had dropped popups.  
The popups recorded not only the whales, but also ships and other sounds that humans put into the sea.  For instance, sounds from a seismic survey being carried out in the summer of 2007 were heard on both the popup on Kelvin Seamount, as well as that in the Gully, even though these were 700 kilometres apart.  The popup recordings emphasize the importance of their own sounds to the whales, as well as the pervasiveness of our human noise in the ocean.

“The device, known as a "pop-up," includes a microprocessor, hard disk for data storage, acoustic communications circuitry, and batteries, all sealed in a single 17-inch glass sphere. An external hydrophone is connected to the internal electronics through a waterproof connector. At the conclusion of a mission, the positively buoyant sphere separates itself from its anchor and "pops up" to the surface for retrieval.”
Quotation taken from http://www.birds.cornell.edu.