The whale brethalyzer

Today we went up the hill again to listen for the missing tag in vain. Bubby, the aerial camera, got a work out from the ship's tender (he needs more work) and the breathalyzer got an inshore trial. Then went offshore about 12 miles southeast of the Kaikoura Peninsula and found a whale in some large swells, but decided that the breathalyzer needed a calmer day for its first deployment. We were able to attach a tag, however.

Diving marine mammals live a life of dual constraints. One the one hand, they want to maximize their time underwater to increase foraging success and the number of prey captured. On the other hand, they need to return to the surface to replenish their oxygen stores, which they use to generate energy while underwater.

In a changing environment, where prey density may have been reduced either by overfishing or increasing temperature of surface waters, marine mammals may have to dive longer to catch enough food to survive. Consequently, oxygen management becomes the limiting factor in the time they can spend underwater and, consequently, the amount of food they can capture during each dive. For this reason, physiologists are interested in measuring the metabolic rate, or the rate of oxygen consumption, in marine mammals.

In smaller, captive species, physiologists can measure expired oxygen fairly easily and, from this, estimate the metabolic cost of longer dives. Measuring the oxygen consumption in large whales, on the other hand, has been a bit more difficult. To do this it is necessary to measure to volume of air exhaled in a unit of time and to determine the composition of the expired gas.

To measure the amount and composition of air a sperm whale exhales, we have to place a flow meter and gas analyzer directly over the animal's blowhole when it exhales. To do that, we have to come within a few meters of a while while it is at the surface—not an easy task when you are dealing with an animal that may weigh up to 40 tons that swims at one or two knots in an open ocean with varying swell.

Mike Morrissey, New Zealand Department of Conservation
wearing a helmet camera. (Luis Lamar, Advanced Imaging &
Visualization Lab, WHOI)

We have had the opportunity to learn how to approach these giants in kayaks from our colleague Mike Morrissey at the Department of Conservation. This approach first involved transporting a kayak close to a whale by small boat. After launching the kayak, we approached the whale from the side until we were within one or two meters, at which point we were going to extend a pole to measure and sample the exhaled air.

On the second day of the cruise, we practiced approaching a whale and came within four or five meters before the animal increased its speed and finally decided to dive. During the days that followed, we came closer but realized that managing electronic equipment and a six-meter carbon fiber pole while at the same time paddling next to a whale would minimize our chances of placing the flow meter over the blowhole successfully. Instead, we will attempt close encounters with the whales using one of the small boats. For this purpose, we have rigged one so that we can extend our reach with the precision we need to capture the exhaled gases. We are now waiting for calmer sea conditions so we can test our idea and possibly be the first who captures the exhaled gases of a sperm whale.

Micah Brodsky with the Mark 2 Whale Brethalyzer
(Luis Lamar, Advanced Imaging & Visualization Lab, WHOI)

To measure the volume of expired air we are using a custom-made flow meter, which we have named the whale breathalyzer. BRETHALYZER The breathalyzer is secured to the end of a carbon fiber pole and connected to a pressure transducer that measures gas flow. It also includes an oxygen and carbon dioxide analyzer, which measures the gas composition of the expired air.

The captured air will allow us to estimate the amount of oxygen consumed during the whale's previous dive and get a better picture of the work it to capture its prey. Once we have captured expired air from several whales, we can examine work effort using the DTAG data and create a better picture of how much energy it takes to capture a giant squid.

After fabricating several prototypes from a variety of materials, this second-generation prototype was designed and built out of carbon fiber. The experience, hard work and dedication of the folks mentioned below made it possible to take an idea and transform it into a completed prototype in a record five days.

Dr. Brodsky and Dr. Fahlman would like to thank Trevor and Penny Austin at PaxArms; and Andy, Davie, and Jenny from Davie Norris Boatbuilders.