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Researchers Watch For Effects of Oil on the Gulf's Endangered Behemoths

7 July 2010 5:29 pm
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In the Gulf of Mexico, oil has fouled a key habitat of one of the most impressive creatures on Earth: the sperm whale, the world's largest toothed whale. A group of about 2000 of these whales, which are listed as endangered in the United States, regularly ply the continental shelf from Texas to Florida. The behemoths—males can grow to 16 meters and weigh as much as 40,000 kilograms—can dive to depths of more than 1000 meters to feed, staying there for up to an hour at a time.

Now the National Oceanic and Atmospheric Administration has launched a suite of studies to track how oil might affect Gulf of Mexico sperm whales over the next few months. These studies will include tissue sampling, population surveys, tagging, and several types of acoustical monitoring. One of the lead investigators is Bruce Mate, a cetacean ecologist at Oregon State University's Hatfield Marine Science Center in Newport. His team will tag two dozen whales with radio transmitters, enabling researchers to watch for changes in their movements and behavior. Another is Christopher Clark, a bioacoustician at Cornell University, who is overseeing the deployment of 22 microphone units to the gulf's bottom. These units will record the calls and echolocation clicks of sperm whales and Bryde's whales over the next 100 days, providing an initial picture of how the whales are responding to the oil. ScienceInsider spoke with Mate and Clark separately about their projects and compiled their answers.

Q: Where in the gulf do sperm whales like to hang out?
B.M.:
That makes it sound recreational. Most of these animals are working pretty hard, feeding on deep-water squid. ... Some live way off shore, but the ones I have studied prefer the continental slope area [at depths from 500 meters to 2000 meters], and that extends along the entire northern bound of the gulf. ... The area of the spill is one of the more preferred areas.

Q: Why are sperm whales in danger from being oiled?
C.C.:
Sperm whales have high metabolisms. They have to eat all the time. This puts them in greater risk because they're diving through the water column. ... They dive deeply, so they would be diving vertically through all these different layers of stuff.

Q: How do you tag a sperm whale?
B.M.:
You're in an inflatable boat 24 feet long. ... You very carefully drive up on the animals [while they're surfacing]. This isn't a rodeo, this is slow. ... We basically mosey up to them. ...The radio transmitter goes on the form of a dart—it's a subdermal tag, and all that's showing at the surface is the antenna. ... The dart would fit through my wedding band, and it's a bit longer than your Bic pen. It's coated in part with long-term dispersant antibiotic, so it fights against bacterial infections.

Q: What might happen to a whale if it comes in contact with oil?
B.M.:
Probably the main concern is respiratory, particularly close to the spill site where there are a lot of volatiles. It's probably the same concern people have around there. ... If there's inhalation, there is concern about what that might do in the lungs.

Q: What will you learn from tagging sperm whales now?
B.M.:
We did 5 years of work here from 2001 to 2005 and tagged 57 sperm whales. We established their home ranges, their core areas, looked at the variability between individuals in their movement and surfacing rate. ... We've got a baseline here that's really unprecedented. There isn't a sperm population now anywhere in the world [whose movements are] better known. We're very, very fortunate.

We'll be looking at how [the newly tagged whales] do over time, what they do over time, compared to the control group. ... Can they detect [oil] and avoid it? Do the characteristics of their movements change dramatically? The size of home range and core areas may shift, as well as the time they spend at the surface. ... It will take some time once we have the whales tagged to see if there are significant changes.

Q: Describe how you'll do the acoustical studies.
C.C.:
What we've been installing for the last 3 weeks off a NOAA ship are large pumpkin-sized recording systems. ... They drop down to the bottom of the ocean, and they're completely autonomous. After 100 to 110 days, we go back with a ship and lower a loudspeaker and play an acoustic code. Each pumpkin has its own acoustic code it's listening for, and that triggers the unit to come back to the surface.

Q: Where will these units be?
C.C.:
The depth is anywhere from 200 meters to 1500 meters, right along that break where the continental shelf ... goes down into deep water. ... That's the restaurant, the place where they congregate. We're deploying a network that will, once it's in, go all the way from western Louisiana ... to the tip of Florida. ... Right now, we're slated to have 22 deployed, separated by anywhere from 20 to 30 miles [32 to 48 kilometers] ... covering a 400- to 450-mile [640- to 720-kilometer] stretch.

Q: What will you learn from the recordings?
C.C.:
First, [the recorded sounds] will tell you, we've got a whale of this particular species [here]. Next, we'll see if we can figure out how many are there. ... [We'll be able to] look at this whole strip ... and see the [numbers of] sperm whales and Bryde whales and bottle-nosed dolphins. ... [It will be] like a sea-surface temperature map, except it's whale occurrence. ... [The difficult part] is where you're trying to say, ... is there any relationship of that variability [in numbers of whales] with the stressor. For example, we might ask, "We should have seen them in this gorge by October and November, but we're not seeing them this year, and is that related?"

This is a [rapid] response right now—let's get out and get something in the water to start. ... But this can't be a 3 month wunderkind. … After we get these [recordings] out of the water, we'll be thinking about what we're going to do next.

*The original version of this item incorrectly identified the location of Oregon State University facility where Bruce Mate works. It is in Newport.

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