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LatestPhoto
A Killer Whale (Orcinus Orca) approaches Odyssey.
Photo : Chris Johnson

April 7, 2004
Killer Whales - Encountering Transients
Real Audio
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Log Transcript

This is Genevieve Johnson speaking to you from the Odyssey on our final research leg in the Maldives.

Bob Pitman, a visiting scientist from the southwest Fisheries Center in La Jolla, California, is onboard hoping to sight, photograph and collect tissue samples from killer whales. However, in our final days of research, our hopes of finding them are beginning to fade.

Yesterday during lunch, we turned off the engine in order to drift and enjoy the calm, sunny conditions. As soon as the engine was cut, we detected dolphin clicks and whistles on the acoustic array (underwater microphone). Moments later, we sighted a group 500 meters ahead. Suddenly the dolphins erupted from the surface of the sea leaping clear of the water and 'running' at top speed. Something was chasing them. Bob turned to me and said - "we have killer whales."

Bob Pitman describes what happened next.

Bob Pitman - Field Biologist: Southwest Fisheries Center

    "Initially, we saw some splashing in the water and we knew that there were some dolphins. They seemed to be moving fairly leisurely across our bow. We started up the boat and started approaching them and they took off at high speed away from the boat. At the time, we thought they were Tursiops - bottlenose dolphins. So I went up top to look around to see if I could get a better look at them. I saw a couple of big dorsal fins at the rear of the school. All of a sudden the entire school at one time was in the air, running away at full speed. We went over toward the killer whales. The killer whales had cut out a couple of dolphins at the rear of the school. That is when they broke up into two separate groups - each one with their own dolphins."

    It is very fortunate for us to find them in a feeding situation. They are a lot easier for us to get biopsy samples if they are busy feeding. We got three [biopsies] out of that group which is really good. We can learn a lot about social structure, especially these pelagic tropical populations by getting that information as well as the genetic information on the type of killer whale it is."
LatestPhoto
Bob Pitman - Field Biologist: Southwest Fisheries Center
Photo : Chris Johnson

Genevieve Johnson:

Scientists now recognize that killer whales have evolved to form at least two genetically distinct types. Not only are there differences in feeding strategies, but also group size and social structure. This group consisted of transient, or mammal eating, killer whales.

Bob Pitman:

    "Yes, we are very lucky. There are different kinds of killer whales around the world - some of them eat fish, some of them eat mammals. Some of them many be more generalist - we are not sure yet. For instance, we don't know which forms eat sea turtles. We're interested in collecting tissue samples from killer whales anywhere we can and it's an added bonus if we can get killer whale actually feeding at the time because we know what kind of killer whale they are and see how that matches their genotype."

Genevieve Johnson:

We watched as the killer whales split up into two groups - one consisting of a huge adult male and a smaller animal, the second - adult females, juveniles and a calf. Each group pursued their own dolphin in a different direction.

Transient killer whales feed on marine mammals ranging from dolphins and porpoises to the largest animal ever to inhabit the earth - the blue whale.

Bob Pitman:

    "Mammal eating killer whales generally are in smaller groups - 6,8,10 is kind of the norm. And, that is what you typically find in the tropics. There aren't big enough runs of fish out here for them to feed on. You get into coastal areas and you have large stocks of fish - then you start getting fish specialists. And, in Antarctica for instance, off of northern Europe and the Pacific Northwest and they feed on different kinds of fish - whatever is locally abundant. They have very large schools. I have seen schools of 250 killer whales in one group up in the Bering Sea. The Japanese reported seeing schools of 400-500 killer whales in Antarctica - those were fish eating killer whales too.

    But, mainly in the tropics, it's starting to look like they're all mammal eaters. There are some populations around islands that specialize on rays and sharks but we don't know if they eat mammals part-time or not. It's part of what we are here to find out. Today was a good day for us."
LatestPhoto
A killer whale porpoising in pursuit of a bottlenose dolphin.
Photo : Chris Johnson

Genevieve Johnson:

We stayed with the group for almost two hours constantly recording any vocalizations on our acoustic array. It is interesting to note that throughout the attack we didn't detect any sound from the killer whales.

Bob Pitman:

    "Killer whales that eat fish - for the most part, fish can't here any of that [killer whale vocalizations] so they are communicating all of the time because they are in larger groups, they tend to be all related individuals. They are chatting all of the time as they move along and are passing along information and just keeping track of each other.

    If you are a killer whale that eats marine mammals - they [marine mammals] have acute hearing just as you do, so they have to use a different strategy. If you are going to chase bottlenose dolphins, you have to be pretty quiet until you actually round up a couple of them and then you can start 'talking'. In general, mammal eaters don't say a whole lot even when they are in a situation where they are not hunting. They have just got used to being silent most of the time. We are going to have to go back and listen to the tapes again. There is probably something in there but typically we don't expect much from mammal eaters."

Genevieve Johnson:

Killer whales are the largest member of the dolphin family and like all toothed whales, are extremely social. They are often referred to as the 'wolves of the sea' due to their co-operative hunting strategies.

Bob Pitman:

    "They are not particularly fast - I think that 'co-operative' is the key word. They learn to work these together. I think that one killer whale chasing one bottlenose dolphin - the bottlenose dolphin might get away most of the time. When you have 4 or 5 killer whales and one bottlenose dolphin, then they do kind of 'tag-team' and they can wear them down and wear them out. I think it is cooperation. I think that they make it look kind of easy but you don't know how often they miss. There aren't a lot of killer whales here - we have been out for about two weeks now and this is the first group we have seen. There is a good possibility we wouldn't see any. Killer whales are generally rare in the tropics. So apparently the feeding isn't all that good here. "

Genevieve Johnson:

With over thirty years of field experience, Bob rarely sees killer whales feeding. "You would be lucky if one in twenty killer whale sightings involved feeding," he told the crew. We can hardly believe our good fortune. This is our only third killer whale sighting in four years!

LatestPhoto
After the attack, the group came together travelling slowly beside Odyssey.
Photo : Chris Johnson

Every cetacean sighting at sea has value, though some are more elusive and perhaps more spectacular than others. The next day, Bob reflected on the sighting.

Bob Pitman:

    "To me, the single most impressive, biological sight that you can see in the world today, in the ocean, is seeing killer whales traveling at flank speed, porpoising out of the water after some other prey - usually dolphins because they 'run' pretty fast. There is no spectacle to compare it to that. There is no predator as big or as powerful and probably hasn't been since dinosaurs roamed the earth. It's truly impressive, I have only seen it a few times and we had it yesterday. So, it's been a great trip."

Genevieve Johnson:

In the next Odyssey log, we talk to Bob Pitman about his innovative research on killer whales in Antarctica.

Links:

Log written by Genevieve Johnson.

 
 
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