Sunday, June 12, 2016

Hybrids Among the Whales

(by Matt Bille with help from Dr. Darren Naish and Richard Ellis)
From Shadows of Existence, 2006, Hancock House
Unusual cetaceans are most often thought to be anomalous individuals of a known species or members of an unknown species. In some cases, there is a third alternative: the animal might be a hybrid. There are a surprising number of cases in which different species of cetaceans have interbred, with some striking results.
For example, the skull from a whale killed in Greenland in 1986 or 1987 appears to be evidence of a hybrid between the two known monodonts, the beluga and the narwhal. The skull was spotted in 1990 by Mads P. Heide-Jorgensen of the Greenland Fisheries Research Institute. It was sitting on the roof of a tool shed in the settlement of Kitsissuarsuit.
Hunter Jens Larsen, who killed three identical whales of the type the skull came from, recalled the animals seemed very strange to him. They were a uniform grey color, showing neither the distinctive white of a beluga nor the mottled back of a narwhal. Their tails looked like a narwhal's, which has distinctive fan-shaped flukes with convex trailing edges, but their broad pectoral flippers resembled a beluga’s. While these cetaceans had no horns, analysis of the skull indicated two teeth showed growth patterns resembling the spirals of a narwhal tusk. These teeth may have protruded outside the mouth.
Hybridization is also known to have occurred between the two largest animals on Earth, the blue whale (Balaenoptera musculus) and the fin whale (B. physalus). In a 1998 article in Marine Mammal Science, Martine Berube and Alex Aguilar reported finding five such examples documented in scientific literature. The authors devoted most of the article to a hybrid caught off Spain in 1984. This animal showed features intermediate between the two parents. The whale was four years old, and, at sixty-three feet in length, “anomalously large” for its age. Another instance, described in the Journal of Heredity in 1991, concerned a similar hybrid caught off Iceland in 1986. In the 1986 case, the whale turned out to be a pregnant female. Analysis of the fetus indicated the father was a blue whale. This was the first case in which such a hybrid was proven to be fertile.
These hybrids tend to be dark grey and are usually mistaken for fin whales. Curiously, an author named A. H. Cocks, writing in 1887, stated there were three kinds of giant baleen whales caught off the Norwegian coast. One type appeared intermediate between the blue and fin whales, so much so that Cocks called it the “bastard” and suggested all such animals were hybrids. If this is an accurate deduction, hybridization between these two species has been going on for a long time.
Such a hybrid has figured in the controversy over the continuation of whaling for “scientific research” in Japan. While meat from the minke whales (Balaenoptera acutorostrata) taken in this program is sold legally in Japanese markets, the government has always denied that meat from any protected species is sold or imported. This was disproved when a sample purchased in a Japanese market in 1993 was traced to a specific whale killed off Iceland in 1989. This was possible because the whale involved was so distinctive – a blue/fin hybrid. Such animals are still reported off Iceland. Indeed, a recent hybrid sighting near that island nation is even mentioned in promotions for a whale-watching tour company.
More recently, a new kind of hybrid was reported. A calf spotted near Tahiti in 2000 with its mother, a humpback whale, looked like a hybrid between a humpback and a blue. The calf was abnormally large, yet with pectoral fins that were shorter than normal for its species (the humpback is the only member of its genus, Megaptera, which is named for the whale’s oversized pectoral fins). The calf also displayed the coloration of a blue whale. The parents are not just from different species but different genera. Intergeneric hybrids are freakishly rare and always unexpected. Mammologist Michael Poole speculated that, with blue whales still rare and thinly spread out over the oceans, loneliness may have driven a male blue to seek an unusual mate.
In a Japanese aquarium, a male Risso’s dolphin (Grampus griseus) produced calves with three different bottlenose dolphins (Tursiops truncatus). In 1979, the Whales Research Institute in Tokyo used a photograph of one of these intergeneric calves on a Christmas card. Richard Ellis, who is well-known as both a writer and an artist specializing in cetaceans, wrote, “…when I opened the envelope and saw a shiny grey, short-beaked cetacean, I was struck dumb: I had been studying pictures of these animals for years, and before me was an animal I couldn’t even begin to identify.” In 1981, another aquarium in Japan reported a male false killer whale (Pseudorca crassidens) and a female bottlenose had produced a calf.
While the blue whale-humpback whale mentioned above is the most spectacular example of an intergeneric cross reported in the wild, there have been a few other incidents. Robin Baird wrote in 1998 that a fetus recovered from the corpse of a Dall’s porpoise (Phocoenoides dalli) proved to have an unusual father: a harbor porpoise (Phocoena phocoena). Baird found this particularly intriguing because there are several other reports of unusually pigmented cetaceans with the general size and form of Dall’s porpoises. Although Dall’s porpoises are notably variable in their pigmentation, Baird suggests some of these cases are due to ongoing hybridization with harbor porpoises. Another intergeneric hybrid, this one between the long-beaked dolphin (Delphinus capensis) and the dusky dolphin (Lagenorhynchus obscurus) was nabbed off Peru.
In 2001, an apparent hybrid between a dusky dolphin and a southern right whale dolphin, Lissodeplhis peronii, was photographed among a school of duskies. This very unusual-looking animal was about seven feet long, larger than normal for a dusky. It sported a solid black upper body and was completely white underneath, lacking the intermediate shades normally present on a dusky’s body. On the other hand (or flipper), it had black pectoral fins, whereas the right whale dolphin’s are white, and it had a small triangular dorsal fin. Right whale dolphins have no dorsal fin at all.
Finally, three odd-looking dolphins which washed up on an Irish beach in 1933 were identified by one expert as hybrids between the bottlenosed dolphin and Risso's dolphin. While the match between these two species was proven viable by the incident from captivity described above, not all cetologists accept the hybrid interpretation in this case.
The popular bottlenose seems to be the main instigator of hybridization in captivity. One paper recorded twenty-one incidents in which a Tursiops mated successfully with another species. It’s true there are more bottlenose dolphins in captivity than any other cetacean, but that’s still quite a surprising record. To indulge in a completely illogical, yet human, thought, it's enough to make people wonder what's behind this animal's famous "smile."

Anonymous. 2000. “Loneliness might have prompted whale mis-match,” Australian Broadcasting Company report, September 1.
Baird, Robin, et. al., 1998. “An intergeneric hybrid in the family Phocoenidae,” Abstract, posted to MARMAM@UVM.UVIC.CA mailing list, March 12.
Baird, Robin. 1997. Personal communication, March 28.
Berube, Martine, and Alex Aguilar. 1998. “A New Hybrid Between a Blue Whale, Balaenoptera musculus, and a Fin Whale, B. physalus: Frequency and Implications of Hybridization,” Marine Mammal Science 14(1), January, p.82. Carwardine, Mark. 1995. Whales, Dolphins, and Porpoises. London: Dorling Kindersley.
Ellis, Richard. 2000. Personal communication, March 10.
Ellis, Richard. 1989. Dolphins and Porpoises. New York: Alfred A. Knopf.
Heide-Jorgensen, Mads, and Randall R. Reeves. 1993. “Description of an Anomalous Monodontid Skull From West Greenland: A Possible Hybrid?” Marine Mammal Science 9(3), July, p.258.
MICS Research. No date. “Blue Whale Research Session in Iceland with Richard Sears,”
Naish, Darren. 2001. Personal communication, September 28.
O’Neill, Michael. 1999. “DNA Breakthrough May Aid Monitoring of Commercial Whaling Ban,” BioBeat,, January 15. Redmond, Ian. 1993. “Beluwhales break out,” BBC Wildlife, November, p.12.
Rice, Dale. 1998. Marine Mammals of the World. Lawrence, KS: The Society for Marine Mammology. Spilliaert, R., et. al. 1991. “Species Hybridization between a Female Blue Whale (Balaenoptera musculus) and a Male Fin Whale (B. physalus): Molecular and Morphological Documentation,” Journal of Heredity 82(4), p.269.

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