On a possible hybrid between a fin whale and a blue whale
by Klaus Barthelmess
(published November 2008)
This webposting also presents photographs of that whale. They were taken by me with a cheap camera and are of fairly poor quality, and hence were never published. They were recently scanned from scratched slides, have been digitally remastered and show the black baleen, the shape of the rostrum, of the flipper, and of the huge dorsal fin, as well as detail of the pigmentation pattern.
... [The article opens with general remarks on my sojourn on the Icelandic whaling station and the Icelandic research whaling program of the 1986 season].
“Whaling operations commenced on 16 June  with two steam whale catchers. Vessels reach the whaling ground, some 140 to 170 nautical miles west of Iceland, after about 12 to 15 hours of steaming. Per whaling trip catchers are permitted to bring in two fin whales or three sei whales or two fin and one sei whale. Processing of the carcasses has to commence within 26 hours. From 07:00 to 23:00 hrs the whaling station makes radio contact with the whale catchers in two-hour intervals, ia receiving intelligence about all sightings of large whales. The whale species most commonly seen at the beginning of the season was the humpback whale, followed by fin whales. During the first ten days of the operations, blue whales were seen during every third or fourth whaling trip, sometimes in proximity of fin whales. Sei whales were not expected until the end of July.
On 22nd June , at about 01:00 hrs, one of the whale catchers brought in a whale, which upon closer examination on the flensing platform was found to display [morphological] characteristics of both the fin whale and the blue whale. It was a female of 70 feet (21.3 m) length.
The first general impression was that of a bulkier body than that of the more “slender” fin whales; the whalers rejoiced about a particularly “fat” whale. The shape of the head [rostrum] was slightly curved. The dorsal fin was of an unusual, almost sword-like form and had a length of about 40 cm [actually 56 cm], much unlike the small fins characteristic of blue whales. The back had the grey-black colour typical of fin whales. The ventral side was white, as were the undersides of the flippers. However, the colour pattern was not asymmetrical as in fin whales, but largely symmetrical. Near the navel, white pigmentation spots were visible on slate-grey ground, which is a colour pattern normally characteristic of the entire underside of the blue whale. The colour of all the baleen in situ, as well as the palate, was black. However, the individual baleen slabs were thinner than with blue whales, and when taken out, they displayed lengthwise striations of black and lighter colour. Unfortunately both tympanic bullae (ear bones) could only be retrieved broken. But even so it was apparent that they had a more slender form than those of fin whales. Regrettably none of the biologists present at the whaling station was in possession of an image of blue whale bullae, but from my familiarity with 20th century whaler folk art I had the vague idea that “slender” ear bones came from blue whales.
These preliminary osteological and morphological findings generated the impression that this whale (No. 5 of the 1986 whaling season) could be a hybrid. Strangely enough, the ovaries of this animal had corpora albicantia. Accordingly, in the station journal this whale was recorded was “fin whale ?” [with a question mark]. It is hoped that tissue samples collected by biologists from the USA, Canada, Iceland, Spain and France will yield interesting insights.
According to Dr. Paul Brodie (Fisheries and Oceans, Canada), one of the scientists present at the whaling station, the question of hybridisation in rorqual whales has been adressed several times in the past, but not conclusively. During his own work at the whaling station in Nova Scotia, Brodie noted several whales with similar characteristics. Also people at the Icelandic whaling station remembered having seen one or two similar specimens in the past.
During later research in the library of the Kendall Whaling Museum [Sharon, Massachusetts] I came across a report that made it clear, that already in the 1880s, for the shore whalers of northern Norway, the possibility of hybridisation between blue and fin whales was not a question, but a certainty:
“Nearly universally recognized among the Finwhalers is the so-called “Bastard”, from its having been supposed to be the offspring of mixed parentage - of a Blue and Common Rorqual. This variety appears to attain to larger dimensions than the typical form [of the common or fin whale; KB], and is described as grey, rather than the usual white, on the under side; on one side the baleen plates are for a short distance at the anterior end entirely white, while the remaining portions are darker than the normal colour” (Cocks, 1887, p. 10).”
... [the article closes with personal observations made during whaling].
COCKS, A. H. (1887):
The Finwhale Fishery of 1886 on the Lappland Coast.
The Zoologist 11, p. 207-222
This whale was later genetically established to be a hybrid:
SPILLIAERT, R., G. A. VIKINGSSON, U. ARNASON, A. PALSDOTTIR, J. SIGURJÓNSSON und A. ARNASON (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), S. 269-274
In later years, a total of five blue whale ∞ fin whale hybrids has been ascertained genetically:
BÉRUBÉ, M. und A. 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), S. 82-98
A comparison of the mitochondrial DNA of blue and fin whales revealed an assumed evolutionary split >= 5 million years ago. The genetic difference is as high as it may be for hybridizing mammals :
ÁRNASON, Ú. und A. GULLBERG (1993):
Comparison between the complete mtDNA sequences of the blue and the fin whale, two species that can hybridize in nature.
Journal of Molecular Evolution 37(4), S. 312-322
Two newspaper article have been published about this 1986 hybrid:
Recino, Angela: "Zoologische Sensation entdeckt: Mischling zwischen Finn- und Blauwal", in: Kölnische Rundschau, 28. Oktober 1991.
Kietzmann, Helga: "Mutter Blauwal, Vater Finnwal. Bemerkenswerter Fall eines Furchenwal-Hybrids", in: Neue Zürcher Zeitung, 6. Mai 1992, S. 71.
Many thanks to Michael "Mike" L. Baird, bairdphotos.com for providing the header image. It's a blue whale off Santa Cruz Island in the Channel Islands, near Santa Barbara, California.