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MARINE MAMMAL SCIENCE, 20(2):329-334 (April 2004) 0 2004 by the Society for Marine Mammalogy

PYGMY FIN WHALES

ROBERT CLARKE Apartado 40 Pisco, Peru

E-mail: robertclarke007@hotmaiI.com

I propose that in the southern hemisphere there exists a subspecies of pygmy fin whales, dark in color, and possibly with black baleen. Their distribution and movements parallel those of pygmy blue whales. The habitat of both subspecies is between low latitudes and the mid-fifties south, although there is a migratory phase where sexually immature whales penetrate far south in the Antarctic. In pygmy blue whales, I propose that these are the myrbjonner or "marsh bears" of Norwegian whalemen, and in pygmy fin whales these are the "small, dark fin whales," both kinds mentioned by Bennett (1922)' and Mackintosh (1942). My proposal for pygmy fin whales was prompted by a fin whale, notably dark in color, a female, physically mature at 65.0 ft (19.8 m), that I examined far south in the 1947/1948 whaling season, a stray in the present proposal. Additionally there are three records of whales which I believe to be pygmy fin whales in low and middle southern latitudes. The presence of some unknown proportion of whales from such a subspecies may explain the smaller sizes of fin whales at sexual and physical maturity in past Japanese catches around 50"s compared with those at sexual and physical maturity in British and Norwegian catches between 60" and 65"S, demonstrated by Clark (1983). Biological data from Japanese whaling around 50"s may throw light on this matter, and perhaps a comparison of vocalizations, but especially an analysis of DNA from skin samples compared between fin whales from the two areas. I expect this to confirm a third subspecies of fin whales, the pygmy fin whale (Balaenoptera pbysalus patacbonica Burmeister 1865).

Clark (1983) showed that past Japanese catches of fin whales (Balaenoptera pbysalu.r) in middle southern latitudes from several areas and in several seasons had mean lengths at sexual maturity which were 2-3 ft (0.6-0.9 rn) shorter than corresponding lengths from British and Norwegian catches, and similarly the mean lengths at physical maturity were 0.6-0.9 m shorter than those from British catches, there being no data on physical maturity from Norwegian catches. He noted also that "Japanese catches were almost all taken at considerably lower latitudes (45"-55"S) than British and Norwegian catches (60"-65"s). Best (1989) proposed that different procedures for measuring whales could account for the different results, but the stability over various seasons of the inconsistencies

Report of the whaling season 1921-22 at Graham's Land. British Colonial Office. Enclosure to Falkland Islands Despatch No. 68 of 15 May 1922 (unpublished).

330 MARINE MAMMAL SCIENCE, VOL. 20, NO. 2, 2004

suggested that some other factor was involved. Clark (1 983) considered various explanations including “the possibility of latitudinal segregation by reproductive condition,” but he rejected these because Soviet estimates of the lengths of female fin whales at sexual maturity were always intermediate between those from British and Norwegian fleets in high latitudes and those from Japanese fleets in middle latitudes, irrespective of where the Soviets were whaling. However, Yablokov (1994) and Zemsky et al. (1995) have revealed that the published data from Soviet whaling in the Southern Ocean were largely falsified. Moreover Mikhalev (1997) added “Although false reporting was more to understate the numbers of whales taken. . . . the sizes of whales taken, their sex and biologicdl state were also false, as were the period and areas of work” (my italics). So the falsification extended to the mean length at sexual maturity and the Soviet estimates in Clark’s table 3 can now be disregarded.

Here I propose that the reason for these inconsistencies in body size resulted from a longitudinal separation, and they are explained if some part of the Japanese catch were taken from a subspecies of pygmy fin whales which, when sexually and physically mature, does not normally penetrate into antarctic waters.

In his unpublished report from the South Shetlands and Graham Land in 1922, Bennett said “Similarly there are two forms of Fin-whale so far without a characteristic difference, except size, poorness in oil and absence of diatoms on the skin. Frequently these small Fin-whales have a ‘Penella’ parasite that I have not so far noticed in the larger and fat variety.” Mackintosh (1942) also mentioned that the antarctic whalers recognized a small fin whale, darker than the normal fin whale and with the pigment spreading farther round the ventral surface. They were found to be sexually immature, so Mackintosh concluded that they were a color variety and not a subspecies. On the contrary I believe these small, dark, fin whales to be a migratory phase of the pygmy fin whale, which, when immature, penetrates into antarctic seas.

During the antarctic season 1947-1948, in Area IV a few miles north of the pack ice in 63”48’S, 86”37’E, I examined on 7 February 1948 what I believe to have been a mature pygmy fin whale. This was whale serial number SH1057, a fin whale 65.0 ft (19.8 m) long. The blubber thickness measured 9 cm, there were few oval scars and diatom film was absent. Stomach contents were abundant. The mammary glands were not examined. The collapsed diameter of the uterine cornua measured 10 cm. There was no fetus. In one of the ovaries there was a regressing corpus luteum, and a few developing follicles were present in each ovary. In the vertebral column the epiphyses of the 12th lumbar and 12th and 8th thoracics were fused to the centra with no join visible, and the 4th thoracic was fused but with the join visible. Also I noted in my journal on 11 February that the whale was very dark in color.

From the absence of diatom film this pygmy fin whale must recently have arrived in the Antarctic. It could not long have been sexually mature and, judging from the fewness of the oval scars, must still have been fairly young. Yet, since ankylosis of the vertebral epiphyses to the centra is completed in the anterior thoracic vertebrae of fin whales (Wheeler 1930), the whale had just attained physical maturity,

NOTES 33 1

although it was only 19.8 m long. It was quite isolated in size from the 13 other physically mature fin whale females which I examined during the expedition: these ranged from 71.5 to 77.0 ft (21.8 to 23.5 m) with average length 73.9 2 1.7 SD ft (22.5 2 0.5 m). Clark (1983, table 2) reported mean lengths for female fin whales at physical maturity ranging from 69.8 2 0.3 ft (21.3 2 0.1 m) in the Japanese 1961 catch at about 50”S, to 74.9 2 0.4 ft (22.8 2 0.2 m) in the British 1959 catch taken in a higher latitude at about 60”s.

The female just described was the only putative pygmy fin whale which I identified among the 306 fin whale carcases I examined biologically during the 1947/1948 season. However, there were two very small whales, 63.5 ft (19.4 m) and 64.5 ft (19.7 m) long among the 39 physically mature male fin whales I examined. These mature males ranged from 63.5 to 73.0 ft (19.4 to 22.3 m), the average being 68.1 2 2.0 ft (20.7 -t 0.6 m). But I did not note whether or not the two smallest whales were especially dark in color so I place no emphasis on them here, although these two were probably pygmy fin whales.

There are three records of rorquals, apparently fin whales, which were small and dark in color from south temperate and equatorial latitudes. I propose that these whales were pygmy fin whales. Burmeister (1865) described a new species of fin whale, stranded near the mouth of the River Plate at about 35”S, which he proposed to call Balaenoptera patacbonica. He said nothing about the body color, but he described the skeleton and went on to say that the baleen was entirely black, “without any other color.” This is remarkable because no other rorqual so far described has entirely black baleen except the blue whale. Lahille (1905) further described specimens of B. patacbonica, again from the River Plate. He said that adults of the species were “longer than 18 m” (59 ft). Presumably they were not much longer: Mackintosh (1942, table 2) gave the maximum lengths of male and female fin whales as 74 and 81 ft (22.6 and 24.7 m), respectively. Lahille described the color of B. patacbonica as a homogeneous blackish gray, much clearer on the belly. Christensen (1926) again identified B. patacbonica during observations made off the coast of Ecuador by S.S. Tioga in 1912, S.S. Capella in 1914 and M.S. Floreana in 1925-1926. He said that this fin whale (B. patacbonica) was “almost black, thin and very shy. It does not move very fast, and according to observations from various whaling stations in South America, it does not appear to have any particular migration route. It is most often seen off the coast in May and June.” Hershkovitz (1966) gives B. patacbonica as a synonym of B. pbysahs. Rice (1998) does not mention B. patacbonica.

I have proposed that the “small, dark fin whales” of Bennett and Mackintosh are sexually immature pygmy fin whales migrating to far southern latitudes. I here propose that most sexually and physically mature pygmy fin whales do not penetrate farther south than about 55”s. If Japanese vessels were whaling around 50”s on a population containing some unknown proportion of pygmy fin whales then the results discussed by Clark (1983) are completely explained. Further, this would explain why there was only one whale which was certainly a pygmy fin whale, full grown while still quite small, among the 306 fin whales which I examined so much farther south in 1947/1948.

Biological data, on external characters and morphometry, and on sexual and physical maturity may be available from Japanese fin whaling to test this proposal.

332 MARINE MAMMAL SCIENCE, VOL. 20, NO. 2, 2004

Something might be done by comparing recorded vocalizations (Clarke et al. 2002). Especially significant would be a comparison in the southern summer of DNA fingerprinting from fin whales in low and middle latitudes with DNA from those in the Antarctic: this can be done by collecting sloughed skin or by skin samples taken with a crossbow, methods successfully employed on the sperm whale by Whitehead et al. (1990). Rice (1998) recognized two subspecies of fin whales proposed by Tomilin (1967): Balaenoptera physalzls physalzls Linnaeus 1758 in the northern hemisphere and B. p. qzloyi Fischer 1830 in the southern hemisphere. I believe that the investigations suggested here should add a third subspecies, possibly with black baleen, the pygmy fin whale, Balaenoptera pbysalzls patachonica Burmeister 1865. The type is in the Buenos Aires Museum.

It is understandable why pygmy fin whales have been so long overlooked. Open- boat whaling was conducted in low and middle latitudes for sperm whales and gray whales, and in high northern latitudes for right whales, but fin whales were not hunted, being two fast and sinking when killed. Beginning in the 1860s, there has been little modern whaling for fin whales in low latitudes; indeed, little until the 1950s in middle latitudes north and south.

There is a striking parallel between the distribution of the proposed pygmy fin whale and that of the pygmy blue whale Balaenoptera mzlsczllzls brevicazlda Ichihara 1966. Norwegian whalers in the Antarctic spoke of a distinct class of blue whales, small and with pale spots on the ventral surface, which they called myrbjonner or “marsh bears” (Bennett 1922,’ 1931, p. 56; Mackintosh 1942). They are sexually immature and Mackintosh believed them to be a color variety of the normal blue whale and not a subspecies, but at that time the pygmy blue whale had not been discovered. Ichihara (1966) reserved judgment upon them, although their small size and body color are attributes of the pygmy blue whale. I propose that they correspond to the “small, dark fin whales,” immature whales migrating far south in the Antarctic. A pygmy form has been recognized in three other species of balanopterid whales. Best (1985) and Arnold et al. (1987) have recognized a dwarf subspecies of the minke whale (Balaenoptera acutorostrata) from middle latitudes of the southern hemisphere. Best (1974, 1977) has described inshore and offshore forms of Bryde’s whale (Balaenoptera edeni) off South Africa, where the inshore form is smaller, and Ramirez (1986) described inshore and offshore forms off Peru where he found the inshore form to be larger, but in this species the geographical separation of the forms is longitudinal and not latitudinal. If the sei whale (Balaenoptera borealis) should be found to have a pygmy form then the existence of two forms, differing in size and geographical range, would be a character of all species of southern rorquals. Perhaps this is an adaptation to the economy of the sea where whales can sacrifice size to populate areas with less food than in the Antarctic and inshore waters.

ACKNOWLEDGMENTS

In the antarctic season 1947/1948, I was Whale Fishery Inspector on board Messrs Christian Salvesen & Co’s vessel F1. F. Southern Harvester where I also conducted a research

NOTES 333

program for the Discovery Investigations of the British Colonial Office. I recall with pleasure the cooperation of the late Captain Konrad GranGe and of his officers and men.

I extend my best thanks to my friend and colleague Mr. Sidney G. Brown of 24, Orchard Way, Oakington, Cambridge who, while a member of the U.K. Sea Mammal Research Unit, not only sent me photocopies of appropriate pages from my whale logbook 1947/1948 but also sent me a copy of the late A. G. Bennett’s Report to the British Colonial Office (1922) which was previously unknown to me. I thank my wife, Obla Paliza, for a timely observation.

Dr. W. G. Clark, now with the International Pacific Halibut Commission, P. 0. Box 95009, Seattle, and Dr. Ray Gambell, formerly Secretary of the International Whaling Commision, have kindly reviewed an earlier version of the manuscript. For the present version I am grateful for the observations of W. Don Bowen, Robert L. Brownell and an anonymous reviewer. Mr. Neil McLeod, formerly of the British National Institute of Oceanography, kindly translated from the Norwegian the paper by Christensen (1926).

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Received: 17 March 2003 Accepted: 9 October 2003