Rorqual Hybrids

Family Balaenopteridae

fin whale


humpback whale breaching Humpback whale. Image: Wildlife Conservation Society (T. Collins).

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Balaena mysticetus [Bowhead Whale]
× Eubalaena japonica [North Pacific Right Whale] NHR. A whale photographed in the Bering Strait in 2009 was thought to be this hybrid. Kelly et al. 2010

Balaenoptera acutorostrata [Common Minke Whale]
× Balaenoptera bonaerensis (♀) [Antarctic Minke Whale] NHR. These whales normally have disjunct ranges, but genetic analyses have confirmed that a female Antarctic minke whale that made an unusual migration to Arctic waters did in fact produce a hybrid with a common minke whale. This was the first documented case of such migration between the two hemispheres and of hybridization between these two whales. Glover 2010.

Balaenoptera bonaerensis [Antarctic Minke Whale] See: Balaenoptera acutorostrata.

blue whale fin wale hybrid Above: Photo of a hybrid between blue whale and fin whale taken at Skjálfandi Bay, Iceland. When photographed in 2016, this individual had been returning to the bay annually since at least 2012. Its parentage was genetically verified from a skin sample by HAFRO, Iceland's marine research center in Reykjavik (Sarah Arndt, personal communication). Image: Sarah Arndt. More information

whale spout A second photo to show the huge spout of the Skjálfandi Bay hybrid (same animal as above). Image: Sarah Arndt.

Balaenoptera musculus [Blue Whale]
× Balaenoptera physalus (↔) [Fin Whale] ONHR. These whales occur in mixed schools. CON: All oceans (hybrids have been reported from both the northern Atlantic and northern Pacific). HPF(♀♀). In the latter half of the twentieth century only five hybrids, three female and two male, have been reported. Three were caught off Iceland during the 1980s and their hybridity was confirmed by molecular analysis. One was pregnant (after backcrossing with a blue whale). Spilliaert et al. (p. 188) thought the presence of a corpus albicans in this individual indicated a prior pregnancy. Another hybrid was killed off the coast of Spain in 1984. Doroshenko reported a hybrid captured in 1965 off Kodiak Island (Gulf of Alaska). In addition, a blue whale/fin whale hybrid has been observed returning annually to Skjálfandi Bay, Iceland (see photos above taken in 2016). Its dorsal fin and dark skin color are similar a fin whale, but its size and markings are like those of a blue (more information). Such hybrids have long been known and were far more common formerly, when blue and fin whales were themselves more abundant. In Norwegian waters alone, Cocks (1887, pp. 217-218) lists ten such hybrids captured in the single year of 1886, and says (p. 216) that they were well-known to the whalers:

Nearly universally recognised 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 [i.e., than the Fin Whale], 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.

He goes on to give the lengths of many captured whales, both pure fin whales and fin whale/blue whale hybrids. One such hybrid, he says, reached

the remarkable length of 80 1/2 Eng. ft. This Whale was shot by the ‘Murmanetz’ on April 9th, the harpoon going well in just behind a flipper, that is, somewhere very close to the heart, and the shell exploded. The wound, instead of proving almost immediately fatal, seemed to madden the victim, and it rushed away at great speed and towed the steamer, with the propeller working full speed astern, for four hours when the 'Welda' being sighted, she was signalled to assist, and this vessel, steaming up at an angle, succeeded in lodging a harpoon just behind the flipper on the opposite side to the first; this shell also exploded properly. The Whale in this mortally wounded condition actually towed the two steamers steaming full speed astern, with a boat from each constantly lancing it, for two hours before it succumbed (Cocks 1887, p. 217).

However, Cocks had earlier (pp. 213-214) listed the sizes of numerous captured blue whales, and some of these attained to even greater lengths. So fin-blue hybrids appear to be intermediate in size between their parents, as is the case in most, but not all, hybrid crosses. Two of the female hybrids listed by Cocks (see pp. 217 and 218) were pregnant. Árnason 1995; Árnason and Gullberg 1993; Árnason et al. 1991; Spilliaert et al. 1991; Bérubé and Aguilar 1998; Doroshenko 1970.
× Megaptera novaeangliae (♂) [Humpback Whale] NHR. CON: Oceans worldwide. Folkens et al. (2002, pp. 236-237) say that "unlikely as it would seem given the considerable differences in size and morphology between the two species, there is one well-documented report of a Humpback-Blue Whale hybrid from the South Pacific." Blue whales (~30 m) are nearly twice as long as humpbacks (~17 m), and far heavier (maximum weight 180,000 kg vs. ~40,000 kg). Internet reports say the mother was a blue whale.

Balaenoptera physalus [Fin Whale] See: Balaenoptera musculus.

Eschrichtius robustus [Grey Whale]
× Megaptera novaeangliae [Humpback Whale] NHR. Waddell et al. (2000, p. 317) mention a hybrid, but give no details. CON: Pacific.

Eubalaena japonica [North Pacific Right Whale] See: Balaena mysticetus.

Megaptera novaeangliae [Humpback Whale] See: Balaenoptera musculus; Eschrichtius robustus.

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By the same author: Handbook of Avian Hybrids of the World, Oxford University Press (2006).

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