Caperea marginata (Gray, 1846)

Russell A. Mittermeier & Don E. Wilson, 2014, Neobalaenidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 214-220 : 219-220

Pygmy Right Whale

Caperea marginata

French: Baleine pygmée / German: Zwergglattwal / Spanish: Ballena pigmea

Other common names: \ Vestern Australian Whale

Taxonomy. Balaena marginata Gray, 1846 ,

“Inhab. W. Australia.”

This species is monotypic.

Distribution. Southern Hemisphere, circumpolar, generally between 30° S and 55° S but can occur north to 19° S if cold currents are present.

Descriptive notes. Total length 590- 650 cm; weight 2850-3863 kg. Female Pygmy Right Whales are slightly longer than males. In a sample of physically mature skeletons, females averaged 634 cm in length and males 610 cm. The smallest physically mature specimen (a male) was 590 cm. Weights of only five adult Pygmy Right Whales have been recorded. Flippers are 66-90 cm, dorsalfin is 21-35 cm, and flukes are 135-200 cm. Relative to body length, several external measurements increase in length as an individual grows from juvenile to adult: dorsal fin from ¢.3% to 5%, flippers from c.11% to 13%, and flukes from c.23% to 29%. Flukes have a distinct median notch that is 5-9 cm deep. Body of the adult Pygmy Right Whale is broad, giving it a bulky appearance. Flippers are small compared with other baleen whales and are slightly rounded at their tips. Relative to total body length of an adult Pygmy Right Whale, dorsal fin is situated ¢.65% of the way back from tip of rostrum. Newborns are c.200 cm in length at birth; the smallest stranded individual was 190 cm, and largest fetus had a 212cm body length. Pygmy Right Whales are medium to dark gray above and almost white below. There are several distinctive crescent-shaped, pale markings on and just behind the head. The one above the flipper is similar to the Antarctic Minke Whale ( Balaenoptera bonaerensis ), but the Pygmy Right Whale has a gray flare running forward of the eye. The most distinctive external features of the Pygmy Right Whale are absence of throat grooves, arched jaw (similar to but not as marked as in the true right whale family, Balaenidae ), very narrow rostrum when seen from above, and, if mouth is open, long baleen plates and a white or cream band of gum into which they are embedded. This latter feature is often observed at the water’s surface because there is a tendency for rostrum to be raised out of water at an angle. Two to eight mandibular hairs and several maxillary hairs are present on neonatal Pygmy Right Whales; mandibular hair follicles can persistent into adulthood. There are 213-265 baleen plates on each side of the upper jaw. Color and form of baleen plates are unique to the Pygmy Right Whale: they are long (longest plate 88 cm) and narrow, and white to cream with a darker external band of black, brown, or deep gray; baleen bristles are the same color as the inside of baleen plates and very fine in texture (0-1 mm diameter). They were described by Gray in 1870 as “the most beautiful, the most Flexible, most elastic, and the toughest whalebone or baleen yet discovered.” Baleen plates are short at birth (longest plate c.6 cm) and grow more rapidly after weaning at an estimated five months of age.

Habitat. There have been few sightings oflive Pygmy Right Whales “at sea,” and much of the perceived knowledge of habitat use comes from localities of stranded and beachcast whales. Pygmy Right Whales have been seen in the open ocean, on continental shelves, and close to the coast of southern continents but not Antarctica. Enrichment by abundant meso-zooplankton (e.g. upwelling and convergences) is likely an important factor in determining where Pygmy Right Whales live. Distribution of the Pygmy Right Whale encompasses waters where sea surface temperatures are ¢.5-20°C.

Food and Feeding. Thereis limited information on the diet of the Pygmy Right Whale. Stomach contents ofsix individuals have been reported, and copepods and small euphausiids were abundant in some cases. Amphipods have also been recorded. Calanoid copepods included Centropages brachiatus and Calanoides carinatus in an individual from South Africa and Calanusfinmarchicus in individuals caught in the South Atlantic. Small euphausiids found in stomachs of a few stranded Pygmy Right Whales from New Zealand and Australia have not identified to species, but the small euphausiid Nyctiphanes australis is abundant in that region. The amphipod Themisto guadichaudii was present in small amounts in a stranded juvenile Pygmy Right Whale from South Africa. Knowledge ofthe life cycle of trematodes and cestodes found in intestines of Pygmy Right Whales may augment insight on what species they consume. Mode of feeding has not been confirmed, but very long baleen plates and lack of throat grooves suggests a similar mode to right whales and Bowhead Whales (i.e. skimming as opposed to gulping). Presence of a few bird feathers in stomachs of Pygmy Right Whales may indicate surface-feeding behavior. Several groups of Pygmy Right Whales have been observed feeding at or near the Subtropical Convergence south of Australia and New Zealand, and individuals have been seen feeding in coastal areas. Suspected feeding behavior was observed in a 3m juvenile that was studied during an extended stay in a large bay on the southern coast of Australia. The juvenile’s behavior included surface skimming and stirring up sediment in a sea grass bed; abundant plankton was reported in the bay at the same time. There is some evidence that Pygmy Right Whales feed in upwelled water on the continental shelf, over seamounts, and at the Subtropical Convergence in the region of Australia and New Zealand. Off Namibia, there appears to be an association with the cold, highly productive Benguela Current.

Breeding. Birthing grounds have not been reported for the Pygmy Right Whale. Stranding records provide some evidence that births and nursing may be more common in the northern parts of its distribution, which are north of ¢.41° S in the region of Australia and New Zealand. A preponderance of stranded juveniles of about weaning length along the Namibian coast is evidence of a similar trend off Africa. Mating of Pygmy Right Whales has not been observed. A protracted birthing and mating period of about eight months has been suggested, possibly in April-October. Gestation length is not known, but limited indirect information suggests that it is likely 10-12 months. To date, there is no confirmed evidence of twinning although there is an unconfirmed report of two late-stage fetuses in a stranded female from Tasmania in 1960. Left and right ovaries are functional. Only seven fetuses and neonates have been sexed, giving a ratio of four males to seven females. Future studies of the reproductive organs of stranded individuals may reveal if a post-partum estrus occurs in the Pygmy Right Whale, as it does rarely in some other species of baleen whales. Like all cetaceans, female Pygmy Right Whales have twoteats located in smallslits, one on each side of the urogenital slit. Mammary glands of a female with a late-term fetus (212 cm in length) were 80-90 cm long and not producing milk. Testes of a mature male were c.0.9-1 kg. Although there are no age estimates for Pygmy Right Whales, age at weaning was calculated by plotting body lengths of stranded individuals for fetuses and pre-weaning juveniles against month of death. Estimated age at weaning was about five months, which is consistent with some other species of baleen whales. Body length at weaning is probably 300-350 cm. Too few specimens have been studied to accurately determine length at sexual maturity, but it is likely 450-550 cm in both sexes. Additional evidence to support this hypothesis is that all individual Pygmy Right Whales studied to date, greater than or equal to 590 cm in body length, were physically mature and sexual maturity precedes physical maturity in most mammals.

Activity patterns. There have been very few observations of live Pygmy Right Whales, the longest duration of which was a 3m juvenile that remained in Portland Harbour, Victoria, Australia, for just over two months. During much ofits stay in the harbor, it surfaced to breathe at intervals of c.1-5 minutes. Some resting behavior was observed during the day, but swimming and long and short dives were noted for much of the day. Suspected feeding behavior was observed on the bottom of the shallow bay during the day and at the surface at dusk. During brief encounters, groups of Pygmy Right Whales have been seen swimming slowly just below the surface in morning daylight hours and, in one case, moving in a quite closely packed circle. Almost all observations of Pygmy Right Whales have been made during the day. Several sightings have noted dives of 3—4 minutes and swimming speeds of 3-8 knots (nautical miles/h), although it is not known if this is a maximum speed. Maximum and normal dive depths are not known. Flukes do not appear at the surface during the beginning of a dive, as is the pattern for some species of baleen whales.

Movements, Home range and Social organization. There are no data on long-range movements of individual Pygmy Right Whales. Observations have been made of individuals in protected coastal waters where they traversed distances ofless than 5 km.

A single Pygmy Right Whale was seen swimming up and down along the shore in shallow water for 4-5 weeks in summer. In keeping with other primarily pelagic cetaceans, the Pygmy Right Whale is unlikely to have a defined a home range. Presence of oval scars, often very numerous, attributed to the cookie-cutter shark (Zsistius spp.) on many Pygmy Right Whales suggests that they spend at least some time in warm waters of the tropics and warm temperate zone where these sharks live. This, and the fact that there is evidence for differential relative ages north and south of c.41° S off Australia and New Zealand, may indicate migration of Pygmy Right Whales. It has been suggested that movements are related to feeding in pelagic and continental shelf environments. All inshore observations of Pygmy Right Whales have been of 1-2 individuals, often mother—offspring pairs. There have also been several incidences of adult females stranded with juveniles of about weaning size. Offshore and oceanic sightings have involved groups of three to more than 100 individuals, nine of which were groups of less than 15 individuals. The Pygmy Right Whale has been observed with seabirds and other cetacean species, including the Sei Whale ( Balaenoptera borealis ), dolphins (possibly Lagenorhychus sp.), and “blackfish” (possibly pilot whales, Globicephala sp.). Almost nothing is known of communication among Pygmy Right Whales. Sounds produced by a c¢.3m individual in an inshore environment were recorded by hydrophone, and they were simpler than most other species of baleen whales. This juvenile made only one type of sound, a short, intense thump-like pulse or tone burst with a down sweep in frequency and decaying amplitude. This almost always occurred in pairs and was audible to human divers. Observations of a live-stranded juvenile in Namibia were similarly described, and the vibrations of the sound could be felt through soles of feet of humans nearby. Laryngeal apparatus of the Pygmy Right Whale is significantly different from other species of baleen whales in that the laryngeal sac is very large and offset to the right side of the thorax. This structure may allow large amounts of air to be recycled when producing sound during submergence.

Status and Conservation. CITES Appendix I. Classified as Data Deficient on The IUCN Red List. Convention for Migratory Species Appendix II. Unlike most other species of baleen whales, the Pygmy Right Whale was never a target of whaling due to its small size and protection (along with right whales) under international agreement since 1935. Russian whalers took a few individuals for scientific study during the 1970s in the South Atlantic Ocean. There are also instances of Pygmy Right Whales being killed in inshore fishing nets and carcasses used for meat or scientific purposes. There are no estimates of abundance, and judging by the frequent strandings in Australia and New Zealand, there is no immediate concern for the future of the Pygmy Right Whale. If climate change alters patterns of plankton abundance and distribution, there may be a flow-on effect to the Pygmy Right Whale andits distribution will move south to find its prey. More information is needed on the importance of continental shelf and inshore plankton as a food source for Pygmy Right Whales.

Bibliography. Arnold (1987), Baker (1985), Barnes & McLeod (1984), Beddard (1901), Best (2007), Bisconti (2012), Buchholtz (2011), Budylenko et al. (1973), Burns et al. (1993), Dawbin & Cato (1992), Fitzgerald (2012), Fordyce & Marx (2012), Gill et al. (2008), Gray (1846, 1864, 1870, 1873), Hector (1870, 1873), Hershkovitz (1966), Iredale & Troughton (1934), Ivashin et al. (1972), Kemper (2002, 2008, 2009), Kemper & Leppard (1999), Kemper, Dutton et al. (1997), Kemper, Gibbs et al. (1994), Kemper, Middleton & van Ruth (2013), Leeney et al. (2013), Lockyer (1984), Marx (2011), Matsuoka, Pitman & Marquez (2005), Matsuoka, Yoshihiro & Pastene (1996), Munday et al. (1982), Pavey (1992), Reeb & Best (1999), Rice (1998, 2009b), Ross et al. (1975), Sasaki et al. (2005), Sekiguchi et al. (1992).

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Distribution. Southern Hemisphere, circumpolar, generally between 30° S and 55° S but can occur north to 19° S if cold currents are present.