Feresa: The Growling Wolf-Dolphin

The dolphin Feresa attenuata has been bestowed with dreadfully stupid common names. Feresa has been recognized as distinct from Orca since Gray (1871), which makes "Pygmy Killer Whale" both inappropriate and archaic. The alternative "Slender Blackfish" is actively misleading as the superficially similar Pseudorca is more slender (Reeves et al. 2002) and well-lit color photographs in Rossi-Santos et al. (2006) show that the species is actually brown, contra every illustration. I'll be calling the dolphin "Feresa" from here on out (I'm also not too fond of  "attenuata") as my alternate suggestion in the title is a tad verbose.

Feresea... maybe. This species can be distinguished from Pseudorca by having a proportionally larger dorsal fin (2 base lengths away from the blowhole vs. 2.5) and by having a clearly demarcated cape; Peponocephala can be distinguished by having pointed flipper tips, a pointed head when viewed from above, and no white extending around the face (Baird 2010). I think this is the case in the above photo, but I'm not entirely certain. Photo by Gary L. Friedrichsen from WoRMS.

Feresa is one of the most poorly-known toothed whales (McSweeney et al. 2009) and single sightings or strandings are still viewed as deserving publication (Baird 2010). Prior to 1954, the species was known from only two skulls (Reeves et al. 2002), making it extremely poorly-known even compared to beaked whales. What makes this absolutely shocking is that Feresa is not a cryptic species. They are known from the tropics and subtropics worldwide, are easy to detect in visual surveys, do not take extended dives, and (contra Leatherwood et al. 1982) do not avoid vessels (McSweeney et al. 2009). While their surface behavior is normally subdued compared to other dolphins, they have been observed jumping high above the surface and even riding on bow waves (Reeves et al. 2002). It appears that while a deep-water habitat and confusion with Pseudorca and Peponocephala can explain the lack of observations to a degree, the main factor is probably the species being rare (McSweeney et al. 2009).

In 1965 - a little over a decade after the external appearance of the animal became known - Feresa was held in captivity. Pryor (1991) remarked that one individual behaved "more like a wolf than a normal dolphin" would "growl and snap like as canid" and "not hesitate to attack people and other cetaceans". Since when are cetaceans capable of growling? This behavior has led some to presume that Feresa preys on mammals in the wild (Leatherwood et al. 1982) and aggression towards other dolphins has been observed whilst individuals were trapped in tuna seines (Reeves et al. 2002). Considering that both situations occurred in cramped and undoubtedly stressful environments, I think it is completely unfounded to conclude that Feresa is a pugnacious marine mammal-killing macropredator with the available evidence. Stomach contents have included squid and fish (Rodríguez-López and Mignucci- Giannoni 1999; Zerbini & Santos 1997)

Feresa skeleton. From Wikipedia Commons.

The skeleton of Feresa does appear superficially Orca-like, however, it is not a particularly close relative, hence my strong dislike of the "Pygmy Killer Whale". There is some disagreement as to how closely they are related; Slater et al. (2010) places Orcinus (and Orcaella) as the most basal delphinids, however Vilstrup et al. (2011) consider both to be both members of the clade Globicephalinae, but with Orca as the most basal member and Feresa as a derived member and close relative of Peponocephala and Globicephala. This seems like a very interesting group, and perhaps I'll give it some more coverage.


References:

Baird, R. W. (2010). Pygmy Killer Whales (Feresa attenuata) or False Killer Whales (Pseudorca crassidens) Identification of a Group of Small Cetaceans Seen off Ecuador in 2003. Aquatic Mammals 36(3), 326-327. Available.

Gray, J. E. (1871). Supplement to the Catalogue of seals and whales in the British Museum. Available.

Leatherwood, S., Reeves, R. R., Perrin, W. F., & Evans, W. (1982). Whales, dolphins, and porpoises of the eastern north pacific and adjacent arctic waters (NOAA Technical Report NMFA Circular 444). Washington, DC: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service. Partially Available.

McSweeney, D. J., Baird, R. W., Mahaffy, S. D., Webster, D. L., and Schorr, G. S. (2009). Site fidelity and association patterns of a rare species: Pygmy killer whales (Feresa attenuata) in the main Hawaiian Island. Marine Mammal Science 25(3), 557-572. Available.

Pryor, K. (1991). Mortal remains: Studying dead animals. In: Pryor, K. & Norris, K. S. (eds.) Dolphin Society: Discoveries and Puzzles. University of California Press: Berkeley. Available.

Reeves, R. R., Stewart, B. S., Clapham, P. J., & Powell, J. A. (2002). National Audubon Society Guide to Marine Mammals of the World. Alfred A. Knopf: New York.

Rodríguez-López, M. A. & Mignucci-Giannoni, A. A. (1999). A stranded pygmy killer whale (Feresa attenuata) in Puerto Rico. Aquatic Mammals 25(2), 119-121. Available.

Rossi-Santos, M., Baracho, C., Neto, E. S., & Marcovaldi, E. (2006). First sightings of the pygmy killer whale, Feresa attenuata, for the Brazilian coast. JMBA2 - Biodiversity Records. Available.

Slater, G. J., Price, S. A., Santini, F., and Alfaro, M. E. (2010). Diversity versus disparity and the radiation of modern cetaceans. Proceedings of the Royal Society B 277(1697), 3097-3104. Available.

Vilstrup, J. T., Ho, S. Y. W., Foote, A. D., Morin, P. A., Kreb, D., Krützen, M., Parra, G. J., Robertson, K. M., de Stephanis, R., Verborgh, P., Willerslev, E., Orlando, L., & Gilbert, M. T. P. (2011). Mitogenomic phylogenetic analyses of the Delphinidae with an emphasis on the Globicephalinae. BMC Evolutionary Biology 11(65). Available.

Zerbini, A. N. & Santos, M. C. O. (1997). First record of the pygmy killer whale Feresa attenuata (Gray, 1874) for the Brazilian coast. Aquatic Mammals 23(2), 105-109. Available.