Pygmy killer whales (Feresa attenuata) are a very poorly known species (Donahue & Perryman, 2009; McSweeney et al., 2009), and single sightings or strandings still often warrant publication. Castro (2004) reported an encounter with a school of small cetaceans off Ecuador in 2003, identified by the author as pygmy killer whales, and described details on the behavior of the group. Features noted in the field that were used to determine the species included estimates of their small size (1 to 2.5 m), rounded tips to the flippers, a rounded head when viewed from above, and white around the mouth. The species most frequently confused with pygmy killer whales is the melon-headed whale (Peponocephala electra), which are similar in size but have pointed tips to the flippers and a pointed head when viewed from above. Adults of both species typically have white lips, but adult pygmy killer whales also have white extending onto the face around the mouth.
Citation:
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. doi: 10.1578/AM.36.3.2010.326
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