False killer whale (Pseudorca crassidens)

The United States Navy’s marine species monitoring program addresses four general topics surrounding the impact of mid-frequency active sonar (MFAS) on protected species: occurrence, exposure, response, and consequences.

The false killer whale (Pseudorca crassidens) is regarded as Data Deficient globally and in Australia. In most parts of its range, there is little information on its social behaviour, dispersal or ecology. The present study is the first assessment of its movement patterns in Australian waters, on the basis of satellite tracking of four individuals, in the Arafura and Timor Seas from late March to early July 2014. When initially tagged, the four individuals occurred in a single group; they then showed generally similar movement patterns and regularly re-associated.

Data limitations frequently result when monitoring endangered populations that are rare, cryptic, or inaccessible.  Appropriately using the best available data to meet management mandates for these populations is a common conservation challenge.  False killer whales (Pseudorca crassidens) occur as three distinct populations in Hawaiian waters, including a population resident to the main Hawaiian Islands (MHI) that is endangered under the U.S. Endangered Species Act and strategic under the U.S.

Species misidentification is a common problem for some groups of cetaceans, and may lead to inaccurate descriptions of behavior, habitat use, group size, abundance, or acoustic characteristics, among other things. Four tropical species of “blackfish” overlap broadly in their ranges and are often confused at sea owing to their similar gray-black coloration, bulbous head without a beak, and falcate dorsal fin: pygmy killer whales, melon-headed whales, short-finned pilot whales, and false killer whales.

False killer whales are highly social, known for maintaining strong, long-term bonds and engaging in cultural behaviors including prey-sharing and mass stranding that may make them vulnerable to anthropogenic impacts. An endangered main Hawaiian Islands population includes three recognized social clusters (C1, C2, C3). Although they appear longitudinally stable, all three are interconnected and some individuals are regularly associated with multiple clusters.

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