Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
1991, 2003). As noted earlier, identification to species for this genus is difficult, particularly at sea.
Based on the known preference of these two species for deep waters, Kogia are expected to
occur from the vicinity of the shelf break to seaward of the Marianas study area and vicinity
(Figure B-10). For example, in the Hawaiian Islands, Kogia were found in waters with a mean
bottom depth of 2,004 m (Baird et al. 2003a). There is a low or unknown occurrence for these two
species between the 50 m isobath and the shelf break in this area (Figure B-10). At the Society
Islands, a dwarf sperm whale was sighted in relatively shallow waters (bottom depth of 120 m)
(Gannier 2000) and MacLeod et al. (2004) reported sighting Kogia most often in waters with a
bottom shallower than 200 m in the northern Bahamas. Occurrence patterns are expected to be
the same throughout the year.
Behavior and Life History—Kogia species have small group sizes (mean group size is usually two
individuals) (Willis and Baird 1998a). A recent study of Kogia in South Africa has determined that
these two species have a much earlier attainment of sexual maturity and shorter life span than other
similarly sized toothed whales (Plön and Bernard 1999). Sexual maturity is attained at around 4 years
in both sexes of both species. Kogia feed on cephalopods and, less often, on deep-sea fishes and
shrimps (Caldwell and Caldwell 1989; Baird et al. 1996; Willis and Baird 1998a; Wang et al. 2002). A
typical observation of this species is animals logging at the water surface for periods of up to a few
minutes then slowly sinking or slow rolling out of sight and not being resighted (e.g., Baird 2005).
Willis and Baird (1998a) reported that Kogia make dives of up to 25 min. A satellite-tagged pygmy
sperm whale released off Florida was found to make long nighttime dives, presumably indicating
foraging on squid in the deep scattering layer (Scott et al. 2001).
Acoustics and Hearing—Pygmy sperm whale clicks range from 60 to 200 kHz, with a dominant
frequency of 120 kHz (Thomson and Richardson 1995). There is no information available on dwarf
sperm whale vocalizations or hearing capabilities. An auditory brainstem response study indicates
that pygmy sperm whales have their best hearing between 90 and 150 kHz (Ridgway and Carder
2001).
♦ Cuvier’s Beaked Whale (Ziphius cavirostris)
Description—Cuvier's beaked whales are relatively robust compared to other beaked whale species.
Male and female Cuvier's beaked whales may reach 7.5 and 7.0 m in length, respectively (Jefferson
et al. 1993). This species has a relatively short beak, which along with the curved jaw, resembles a
goose beak. The body is spindle-shaped, and the dorsal fin and flippers are small, as is typical for
beaked whales. A useful diagnostic feature is a concavity on the top of the head, which becomes
more prominent in older individuals. Cuvier’s beaked whales are dark gray to light rusty brown in
color, often with lighter color around the head. In adult males the head and much of the back can be
light gray to white in color, and they also often have many light scratches and circular marks on the
body (Jefferson et al. 1993).
Status—There are no abundance estimates for the Cuvier’s beaked whale in this area. The Cuvier’s
beaked whale is designated as data deficient on the IUCN Red List (Reeves et al. 2003).
Habitat Preferences—Beaked whales normally inhabit deep ocean waters (>2,000 m) or continental
slopes (200 to 2,000 m) and only rarely stray over the continental shelf (Pitman 2002). Cuvier’s
beaked whales are generally sighted in waters with a bottom depth greater than 200 m and are
frequently recorded at depths of 1,000 m or more (Gannier 2000; MacLeod et al. 2004). They are
commonly sighted around seamounts, escarpments, and canyons. MacLeod et al. (2004) reported
that Cuvier’s beaked whales occur in deeper waters than Blainville’s beaked whales in the Bahamas.
Distribution—The Cuvier's beaked whale is the most widely distributed of all beaked whale species,
occurring in all three major oceans and most seas (Heyning 1989). This species occupies almost all
temperate, subtropical, and tropical waters, as well as subpolar and even polar waters in some areas
(MacLeod et al. in press). In the western Pacific, records range from Japan to southern New Zealand
(MacLeod et al. in press).
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