habitat_narrative
Marine
Little is known about the key behavioural and ecological characteristics of beaked whales. Typically, these species occur in deep, offshore waters, and are considered to have long, deep-diving capabilities. Their occurrence is generally associated with topographic features, including slopes, escarpments, canyons and oceanic islands (Macleod et al. 2006). The stomach contents of stranded beaked whales suggest that their primary food source includes deep-water, mesopelagic cephalopods, although MacLeod et al. (2003) found that benthic fish and crustaceans also constitute important prey items for these species. Ziphius and Hyperoodon spp. prey upon significantly larger species, compared to Mesoplodon spp. (MacLeod et al. 2003).Berardius arnuxii are commonly associated with regions beyond the edge of the continental shelf within cold temperate and subpolar waters (Kasuya 2002), but have been occasionally sighted within shallower waters, along continental slopes, or around seamounts (Jefferson et al. 1993). This species may be one of the most proficient deep-water divers of all marine mammals, capable of diving for over an hour, to depths of 1,000 m, and swimming under sea ice for at least 7 km on a single breath (Hobson & Martin 1996). Although there are no data specific to the diet of B. arnuxii, the closely related B. bairdii was found to consume mostly deep-sea fish and squid. Additionally, B. bairdii males were found to mature younger and at shorter body lengths than females, and have a much lower rate of mortality than females (Kasuya et al. 1997). Female and male B. bairdii may live to 54 and 84 years of age, respectively (Kasuya et al. 1997). Berardius arnuxii have occasionally been reported trapped within pack ice, more than 60 km from open water, which may account for some natural mortality of this species (Taylor 1957).
During the summer, H. planifrons is associated most frequently with regions within 100 km of the Antarctic ice edge. Generally, they prefer deep waters beyond the continental shelf, usually more than 1,000 m deep, and are considered rare in waters shallower than 200 m. They have also been documented in the steep thermocline, where the Agulhas Current and Antarctic waters meet (Cockcroft et al. 1990). Analyses of the stomach contents of this species have revealed that squid forms the major constituent of their diets (Ross 1984; Sekiguchi et al. 1993; Slip et al. 1995). Sekiguchi et al. (1993) found the remains of four Antarctic squid and four subantarctic squid in the stomachs of two individuals washed up in January, which indicated a recent migration from the Southern Ocean to South African waters in summer. Sightings of calves, approximately 3.5 m long, in January suggests that calving may take pace during the early summer months (Ross 1984).
Indopacetus pacificus has been observed in schools of up to 100 individuals, and in association with other cetaceans, such as Short-finned Pilot Whales (Globicephala macrorhynchus) and Bottlenose Dolphins (Tursiops truncatus). This species favours tropical and subtropical regions of the Indo-Pacific, with surface water temperatures between 21â31 °C. No information is available regarding their feeding habits, aside from the stomach contents from a specimen in Japan, demonstrating their consumption of cephalopods (Yamada 2002). Little data are available regarding the reproductive seasonality of this species.
Mesoplodon species occur commonly in deep-waters and along continental slopes, where prey availability may be enhanced by the interactions between ocean currents and topography (MacLeod & Zuur 2005). Beaked whales are believed to be suction feeders (Heyning & Mead 1996), feeding predominantly on squid and deep-water fish. Mesoplodon densirostris is no exception. Sekiguchi et al. (1992) and Ross (1984) reported stomach contents containing the remains of Buttersnoek (Lepidopus caudatus) and lanternfish (Lampanyctus spp.). Off Hawaii, schools of between three and seven Blainvilleâs Beaked Whales were observed by Shallenberger (1981). Having documented groups of up to six individuals, Gambell et al. (1975) suggested that M. grayi form small schools. Mesoplodon grayi calves may be born in spring and summer, at lengths of approximately 2.1 m (Baker 1983). Sekiguchi et al. (1996) reported that the diet of M. layardii consisted primarily of squid in South African and New Zealand waters, with small numbers of fish and crustaceans. Stable isotope analyses revealed that M. mirus feed at a similar trophic level to other species of this genus, but may feed on smaller prey than H. ampullatus (Northern Bottlenose Whale), and at a lower trophic level than that of Z. cavirostris (MacLeod 2005).
Similar to other beaked whales, Z. cavirostris is most frequently associated with deep waters for feeding. Dive durations of 30 minutes (Miyazaki & Wada 1976) and 40 minutes have been recorded. Using suction techniques (Heyning & Mead 1996), they consume mostly deep-sea squid, but also fish and crustaceans (MacLeod et al. 2003), feeding both within the water column as well as near the bottom. Sexual maturity is reached at lengths of over 5.5 m (Omura et al. 1955; Nishiwaki & Oguro 1972), and breeding and calving of this species may span over a number of months (Ross 1984). Calves are born at lengths of approximately 2.6 m.
Ecosystem and cultural services: Marine mammals integrate and reflect ecological variation across large spatial and long temporal scales, and therefore they are prime sentinels of marine ecosystem change; migratory whales may be used to investigate broad-scale shifts in ecosystems (Moore 2008).
