Beaked Whales of the Genus Mcsoplodon 



Five species of mesoplodonts are known from the eastern North 

 Pacific, mostly from stranding records, as beaked whales are rarely seen 

 and positively identified alive at sea. Of those species, two are unknown 

 from waters in or near the SCB - Ste|neger's beaked whale, Miscplodon 

 stejnigm True, 1885, is not reported from south ot Monterey and is 

 apparently restricted to cold temperate and subpolar waters; and 

 Blainville's beaked whale, M. dinsirosins (Blainville in Desmarest, 1817), 

 is known along the North American west coast only from single 

 strandings m San Mateo County and San Francisco and is apparently 

 ordinarily restricted to pelagic southern temperate and tropical waters. 

 The other three species warrant only brief mention here, as they are 

 not likely to be seen at sea except by the most diligent and persevering 

 observers, or identified correctly at sea or on the beach except by 

 specialists. 



Huhbs' beaked whale, M. carlktihbsi Moore, I96j, has been found 

 stranded from British Columbia to San Diego, California and has been 

 postulated to live in association with the confluence of the subarctic 

 and California Current systems, rarely if ever ranging north o( the 

 former's influence or south of the latters. If this is in fact the case, 

 Hubbs' beaked whales from the southern portions of the species' range 

 in the eastern North Pacific might well be present in or near the SCB 

 and CINMS at an\- time of year that the California current is flowing 

 strongly near shore. 



The ginkgo-toothed beaked whale, Af. ginkgcdcm Nishiwaki and 

 Kamiya, 1958. is known in the northeastern Pacific from only two 

 records, one from Malarimo Beach, Scammon's Lagoon, Baja Califor- 

 nia and a second from Del Mar, California. The species appears more 

 common in the Harm temperate and tropical waters of the western 

 North Pacific and Indian oceans. 



Hector's beaked whale, M. heclori (Gray, 1871), is best known from 

 the Southern Hemisphere. In recent years its presence in the SCB has 

 been confirmed by four strandings on Southern California beaches, in 

 the months of May, September and December, and sightings near 

 Catalina Island m July and 50-75 nm west of San Diego, near San 

 Clemente Island, in September. 



All species of beaked whales are known to feed on scjuid and are 

 generally believed to be inhabitants of the high seas. Sightings of 

 unidentified beaked whales of the genus Mesoplodon have been mostly 

 over the Santa Rosa-Cortez Ridge, near Rodrigues Sea Mount and 

 west of the outer Channel Islands. It is not known whether forays of 

 these species onto continental shelf waters of the SCB are common or 

 exceptional, but it is the present working hypothesis that no beaked 

 whales are likely to be seen in the SCB except in deep water regions. 



Figure ji. Stranded beaked whales, probably Blainville's or Hubbs' beaked 

 whales, get some close up attention. Except for adult males, in which the 

 emerged teeth are helpful clues, beaked whales are difficult or impossible for 

 the novice to correctly identifv'. Even specialists often have to examine the 

 prepared -ikull. Photos hv P. C. Houorth. 



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