Biological data on two Hector's beaked whales, &lt;i&gt;Mesoplodon hectori&lt;/i&gt;, stranded in Buenos Aires province, Argentina

H L Cappozzo,A Saubidet,M F Negri,B Mahler,V V Lia,P Martinez,A Gianggiobe

doi:10.5597/lajam00076

Abstract

Beaked whales or ziphiids are the least known cetaceans, and are among the least studied of all mammalian groups. In August and September of 2002, a male and a female beaked whale stranded alive on the Argentine coast, 110km away from each other. The specimens died shortly after the stranding and their bodies were collected for dissection and analysis. The specimens were identified as belonging to the genus Mesoplodon. Further measurements of the skulls, shape and location of teeth as well as molecular analyses of the mtDNA control region and cytochrome b, allowed unambiguous identification of both specimens as Hector's beaked whale, Mesoplodon hectori. The color pattern was different between male and female. Standard length was 3.94 meters for the male and 3.84 meters for the female. The female's vertebral formula was C7 + T10 + L11 + Ca21 = 49. Histo-pathological analysis of the female revealed the presence of Sarcocystis sp. in the skeletal muscle, and lung lesions related to parasitic damage and pneumonia or chronic infection. The stomach of both individuals was empty. The digestive tract of both specimens was infected by larval stages L4 of Anisakis sp. The female was also infected by Tetrabothrius sp. and Bolbosoma sp. while Braunina cordiformis was only found in the male. Different composition of parasitic fauna suggests possible sex-related differences in the diet or individual variability. Total length, teeth eruption (in the male) and the degree of vertebral epiphyses fusion suggest that both individuals were mature.

Highlights

Beaked whales are poorly known cetaceans and among the least studied of all mammalian groups (Dalebout et al, 1998)
The specimens stranded at Mar del Plata and Quequén coasts were identified as Hector’s beaked whales, Mesoplodon hectori, based on features of the skull, and shape, size and placement of the teeth
The stranding of two individuals of the same species only three weeks and 110km apart from each other could be considered as a unique biological event, as both stranding events occurred within the same general area and time frame

Summary

Introduction

Beaked whales (family Ziphiidae) are poorly known cetaceans and among the least studied of all mammalian groups (Dalebout et al, 1998). Out of 21 ziphiid species, 14 belong to the genus Mesoplodon, which is the most diverse genus among all cetaceans (Dalebout et al, 1998; 2004; Mead, 2002; Pitman, 2002). Their preferential habitat is deep oceanic waters which makes them difficult to observe or strand. Mesoplodon species are very similar, rare and difficult to identify from sightings at sea and even from strandings (e.g. Gales et al, 2002; Pitman, 2002; Laporta et al, this issue)

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