Skull Morphometry of the two subspecies of Long-finned Pilot Whale (Globicephala melas, Traill 1809)

MARINA, TOMÁS IGNACIO; GOODALL, RAE NATALIE; MARCHESI, MARÍA CONSTANZA

Congreso; 21st Biennial Conference on the Biology of Marine Mammals; 2015

The long-finned pilot whale (Globicephala melas, Trail 1809) inhabits the cold temperate waters of both the North Atlantic and the Southern Ocean, such that there are two widely-separated, anti-tropical populations. There are slight morphological differences between the two populations and they are accorded subspecies status: G. melas edwardii in the Southern Ocean and G. melas melas in the North Atlantic. This is the first study that characterizes and compares the skull morphometrics of the two subspecies. Only adult specimens were included in the analyses. The cranially mature sample totaled 93 specimens, 69 from the southern South Atlantic Ocean (edwardii subspecies) and 24 from the North Atlantic Ocean (melas subspecies). Skull morphometric data was collected with the aim of providing new information on the cranial characterization of the species and distinction between the two subspecies. Twenty-one measurements were taken using an anthropometer following Perrin (1975). On average, the skull of the edwardii subspecies was larger than that of the melas subspecies. Almost all measurements were larger in the Southern Ocean subspecies, with the exception of the preorbital and zygomatic widths. Significant differences were found in most of the measurements taken, with all the significant characters being larger in the Southern Ocean subspecies. Although the rostra of the edwardii subspecies were longer, there was no important difference in the widths. According to the Principal Component Analysis, the following were the characters that explain most of the variance between the subspecies: rostrum to external and internal nares, and length of orbit. The present work brings a new line of evidence to help re-assess the current taxonomy of Globicephala melas. Further research is needed to infer if these differences in skull morphometrics could have implications in the feeding strategies.