48 
Wm. David Webster et al. 
North Carolina waters throughout the year. Monthly variation can be 
explained by the tendency to mass strand by pilot whales, the rough- 
toothed dolphin, and possibly Risso’s dolphin. It is difficult to explain 
significant monthly variation exhibited by the Atlantic spotted dophlin 
( Stenella frontalis (G. Cuvier)), which includes stranding records previously 
attributable to S. plagiodon (Cope), a species once thought to inhabit 
the Atlantic Ocean. Taxonomic uncertainty in the genus and the difficulty 
in identifying individuals have been presistent sources of error; however, 
the recent revision of Stenella in the western North Atlantic Ocean 
(Perrin et al. 1987) should help alleviate future misidentifications. 
Significant monthly variation in stranding by Kogia simus might best 
be explained by a behavior displayed by its close relative, the pygmy 
sperm whale ( Kogia breviceps (Blainville)). In southeastern North Carolina, 
we have noticed that strandings of K. breviceps frequently involve 
females in the process of giving birth or mother-offspring pairs, a 
behavior also reported by Winn et al. (1979). These seven species 
account for approximately 17% of the total number of strandings reported 
from North Carolina. 
The remaining seven species of cetaceans are relatively rare in 
North Carolina waters, and scanty stranding records provide little informa- 
tion about their resident status in the state. The killer whale ( Orcinus 
orca (Linnaeus)), false killer whale ( Pseudorca crassidens (Owens)), 
True’s beaked whale ( Mesoplodon mints True), and Cuvier’s beaked 
whale (Ziphius cavirostris G. Cuvier) are thought to be year-round 
residents (Leatherwood and Reeves 1983), but the Atlantic white-sided 
dolphin (Lagenorhynchus acutus (Gray)) inhabits the northern North 
Atlantic Ocean (Leatherwood and Reeves 1983) and seldom ventures 
into North Carolina waters. The pygmy killer whale ( Feresa attenuata 
Gray) and long-snouted spinner dolphin (Stenella longirostris (Gray)) 
probably enter North Carolina waters during the warmer months of 
the year (Leatherwood and Reeves 1983). Collectively, this group of 
species constitutes only about 2% of the total number of strandings 
reported from North Carolina. 
Although marine mammal strandings provide a fortuitous source 
of information on animals that are not typically accessible, there are 
inherent biases in conclusions derived from stranding data. Neritic 
species strand more frequently than pelagic species, so stranding fre- 
quencies are less likely to reflect accurately the abundances of pelagic 
species. Larger-bodied species and mass strandings are more likely 
to be reported than small-bodied species or single strandings. Also, 
the Gulf Stream and Labrador Current could transport dead or dying 
animals beyond their normal ranges and into North Carolina waters. 
