Cetacean remains and strandings in the Galápagos Islands, 1923-2003

Abstract

A compilation of data on cetacean remains and strandings found on the shores of the Galápagos Islands, eastern equatorial Pacific, for the period 1923-2003 is presented. Information is available for 87 records belonging to 13 species. Four species account for 71% of the records: Tursiops truncatus, Globicephala macrorhynchus, Delphinus delphis, and Ziphius cavirostris. Visitor sites and the vicinity of population centers yielded most of the records; no other geographic pattern was evident in the strandings. The stranding record reflects the odontocete communities of nearshore and upwelling environments in the Galápagos. Morphometric and meristic measurements are presented for 17 skulls belonging to T. truncatus, Stenella attenuata, D. delphis, and S. coeruleoalba. The measurements for T. truncatus are consistent with the offshore ecotype, although in the Galápagos the species predominantly occupies the nearshore environment. The stomach contents of a young Z. cavirostris included seven species of cephalopod and two crustaceans. Mass strandings of Z. cavirostris (n=2) and G. macrorhynchus (n=2) have been witnessed and documented, while remains of multiple individuals found together on the beach suggest additional mass strandings of Pseudorca crassidens, S. attenuata, T. truncatus, and G. macrorhynchus. Some of the records could be attributed to confirmed or presumed interaction with human activities including industrial-scale fishing, pollution, and loud sound sources.