Humpback whales and other marine mammals off Costa Rica and surrounding waters, 1996-2002
Rasmussen, K., J. Calambokidis, and G.H. Steiger. 2002. Humpback whales and other marine mammals off Costa Rica and surrounding waters, 1996-2002. Report of the Oceanic Society 2002 field season in cooperation with Elderhostel volunteers. Cascadia Research, 218½ W Fourth Ave., Olympia, WA 98501. 32pp
Since 1996, Cascadia Research has been conducting research on humpback whales and other marine mammals off the Pacific coast of Costa Rica and surrounding areas of Central America. The principal objectives are to examine aspects of humpback whale use of Central America including, the number, habitat preference, timing, behavior and migrations of humpback whales as well as document the occurrence of other marine mammals species.
The research has been conducted in collaboration with the Oceanic Society and with Elderhostel volunteer support. Small boat surveys from 1996-2002 were conducted primarily from Drake Bay on the north side of the Osa Peninsula, Costa Rica. Surveys were also conducted off of northern Costa Rica in 1999-2002, and off Panama in 2001-2002. All humpback whales seen were approached to obtain identification photographs of individual animals. Acoustic monitoring and recording for humpback song was conducted as an integral part of the visual surveys. Four aerial surveys were conducted in 2002 covering the entire Pacific coast of Costa Rica, and the western Pacific coast of Panama.
Humpback whales were consistently sighted in all years off southern Costa Rica, most whales found between the mainland and Canos Island where our principal survey effort was concentrated. Our success in finding whales in surveys off northern Costa Rica and Panama was more variable. The overall group composition for humpback whales off Costa Rica is not very different than has been reported in other wintering areas and included singles, cows with calves, and occasionally larger surface-active groups.
With the effort in 2002, 81 different individual humpback whales that has been identified off Central America (including S. Mexico to Panama) in winter months. Of these, 69 (85%) have been also seen off California, a match rate that indicates these whales exclusively migrate from the California feeding aggregation. This overall rate is higher than has been documented between any other winter and feeding regions that scientists have examined. whales feeding off southern California were more likely to migrate to Central America than those feeding of northern California, Oregon, and Washington. The longest migration documented was from Newport, Oregon, to Costa Rica (5,524 km) and the shortest documented transit was 56 days.
Since 2001, we have also begun to study the presence of humpback whales off of Costa Rica and Panama during the southern hemisphere wintering season (Northern Hemisphere summer). Of the 25 individuals identified off of Costa Rica and Panama during this season, three have also been identified feeding off the Antarctic Peninsula. This is the first documented migration between hemispheres and sets a new record for the longest migration by an individual mammal (8,400 km each way).
We documented sightings of 10 other marine mammals species besides humpback whales in our surveys. Spotted and bottlenose dolphins were the most common other species encountered. The increased tourism and other development in these regions makes it critical to document the occurrence of marine mammals and identify potential threats.