AGE AT FIRST CALVING OF FEMALE HUMPBACK WHALES IN SOUTHEASTERN ALASKA

Abstract

Female humpback whales in southeastern Alaska have never been observed with their first calf at ages 5 to 7 years, the documented age at first reproduction in the Gulf of Maine humpback whale population. Long-term sighting histories of 10 individually identified females of known age in southeastern Alaska were used to address this issue. These females were sighted with their first calf at ages 8-16 (mean 11.8) years, significantly older than observed in the Gulf of Maine where 5.91 years is the mean age at first calving. We summarize potential sources of bias and other factors that likely contributed to the difference in age at first calving. Despite their limitations, these are the only available data to assess the age at first calving in North Pacific humpback whales. Figure 1. Stable markings on the ventral tail flukes of humpback whales, like this one photographed in Glacier Bay, Alaska, allow individuals to be identified over many years. Christine M. Gabriele and others 159 1 Glacier Bay National Park, P.O. Box 140, Gustavus, AK 99826 2 University of Alaska Southeast Sitka Campus, 1332 Seward Ave.,