Steven K. Katona

Identification of Humpback Whales by Fluke Photographs

Among the large baleen whales, humpbacks are notable for the variety of different white and black patterns and slight morphological differences which can be observed between individuals (Lillie, 1915; Matthews, 1937; Pike, 1953; Schevill and Backus, 1960). Observations in the field and inspection of photographs suggest that variations in the shape of the dorsal fin or in the disposition of body scars can sometimes be used to identify individual humpback whales. It is primarily the pattern on the underside of the flukes which appears to us to provide the most positive discrimination between individual humpback whales. This pattern varies from nearly all white to nearly all black, but characteristically contains a variety of black or white patches, lines or streaks.

Identifying Humpback Whales using their natural markings

One must suppose that even before Melville transformed the true story of an unusually lightcoloured Sperm Whale named Mocha Dick into his epic novel, Moby Dick , and certainly afterwards, whalers and zoologists working in the whaling industry have noted that pronounced morphological differences often exist among whales of the same species and stock (Lillie, 1915; Matthews, 1937; Pike, 1953). During the past 15 years, scientists studying living whales have commented on individuals with odd marks, scars, pigmentation patterns or albinism, deformities, algal films or the shape and position of external features such as the dorsal fin.

Segregation of migration by feeding ground origin in North Atlantic humpback whales (Megaptera novaeangliae)

Results from a large-scale, capture–recapture study of humpback whales Megaptera novaeangliae in the North Atlantic show that migration timing is influenced by feeding ground origin. No significant differences were observed in the number of individuals from any feeding area that were re-sighted in the common breeding area in the West Indies. However, there was a relationship between the proportion (logit transformed) of West Indies sightings and longitude (r 2 = 0.97,F1,3 = 98.27,P = 0.0022) suggesting that individuals feeding farther to the east are less likely to winter in the West Indies. A relationship was also detected between sighting date in the West Indies and feeding area. Mean sighting dates in the West Indies for individuals identified in the Gulf of Maine and eastern Canada were significantly earlier than those for animals identified in Greenland, Iceland and Norway (9.97 days, t179 = 3.53, P = 0.00054). There was also evidence for sexual segregation in migration; males were seen earlier on the breeding ground than were females (6.63 days, t105 = 1.98, P = 0.050). This pattern was consistently observed for animals from all feeding areas; a combined model showed a significant effect for both sex (F1 = 5.942, P = 0.017) and feeding area (F3 = 4.756,P = 0.0038). The temporal difference in occupancy of the West Indies between individuals from different feeding areas, coupled with sexual differences in migratory patterns, presents the possibility that there are reduced mating opportunities between individuals from different high latitude areas.

History, migration and present status of humpback whales Megaptera novaeangliae at Bermuda

Abstract Historical accounts show that humpback whales Megaptera novaeangliae have frequented Bermuda waters, which are located half-way between wintering and summering grounds in the western North Atlantic, since the early 17th century. There were more humpbacks present in the 17th, 18th and 19th centuries than there are today. It also appears that humpback whales utilised the Bermuda area from February to May during these centuries, while today they occur at Bermuda for only three to four weeks in April. Humpbacks probably used Bermuda as a breeding ground in winter during these previous centuries and it may be an area that will be repopulated during winter if and when the population recovers from over-hunting. Using the distinctive pattern of pigmentation on the under-sides of the tail flukes, 104 individual humpback whales were identified at Bermuda and 44 of these have also been seen at other locations, including all the major summering and wintering grounds in the western North Atlantic. Chi-square analysis of these resighting shows that the whales occur at Bermuda in the expected proportions, relative to the samples, from the summering and wintering grounds. Contemporary utilisation of Bermuda by humpbacks is as a mid-ocean habitat through which all members of the western North Atlantic population migrate during spring. There is also evidence suggesting that humpback whales feed at Bermuda on deep water scattering layers during their stop-over.

Reproduction of Photographically Identified Fin Whales, Balaenoptera physalus, from the Gulf of Maine

We photographically identified 534 individual fin whales ( Balaenoptera physalus ) in the Gulf of Maine from 1980 to 1988, including 64 females and 40 young. Arrival patterns of mother-young pairs were similar to other whales within years. Individual females showed strong site fidelity to either the northern or southern Gulf of Maine, suggesting substock separation on the feeding range. Gross annual rates of reproduction (proportion of individuals that were young-of-the-year) for the Gulf of Maine ranged from 0.03 to 0.12 ( X = 0.08) among years. Greater proportions of young were observed in samples from the southern Gulf of Maine ( X = 0.12) than in the northern Gulf of Maine ( X = 0.05). Greater proportions of females also were observed in the southern Gulf of Maine ( X = 0.22) than in the northern Gulf of Maine ( X = 0.10). The average time between consecutive births was 2.71 years, which represented a crude birth rate of 0.37 young per mature female per year. We estimated a potential mean interval of birthing of 2.24 years by making some assumptions for three females with incomplete sighting histories. The overall gross annual rates of reproduction that we observed were similar to rates predicted by harvest data, but rates from the northern Gulf of Maine were less than predicted. Spatial segregation of sexes or age classes may be occurring within the Gulf of Maine.