Date of Award
Program or Major
Doctor of Philosophy
Twenty two years of North Atlantic right whale data were analyzed. Several measures indicate reproduction in North Atlantic right whales is in a decline. Calving intervals have increased from about 3.3 years in the 1980's to over 5 years, and the age of first parturition is estimated to be 11 years. Females may lose calves before they are detected, artificially increasing the apparent age of first parturition and possibly affecting estimates of calving interval. Northern feeding habitat use patterns do not appear to affect reproduction.
Right whale mortality data was analyzed by age, sex, and habitat use patterns. A total of 46% of all confirmed mortalities are due to human activities. The characteristics of animals presumed dead from long gaps in sighting histories match known anthropogenic mortalities, but not those attributable to natural mortality. Sighting probabilities vary significantly by age, habitat-use pattern and individual. Tag-recapture models of extremely small populations are vulnerable to such heterogeneity, since animals missing for extended periods can create spurious estimates of survivorship, growth rates, and population viability.
An analysis of satellite-tracked movements of two adult female right whales in the Gulf of Maine, one with a calf and one without, examined relationships between whale movements and sea-surface temperature, distance to front, frontal density, depth, and bottom slope. The cow was primarily influenced by sea surface temperature and the non-calving adult female was primarily influenced by the "distance to fronts". The movements of the cow may reflect the immature thermoregulatory requirements of her calf. In contrast, the movements of the non-calving female appear to be independent of temperature, and may indicate the use of frontal boundaries for navigation and food-finding.
Fishing entanglements and collisions with ships are approximately equally responsible for nearly half of all right whale deaths. There are large gaps in the data that inhibit informed mitigation. Right whales face serious problems, but as a long-lived species, a decadal period crisis does not necessarily spell extinction.
Kraus, Scott Douglas, "Birth, death and taxis: North Atlantic right whales in the twenty-first century" (2002). Doctoral Dissertations. 90.