A LACTATING RECORD-AGE ST. LAWRENCE BELUGA (DELPHINAPTERUS LEUCAS)

• Published in: Marine mammal science 1999-07, Vol.15 (3), p.854-859
• Main Authors: Malpine, Donald F., Kingsley, Michael C. S., Daoust, Pierre-Yves
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Delphinapterus leucas; Fundamental and applied biological sciences. Psychology; Mammalia; Marine; Vertebrata
• ISSN: 0824-0469; 1748-7692
• DOI: 10.1111/j.1748-7692.1999.tb00848.x

Belugas, Delphinapterus leucas, resident in the St. Lawrence estuary were accorded "endangered" status for the first time in 1983. This status was based on a "Committee on the Status of Endangered Wildlife in Canada" status report suggesting a population size of 300-350 animals in 1977 and indications that the number of animals was declining. On 25 May 1996 a freshly dead beluga was found floating in Miramichi Bay off Escuminac, New Brunswick (47 degree 05 theta N, 64 degree 55 theta W). Organochlorine levels for the specimen reported here were at the low end of the recent range of values for stranded St. Lawrence belugas. There were no obvious signs of cause of death, although bloody abrasions on the trailing edge of one flipper were present. The beluga was a female of 335 cm standard length and 527 kg total weight. The animal was short for a St. Lawrence beluga of this age: the asymptote of a Gompertz growth curve fitted to data from beach-cast St. Lawrence females was 362 cm. Blubber thickness in the middorsal region of the Escuminac beluga was 11 cm. A small quantity of milk was evident in the mammary glands, indicating the later stages of lactation. It has been remarked that beach-cast female belugas from the St. Lawrence population present a lower than normal rate of reproductive activity, especially the older ones. However, precise measures of the age structure of the live population have not been possible. Reproductive senescence does occur, but it has been interpreted as indicating a low birth rate in the entire population. However, naturally dead belugas in the St. Lawrence River and Estuary have often died from pathological conditions that may have lasted for some time before death, so they cannot be considered representative of the reproductive status of the live population. That the female beluga recovered at Escuminac, apparently killed accidentally, was reproductively active is therefore significant. The beluga reported here supports the use of the Alaska schedule to describe birth rates for the St. Lawrence population.