Age structure and longevity in North Atlantic right whales Eubalaena glacialis and their relation to reproduction

Abstract

Although there are a number of techniques for determining age in dead baleen whales, few exist for live, free-swimming animals. Photo-identification records of 374 cataloged individuals through 1996 were used to assess the age of first parturition, the age structure and the longevity of the North Atlantic right whale Eubalaena glacialis. Nearly the entire population is identified and the majority of the whales have extensive sighting histories dating from 1980, with some earlier sightings dating as far back as 1935. The observed mean age at first parturition for females with complete sighting histories (n = 13) is 8.7 yr and the age at which whales are considered adults, based on the mean age of first observed parturition for all known-age females (n = 20), is 9 yr. Juveniles and calves constitute 26 to 31 % of the population, considerably less than in other baleen whale species One wha1.e is at least 65 yr old, and reproductive histones of others span up to 29 yr. Although the 65 plus yr old whale is possibly reproductively senescent, her apparent lack of calving may be due to anthropogenic factors or to undocumented calvings.

Paralytic shellfish poisoning (PSP) toxins in North Atlantic right whales Eubalaena glacialis and their zooplankton prey in the Bay of Fundy, Canada

“…Long-term shipboard and aerial surveys of right whales throughout their known migratory range have provided over 25 yr of data on the life history of individual whales (Hamilton et al 1998, Kraus et al 2001.…”

Fecal glucocorticoids and anthropogenic injury and mortality in North Atlantic right whales Eubalaena glacialis

“…mitochondrial haplotype, microsatellite profiles) was used to associate fecal samples with individual whales, using criteria described by Gillett et al (2010) and Doucette et al (2012). Whales were classified by age following Hamilton et al (1998): calves <1 yr; juveniles 1−8 yr; adults ≥9 yr (or the year before first calving in fe males). Extensive survey effort in the NARW calving ground and other habitats enabled identification of the vast majority of calving females, allowing for determination of reproductive status in adult females as either pregnant, lactating, or resting (i.e.…”

Blubber thickness in right whales Eubalaena glacialis and Eubalaena australis related with reproduction, life history status and prey abundance

“…Since data from Hamilton & Cooper (2010) suggest that peak calving occurs in December or January and the blubber thickness measurements were collected from late July to early September, calves were approximately 8 to 9 mo old when measured. Sexual maturity occurs at approximately 9 yr of age ; therefore, whales were classified as juveniles if they were between the ages of 1 and 8 yr and as adults if they were ≥9 yr old, had a sighting history of at least 9 yr (Hamilton et al 1998) or, for females, if they were consistently sighted in close association with a calf (Knowlton et al 1994). Males were assumed to reach sexual maturity at the same age as females.…”