Aerial photogrammetry of southern right whales, Eubalaena australis

Abstract

Between July or August and November 1988 and 1989, 72 cow‐calf pairs of right whales (Eubalaena australis) were measured photogrammetrically from the air off De Hoop, South Africa. Median coefficients of variation ranged from 1.29 to 4.56%, being lowest in cows and calves for measurements of total length. Fifty‐seven adult cows measured from 12.37 to 15.54 m in length, with females photographed for the first time with a calf (= primiparous) being smaller than females that had been seen for the first time with a calf at least five years previously. The lengths of 72 calves ranged from 4.53 to 9.24 m, with those from primiparous females being significantly smaller than calves of multiparous females in every month except July. For 37 calves photographed on more than one occasion the growth rate averaged 2.8±0.7 cm per day, with no significant difference between growth rates of calves from primiparous and from other females, and no significant decrease in growth rate between July/September and September/November. Calves grew from an average of 40% of their mother's length in late July to 51% by mid‐October. The size distribution of the adult females was no different from that of 25 adult females landed at South African whaling stations between 1911 and 1963 (after adjustment for possible differences in measurement techniques). Five near‐term foetuses recovered in June‐August in the same whaling operations also agree closely with the size of calves predicted for 1 August. In a comparison with 17 calves stranded or dying accidentally on the South African coast, most of the accidentally caught animals agreed closely in size with the sample of photogrammetrically measured animals, while most of the stranded animals were equal to or smaller in size than the smallest length interval in the photogrammetrically measured animals. The calves of primiparous females may therefore suffer a higher natural mortality rate than those of multiparous females.

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

“…4a), a time during which rapid growth in length occurs, 2.8 ± 0.7 cm d -1 (Best & Rüther 1992). The blubber of E. glacialis calves measured in the late months of suckling was as thick as older juvenile whales (7 and 8 yr old whales) and much thicker than the younger juveniles (Fig.…”

“…Whales belonging to these 2 species appear to be comparable in size (Best & Rüther 1992, W. L. Perryman pers. comm.…”

“…1 calf was born in 2000 versus 31 calves in 2001; Kraus et al 2007), but showed a steady increase in E. australis off the coast of South Africa (Best et al 2001). Mean calving intervals for mothers of 2 or more calves in the North Atlantic increased from 3.67 yr (1987to 1992Knowlton et al 1994) to over 5 yr (1996 to 2003) and decreased to 3.2 and 3.5 yr in 2004 and 2005, respectively (CIs not stated) (Kraus et al 2007). In contrast, mean calving intervals for E. australis of the South African population remained steady at 3.12 yr (95% CI: 3.07, 3.17) from 1979 to 1995 (Best et al 2001).…”

Unexplained recurring high mortality of southern right whale Eubalaena australis calves at Península Valdés, Argentina

“…Mean calf length at birth is 5.5 to 6.1 m (Best 1981, Whitehead & Payne 1981, Best & Rüther 1992, but smaller calves, ranging from 4.5 to 5.5 m, can survive and comprised more than one-fifth of 72 living right whale calves measured off South Africa (Best & Rüther 1992). Calves grow as much as 3 m during their 2 to 3 mo on the calving ground (Best & Rüther 1992) while being nursed by their fasting mothers. Calves have not been seen to feed independently during their first 3 mo of life (Thomas & Taber 1984).…”

Coastal distribution, movements and site fidelity of right whales Eubalaena australis off South Africa, 1969–1998

“…Monthly photogrammetric helicopter surveys were flown in the De Hoop area of the coast from August to November 1988 and from July to November 1989 (Best and RUther 1992), on which 100 different cowcalf pairs were photographed. Resightings of these pairs off De Hoop (or elsewhere during the October surveys in 1988 and 1989) produced information on same-season dispersal and approximate residence time.…”