The high variability in reproductive performance of North Atlantic right whales Eubalaena glacialis compared to southern right whales Eubalaena australis may reflect differences in lipid reserves. Amplitude-mode ultrasound was used to measure the thickness of right whale integument (epidermis and blubber, herein referred to as blubber thickness) in E. glacialis in the Bay of Fundy, Canada for 5 summer seasons and in E. australis off the South African coast for 2 austral winter seasons. E. glacialis had significantly thinner blubber layers (mean ±1 SD = 12.23 ± 2.16 cm, n = 172) than E. australis (16.13 ± 3.88 cm, n = 117), suggesting differing levels of nutrition between the 2 species. Blubber was thickest in females measured 3 to 6 mo prior to the start of pregnancy (E. glacialis), thinner during lactation (E. glacialis, E. australis) and then thicker with time after weaning (E. glacialis). These results suggest that lipids in blubber are used as energetic support for reproduction in female right whales. Blubber thickness increased in calves during suckling (E. glacialis, E. australis) but subsequently decreased after weaning (E. glacialis). Juvenile and adult male E. glacialis blubber thicknesses were compared between years of differing prey Calanus finmarchicus abundances (data from Pershing et al. 2005; ICES J Mar Sci 62:1511-1523; during a year of low prey abundance whales had significantly thinner blubber than during years of greater prey abundance. Taken together, these results suggest that blubber thickness is indicative of right whale energy balance and that the marked fluctuations in North Atlantic right whale reproduction have a nutritional component.

Skin (integument) anatomy reflects adaptations to particular environments. It is hypothesized that cetacean (whale) integument will show unique anatomical adaptations to an aquatic environment, particularly regarding differences in temperature, density, and pressure. In this study, the gross and histological structure of the southern right whale integument is described and compared with terrestrial mammals and previous descriptions of mysticete (baleen whale) and odontocete (toothed whale) species. Samples were taken of the integument of 98 free-swimming southern right whales, Eubalaena australis, and examined by both light and electron microscopy. Results show that three epidermal layers are present, with the stratum corneum being parakeratotic in nature. As in bowhead whales, southern right whales possess an acanthotic epidermis and a notably thick hypodermis, with epidermal rods and extensive papillomatosis. However, unlike bowhead whales, southern right whales possess an uninterrupted hypodermal layer. Surprisingly, the integument of balaenids (right and bowhead mysticetes) in general is more like that of odontocetes than that of the more closely related balaenopterids (rorqual mysticetes). Similarities to odontocetes were found specifically in the collagen fibers in a fat-free zone of the reticular dermal layer and the elastic fibers in the dermal and hypodermal layers. Callosities, a distinctive feature of this genus, have a slightly thicker stratum corneum and are usually associated with hairs that have innervated and vascularized follicles. These hairs may function as vibrissae, thus aiding in aquatic foraging by allowing rapid detection of changes in prey density. Although the thick insulatory integument makes right whales bulky and slow-moving, it is an adaptation for living in cold water. Epidermal thickness, presence of epidermal rods, and callosities may act as barriers against mechanical injury from bodily contact with conspecifics or hard surfaces in the environment (e.g., rocks, ice). Anat Rec, 290:596-613, 2007. 2007 Wiley-Liss, Inc.

Collecting skin biopsies from large whales for genetic analysis is often subject to national permit, and in the case of cow‐calf pairs, it may be prohibited. We present results of 906 biopsy attempts on southern right whales (Eubalaena australis) in South African waters between 1995 and 1997, including 147 cow‐calf pairs. Our sampling success was higher for biopsy darts with a bore of 4 mm compared to 4.6 mm. Contact periods averaged 17.7 min for cow‐calf pairs and 25.4 min for whales unaccompanied by calves. There were no significant differences in the short‐term reactions of males and females to biopsying, but the reaction of single animals of either sex was greater than for larger groups. Cows accompanied by calves had the strongest reactions, which were significantly greater than even single females. We found evidence of sensitization to repeat biopsying (over periods of hours to 65 days) for cows but not calves (n = 20). We compared the subsequent reproductive history of 117 biopsied cows with that of 163 unbiopsied cows from the same years, and we compared the distribution of calving intervals for biopsied animals with 829 intervals recorded from 1985 to 1995. We did not detect any adverse effects on the proportion of successful reproductive cycles, and hence calf survival, or the proportion of longer‐than‐normal cycles, although the power of all the statistical tests was low. We concluded that any prohibition on the biopsy sampling of cow‐calf pairs should be carefully reconsidered in the light of the valuable genetic insights such sampling could achieve.

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