Desray Reeb

Composition and possible function of social groupings of southern right whales in South African waters

We collected behavioural data and skin samples for molecular sex determination from 327 right whales (Eubalaena australis) in the coastal waters of South Africa between July and October, 1995 and 1996, as well as from 147 cows with calves-of-the-year between August and October 1996, September and November 1997. Data on group size, composition and behaviour were also available for 85 sightings of right whales south of 40degreesS. Although right whales are considered to be relatively non-social, only 23.3% of animals (apart from cow-calf pairs) encountered in South African waters were alone (N = 649), compared to 84.6% of animals seen south of 40degreesS in summer (N = 94). Of the pairs other than cows with calves encountered off South Africa, 31.0% (N = 58) were believed to be composed of cows with last-years calves (=yearlings): 93.3% (N = 15) of these yearlings were female, suggesting a possible mechanism for female philopatry. The incidence of these mother-yearling pairs dropped sharply after early August, indicating the abrupt weaning of some calves at an age of approximately one year. Most other animals were observed either in surface-active groups (SAGs) that indulged in apparent courtship behaviour, or in non-surface-active groups (non-SAGs). SAGs tended to be larger on average than non-SAGs (4.45 animals, N = 33, range 2-10, versus 2.57 animals, N = 108, range 2-5, respectively), and males predominated, while females predominated in non-SAGs. The number of animals participating per SAG increased through the season, whereas the size of non-SAGs remained constant. Given that most conceptions in southern right whales are estimated to occur in a 118-day period around mid-July, the observed increase in group size through late August and September may be due to declining availability of receptive females. Focal animals in SAGs proved to be predominantly female (83.3%, N = 24) and non-focal animals predominantly male (85.2%, N = 61): a few groups observed late in the winter season had a male rather than female focal animal. Sighting histories of the focal females revealed that none was seen with a calf in the 17 years that preceded the surveys, but four had been seen as calves, 2-5 (average 3.75) years previously. Six females were photographed with calves from 2 to 5 years after being the focal animal in a SAG, which is consistent with the observation that most focal females in SAGs were young, pre-pubertal animals, and therefore being the focal animal did not normally result in conception. It is still unclear where (and when) conceptions occur in southern right whales, but it is hypothesised that the focal females are practising a mating strategy in which the chances of conceiving with a larger male will be maximised. As neonatal survival is partly related to size, the female will in this way protect her substantial investment in time and energy represented by the calf.

Structure of the integument of southern right whales, Eubalaena australis

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.

BIOPSYING SOUTHERN RIGHT WHALES: THEIR REACTIONS AND EFFECTS ON REPRODUCTION

Abstract 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.

Yeast infection in a beached southern right whale (Eubalaena australis) neonate

A female southern right whale (Eubalaena australis) neonate was found stranded on the Western Cape coast of southern Africa. Skin samples were taken the same day from three different locations on the animal’s body and stored at −20 C. Isolation through repetitive culture of these skin sections yielded a single yeast species, Candida zeylanoides. Total genomic DNA also was isolated directly from skin samples. Polymerase chain reaction analysis of the internal transcribed spacer region of the fungal ribosomal gene cluster revealed the presence of Filobasidiella neoformans var. neoformans, the teleomorphic state of Cryptococcus neoformans. Fungal infections in cetaceans seem to be limited when compared to infections caused by bacteria, viruses and parasites. However, Candida species appear to be the most common type of fungal infection associated with cetaceans. To our knowledge this is the first report of a C. zeylanoides infection in a mysticete, as well as the first report of a dual infection involving two opportunistic pathogenic yeast species in a cetacean.

EVIDENCE OF POSTNATAL ECDYSIS IN SOUTHERN RIGHT WHALES, EUBALAENA AUSTRALIS

Abstract This paper presents evidence of the presence and subsequent loss of postnatal skin in an ecdysis-like process in southern right whales, Eubalaena australis. Individuals whose skin was noticeably uneven, spongy, broken, and often light gray in color formed ≥20% of right whale neonates seen on the South African coast on any day up to and including the 1st week of September. Thereafter ≥85% of calves were of the normal, smooth-skinned appearance. The 50% transition point between the 2 forms occurred on 31 August (95% CI 1.1 days), or about a week after birth. Histological analysis of skin from stranded neonates showed a definite cleavage plane in the midepidermis, the mechanical integrity of which was further compromised by low concentrations of desmosomes and intracellular filaments. We propose that focal edema develops between the cells and forms the cleavage plane, which eventually leads to separation of the outer epidermal cell layer (cf. spongiosis in humans). The movement from the intrauterine to the oceanic milieu, and the osmoregulatory consequences thereof, may be a catalytic factor for this process to occur. This ecdysis may have important consequences for the cyamid fauna of neonatal right whales.

Diurnal movements and behaviour of Heaviside's dolphins, Cephalorhynchus heavisidii, with some comparative data for dusky dolphins, Lagenorhynchus obscurus

The sympatric Heavisides (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) are poorly studied in South Africa and are potentially at risk from anthropogenic threats Including fisheries bycatch. As part of a larger study, shore-based observations were made in a small bay (∼1000 m wide) in the Western Cape, South Africa, during the summer months of 1999–2001 to gather data on their nearshore movements and behaviour. Heavisides dolphins exhibited a diurnal onshore—offshore migration and the sighting rate varied significantly with time of day and brightness of the moon, with numbers being markedly higher before 12:00 and nearer a full moon. These patterns were presumed to be linked to the vertical migration of their principal prey, Juvenile hake Merluccius species and Heavisides dolphins appeared to be resting and not feeding Inshore during the day. Sightings of dusky dolphin showed no predictable variation with time of day but their numbers Inshore were significantly lower when upwelllng conditions existed offshore. Larger groups of Heavisides dolphins (especially groups of four) were more active (leaps, etc.) than smaller groups, but behaviour was not linked to environmental factors. The dissimilar responses to environmental conditions suggest that sympatry in these two species is mediated by niche as well as prey differentiation.

Near-shore distribution of Heaviside’s (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) at the southern limit of their range in South Africa

Photo-identification surveys over three years along 390 km of coastline north of Cape Town, revealed that Heavisides dolphin distribution was consistent between years and higher in areas more exposed to swells and with greater long-term availability of small hake Merluccius capensis (their principal prey). Dusky dolphin sighting rates varied considerably between years, but were generally higher in areas with lower hake availability and sandier shores (mostly straighter coastline). Large groups of 50–200 dusky dolphins were only seen in St Helena Bay the site of a wind-driven upwelling zone. Heavisides dolphins were found in shallower, cooler water than dusky dolphins and were more likely to be seen during brighter phases of the moon (when nocturnal light conditions may influence the vertical migration patterns of prey) and in areas of high hake abundance, Near-shore fishing activity was higher in the northern half of the study area and clustered around harbours. Set netting occurred only at Yzerfontein and St Helena Bay, but due to changes in the industry is currently thought to be a low threat to the population. Interactions between Heavisides and dusky dolphins were usually neutral and sympatry appears to be mediated by differences in overall range and the type and size of prey species taken.

Fungi associated with the skin of a southern right whale (Eubalaena australis) from South Africa

Abstract Cutaneous fungi are known to affect parts of the outermost skin layers of mammals, including the epidermis, stratum spinosum and stratum corneum, as well as mucocutaneous membranes, genitalia or external ears. Relatively little is known about fungal infections of Mysticete cetaceans and studies are needed to determine the fungal diversity associated with these marine mammals. This case report was aimed at identifying the fungi associated with the skin of a diseased neonatal southern right whale (Eubalaena australis) found stranded in the Western Cape Province of South Africa. Initial physical examination on site revealed hyperplasia of the follicular and epidermal epithelium. Preliminary examination of skin biopsies using scanning electron microscopy indicated that the skin was colonized by fungal hyphae. Isolation methods yielded a number of fungal isolates, which were identified using standard morphology and rDNA sequence data. These analyses confirmed colonization of the cutaneous layers by species belonging to the genera Fusarium, Chaetomium and Penicillium. Moreover, all isolates were capable of degrading keratin, indicating that skin may act as a natural substrate for these fungi. This study is the first report of the association of these fungi with southern right whale skin.