Distribution of southern right whale (Eubalaena australis) cow-calf pairs along the South African Coast: 1979-2019
By
Magali Terreri
Submitted in partial fulfilment of the requirements for the degree of
MSc (Zoology)
At the Institute of Zoology University of Innsbruck Austria
September 2020
Internal supervisor: External supervisor:
Dr. Engelbert Hobmayer Dr. Els Vermeulen Faculty of Biology Mammal Research Institute Department of Zoology Whale Unit University of Innsbruck University of Pretoria Austria South Africa
Table of Contents 1. Introduction ...... 3 1.1 Taxonomy ...... 3 1.2 Range and migration ...... 4 1.3 Distribution on the South African coast ...... 5 1.4 Why “right whale”? – historical background ...... 6 1.5 Description ...... 6 General information ...... 6 Callosities ...... 8 Colouration ...... 9 1.6 Reproduction ...... 13 1.7 Cow-calf interactions ...... 15 2. Material and Methods ...... 16 2.1 Aerial Surveys ...... 16 2.2 Natural marking for individual identification ...... 16 2.3 Collected Data and Analyses ...... 17 3. Results ...... 20 3.1 Coastwise distribution of cow-calf pairs ...... 20 3.2 Calving intervals and coastal distribution ...... 21 3.3 Reproductive experience and coastal distribution ...... 27 3.4 Coastal movements of cow-calf pairs and site fidelity ...... 31 4. Discussion ...... 36 5. Conclusion ...... 41 6. References ...... 42 7. Acknowledgments ...... 48 8. Declaration of Academic Honesty ...... 49
1. Introduction
1.1 Taxonomy
Cetartiodactlya is a supraorder in the class of the Mammalia. It contains two morphologically and ecologically different orders: the Artiodactlya and the Cetacea (Burda et al. 2008, Westheide & Rieger 2015). Within the order Cetacea, there are two distinctive suborders: the Mysticeti (baleen whales) and the Odontoceti (toothed whales) (figure 1). The southern right whale (Eubalaena australis) belongs to suborder Mysticeti and the family Balaenidae. In 1758, Carl Linnaeus classified the right whales in the genus Balaena. In 1822, Desmoulins describes the southern right whale as Balaena australis. In 1864, Gray proposed the genus Eubalaena for the right whales, as they were different from the bowhead whales (Balaena mysticetus). Rice, in 1998, placed the right whales in the same genus as the bowhead whale and named two different subspecies: Balaena glacialis glacialis (population in the Northern Hemisphere) and Balaena glacialis australis (population in the Southern Hemisphere). Rice recognized the right whales from all the oceans as one species. Back then, the classification of the southern right whale and the number of species in the genus Eubalaena were unclear. However, recent molecular analyses (Rosenbaum et al. 2000, Gaines et al. 2005) revised the right whale phylogeny and proved that there are 3 different right whale species: Eubalaena australis (southern right whale), Eubalaena japonica (North Pacific right whale) and Eubalaena glacialis (North Atlantic right whale). The southern right whale is the only member of the genus found in the Southern Hemisphere.
Figure 1. Classification of Cetaceans (from Westheide & Rieger 2015)
1.2 Range and migration
The southern right whale is found only in the Southern Hemisphere (figure 2) between 16°S and 65°S of latitude (Bannister 2001). During the austral summer, they are located in their feeding grounds at higher latitudes (e.g. Mate et al. 2011), whereas in winter, the whales migrate to their calving and breeding grounds at lower latitudes in the coastal waters of South America, South Africa and Australia/New Zealand (Bannister 2001). Distribution Map Eubalaena australis
Figure 2. Range of the Southern right whale (from Cooke & Zerbini 2018)
1.3 Distribution on the South African coast
The southern right whale distribution along the south African coast is predictable because it always follows the same pattern (Best 2000). The distribution is non-uniform and some areas along the coast have a higher whale density than others (Best 2000). The philopatry of female southern right whales also influences this discontinuous distribution, as 93.4 % of cows return to the area where they had their first calf (Best 2000). In 2000, Best suggested that not only the philopatry, but also environmental characteristics may be a reason for this distribution pattern along the coast. In 2004, Elwen & Best analysed the topographical characteristics to define the different areas along the South African coast and their influence on the broad and small scale distribution of southern right whales. Environmental factors such as calmness of the water, the nature of the sea bed, the slope of the sea bed and the depth of the water were considered. Their results suggested that female southern right whales with their calves favour areas with sandy
©beaches, The IUCN Redshallow List of Threatened water and Species: protected Eubalaena from australis seasonal – published wind in 2018. and open ocean swell (Elwen & 3 http://dx.doi.org/10.2305/IUCN.UK.2018-1.RLTS.T8153A50354147.en Best 2004b,c). Unaccompanied whales (males and non-calving females) have a different distribution pattern, as they favour deeper waters and are found further offshore (Elwen & Best, 2004b,c). Sandy substrates are favourable for cows with calves as it provides protection against injuries from rocks and also serves as an acoustic dampening, thus protecting from predation. The main nursery areas in the South African coastal waters are De Hoop and St Sebastian Bay while the main breeding area is Walker Bay (Elwen & Best, 2004b,c).
1.4 Why “right whale”? – historical background
In whaling history, the right whales got their names because it was, for the whalers, the right whale to hunt. They are generally in close proximity of the shore in their breeding grounds, they move slowly, float when killed, have long tapering baleens, and have a thick blubber layer (ideal for oil production) - thus making it the right whale to hunt with a high commercial value (Best 2007). During the whaling industry, the southern right whale population was decimated and came close to extinction. Between 1804 and 1877, an approximate number of 2,600 right whales were killed per year (both northern and southern right whales), but in the early 20th century, less than 100 right whales were killed per year due to low population numbers (Best 1970). Since 1935, right whales are internationally protected (League of Nations Convention on the Regulation of Whaling) and are recovering ever since (Best et al. 2001, Brandão et al. 2011).
1.5 Description
General information
Southern right whales have some characteristics which distinguish them from other whales (figure 3): they have no dorsal fin, their pectoral fins have a rectangular shape, they have a V- shaped blow and they have characteristic callosities (calcified skin patches) on their heads (Best 2007).
a b
c d
Figure 3. Right whales have a) no dorsal fin; b) rectangular pectoral fins, c) a V-shaped blow, and d) callosities on their heads (images source: Marine Mammal Research Institute Whale Unit)
The length of an adult female is on average 13.9 m (between 12.4m and 15.5m) (Best & Rüther 1992). According to measurements in Tormosov et al. (1998), male southern right whales tend to be smaller than females. Average weight of an adult southern right whale lies anywhere between 40 and 50 tonnes (Best, 2007).
118 S.-Afr. Tydskr. Dierk. 1990,25(2)
total, 16,7% of identified non-calves suitably photo- Table 2 Incidence of lip callosities in south- graphed off South Africa had white or grey dorsal marks ern right whales or both, and this greatly assisted in the matching process. Number of lip Argentina South Africa callosities (n = 188) (n = 245) Callosity patterns Unlike any of the natural markings mentioned above, None 38 (20,2) 64 (26,1) callosities are a universal feature of southern right One whales. This makes their natural variation extremely Right only 11 ( 5,9) 22 ( 9,0) useful for individual identification. The distribution of Left only 1 ( 0,5) 2 ( 0,8) callosities in general is similar to that described by Payne Two 138 (73,4) 157 (64,1) et al. (1983), and his nomenclature has been followed (Figure 3). As described by Payne et al. (1983), callosities appear Because of their greater visibility in aerial photo- in the newborn calf as smooth rounded protruberances, graphs (and perchance because it is these callosities that at least the larger ones of which split and crack with age are the most variable), the principal features used to as they grow in size. Their distribution appears to distinguish individual whales have been the rostral correspond to the position of facial hairs (Matthews islands and lip callosities, as well as the shape of the 1938; Omura et al. 1969). Probably because of their posterior edge of the bonnet. effects on the rate of water flow these callosities are The variation in lip callosities can be compared with frequently associated with large numbers of cyamids, data from Argentina (Table 2). The proportions of and (as originally suggested by Schevill, Moore & animals with two, one or no lip callosities were similar in Watkins 1981) it is probably a combination of the colour both localities (X 2 = 4,42; 2 df; p > 0,10). As described of these ectoparasites and of the callosity tissue itself that by Payne et al. (1983), there was a definite asymmetry in provides the contrast with the (usually) black surrourid- the distribution of lip callosities in the whales that ing skin discernible in aerial photographs. As the cya- carried only one, nearly all being found on the right hand mids are mobile, this contrast (and the resultant outline side. of the callosity) can and does change with time, a fact that is crucial to an interpretation of aerial photographs Matching individuals Callosities of callosity patterns. As a first step in the matching procedure, the complete