Distribution of southern right (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 Research Institute Department of Zoology Whale Unit University of Innsbruck University of Pretoria Austria

Table of Contents 1. Introduction ...... 3 1.1 ...... 3 1.2 Range and migration ...... 4 1.3 Distribution on the South African coast ...... 5 1.4 Why “”? – 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 (Burda et al. 2008, Westheide & Rieger 2015). Within the Cetacea, there are two distinctive suborders: the Mysticeti ( ) and the Odontoceti (toothed whales) (figure 1). The (Eubalaena australis) belongs to suborder Mysticeti and the family . In 1758, classified the right whales in the . 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 and named two different subspecies: Balaena glacialis glacialis (population in the ) and Balaena glacialis australis (population in the Southern Hemisphere). Rice recognized the right whales from all the oceans as one . 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 Africa and / (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 (Elwen & Best, 2004b,c).

1.4 Why “right whale”? – historical background

In 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 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 . 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: 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 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 & 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

In the only two fresh stranded right whales examined Callosities are raised and thickened patches of skin on the head of the right whales. In newset- of colour photographs available for anyone by the author that were not calves, the major callosities born calves, callosities are smooth protrusions that become rough and scarred over timeindividual was examined under 8x magnification and the (e.g. chin, bonnet and eyebrow) were also inhabited by placed in one of several alternate classes under (Payne et al. 1983). These callosities are covered in colonies of cyamids (whale lice), which

the burrowing barnacle Tubicinella sp. In one animal an

four separate categories, namely dorsal body colour (all

give the callosities the typical grey-whitish colouration (Payne et al. 1983). The general

estimated 110 Tubicinella were located in the chin black, grey markings only, grey and white markings,

distribution of the callosities on the head are mostly in areas where hair follicles are present; callosity, 68 in the eyebrow and six in the bonnet, with· white markings only, no data), incidence of lip callosities represented in figure 4. They can be found in different areas of the head: the bonnet is the two in the posterior blowhole islands and one in the first (none, on one lip only, on both lips, no data), size of lip

largest callosity in right whales; the coaming is a single callosity in front of the blowholes; the mandibular island. These two whales, both stranded in callosities (length of larger less than half, about half or

postSeptember,-blowhole island were is one orrespectively two callosities (rarelyonly more) 10,06 right m behind and the9,25 blowholes, m themore than half distance from posterior edge of bonnet to

long, and thus probably juvenile; in adults the number of chin callosities are on each side of the lower jaw; the eyebrow callosities are right above eachanterior edge of coaming) and number of rostral

eye;barnacles the rostral and present mandibular could islands obviously are little callosities be greater.that can vary If in thisnumber is and arecallosities (minimum-maximum number).

locatedso, alongtheir the presence rami of the lower could jaw (mandible)contribute and between substantially the bonnet andto thethe coaming; These classifications were entered on a Paramount stability, conformation and even colour (the cirri and punch card (together with data on the area, photogra- the lip callosities are on the upper edge of the lower lip and range from a small spot to a strip

mantle being light yellow) of the callosities. x (Payne et al. 1983). pher, behaviour, age and sex of the animal). A 7 8 cm

black-and-white enlargement of the head region of the

whale (and a similar size print of any coloration feature Post- blowhole not visible on the head photograph) was also pasted on island

the card. Additional information (exact date and locality of all sightings) was entered on the back of the card .

...... Eyebrow

The card for a newly photographed (and therefore

Coaming.

unknown) whale could then be compared with all known

...... Lip Rostral animals on file and all those individuals that did not

island , resemble the unknown animal in all four categories , ...... Mandibular rapidly excluded. As an example, for the 72 individuals island

Chin

from the 1984 survey, this procedure resulted in from

72,9 to 100 % (mean 88,2%) of the total file being

Borinet excluded for each unknown animal examined.

The remaining candidates for a match were compared

Figure 4. Nomenclature of the callosities on the head of a southern right whale (from Best 1990b)

Figure 3 Nomenclature of the callosities on the head of a visually with the unknown animal, using the black and

southern right whale (hatched structures are universal, white prints on the cards. If a possible match was found, Theunhatched callosity pattern are on highly the head variable of the whales features.) is very distinctive and unique to each and everya final comparison was made between all the original

individual. On photographs, the contrast between the dark skin and the grey-whitish colouration of the callosities (due to the whitish cyamids) makes it possible for researchers to identify whales (Payne et al. 1983, Best 2007).

Colouration

Other distinctive markings, useful to researchers for the identification of southern right whales, are the dorsal colouration patterns (Payne et al. 1983). Wounds and skin shedding can also help identify whales but the patterns are not permanent and is therefore only useful for a short time period: wounds stay for a few years and peeling skin only e.g. for a photographing sequence during a survey (Payne et al. 1983, Best 1990b). The other dorsal colourations stay permanently throughout the whale’s life and can therefore be used for the identification of individuals (Payne et al. 1983, Best 1990b). In total, 6 dorsal skin colouration patterns (table 1) have been described for the southern right whales: black, white blaze, partial grey-morph, and grey morph which is also known under the name of brindle. The fifth colouration is a combination of partial grey-morph with a white blaze and the sixth colouration is a combination of grey morph with a white blaze (Payne et al. 1983, Best 1990b, Schaeff et al. 1999).

Table 1. Description of the dorsal colouration patterns in southern right whales (from Schaeff et al. 1999)

In general, southern right whales are black (wild-type) and have a ventral white blaze (Eroh et al. 2017) (figure 5a). This ventral white blaze is ranging from a small patch to a to a large blaze sometimes extending to the side or even the dorsal part of the body (Best 2007). A dorsal white blaze (figure 5b,c) can also be present in southern right whales: they are white patches of unpigmented skin with very distinctive outline and which do not change over time (Payne et al. 1983, Best 1990b). Whales can also be partial-grey morphs (figure 5d), which means they have a patch of whitish or bluish-grey coloured skin with a more complex and irregular outline than the white blaze. Partial-grey morph colouration is usually lager in size than the white blaze, darkens with age turning brownish-grey (figure 5e) and the outline doesn’t change over time (Payne et al. 1983, Best 1990b). Grey morphs lack the black pigmentation over the entire body. They appear almost completely white as calves with scattered black spots, especially in the neck region (figure 5f). With age, the colouration darkens and becomes grey or brownish-grey (figure 5g) (Payne et al. 1983, Best 1990b). A combination of white blaze and partial-grey morph (figure 5e) or white blaze and grey morph (figure 5h) can also occur together, where the white blaze stays unchanged over time and the partial-grey morph and grey morph colouration respectively darkens over time.

a b c d

e f g h

Figure 5. Different dorsal colourations in southern right whales. a) black, b) white blaze, c) white blaze, d) partial-grey morph, e) partial-grey morph with white blaze, f) grey morph calf, g) grey morph adult, h) grey morph with white blaze (images source: Mammal Research Institute Whale Unit)

The colouration patterns described above are genetically influenced. The phenotypes grey morph (genotypes XgXg and XgY) and partial-grey morph (genotype XGXg) are controlled by an X-linked gene and the white blaze phenotype is controlled by an autosomal gene, and both are inherited independently from each other (Schaeff et al. 1999). The dorsal white blaze is distributed equally amongst males and females (Best 2007). The partial-grey morph colouration is female-specific and resulting from the heterozygote genotype XGXg (Schaeff et al. 1999). Analyses carried out by Schaeff et al. (1999) showed that the black colouration (XGXG, XGY) is the most common. Amongst all individuals genetically sexed, all partial-grey morph were females (as this genotype is female-specific) and all grey-morphs were males (XgY). Best (2007) stated, that 94% of grey morphs are males and grey morph females (XgXg) are very rare. In fact, to produce grey morph female calves, the association of a grey-morph (XgY) male and a partial-grey morph or grey morph female (XGXg or XgXg) is needed.

The colouration is not found to influence the fertility or the reproductive success of the right whales (Schaeff et al. 1999).

Eroh et al. (2017) analysed the grey morph phenotype of southern right whales on a cellular and ultrastructural level and observed that lack of black pigmentation in the skin of grey morph whales is due to a lesser amount of melanocytes. The melanosomes in the skin of grey morphs are smaller than those in the skin of a wild-type black colouration. The grey morph phenotype is not to be confused with albinism, as this is a pigmentation pattern associated with either the absence of melanocytes or the inability of them to synthesize melanin (Eroh et al. 2017).

1.6 Reproduction

As in other baleen whales, the reproduction cycle of the southern right whales is synchronized with their feeding cycle and thus their annual migration (Braham & Rice 1984). By monitoring the years in which cows are photographed with successive calves in their breeding grounds, it is possible to calculate the calving interval.

A southern right whale cow normally gives birth to a calf every 3 years (Payne 1986, Knowlton et al. 1994, Best et al. 2001), including 1 year of gestation, 1 year of lactation and 1 year of resting (figure 6). However, calving intervals of 2 to 23 years have previously been reported (Best 2011a). A 2 year calving interval takes place after a cow loses a neonate resulting in the ovulation the subsequent year (there is no need for a rest-year) (Burnell 2001). A 4 year calving interval is believed to occur when a cow loses the foetus early in pregnancy or fails to fall pregnant, and shifts to an additional resting year before the next gestation period (Knowlton et al. 1994). Burnell (2001) points out in his study, that a part of the Australian southern right whale population might have a normal calving interval of 4 years, as the proportion of cows calving after 4 years is high. Elwen & Best (2004a) suggest that a 4 year calving interval might also be induced by a lack of food, resulting in the cows needing an additional resting year to regain the required body condition to go through a pregnancy. A 5 year calving interval can also be interpreted as a calving failure, when the cow loses the foetus late in pregnancy or when the newborn calf dies, in which case the calf is not observed (Knowlton et al. 1994). A 5 year calving interval can thus be seen as a 3 year calving interval followed by a 2 year calving interval (Knowlton et al. 1994).

Nursing 1 year

One calf every 3 years

Gestation Resting 1 year 1 year

Figure 6. Normal reproduction cycle of southern right whales in a best case scenario

The gestation period lasts about 1 year and a cow gives birth to one single calf (Best 1994, Braham & Rice 1984)

There is no exact period known for the nursing time. According to Tormosov et al. (1913), lactation in southern right whales lasts 7 to 8 months. The calf remains with its mother throughout the winter following the year of birth (Braham & Rice 1984).

Southern right whales reach their sexual maturity between 6 and 9 years of age (Payne 1986, Knowlton et al. 1994, Braham & Rice 1984, Best et al. 2001).

1.7 Cow-calf interactions

Thomas & Taber (1984) defined three stages of cow-calf behavioural interactions from after birth until the start of migration. The first stage is the “newborn travel stage”, where both the cow and the calf travel continuously right after birth. There may be three reasons for the constant swimming: it is thought to improve the newborn calf’s swimming and breathing capabilities, to prevent the calf from sinking because of his lack of buoyancy, and to serve as a defence against predators. The second stage is called the “calf play stage”. After 3-4 weeks of rapid travel (newborn travel stage), the cows and calves slow down the travel speed, the cows rest in shallow waters and the calves play intensively around their mothers. This stage is supposed to increase the calves’ motor skills, strength and coordination. Cows are resting to save energy for the upcoming migration, also because they are fasting while lactating during their stay in the breeding grounds. The third stage is the “pre-migratory stage”, starting a few days before leaving the breeding grounds and initiating the migration to the feeding grounds. In this stage, calves reduce their play time and increase, together with their mother, the rapid traveling. The cows and calves coordinate their movements and strengthen their muscles, which is thought to be a preparation for the upcoming migration.

2. Material and Methods

2.1 Aerial Surveys

To monitor the South African population of southern right whales, annual helicopter aerial surveys are flown along the south coast of South Africa since 1979. The survey is performed late September / early October, when the number of whales along the coast is believed to peak (due to 90% of the calves being born) (Best, 1994). The survey area (figure 7) extends from Muizenberg () to Natures Valley and is divided into “bins” of 20 min of longitude wide, labelled from A (west) to P (east).

South Africa

Walker Bay Muizenberg San Sebastian Bay Natures Valley De Hoop

A B C D E F G H I J K L M N O P

Figure 7. Southern coast of South Africa showing survey area and bins from A to P

2.2 Natural marking for individual identification

These so-called aerial surveys are performed to obtain photographs of the whales for individual identification purposes. The callosities on the southern right whale’s head are unique and remain stable over time, allowing for use in individual identification. During photographic analysis, a specific computer program (called the Hiby-Lovell System) is used to extract such a callosity-pattern (figure 8) and match it with a previously catalogued individual or identify it as a new one. This way, whales can be followed over time and the main population parameters, such as age of first calving, calving interval (how often the same female has a calf), calf survival rates, number of calving females, total population size and population trend over time, can be derived (Mammal Research Institute Whale Unit).

a b Figure 8. a) preparation of callosity information extraction on a cropped picture taken during the aerial survey b) callosity information extracted by the computer program. (images source: MRI Whale Unit, E. Vermeulen)

2.3 Collected Data and Analyses

Between 1979 and 2019, a total of 5,532 cow-calf pairs were counted and 1,779 were individually identified from the photographs taken during the annual helicopter surveys. A total of 624 individuals were seen only once and the other 1,155 were seen at least twice. In these 40 years, there were 5,532 calving events and 3,752 inter-calf intervals.

To examine possible changes in distribution of cow-calf pairs along the South African coast over time as the population increases (Best 1990a), the survey series were divided in four time periods (1979-1988, 1989-1998, 1999-2008 and 2009-2019).

The cow-calf pair distribution along the South African coast is concentrated in some areas, while other areas have a very low density of whales or no whales at all (Elwen & Best 2004). Therefore, the bins outside of the most populated bins (C, D, E, F, G and H) were combined to increase the sample size. Based on Elwen & Best (2004bc), these bins with a low density were put into two categories: the “GLD” (good bin, low density) bins containing potentially attractive calving areas (based on environmental conditions) with a currently low density (A, B, K, L and O) and the “Unatt.” (unattractive) bins with a very low potential attractiveness (I, J, M, N and P).

Site-fidelity was defined as the tendency of a southern right whale cow to be photographed in the same bin (“stay”) or in a different bin (“move”) with successive calves . Furthermore, ‘stay’ was assessed under two definitions: the strict definition (a caw photographed in exactly the same bin with its next calf), and the broad definition (a cow photographed in the exact same or adjacent bin with its next calf) (following Best 2000 and Elwen & Best 2004). Both definitions were used because the strict definition is very relative; a whale could be just at the “border” of a bin which doesn’t especially mean it has “moved” from one calf to another.

The distribution of “experienced” and “inexperienced” cows along the South African coast was also assessed. An inexperienced cow is, per definition, a cow photographed for the first or second time with a calf, whereas an experienced cow is photographed with a third calf or more. As done by Elwen & Best (2004a), site-fidelity at each level of experience was analysed.

As all females photographed with a calf at the beginning of the survey series would be “by definition” inexperienced, only data from 1988 onwards (or after 3 possible calving intervals) were analysed (Elwen & Best 2004a). This time frame of 9 years (three 3-year calving intervals) was chosen as the sighting probability model from Brandão et al. (2011) estimates an average re-sighting rate of 74%, suggesting a 98.3% probability that a cow would have been photographed at least once if it had given birth 3 times in this time frame .

In general, a 3 year calving interval was considered as successful, whereas 2, 4 and 5 year calving intervals were considered unsuccessful (Knowlton et al. 1994). The association between specific areas and reproductive success was investigated through assessing the occurrence of successful and unsuccessful calving intervals in the different bins along the coast, and evaluating the bins occupied after a successful and unsuccessful calving interval.

Chi-squared tests were used throughout the study to compare actual distributions with those expected from the null-hypothesis. When a sample number was less than 5, a Yates correction was applied.

3. Results

3.1 Coastwise distribution of cow-calf pairs

The proportions of cow-calf pairs observed per bin are shown for each survey period in figure 9, showing a non-random distribution.

0,35 0,30

0,30 calf calf 0,25 - - 0,25 0,20 0,20 0,15 0,15 pairs pairs 0,10 0,10 0,05 0,05 0,00 Proportion of cow 0,00 Proportion of cow A B C D E F G H I J K L M N O P A B C D E F G H I J K L MN O P bins b bins a 0,25 0,25 calf calf

- 0,20 - 0,20 0,15 0,15 0,10 0,10 pairs pairs 0,05 0,05

Proportion of cow 0,00 Proportion of cow 0,00 A B C D E F G H I J K L M N O P A B C D E F G H I J K L MN O P c bins d bins

Figure 9: Proportions of cow-calf pairs seen during the aerial surveys off the South African coast: a) 1979-1988; b) 1989-1998; c) 1999-2008; d) 2009-2019

Over time, the proportions of cow-calf pairs in each bin have changed and a general westward distribution shift can be observed.

Over the first two survey periods, 1979-1988 and 1989-1998, bin D and E show a very low proportion of cow-calf pairs, while in the survey period 1999-2008 the proportions in these bins started to increase and increased even more from 2009 to 2019. These bins were previously marked by Elwen and Best (2004b,c) as being attractive yet non-populated calving habitats.

Best (1990a) affirms an increase of the southern right whale population by 6.8% per year. Figure 10 shows the associated increase in cow-calf pair counts of the annual aerial surveys from 1979 to 2019. The course of the curve shows fluctuation from year to year with a last “normal count year” in 2014. From this year onwards, the variation of cow-calf pair counts becomes more extreme.

450

400

350

300 calf pairs - 250

200

150

number of number cow 100

50

0 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017 2019 years

Figure 10: Number of cow-calf pairs seen from 1979-2019

3.2 Calving intervals and coastal distribution

Figure 11 visualizes the changes in calving intervals of female southern right whale over time. Specifically from 2009 onwards, the proportion of 3 year calving interval starts to decrease, while the proportions of 4 and 5 year calving intervals increase. The 2 year calving interval is slightly decreasing, and always low in proportion compared to the others. Noticing this decrease in proportion of a “normal” (3 year) calving interval in the last decade, the following analyses will have an additional focus on this time period.

1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2

proportion of calving interval 0,1 0 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 years

2 yr CI 3 yr CI 4 yr CI 5 yr CI Linear (2 yr CI) Linear (3 yr CI) Linear (4 yr CI) Linear (5 yr CI) a 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 proportion of calving interval 0,1 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 years

2 yr CI 3 yr CI 4 yr CI 5 yr CI b Linear (2 yr CI) Linear (3 yr CI) Linear (4 yr CI) Linear (5 yr CI)

1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2

proportion of calving interval 0,1 0 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 years

2 yr CI 3 yr CI 4 yr CI 5 yr CI c Linear (2 yr CI) Linear (3 yr CI) Linear (4 yr CI) Linear (5 yr CI)

Figure 11: calving interval changing over time. a) 1988-2019; b) 2000-2019; c) 2007-2019

Table 2 depicts the frequencies of 2, 3, 4 and 5 year calving intervals following the first, second and third to fifth calf. Results showed there was a significant difference in the proportion of 2 and 4 year calving intervals when compared to 3 year calving interval, with the proportion of the 2 and 4 year calving intervals being highest after the first calf (chi2 = 17,203 (Yates correction); p < 0.01; df = 4 for 2 year and chi2 = 17,219; p < 0.01; df = 4 for 4 year). Comparing 5 and 3 year calving intervals shows that there is no significant difference in their pattern (chi2 = 2,4699; p = 0,65004; df = 4). The frequency of the 5 year calving interval is generally very low (compared to 3 or even 4 year calving interval). However, the frequency of the 2 year calving is even lower. For further analyses considering successful and unsuccessful calving intervals, the 2, 4 and 5 year calving intervals were summed and defined as reproductive failure (unsuccessful calving intervals).

Table 2: Number of 2, 3, 4 and 5 yr calving intervals observed following successive calves (1998-2019)

Interval Calf 1 Calf 2 Calf 3 Calf 4 Calf 5 Calves 3-5 21 6 2 4 3 9 2 yr (3,0%) (1,2%) (0,5%) (1,2%) (1,3%) (0,9%) 450 367 327 233 176 736 3 yr (63,9%) (71,5%) (77,1%) (72,4%) (73,3%) (74,6%) 158 87 52 48 41 141 4 yr (22,4%) (17,0%) (12,3%) (14,9%) (17,1%) (14,3%) 75 53 43 37 20 100 5 yr (10,7%) (10,3%) (10,1%) (11,5%) (8,3%) (10,1%)

There was no significant difference among the calving intervals in the different, regrouped, bins (figure 12a) for the time period 1979-2019 (chi2 = 28.99 (Yates correction); p = 0.0644; df = 21). However, there was a significant difference when looking at all the bins separately

(figure 12b) for the same time period (chi2 = 79.8 (Yates correction); p = 0.0001; df = 45).

n=454 n=220 n=170 n=485 n=736 n=686 n=120 n=54 100%

90% 80% 70% 60% 50% 40% 30% 20% proportion of calving interval 10% 0% C D E F G H GLD Bins Unatt. Bins bins

a 2 yr CI 3 yr CI 4 yr CI 5 yr CI

n=13 n=37 n=454 n=220 n=170 n=485 n=736 n=686 n=21 n=6 n=22 n=37 n=15 n=6 n=11 n=6 100%

90%

80%

70%

60%

50%

40%

30% proportion of calving interval 20%

10%

0% A B C D E F G H I J K L M N O P bins

2 yr CI 3 yr CI 4 yr CI 5 yr CI b Figure 12: 2, 3, 4 and 5 yr calving intervals from 1979 to 2019; a) regrouped bins, b) all bins

There was no significant difference in the ratios of successful and unsuccessful calving intervals between the regrouped bins in both analysed periods of time (1988-2019: chi2 = 9.03; p = 0.251; df = 7; 2009-2019: chi2 = 10.7; p = 0.152; df = 7) (figure 13a,c). By looking at all the bins separately, still no significant difference can be found (chi2 = 12.8; p = 0.621; df = 15) (figure 13b), although no statistical test could be performed for the period 2009-2019 due to missing values (figure 13d).

After an either successful or an unsuccessful calving interval, cows were not found to occupy a certain bin rather than another (chi2 = 10.99; p = 0.152; df =7).

n=421 n=219 n=164 n=448 n=622 n=59 n=96 n=40 100%

90% 80% 70% 60% 50% 40% 30% 20%

proportion of calving interval 10% 0% C D E F G H GLD Bins Unatt. Bins bins

a successful CI unsuccessful CI

n=12 n=28 n=421 n=219 n=164 n=448 n=622 n=593 n=17 n=5 n=17 n=29 n=8 n=5 n=10 n=5 100%

90% 80% 70% 60% 50% 40% 30% 20%

proportion of calving interval 10% 0% A B C D E F G H I J K L M N O P bins

successful CI unsuccessful CI b n=112 n=81 n=52 n=95 n=160 n=122 n=30 n=12 100% 90% 80% 70% 60% 50% 40% 30% 20%

proportion of calving interval 10% 0% C D E F G H GLD Bins Unatt. Bins bins c successful CI unsuccessful CI

n=3 n=14 n=112 n=81 n=52 n=95 n=160 n=122 n=5 n=0 n=3 n=6 n=3 n=3 n=4 n=1 100%

90% 80% 70% 60% 50% 40% 30% 20%

proportion of calving interval 10% 0% A B C D E F G H I J K L M N O P bins

successful CI unsuccessful CI d Figure 13: Comparison of unsuccessful and successful right whale calving intervals (in %) between each bin (or groups of bins) on the South African coast. a) time period 1988-2019 regrouped bins; b) time period 1988-2019 all bins; c) time period 2009-2019 regrouped bins; d) time period 2009-2019 all bins

3.3 Reproductive experience and coastal distribution

Comparing the ratios of experienced and inexperienced cows in the regrouped bins (figure 14a,c) showed a significant difference for both analysed time periods (1988-2019: chi2 = 34.2; p < 0.001; df = 7 ; 2009-2019: chi2 = 22.5; p = 0.002; df = 7). Looking at this more into detail for all the bins (figure 14b,d), it is clear that the easterly bins have a significant increased proportion of inexperienced females (1988-2019: chi2 = 61.5

(Yates correction); p < 0.001; df = 15 ; 2009-2019: chi2 = 39.02 (Yates correction); p = 0.0006; df = 15).

n=873 n=505 n=407 n=835 n=1156 n=1031 n=217 n=87 100%

90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% C D E F G H GLD Bins Unatt. Bins bins

a experienced cows inexperienced cows

100% n=28 n=78 n=873 n=505 n=407 n=835 n=1156 n=1031 n=41 n=12 n=39 n=45 n=15 n=8 n=27 n=11 90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% A B C D E F G H I J K L M N O P bins b experienced cows inexperienced cows

n=423 n=286 n=247 n=345 n=491 n=356 n=101 n=37 100%

90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% C D E F G H GLD Bins Unatt. Bins bins

experienced cows inexperienced cows c n=12 n=53 n=423 n=286 n=247 n=345 n=491 n=356 n=18 n=5 n=12 n=12 n=5 n=5 n=12 n=4 100%

90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% A B C D E F G H I J K L M N O P bins

d experienced cows inexperienced cows

Figure 14: Percentage of experienced and inexperienced right whale cows found in each bin or group of bins. a) time period 1988-2019 regrouped bins, b) time period 1988-2019 all bins, c) time period 2009-2019 regrouped bins, d) time period 2009-2019 all bins

Analysing the coastal distribution of experienced and inexperienced females in the abnormal high count year of 2018 (figure 15a) showed no significant difference for the regrouped bins (chi2 = 8,388; p = 0,2997; df = 7). As there were several bins with missing values (figure 15b), no comparison could be made among all the bins separately.

n=92 n=55 n=88 n=52 n=65 n=42 n=24 n=7 100% 90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% C D E F G H GLD Bins Unatt. Bins bins

experienced cows inexperienced cows a n=1 n=19 n=92 n=55 n=88 n=52 n=65 n=42 n=5 n=1 n=4 n=0 n=1 n=0 n=0 n=0 100% 90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% A B C D E F G H I J K L M N O P bins

experienced cows inexperienced cows b Figure 15: Coastal distribution of experienced and inexperienced cows in 2018 (abnormal high count year). a) regrouped bins, b) all bins

3.4 Coastal movements of cow-calf pairs and site fidelity

To study the individual movements of cow-calf pairs and their site fidelity to specific bins, a comparison was made between the bin where a cow was observed with an initial calf and the bin where she was observed with a successive calf (table 3). In total, 24.6% of the cows photographed with their initial calf in a certain bin were photographed in the exact same bin with the successive calf. Another 30.3% of the cows were photographed with a successive calf in an adjacent bin either to the west or east and in total, 70.5% remained within two bins either east or west. From all the females in bins C, D, E, F, G and H – which are the bins with the highest densities of cow-calf pairs (see figure 9) – between 46.6% up to 70.3% were photographed in the same or the adjacent bin (broad definition). Using the strict definition it ranged from 15.3% to 30.8%. All other bin values, using the broad definition, ranged from 0% to 24.1% (0% to 11.1% with the strict definition).

Table 3: Coastwise movements between successive observed calvings of right whales off South Africa, 1979-2019. Bold numbers indicate site fidelity using the strict definition Initial Calf Subsequent calf Total Bins Bins A B C D E F G H I J K L M N O P A 2 0 4 2 6 1 1 2 0 0 0 0 0 0 0 0 18 B 1 1 13 4 3 8 6 10 0 0 0 0 0 0 0 0 46 C 5 27 180 64 49 74 85 83 5 1 4 2 1 0 2 2 584 D 0 8 85 46 35 41 48 32 0 0 2 2 0 0 1 0 300 E 1 0 30 30 33 39 49 27 2 0 0 0 0 0 0 1 212 F 3 8 80 55 48 121 167 114 4 1 3 1 2 2 1 0 610 G 1 9 87 86 75 187 289 186 5 0 4 5 2 1 4 1 942 H 3 11 115 53 51 134 232 244 8 0 5 9 1 0 1 1 868 I 1 0 4 3 0 5 7 6 1 0 0 1 0 1 0 0 29 J 0 0 1 2 0 1 0 3 1 0 0 0 0 0 0 0 8 K 0 0 3 0 2 3 4 9 2 2 1 4 1 0 0 0 31 L 0 1 8 2 3 10 7 17 1 0 0 0 0 0 0 0 49 M 0 0 2 0 2 3 4 6 0 0 0 1 2 0 0 0 20 N 0 1 1 0 0 1 1 0 0 0 0 0 1 1 0 0 6 O 0 0 4 3 1 2 4 4 1 0 1 0 0 1 0 0 21 P 0 0 0 0 1 1 0 4 1 1 0 0 0 0 0 0 8 Total 17 66 617 350 309 631 904 747 31 5 20 25 10 6 9 5 3752

The number of cows moving to the west after a successive calf (n=1,585) was higher than the ones moving to the east (n=1,246) . The coastal distribution of cows observed with their initial and again with their subsequent calf was compared. There was a significant difference between the proportions in bins A-G (cows moving to the west) and the proportions in bins H-P (cows moving to the east) (chi2 = 23.36, p <0,01 ; df = 1). The number of cows with an initial calf are highest in bins A-G (n=2,712) compared to bins H-P (n=1,040). The majority of the cows (n=2,894) had their subsequent calf in bins A-G, while only a minority (n=858) had their subsequent calf in bins H-P.

The proportion of southern right whale cows moving or staying, using the broad definition, is significantly different between the regrouped bins (figure 16a,c) for both analysed time periods (1988-2019: chi2 = 92.9; p < 0.01; df = 7 ; 2009-2019: chi2 = 24.8; p < 0.01; df = 7). The same was found when using the strict definition (1988-2019: chi2 = 96.5 (Yates correction); p <

0.01; df = 7; 2009-2019: chi2 = 20.7 (Yates correction); < 0.01; df = 7). When doing the same analysis looking at all the bins (figure 16b,d), using the broad definition, there is a significant difference for both analysed time periods (1998-2019: chi2 = 203.1 (Yates correction); p < 0.0001; df = 15 ; 2009-2019: chi2 = 57.2 (Yates correction); p < 0.0001; df = 15). When using the strict definition, there was a significant difference for the time period 1998-

2019 (chi2 = 104.3 (Yates correction); p < 0.0001; df = 15) but there was no significant difference for the time period 2009-2019 (chi2 = 33.4 (Yates correction); p = 0.089; df = 15).

n=540 n=297 n=202 n=566 n=806 n=757 n=129 n=53 100%

90% 80%

70% 60% 50%

40%

proportion of cows 30% 20%

10% 0% C D E F G H GLD Bins Unatt. Bins bins

stay (broad definition) move a n=15 n=35 n=540 n=297 n=202 n=566 n=806 n=757 n=25 n=7 n=24 n=36 n=10 n=5 n=19 n=6 100% 90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% A B C D E F G H I J K L M N O P bins

stay (broad definition) move b n=136 n=106 n=63 n=118 n=196 n=141 n=34 n=12 100%

90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% C D E F G H GLD Bins Unatt. Bins bins c stay (broad definition) move

n=3 n=15 n=136 n=106 n=63 n=118 n=196 n=141 n=4 n=1 n=5 n=6 n=3 n=3 n=5 n=1 100% 90% 80% 70% 60% 50% 40% 30% proportion of cows 20% 10% 0% A B C D E F G H I J K L M N O P bins

stay (broad definition) move d Figure 16: Percentage of right whale cows staying or moving using the broad definition following calving in a specific bin or group of bins. a) time period 1988-2019 regrouped bins, b) time period 1988-2019 all bins, c) time period 2009-2019 regrouped bins, d) time period 2009-2019 all bins

Analysing site fidelity (using the broad definition of stay) in relation to calving success, southern right whale cows were more likely to stay in a specific bin after a successful calving interval (chi2 = 6.94; p < 0.01; df = 1) in the period from 1988 to 2019, whereas from 2009- 2019 cows were not found to move or stay after either a successful or an unsuccessful calving interval (chi2 = 1.19; p = 0.275; df = 1). When using the strict definition of stay, no tendency for cows to move or stay after either a successful or an unsuccessful calving interval could be seen, this in both time periods (1988-2019: chi2 = 1.93; p = 0.165; df = 1 ; 2009-2019: chi2 = 0.0393; p = 0.843; df = 1).

Table 4 shows the bin position of 135 photographed and identified calves and their bin positions when seen as cow with their first calf. In total, 23% were photographed in the exact same bin with their first calf as where they were observed as calves themselves. Another 25% were observed in an adjacent bin either to the east or west. The other, 52%, moved more bins to either east or west with some individuals being observed with their first calf 9 or even 12 bins to the east or west as where they were observed as calves. The proportion of whales seen as calves (n=97 in bins A-G, n=38 in bins H-P) and seen as first time mother (n=99 in bins A-G, n=36 in bins H-P) stays almost the same in both the easterly and westerly bins.

Table 4: Distribution of right whale cows first photographed as a calf, both as a calf and when seen with their first calf. Bold numbers indicate site fidelity

Observed as cow with first calf Observed as calf A B C D E F G H I J K L M N O P TOTAL A 0 B 1 1 2 C 1 5 2 1 5 4 8 1 27 D 1 1 3 1 6 E 1 1 1 3 F 5 4 2 7 4 7 1 1 31 G 4 2 9 8 5 28 H 4 1 4 6 8 9 32 I 0 J 1 1 K 0 L 2 2 M 1 1 N 0 O 1 1 2 P 0 TOTAL 0 1 23 9 12 27 27 31 0 0 3 1 0 0 1 0 135

4. Discussion

The present study assesses the distribution of southern right whales along the South African coast, based on 40 years of data. Although this aspect has been studied previously by Best (1990a, 2000) and Elwen and Best (2004a), the present results are the most updated and based on at least 20 more years of data.

The increase of cow-calf pair counts from 1979 to 2019 (figure 10) is likely due to a general population increase (Best 1990a affirmed a population increase of 6.8% per year) and therefore an increase in reproductively active females (Best et al. 2001) and the associated increased densities of southern right whales in each bin.

As previously reported (Best 1990a, Elwen & Best 2004a,b), the distribution of cow-calf pairs along the South African coast continues to be non-random (figure 9). In fact, the majority of cow-calf pairs seem to concentrate in areas that provide protection from swell and winds as well as rocky bottoms. Shallow water, sandy bottoms and gentle slopes are preferred for an improved energy conservation for lactating females, protection against possible mating attempts of adult males and against predation risk on new-born calves (Elwen and Best 2004b). The South African right whales share this habitat preference with right whale populations elsewhere in the world (e.g. Thomas 1984, Rowntree et al. 2001). The presented updated results are in line with Best (1981, 1990a, 2000, 2011b) and Elwen and Best (2004), and have thus been following the same general pattern at least in the last 40 years.

Although the general trend of the non-random distribution remained similar over time, analysing 20 more years of data also revealed changes. As such, the density of cow-calf pairs in bins C, D and E seemed to increase in the past 20 years (figure 9) while densities in bins F, G and H (the main calving area) seemed to slightly decrease. This seems to clearly confirm the previously suggested westward shift in the distribution of cow-calf pairs over the past 40 years (ref. Best 2000,2001, Elwen and Best 2004), and is especially prominent in the past 10 years (figure 9d). Although the previous authors do not formulate a strong hypothesis on the possible reason for such an apparent shift, it may be related to the following four aspects:

1) Re-establishment process post-whaling

As historical catches were dominated by females (Best & Ross 1986), the observed west-ward shift in the past 40 years may be part of a re-establishment process for the ever growing population to areas where they used to be abundant (Best 2011a).

2) Density effect

With a continuous population increase, preferred habitats may reach a certain density of cow-calf pairs which makes an area no longer favourable, leading to the occupation of other areas with optimal environmental conditions.

3) The decrease in the presence of unaccompanied adults

Elwen and Best (2004a) concluded that the harassment of cow-calf pairs by males or juveniles may be more important than previously thought, as predation pressure is relatively low along the South African coast (i.e. shallow waters are preferred to hinder a mating attempt from a male, which can possible injure the calf). However, the presence of unaccompanied adults, including males and juveniles, along the South African coast has dropped dramatically since 2010 with >90% (MRIWU unpublished data). Such a decreased presence of a possible threat to a new-born calf could lead to a reoccupation of previously avoided areas on behalf of the cow-calf pairs.

4) The shift in peak presence of cow-calf pairs

Best (1994) determined that the calving season in South Africa occurs over 118 days around mid-August, with 95.5% of calves being born in this time period. Consideration was therefore given to conduct the annual aerial survey in October being the time of peak calf presence, as most calves would have been born, yet most would not have reached the “critical size” (about 8 m, obtained approximately 2.5 to 3 months after birth) to leave on their annual migration (Best & Rüther 1992). However, recent aerial count surveys conducted additionally to the annual aerial photo-identification survey have indicated a shift in peak presence of cow-calf pairs in the South African breeding ground from early October to late August (MRIWU unpublished data). Based on the lack of signs of earlier birthing (MRIWU unpublished data), this is believed to be related to females leaving the breeding ground more quickly than in previous decades. Further investigation seems crucial due to the potential consequences for the probability of calf survival and therefore population dynamics. Regardless the cause, it is clear that such a shift will lead to the within- season west-ward movement of cow-calf pairs being captured in the annual October aerial survey, which previously was not, biasing the observed data.

Results presented herein clearly show a decrease in the normal 3-year calving interval, with an associated increase in 4- and 5-year calving intervals believed to be related to calving failure (Knowlton et al. 1994). As reproduction is mediated through body condition (and thus foraging success) in most (see Thomas 1990 for a review), an increase in calving failure may be related to a decreased food availability. In fact, a few studies of South America showed a decreased breeding success of southern right whales with decreased availability due to climate anomalies in their main feeding grounds off South Georgia (Leaper et al. 2006, Miller et al. 2011, Seyboth et al. 2016). Similar results have been found for the South African population, with strong correlations between ENSO (El Niño–Southern Oscillation), sea ice extent and ocean productivity in two proposed feeding grounds, and the number of calves observed along the South African coast each year (Van den Berg et al. 2019). Despite this general increase in 4- and 5-year calving intervals in the population, the proportion of such calving intervals in the first successive calves of a female remained the same as found by Elwen and Best (2004a) and thus did not seem to change over time. Additionally, the increase in 4- and 5-year calving intervals seemed unrelated to the bin use (figures 11 and 12). However, the distribution of cows along the South African coast seemed to be influenced by their maternal experience. As such, the proportion of experienced cows (having had 3 or more calves) was significantly lower in the easterly bins compared to inexperienced cows. This results differs from those presented by Elwen and Best (2004a) who indicated no difference in the rations of experienced and inexperienced cows among the bins. Additionally, females tended to move west after successive calves, confirming the preference of westerly bins by experienced females (table 3). The precise reason for this segregation in distribution remains unknown, as in general the distribution did not seem to affect calving success (figure 13). These easterly bins are generally low-density bins, including both those which were described by Elwen and Best (2004a) as potentially attractive based on the local environmental conditions (K, L, O; GLD bins), and those described to have low potential attractiveness (I, J, M, N; Unatt. bins). Elwen and Best (2004a) also described some of the westerly, then still low density bins, as potentially attractive, including A, B, D and E. In the past decade, the density of cow-calf pairs in bin D and E increased substantially, suggesting that with an increased population of southern right whales, potentially attractive bins near the main concentration areas (bin C, F, G and H) were the first to be reoccupied. In this line of thought, it could be suggested that other adjacent, potentially attractive bins, such as bin B, will be the next to be reoccupied. On the other hand, potentially attractive bins K and L may be slightly further away, separated from the main concentration areas through two environmentally unattractive bins (I and J). In the view of reducing energy expenditure when on the breeding ground, it could be argued that experienced females may be more prone to reduce the distance travelled once arriving at the South African south coast (see Mate et al. 2011) and to remain close to the areas in which they previously calved. On the other hand, inexperience females may be more prone to “explore” the coastline in search for their preferred calving habitat. Alternatively, the high density of experienced females in the westerly bins may leave less space for the inexperienced females, although no such scenario could be seen in the extremely high density year 2018 (figure 15).

The general site fidelity of cow-calf pairs to certain bins did not seem to change over time, with results being in accordance to Best (2000) and Elwen and Best (2004a). Also the natal site-fidelity described by Best (2000) did not seem to change over time, as almost half of the whales returned with their first calf to the same general area as where they were born. However, the present results suggest that cows did not move from, nor stayed in, a specific bin after a successful or unsuccessful calving interval. This differs from the results from Elwen and Best (2004a), who indicated that cows were more likely to move after a successful calving interval. Nonetheless, it must be pointed out that photographing a cow in a specific bin during the aerial survey doesn’t specifically mean that the calf has been born in this bin (Best 1990a). The aerial survey takes place in October and the peak of calving season is in August (Best 1994), so in the time cow-calf pairs move along the coast, they might not get photographed in the exact same bin the calf was born, but maybe in the adjacent bin (Best 1990a, Best 2000). Individual philopatry is, according to Best (2000), not a consequence for the predisposition of certain bins being more favoured rather than others, but it’s specific environmental characteristics of the bins that make whales prefer an area rather than another.

5. Conclusion

This study analysed the distribution of southern right whale cow-calf pairs along the South African breeding ground, using 40 years of data. Results of this study confirm the hypothesis of a westward shift in distribution of cow-calf pairs along the South African coast, with the previously low density bins D and E being increasingly occupied as the population increases. This latter is especially prominent in the past 20 years. Results further indicate a clear preference of experienced cows for the westerly bins, concentrating in the area between Muizenberg and Saint Sebastian Bay. The reason for this apparent segregation from inexperienced cows remains uncertain, as the distribution did not seem to affect calving success. However, the reduced residency time of cow-calf pairs and drastic decline of mature males along the South African coast in the past decade could be contributing factors to these distribution patterns. These results are different from those presented by Elwen and Best (2004a), indicating the importance of re-evaluating available information with increased amounts of data.

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I would like to thank the Mammal Research Institute Whale Unit from the University of Pretoria for accepting my application to do research for my master’s thesis and for providing me with the dataset to conduct this research on the southern right whales in Hermanus.

I would like to say a massive thank you to my external supervisor Dr. Els Vermeulen for her guidance, invaluable advice and feedback on my thesis. Thank you for having me in South Africa, for sharing the office and always being there to answer any questions. And thank you for your encouragements and patience throughout the entire time.

I would also like to thank my hosts in Hermanus, Gerda and Brandon Smook, who made my stay in South Africa very comfortable and enjoyable. I specially thank Gerda for her valuable time and help, sharing her statistical knowledge and thus saving me a lot of time and work.

Furthermore I would like to thank my former internal supervisor Dr. Johannes Achatz for additional supervision and feedback on my thesis. Thank you for encouraging me in this project, for sharing the same interest in the subject and for answering any questions.

To Dr. Engelbert Hobmayer, I would like to say thank you for stepping in spontaneously and taking over the supervision of my thesis. Thank you for being present throughout the last steps of my thesis and completion of my degree.

Then I would like to thank the International Relations Office in Innsbruck for accepting my application for the scholarship “Stipendium für kurzfristige wissenschaftliche Arbeiten im Ausland” and thus giving me a little financial support for my research in South Africa.

Finally, I am exceedingly grateful to my parents and my sister for motivating and supporting me to live this experience and to my friends for their support and patience throughout this time. I couldn’t have made it this far without you. 8. Declaration of Academic Honesty

I hereby declare by oath, by my handwritten signature, that I have written the present work independently and have used no other than the specified sources and aids. All passages that have been taken literally or in content from the specified sources are identified as such.

The present work has not yet been submitted in the same or similar form as a Master’s thesis.

Date: Signature: