Whales Eubalaena Australis Research Articles

Acoustic behaviour of southern right whales in relation to numbers of whales present in Walker Bay, South Africa

Estimating numbers of whales present in an area from recorded call rates could be a useful conservation tool. We recorded southern right whale Eubalaena australis vocalisations and presence in Walker Bay on the south coast of South Africa. In all, 45 sessions with synchronous acoustic and visual data were analysed to determine call rates directly (overall call rate, OCR) and in relation to the number of whales sighted (call rate per whale, CPW) and number of groups sighted (call rate per group, CPG). The OCRs were examined in the presence of varying numbers of whales, using a log-linear model to investigate the dependence of the call rate on whale density. The number of whales present exerted a strong quadratic effect on the OCR, which peaked at around 15 whales and decreased to a low rate as whale presence approached a maximum, for all calls combined and for four of their constituent 13 call types: a quadratic trend was present to varying degrees among the remaining call types. Both quadratic and linear trends were absent when OCR was assessed against number of groups present, possibly because group size increased with increasing density of whales. A linear regression on the CPW and CPG suggested that there was a negative inverse relationship with the number of whales and groups present respectively. These findings are important in that, while they preclude the estimation of absolute numbers from call rates, they imply that, under the conditions prevailing in Walker Bay, southern right whales were aware of the presence, arrival and departure of other animals in their vicinity and adjusted their vocal behaviour accordingly.

Population structure and individual movement of southern right whales around New Zealand and Australia

During the last 2 centuries, southern right whales Eubalaena australis were hunted to near extinction, and an estimated 150 000 were killed by pre-industrial whaling in the 19th century and illegal Soviet whaling in the 20th century. Here we focus on the coastal calving grounds of Australia and New Zealand (NZ), where previous work suggests 2 genetically distinct stocks of southern right whales are recovering. Historical migration patterns and spatially variable patterns of recovery suggest each of these stocks are subdivided into 2 stocks: (1) NZ, comprising NZ subantarctic (NZSA) and mainland NZ (MNZ) stocks; and (2) Australia, comprising southwest and southeast stocks. We expand upon previous work to investigate population subdivision by analysing over 1000 samples collected at 6 locations across NZ and Australia, although sample sizes were small from some locations. Mitochondrial DNA (mtDNA) control region haplotypes (500 bp) and microsatellite genotypes (13 loci) were used to identify 707 individual whales and to test for genetic differentiation. For the first time, we documented the movement of 7 individual whales between the NZSA and MNZ based on the matching of multilocus genotypes. Given the current and historical evidence, we hypothesise that individuals from the NZ subantarctic are slowly recolonising MNZ, where a former calving ground was extirpated. We also suggest that southeast Australian right whales represent a remnant stock, distinct from the southwest Australian stock, based on significant differentiation in mtDNA haplotype frequencies (FST = 0.15, p < 0.01; ΦST = 0.12, p = 0.02) and contrasting patterns of recovery. In comparison with significant differences in mtDNA haplotype frequencies found between the 3 proposed stocks (overall FST = 0.07, ΦST = 0.12, p < 0.001), we found no significant differentiation in microsatellite loci (overall FST = 0.004, G’ST = 0.019, p = 0.07), suggesting ongoing or recent historical reproductive interchange.

Inshore occurrence of southern right whales (Eubalaena australis ) at Subantarctic Marion Island

Opportunistic shore-based sightings of southern right whales Eubalaena australis for Marion Island (46°54’S, 37°45’E) were documented at five different times between 1974 and 2009. Whales were sighted between May and September and exclusively on the eastern lee side of the Island. Notwithstanding some observer biases over this time frame, the species appears to be an infrequent visitor to the inshore marine environment of Marion Island.

Inshore Occurrence of Southern Right Whales (Eubalaena australis) at Subantarctic Marion Island

Opportunistic shore-based sightings of southern right whales Eubalaena australis for Marion Island (46°54’S, 37°45’E) were documented at five different times between 1974 and 2009. Whales were sighted between May and September and exclusively on the eastern lee side of the Island. Notwithstanding some observer biases over this time frame, the species appears to be an infrequent visitor to the inshore marine environment of Marion Island.

On the Native Status of the Southern Right Whale Eubalaena australis in Peru

The native status of the southern right whale in Peruvian waters is now firmly supported by six confirmed sightings, including four cow-calf pairs, the northernmost at Pucusana (12°29'S,76°48'W) and off San Bartolo (12°24'S,77°11'W). An unconfirmed report exist from northern Peru. Five of six observations were shore-based, underscoring the importance of neritic habitat for E. australis also in Pacific South America. As sighting intervals have shortened over a period of two decades (near significant trend, P= 0.054) without indication of improved reporting, a guarded optimism for the recovery of E. australis in Peru may be warranted. However, a near-collision event with a fishing boat warns of conservation challenges ahead. As applies to three other cetacean species, the coast of Peru is proposed as the most boreal habitual range for E. australis on the planet, enabled by the cooling effects of the strongest of eastern boundary currents.

Fight or flight: antipredator strategies of baleen whales

ABSTRACTThe significance of killer whaleOrcinus orcapredation on baleen whales (Mysticeti) has been a topic of considerable discussion and debate in recent years. Discourse has been constrained by poor understanding of predator‐prey dynamics, including the relative vulnerability of different mysticete species and age classes to killer whales and how these prey animals avoid predation. Here we provide an overview and analysis of predatory interactions between killer whales and mysticetes, with an emphasis on patterns of antipredator responses.Responses of baleen whales to predatory advances and attacks by killer whales appear to fall into two distinct categories, which we term thefightandflightstrategies. Thefightstrategy consists of active physical defence, including self‐defence by single individuals, defence of calves by their mothers and coordinated defence by groups of whales. It is documented for five mysticetes: southern right whaleEubalaena australis, North Atlantic right whaleEubalaena glacialis, bowhead whaleBalaena mysticetus, humpback whaleMegaptera novaeangliaeand grey whaleEschrichtius robustus. Theflightstrategy consists of rapid (20–40 km/h) directional swimming away from killer whales and, if overtaken and attacked, individuals do little to defend themselves. This strategy is documented for six species in the genusBalaenoptera.Many aspects of the life history, behaviour and morphology of mysticetes are consistent with their antipredator strategy, and we propose that evolution of these traits has been shaped by selection for reduced predation.Fightspecies tend to have robust body shapes and are slow but relatively manoeuvrable swimmers. They often calve or migrate in coastal areas where proximity to shallow water provides refuge and an advantage in defence. Mostfightspecies have either callosities (rough and hardened patches of skin) or encrustations of barnacles on their bodies, which may serve (either primarily or secondarily) as weapons or armour for defence.Flightspecies have streamlined body shapes for high‐speed swimming and they can sustain speeds necessary to outrun pursuing killer whales (&gt;15–20 km/h). These species tend to favour pelagic habitats and calving grounds where prolonged escape sprints from killer whales are possible.The rarity of observed successful attacks by killer whales on baleen whales, especially adults, may be an indication of the effectiveness of these antipredator strategies. Baleen whales likely offer low profitability to killer whales, relative to some other marine mammal prey. High‐speed pursuit offlightspecies has a high energetic cost and a low probability of success while attacks onfightspecies can involve prolonged handling times and a risk of serious injury.

The presence of right whales in summer on the west coast of South Africa: the evidence from historical records

Conventionally, southern right whales Eubalaena australis are portrayed as spending the summer on feeding grounds in the Antarctic and the winter on breeding grounds in coastal waters of the southern continents. Historical whaling records challenge this perception in the case of the Cape of Good Hope whaling ground, where substantial catches were made earlier and later in the year as well as in winter. The hypothesis that these might in part represent whales on migration to and from Namibia is examined in this paper through the use of historical evidence, including the journals of two vessels operating in the region under the French flag in the 1788/89 and 1791/92 seasons. An episode of catching in the St Helena Bay/Saldanha Bay area between 1787/88 and 1791/92 that may have accounted for as many as 1 780 whales was followed by a shift of effort to the Walvis Bay ground in Namibia. If this represented local depletion, it would suggest that whales off the Western Cape were from a different population component to those off Namibia.

ENVIRONMENTAL FACTORS INFLUENCING THE DISTRIBUTION OF SOUTHERN RIGHT WHALES (EUBALAENA AUSTRALIS) ON THE SOUTH COAST OF SOUTH AFRICA I: BROAD SCALE PATTERNS

AbstractAerial surveys over the last 32 yr have shown that the distribution of southern right whales Eubalaena australis along the south coast of South Africa is markedly discontinuous, but highly predictable. A GIS was used at a variety of scales to investigate whether this pattern was related to environmental characteristics. Whale distribution was analyzed as density per 20‐min bin of longitude over two temporal and spatial scales, namely 15 bins for 32 yr, and a wider scale but shorter time period, 23 bins for 19 yr, as well as using three years of GPS accuracy data (15 bins) for finer scale analysis. Environmental factors tested were depth, distance from shore, sea floor slope, protection from swell, protection from wind, and shore type. The majority of whales were concentrated in areas that provided reasonable protection from open ocean swell and seasonal winds, and had sedimentary floors with gentle slopes. They generally avoided exposed rocky shorelines. Cow‐calf pairs were found significantly closer to shore and in shallower water than unaccompanied whales, particularly off sandy beaches. Habitat choice at this time of year may be related both to energy conservation for calves and lactating females (calm sea conditions) and to protection of the new‐born.

Female southern right whales Eubalaena australis: Are there reproductive benefits associated with their coastal distribution off South Africa?

Predictability in both meso- and microscale distribution of southern right whale Euba- laena australis females off the coast of South Africa is attributed to maternal philopatry, as well as favourable environmental conditions (calm water, generally shallow sloping, sedimentary sea bed) conducive to reduced energy consumption and a lowered risk of injury for both cows and calves. Spa- tial differences in reproductive success were compared between favoured (nursery) and non- favoured (non-nursery) areas and related to environmental differences in those areas. Reproductive success was inferred from analysis of calving intervals (3 yr = successful, 2 and 4 yr = unsuccessful; n= 808 calving events). Resighting rates as well as differences in distribution between experienced cows (3 or more calves) and inexperienced cows (1 or 2 calves) were also analysed. Less experienced cows were found to have significantly more unsuccessful calving intervals than experienced cows. No relationship was found between calving success and spatial distribution using calving interval analysis. Significant spatial differences in stranding rates of neonatal calves strongly suggest higher rates of calf mortality in areas dominated by non-cows, independent of environmental conditions. Social structure within wintering grounds was concluded to be more important than previously thought and potentially as important as environmental conditions for calf survival.

Southern Right Whale Eubalaena australis sightings on the Australian coast and the increasing potential for entanglement

Southern Right Whales Eubalaena australis are an endangered species that have been recovering from unsustainable whaling practices and, despite being reported along the east and west coasts of Australia, they have not been duly accounted for in recent risk assessments for marine development. This review of the last decade of sightings highlights northerly movements into temperate and sub-tropical waters, indicates that fatal entanglement has occurred and points toward an increasing likelihood of interactions between migrating whales and inshore marine development. Given that entanglements and vessel strike are preventing the recovery of North Atlantic Right Whales Eubalaena glacialis, we recommend a precautionary approach to risk assessment around Australia and the formation of a national animal entanglement committee with both a pre-emptive role in assessing coastal development applications and a reactive role in the event of entanglement.

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

Counts and photographs of right whales Eubalaena australis taken on aerial surveys of the southern coast of South Africa between 1969 and 1998 have been used to examine patterns of coastal distribution between successive 20-minute bins of longitude. Some bins had consistently higher densities of whales than others, cither of cows with calves or of unaccompanied adults. Apart from an overall increase in density, the centre of distribution shifted 40–60 minutes of longitude to the west over the 30-year period. Most (>93.4%) female calves born on the South African coast returned there to have their first calf, but only 52.9% were photographed with their first calf in the same or an adjacent bin as that of their natal year. This compares with 60.9% of multigravid females that occurred in the same or an adjacent bin as that of their previous calf, with significantly more west-ward (368) than eastward (255) shifts in distribution between calves. Approximate residence times for cow-calf pairs in the De Hoop region were 12–105 (average = 59.0 ± 3.9) days: dispersal rates were low between July and September but increased thereafter. Incidental records of coastwise movement were mainly to the west, but were probably influenced by the survey direction. Distances moved ranged from 6 to 202 km. at average speeds of 0.08–2.89 km·h−1. Theodolite tracking of undisturbed groups of right whales from Cape Columbine produced a similar range of swimming speeds. Inter-calf movements of cows between the survey area and the coasts to both east and west indicated that the entire South African coast could be considered as one homogeneous winter assemblage area for right whales.

Baleen whales: conservation issues and the status of the most endangered populations

AbstractMost species of baleen whales were subject to intensive overexploitation by commercial whaling in this and previous centuries, and many populations were reduced to small fractions of their original sizes. Here, we review the status of baleen whale stocks, with an emphasis on those that are known or thought to be critically endangered. Current data suggest that, of the various threats potentially affecting baleen whales, only entanglement in fishing gear and ship strikes may be significant at the population level, and then only in those populations which are already at critically low abundance. The impact of some problems (vessel harassment, and commercial or aboriginal whaling) is at present probably minor. For others (contaminants, habitat degradation, disease), existing data either indicate no immediate cause for concern, or are insufficient to permit an assessment. While the prospect for many baleen whales appears good, there are notable exceptions; populations that are of greatest concern are those suffering from low abundance and associated problems, including (in some cases) anthropogenic mortality. These include: all Northern Right Whales Eubalaena glacialis, Bowhead Whales Balaena mysticetus of the Okhotsk Sea and various eastern Arctic populations, western Gray Whales Eschrichtius robustus, and probably many Blue Whale Balaenoptera musculus populations. We review the status of these populations and, where known, the issues potentially affecting their recovery. Although Humpback Whales Megaptera novaeangliae and Southern Right Whales Eubalaena australis were also heavily exploited by whaling, existing data indicate strong recovery in most studied populations of these species.

Soviet catches of southern right whales Eubalaena australis, 1951–1971. Biological data and conservation implications

Between 1951/1952 and 1970/1971, a total of at least 3368 southern right whales Eubalaena australis were taken by Soviet whaling expeditions in the Southern Hemisphere, despite the species being internationally protected since 1935. These catches and the associated biological data (presented here for the first time) represent a unique source of information on the distribution, movements, size composition, reproduction and feeding of southern right whales during summer months. Revelation of these previously unreported catches also has implications for the assessment of the current status of right whale stocks. Incorporation of the Soviet catches into population assessments generally leads to higher estimates of the size of the population at protection, but the relative increase in this size depends on the intrinsic rate of increase in the population.

Whale observations from the Knysna Heads, 1903–1906

Sightings of 912 whales made by the pilot(s) at the Knysna Heads on the southern coast of South Africa between 1903 and 1906 provide information on the relative numbers of right whales Eubalaena australis and humpback whales Megaptera novaeangliae before the onset of modem whaling. Very few right whales were recorded, but several hundred humpback whales are estimated to have migrated past Knysna each year, first eastwards and then (from August) westwards, indicating that the whales were linked to a breeding population on the east rather than the west coast of Africa. A land station that opened near Knysna in 1913 took only 16 humpback whales in its second year of operation, demonstrating the extent of the depletion of this species that must have occurred following the onset of modem whaling on the African coast in 1908.

Humpback whales Megaptera novaeangliae and southern right whales Eubalaena australis in Gerlache Strait, Antarctica

AbstractDuring surveys conducted 2–20 April 1986 in Gerlache Strait, Antarctic Peninsula, 103 humpback whales Megaptera novaeangliae and eight right whales Eubalaena australis were sighted. The right whale sightings extend the southern limit of known distribution for the species. Humpback and right whale densities were respectively 0.22 (sd 0.23) and 0.01 (sd 0.06) whales per survey mile. Highest densities for both species were recorded inside bays, rather than in the relatively open water of Gerlache Strait. Both species were feeding on Antarctic krill Euphausia superba. Twenty-three humpback and four right whales were identified individually using photographs of natural features. Also included are sighting records of 18 southern bottlenose whales Hyperoodon planifrons.

Right whales Eubalaena australis at Tristan da Cunha— A clue to the ‘Non-recovery’ of depleted stocks?

Exploitation of the right whale Eubalaena australis population at Tristan da Cunha began about 1819/20, and an estimated 2500 animals were taken by French and American whalers from 1830/31 to 1834/35. Despite obvious depletion, catches continued to be taken from this stock throughout the remainder of the 19th century. Right whales began to reappear at the islands in the 1890s, and by the 1940s and 1950s were numerous enough to be considered a nuisance. Three episodes of illegal exploitation of right whales in Tristan waters by foreign fleets in the 1960s are reported. Shipboard and aerial surveys of the archipelago from 1971 to 1986 indicated that the population was greatly reduced from the level reported in the 1950s. The apparent recovery of right whales at Tristan da Cunha in the 1940s and 1950s seems to have been possible because, unlike nearly all other southern hemisphere stocks, this population was not subjected either to a shore-based fishery in the late 19th century or to a phase of coastal modern whaling in the early 20th century. An estimated 1217 right whales were killed in modern whaling in the southern hemisphere between 1904 and 1936. The apparent failure of other right whale stocks to recover under protection may have been the result of extreme depletion in 1935, so that any subsequent recovery was initially undetectable.

The central nervous system order of the blue whale (Sibbaldus musculus Linnaeus)

Macroscopic anatomical investigations on the brain of the Blue Whale (Sibbaldus musculus Linnaeus, total brain weight without dura: 6500 g), show that this species of cetacea has a degree of cerebralization between that of the primitive Southern Right Whale (Eubalaena australis Desmoulins) and that of the Humpback Whale (Megaptera novaeangliae Borowski). Of the Balaenopteridae examined to date, the Blue Whale has the lowest cerebralization.