Source Name

EG-BAMM, Ryan Reisinger & Bob Pitman

Identification

Killer whales are strongly sexually dimorphic: adult males are typically 1 m or so longer than females but can weigh twice as much. Males have a tall (over 2 m in some cases), triangular dorsal fin whereas adult females and juveniles have a shorter, falcate dorsal fin. The oval or paddle-shaped flippers are also much more massively developed in males than in females. The large head is conical with a poorly defined beak.
The following refers to the genus Orcinus generally. Characteristic features of the different Southern Ocean types are described afterwards.
Killer whales have robust bodies with a conical head and rather blunt snout with a poorly defined beak. The dorsal fin is situated mid-back and is strongly sexually dimorphic: adult males have a tall, typically triangular dorsal fin which may grow to over 2 m in some cases, while adult females and juveniles have a falcate dorsal fin measuring < 1 m in adult females. The pectoral flippers are large relative to the body (as well as absolutely – up to 2.0 m in adult males) and are oval or paddle-shaped, rather than the sickle shape of other dolphins.
Their colouration is striking, consisting of highly contrasting areas of black and white. Ventrally, they are white from the tip of the lower jaw and throat, to behind the anus. This white band narrows between the black flippers and again just behind the umbilicus; it extends up and back on each side of the tail stock forming a conspicuous white patch on each flank. The underside of the flukes is white with a narrow black trailing edge; the caudal peduncle between the flukes and just behind the anus is typically black. There is a white, elliptical ‘eye patch’ above and slightly behind the eye and a grey ‘saddle patch’ behind and below the dorsal fin. Although the eye patch shows individual variation - even within pods - the overall size, shape, and orientation of the eye patch is generally diagnostic for the various Southern Ocean types. The saddle patch is usually conspicuous in high latitude populations but is often reduced or largely absent in warm water populations.
Pack ice, Gerlache and Ross Sea killer whales have a dark grey dorsal cape and lighter grey body, which gives them a distinctly two-tone grey and white appearance when viewed in good light. The cape extends forward and up from the saddle patch’s lowest point, passes over the eye patch and dips back down at the front of the eye patch. Sometimes the cape has a thin white margin formed by a forward extension of saddle patch. Animals often have a yellow cast, due to a film of diatoms (Bennettella ceticola) on the body; this shows up more conspicuously in pack ice and Gerlache killer whales due to their lighter coloration, but is less apparent in the darker, type A whales.
1) Type A killer whale
A black and white form with no visible cape and a medium sized eye patch oriented parallel to the body axis.
2) Large type B or pack ice killer whale
A two-toned grey form with a darker dorsal cape; eye patch at least twice as large as type A killer whale but also oriented parallel to the body axis.
3) Small type B or Gerlache killer whale
A two-toned grey form with a darker dorsal cape; eye patch large – but, on average, not as large as in pack ice killer whale – and oriented parallel to the body, but may be slightly angled. Smaller and slimmer than pack ice killer whale.
4) Type C or Ross Sea killer whale
A two-toned grey form with a darker dorsal cape; eye patch narrow and tilted downwards in the front at a 45° angle, often ill-defined (or ‘wispy’) at the back. Smallest known killer whale (see Size below).
5) Type D or Subantarctic killer whale
A black and white form with no visible cape; eye patch extremely small and oriented parallel to the body axis. Bulbous head. Narrow, backswept dorsal fin.

Size

A worldwide population of at least 50,000 individuals has been estimated but this likely represents a substantial underestimate as abundance data are not available for vast areas. An estimate of 80,400 animals in the Southern Ocean has been produced. The population size around the Crozet Islands is about 100 animals and that at the Prince Edward Islands is about 40 individuals.

Description

Killer whales are among the oceans’ most iconic species. Their large size, striking appearance, complex social structure and top predator status give them great charisma. They are the apex predators in marine ecosystems and, as a species, have an incredibly varied diet. Considered among the most widely distributed non-human mammals on the planet, killer whales occur throughout the world’s oceans.
Killer whales (or orcas) are toothed whales (odontocetes) and the largest members of the dolphin family (Delphinidae). They are currently recognized as a single species - Orcinus orca - but various populations show consistent differences in morphology, foraging behaviour, social organization, vocal behaviour and genetic structure. The differences are so large that in some cases these ‘ecotypes’ are proposed to be different species. Currently, 5 distinct types are recognised in the Southern Ocean:
1) Type A killer whale
2) Large type B or pack ice killer whale
3) Small type B or Gerlache killer whale
4) Type C or Ross Sea killer whale
5) Type D or Subantarctic killer whale

Ecology

Group sizes vary widely, from solitary individuals to groups of several hundred animals. Type A killer whale groups appear usually to be fewer than 20 animals. Pack ice killer whale groups are often less than 10 animals, while Gerlache killer whale groups often number 50 or more. Ross Sea killer whale groups are larger still, with some groups larger than 100 but these may represent several groups coming together for feeding or socializing. Subantarctic killer whales are known only from a single stranding event in 1955 and a small number of recent at-sea sightings. Reported group sizes average 18 individuals, ranging from 9-35.
Very little is known of the social organization of killer whales around Antarctica, but this can presumably be inferred to some degree from long term studies at other locations. Killer whales are very social and show strong, long-term associations between individuals. In the eastern North Pacific fish-eating resident killer whales show lifelong association between mothers and their offspring, meaning individuals never disperse from their natal social unit. The basic social unit – the ‘matriline’ – is a stable group of 2-9 (on average, 4) animals which comprises a female and as many as three generations of her and her daughter’s offspring. One to three matrilines that likely share a common maternal ancestor form a ‘pod’ – a less stable social unit in which the matrilines may be apart for weeks or months – and pods form clans, which are defined by the similarity of their vocal behaviour. Mammal-eating transient (or Bigg’s) killer whales are socially philopatric to a lesser degree, with dispersal occurring in both sexes. This difference in social organization likely arises from the constraints on group size for mammal-eating killer whales in general. Bigg’s matrilines typically contain only an adult female and one or two of her offspring and interactions among matrilines are dynamic, such that there is no unit equivalent to the resident pod. Long-term data from the Crozet Islands demonstrate long-lasting social bonds with pods (in this case, animals which spend more than 50% of their time together) of 1-10 animals. Preliminary findings from the Prince Edwards Islands indicate a social structure similar to that of eastern North Pacific Bigg’s killer whales.
Like other odontocetes, killer whales use sound for echolocation and communication. They produce three distinct types of vocalizations: echolocation clicks, whistles, and pulsed calls. Clicks are short pulses of sound, usually produced in a series, and are used in echolocation for orientation and prey detection. Whistles and pulsed calls are thought to play a role in communication. In the eastern North Pacific, resident killer whales whistles are heard primarily in social situations when whales are close together whereas pulsed calls are heard most often when whales are spread out and foraging, or when groups meet. The most common pulsed calls of resident killer whales are ‘discrete calls’ and pods have unique vocal repertoires or ‘dialects’ of 7-17 of these calls. A portion of this vocal repertoire may be shared with other pods and the degree of similarity in calls reflects relatedness of the pods. These dialects are stable over generations and likely culturally transmitted through vocal mimicry in offspring. Bigg’s killer whales vocalize less and produce more single (or ‘cryptic’) echolocation clicks to avoid being detected by their mammalian prey. Presumably they rely on passive listening as well as vision to detect their prey. Purported Ross Sea killer whales recorded near McMurdo Sound, Ross Sea, produced at least 7 discrete calls. While geographic variation was evident, their vocalizations had a similar structure to eastern North Pacific residents’.
Aerial behaviours such as breaching, spyhopping, lobtailing and flipper slapping are common, particularly while animals are socializing.

Source Name

EG-BAMM, Tracey Rogers

Identification

Long, slim body, with disproportionately large head separated from body by marked constriction at neck. They are dark grey above; lighter below; with light and dark grey spots on throat and sides. They have a characteristic 'reptilian' appearance to their head; a wide gape of jaws and characteristically three-pronged teeth, which makes identification easy. The teeth of the leopard seal have a dual role; the large re-curved canines and incisors are designed for gripping and tearing prey, whereas the upper and lower tricuspid (three cusped) molars interlock to provide an efficient krill sieve. Leopard seals are sexually dimorphic, the females are larger than the males growing up to 3.8 m in length and weighing up to 500 kg, whereas males grow up to 3.3 m in length and weigh up to 300 kg.

Description

Long, slim body, with disproportionately large head separated from body by marked constriction at neck. They have a characteristic 'reptilian' appearance to their head; a wide gape of jaws and characteristically three-pronged teeth, which makes identification easy. The teeth of the leopard seal have a dual role; the large re-curved canines and incisors are designed for gripping and tearing prey, whereas the upper and lower tricuspid (three cusped) molars interlock to provide an efficient krill sieve. Leopard seals are sexually dimorphic, the females are larger than the males growing up to 3.8 m in length and weighing up to 500 kg, whereas males grow up to 3.3 m in length and weigh up to 300 kg.
Leopard seals have a muscular, somewhat reptilian head, with a sinuous neck, highly arched back and long powerful flippers. The body is dark grey above and light grey below and they have white throats with black spots. These distinctive spots are what give the Leopard seal its name. As one might expect, Leopard seals have impressively long, sharp teeth which are well-adapted for cutting and tearing the flesh of prey. Their streamlined bodies are built for speed and power; their smooth, impermiable skin allowing them to easily slice through the water on pursuit dives. These characteristics combined with excellent sight and smell have established Leopard seals as one of the consummate predators of the Antarctic.
Scientists still have much to learn about the reproductive behaviors of Leopard seals due to the difficulty of monitoring breeding sites on the shifting pack ice of the Antarctic. Solitary animals, by nature, Leopard seals come on land only during the breeding season and then only in pairs or small groups. Females dig a hole in the ice early in the austral summer where they give birth to single pup after a 9 month gestation. The female protects the pups until they can take care of themselves.

Leopard seals may live for 26 years or more. Their only known natural predator is the Killer Whale.