White Whales of Wilderness

Annual Migration

Every year, between May and mid December, Humpback and Southern Right whales migrate northwards from the freezing Antarctic waters to nursery grounds in the warmer coastal waters of the African continent to calve.

While the Humpback Whales continue northwards to the tropics, the Southern Right Whales remain along the southern coastline of the western Cape, with aggregations between Cape Agulhas and Plettenberg Bay.

Layers of Blubber

One of the primary drivers of these migrations is their search for warmer water to give birth. Adult Humpback and Southern Right whales have a blubber layer 28cm to 32cm and between 35cm and 42cm respectively to insulate them against the freezing Antarctic waters which are their summer feeding region.

Whale calves, when they are born, have substantially thinner blubber layers and would freeze if they were born in the cold Antarctic waters.

The reason that the Southern Right Whales only migrate as far as the Southern Cape waters is that, because of the adults thicker blubber layer, they would ‘over heat’ in warmer sub tropical and tropical waters.

Colour Variation

In Southern Right Whales there are three colour morphs, namely black, grey and partial grey morphs.

Black morphs are born black and can have a white blaze of variable size, which remains white throughout the lifespan of the whale.

The calf in this mother calf pair is a black morph, while the mother is a partial morph

Partial morphs are born either grey or with black, brown and grey patches which darken as the whale ages.

Grey morphs, which are about 4% of the population, are born white and can have black or brown blazes which also darken with age.

The calf is a grey morph, born white with a black blaze, while the mother is a partial morph as evidenced by the grey brown blaze across her back.

The calf is a grey morph which has turned grey as it aged. It was most likely born white.

Genetic Variation

Southern Right Whales are polymorphic for an X-linked pigmentation pattern known as grey morphism. Most SRWs have completely black skin with white patches on their bellies and occasionally on their backs; these patches remain white as the whale ages. Grey morphs appear mostly white at birth, with a splattering of rounded black marks; but as the whales age, the white skin gradually changes to a brownish grey color.

Studies have shown that both male and female Southern Right Whales have a high level of nursery fidelity which results in the recurrence of grey and partial grey morphs being born at particular nursery locations. The 2022 and 2023 sightings of two grey morph claves in Wilderness would suggest that the chance of future white calves being born in the same area would be high and we can expect more sightings in the future.

Identification Markings

Each Southern Right Whale has distinctive white patches on their head and jaws and sometimes on their tails. Unlike skin pigmentation, these white patches are called callosities. Callosities are rough patches of textured skin that form distinctive patterns on each whale. The callosities are present at birth and are a individual pattern for each whale which allows for an accurate visual identification for whale watchers and cetacean researches.

Callosities are white to grey textured skin on the upper and lower jaws on Southern Right Whales with unique patterns for each whale, allowing for individual identification.

Pale Humpback’s

Humpback Whales are born light grey or white and darken to a dark brown or black dorsal surface within weeks, making it easy to identify the approximate area that a calf was born when a grey calf is seen.

The light grey colour of the Humpback Whale calf indicates that it was recently born. The calves darken within a few days after being born.

Wilderness White Calves

While the main Southern Right Whale nursery areas are Walker Bay, De Hoop Marine Protected Area and Witsand Bay, there are some birthing areas at Plettenberg Bay and at Wilderness.

In 2022, a light grey Southern Right Whale was born in Wilderness Bay and a second white one was born in August 2023.

An unusual sighting in August 2023 was a light grey Humpback Whale calf, the light colour suggesting that it had been born in the area. What makes this unusual is that Humpback Whale normally give birth in the warmer waters of the Eastern Cape all the way up to the Mozambican Channel.

The significance of the birth of a calf in Wilderness Bay is that newborn Humpback Whale calves have a thin layer of blubber with poor insulation and can’t survive in the cooler western Cape waters. With reports of at least three additional grey Humpback Whale calves sighted in the Western Cape, this could be an indication of climate change and sea temperature increases that are sufficient to support calving of this species at more southern latitudes.

Variation in annual whale sightings

Records from an annual census of the Southern Right Whale population along the South African coastline indicate that the average calving interval of has increased from between 3 to five years to as much as 7 years. SRW’s are referred to as capital breeders meaning that the females need to bulk up their fat reserves to be able to migrate to the winter nursery areas where they don’t feed for the approximate 6 months that they are there. This means that they have to bulk feed in their Antarctic feeding grounds.

The increase in the calving interval to seven years would suggest that there is a decrease of their regular food supply, krill and zooplankton, and that the SRW population spends more time bulking up to their target migration weight. The decrease of their food supply is link to a combination of the expansion of a krill fishery in Antarctica and to increased sea temperatures driven by climate change.

A total of 1,136 SRW’s where counted in 2023 which was more than double of the annual count between 2019 and 2022, but still lower than the count of 1,454 recorded in 2018.