MOSSEL BAY NEWS - Two white southern right whale calves were spotted off the coast of Hartenbos last week, with stunning videos and photographs captured by Mossel Bay resident, Michael de Nobrega.
De Nobrega has named them Snowflake and Snow White.
Mossel Bay Advertiser spoke to marine biologist and Garden Route Trail owner Mark Dixon about the rarity of this sighting and other interesting facts about these curious ocean-dwelling giants.
Dixon said the southern right whale has between three and four colour variations, depending on the literature you read, but it is mostly commonly accepted that there are three different variations.
The most common is the normal black morph with a few white callosities on the body, usually the jaw and head and sometimes the tail. Callosities are uniquely patterned patches of textured skin, distinctive from pigmentation.
The second variation is the partial grey morphs. Dixon said they are either born grey or black with a mottled appearance with brown, black and grey patches that will darken as they age.
Snow White and the mother. Photo: Michael de Nobrega
The third is the grey morph, which accounts for 4% of the population. This is the group the two white calves belong to.
Dixon said the grey morphs are born white and can have black and grey patches. He said the calves change to a more brindled colour with black and brown patches within a year.
"In the next 18 months, when the calves and their mothers migrate back from Antarctica, they will be darker in colour," he said.
He said last year there were two white calves born between Mossel Bay and Knysna. "It is a recessive combination gene. If the mother comes back and gives birth here, the chances are that the next time she gives birth in the area, it will also be a grey morph.
"It is quite exciting that in the future there may be more grey morphs," he said.
Migration
Dixon said the southern right whale and the humpback whale will migrate from Antarctica every year between May and mid-December to the southern coastlines of the Western Cape and northern Mozambique respectively.
The southern right whale will remain in the colder waters between Cape Agulhas and Plettenberg Bay due to its thicker blubber layers while the humpback, with its thinner layers, opts for warmer waters.
Snowflake and the mother. Photo: Michael de Nobrega
Calving period and annual sightings
Dixon said the inter-calf period has increased over the years from an average of between three to five years to about seven years.
He said this could be attributed to food depletion. The southern right whale's feeding grounds are in Antarctic waters and the females feed for between three and four months, non-stop to bulk up their reserves to migrate back to warmer waters and feed their calves with milk. The gestation period is 12 months.
"The adults are not gaining enough blubber in three to five years, so now we are seeing calves about every seven years."
Snow White. Photo: Michael de Nobrega
Dixon said the food depletion could be linked to a combination of an increase in krill fishing in Antarctica and an increase in water temperatures due to climate change. With the depletion of food and warmer water temperatures comes a general decrease in the average size of southern right whales.
He said southern right whales photographed between 2022 and 2024 appear to have decreased in size by 13% compared to their average size in the 1970s.
In the last 15 years, there seems to have been an increase in the population. Dixon said that last year, there were 1 136 southern right whales, more than double the annual count between 2019 and 2022. Last year's numbers were lower than in 2018, when 1 454 southern right whales were recorded.
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