Why do baby orcas look orange?

Every time a southern resident calf is born, orca lovers all around the world sigh in relief. The critically endangered population is struggling to stay healthy in an environment full of stressors, including noise, chemical pollution, and a serious lack of food. You might have come across baby orca photos in the news. Have you ever noticed that the calves look orange compared to their moms and other pod members? Why are baby orcas orange? And are there any other orcas that are not completely black and white? Find out in this post.

Credit: Robin Agarwal

A thin layer of blubber

Orca calves are born with very soft skin and appear black and peachy-orange. Scientists believe the orange hue is due to the calves’ thin layer of blubber. When in the womb, fetuses do not need a thick layer of fat to protect their bodies against cold water. In fact, the thickness of orca calves’ blubber is about 2cm, whereas it can be up to 9-10cm in some adult killer whales. So when they are born, their thin blubber causes the blood vessels to be close to the skin, making it appear orange.

After they are born, orca calves nurse regularly on their moms’ fat-rich milk throughout the day. Killer whale milk can contain up to 40% fat and looks like heavy yellowish cream. It allows the calves to develop a thick layer of blubber and grow quickly. During their first year, calves can gain 400 pounds (200 kg)! The first year is also the toughest for baby orcas, and up to 50% of them do not survive. The lack of prey may be the reason behind some of these deaths since some moms cannot keep producing enough good quality milk for their calves.

baby orcas orange
Stranded orca calf in Germany in 2017 after it got separated from its mother – Credit: Whale and Dolphin Conservation

But then why are some adult killer whales yellow?

In some areas of the world, adult orcas look black and yellow instead of black and white. This is the case in Antarctica for example, where killer whale ecotypes B and C usually display yellow skin. The coloration is caused by an accumulation of diatoms, a group of microalgae. Antarctic waters are very rich in nutrients and provide ideal conditions for diatoms to bloom. Scientists believe killer whales cannot really molt in freezing water, which causes them to accumulate a thick layer of these algae on top of their skin. The problem with these diatoms is the potential for bacteria to accumulate, which can cause infections in whales.

Orcas in Antarctica appear yellow because of algae layers on top of their skin – Credit: John Durban / NOAA

However, it seems that killer whales have found a way to molt and “treat” their skin by making short trips towards the tropics. By traveling to warmer waters, scientists think orcas can shed their skin and remove the diatom layers before returning to Antarctica to feed on seals, penguins, and fish. Now that’s some quality skincare routine!

Sources and further reading:

  • Raverty, Stephen, et al. “Pathology findings and correlation with body condition index in stranded killer whales (Orcinus orca) in the northeastern Pacific and Hawaii from 2004 to 2013.” PloS one 15.12 (2020): e0242505.
  • Pitman, Robert L., et al. “Skin in the game: Epidermal molt as a driver of long‐distance migration in whales.” Marine Mammal Science 36.2 (2020): 565-594.
  • Durban, J. W., and R. L. Pitman. “Antarctic killer whales make rapid, round-trip movements to.”Durban, J. W., and R. L. Pitman. “Antarctic killer whales make rapid, round-trip movements to subtropical waters: evidence for physiological maintenance migrations?.” Biology letters 8.2 (2012): 274-277.

Did you like this post? Check out our other posts on killer whales:

Some fish-eating orcas have worn out teeth: Here’s why

Anaïs is the founder of Whale Scientists. She is a PhD student at McGill University working on killer whale ecology and pollution. You can read more about her here.

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