When orcas lose weight, they lose fat from their blubber and if prolonged, this can eventually lead to a pronounced depression behind the blowhole, a condition known as “peanut-head”, as the head looks like an unshelled peanut.

Such extreme weight loss can be caused by malnutrition due to food shortage, or as result of an infectious disease, leading to lack of feeding. In wild mammals, the most commonly recognized cause of weight loss is food shortage.

Orcas have a thick layer of blubber, and peanut-head typically indicates advanced illness, or prolonged lack of food. Therefore, it’s considered a reliable indicator of emaciation and poor body condition. Individuals who have been identified as being in poor condition have a higher probability of dying than individuals who have not.