Orcas start life by hitting snooze
Orca calves don’t sleep regularly for the first few months of their lives, beginning with an extended period without a circadian rhythm. Mothers even suspend their own biological clocks for at least four weeks to keep a watchful eye on their precious new baby. Killer whales and other dolphin species have been observed to stay awake for up to 98 per cent of their baby’s initial two months, while calves only slept for ten per cent of that time.
Adult dolphins rest half of their brains at a time while the other half remains active enough to watch out for danger. Orcas do experience circadian rhythms despite not having a regular 24-hour sleep-wake cycle. The adrenal glands produce a hormone called cortisol that regulates blood pressure and inflammation and plays a huge role in the animal’s fight or flight instinct. This activity is controlled by their internal clock in the same way as a terrestrial mammal.
Orca calves measure 2.6m (8.5ft) at birth andweigh in at around 120–160kg (265–353Ib)