Toothed whales (Odontoceti) are a diverse family of toothed predators that also happen to be extremely communicative and social. Pods of oceanic dolphins, like the Atlantic spotted dolphins (Stenella frontalis), emit a variety of vocalisations as they travel, hunt and socialise together. One of the most important calls in a dolphins acoustic repertoire are the signature whistles, distinctive whistle-like sounds that allow dolphins to identify themselves and one another in the water. Like all vocalisations such whistles evolve through social learning, where calves begin to mimic the sounds of their older peers and eventually develop their own individual call.
Signature whistles are especially important to prevent the separation of dolphin calves from their mothers, a standard situation for young Sperm whales (Physeter macrocephalus). Adult Sperm whales dive to depths beyond 1000m to hunt for squid, a capability that must be learned and taught to the young calves at an early age. Recent studies have shown that Sperm whale calves can already dive to depths of several hundred metres within the first year of their lives, which serve as the first practice dives before they begin to venture into the abyss for. the real thing once they mature. These premature non-hunting dives usually serve as a method for the young animals to track the movement of their older peers hunting in the deep. Like dolphins, Sperm whales emit a series of clicks which are unique for different family pods and allow fellow pod members to locate the rest of their group. Calves that are too young to forage at larger depths are left at the surface while the mature females dive to hunt and often swim to deeper areas of the water column to better hear the clicks of their pod. This allows them to follow the pod movement from shallower depths and thereby quickens reunions at the surface once the hunts are over.
So a young animals instinct to keep up with its mother and the rest of its pod is an important part of a learning process that helps it communicate, hunt and socialise a little better in future and we were lucky to bear witness to such a vital and extraordinary behaviour today.
By Paula Thake
Sightings of the day
15:00 Atlantic spotted dolphins, Sperm whales