Key takeaways
- A set of distinct calls used by one family, learned rather than inherited.
- The more two groups' repertoires overlap, the closer their relationship.
- Their prey has unusually good hearing, which changes how these orcas hunt.
- Clicks for finding things, calls for each other, whistles up close.
Three different noises for three different jobs
Orcas produce sound in three broad categories and it helps to keep them apart, because they are not variations of the same thing.
Echolocation clicks are a sensing tool. The animal emits a sharp pulse and reads the echo, building a picture of what is in the water ahead of it in conditions where eyes are useless. In a dark Arctic fjord in December, this is how a whale sees.
Discrete calls are the social channel. These are the pulsed, creaking, squealing sounds most people picture, and they are used between animals rather than at objects. A given population uses a limited set of them, each one consistent enough to be recognised and catalogued as a type.
Whistles are the third category, higher and more tonal, used mostly at close range within a group. They carry less far and appear to do the quieter interpersonal work.
What a dialect actually is
The interesting part is the discrete calls, because different families do not use the same ones.
Each matriline has a repertoire: a specific set of call types it produces, in specific proportions. The family alongside it in the same fjord will share some of those types and not others, and will have a few of its own. Record enough of it and you can tell which family you are listening to without seeing a single fin.
Calling it a dialect is a deliberate analogy rather than a claim about language. There is no evidence that a particular call means a particular thing in the way a word does. What the calls encode reliably is identity: who is calling, and which family they belong to.
The repertoire is learned. A calf acquires its family's calls by growing up hearing them, exactly as it acquires the family's hunting technique, and a calf raised in a different group would sound like that group instead.
The blow is a breath. The calls stay under the surface.
Reading relatedness through sound
Because dialects are learned and families never split up, the amount of overlap between two repertoires is a record of how recently those two families shared a matriarch.
Groups with many call types in common are close relatives whose lines separated recently. Groups sharing only a few belong to the same broad acoustic grouping but diverged long ago. Groups sharing none may use the same waters and be effectively strangers.
That gives researchers something rare: a way to map the relationships in a population using a hydrophone rather than a biopsy. Sound travels far underwater and does not require a close approach, so a boat can collect this information without disturbing anything.
Combined with photo-identification of fins and saddle patches, it is how the social structure of a population that lives out of sight most of the time has been worked out at all.
It also makes the population legible over time. A repertoire recorded twenty years ago can be compared with one recorded this winter, and where the calls persist the family has persisted with them.
Why these orcas keep quiet while hunting
There is a complication in northern Norway that does not apply to orcas hunting elsewhere, and it is one of the more elegant facts about this population.
Herring hear extremely well. Clupeid fishes have an unusual anatomical arrangement linking a gas-filled space to the inner ear, which extends their hearing far above what most fish can detect, well into the frequencies a hunting whale produces.
So an orca that echolocates its way toward a herring shoal is announcing itself to the shoal. Studies of herring-feeding orcas here have found them using notably few echolocation clicks during a hunt compared with orcas working other prey, relying instead on low-frequency sound and on the coordination of animals that have hunted together for years.
The tail slap fits the same logic. It is a very low-frequency event, which is exactly the range where herring hearing is worst, and it does its damage as a pressure wave rather than as a noise the fish can flee.
Learned
A calf acquires its family's calls by hearing them, not by inheriting them. Raised elsewhere, it would sound like somewhere else.
Can you hear any of this from the boat
Above the waterline, mostly not. Sound crosses from water to air very poorly, and what you hear on deck is the blow, which is a breath rather than a call.
Below the waterline it is a different ocean entirely. A hydrophone dropped over the side of a quiet boat picks up clicks, calls and whistles from animals a long way off, and it is the single most surprising thing about a day with orcas for most people. The fins are the visible part of something that is fundamentally acoustic.
Whether a given boat carries one varies, and it is worth asking rather than assuming. Either way, the engines have to be down for it to work, which is another reason a vessel that arrives early and then sits still sees more than one that keeps moving.
What you can do without any equipment is notice how much quieter everything gets when a pod is close. People stop talking, the crew cut the engines, and the only sounds left are the blows and the birds. That silence is not reverence. It is how you hear anything at all.
