Communication
lies at the core of orca social awareness. Family members
are seldom out of hearing range of one another. Their
calls, as loud as a jet plane's engines, echo over many
miles in the ocean. Everyone knows where he or she is
and where everyone else are. Given the strength of their
attachments to each other, this must have a very calming
effect on them. Communication is an essential ingredient
of
the glue that brings harmony to the orca community.
Orcas
make three types of vocalizations: clicks, whistles and
pulsed calls. The clicks are part of the whale's sonar and
are used for echlolocation: for finding and locating food
sources, for defining other objects in the ocean and locating
the whale in its environment. Whistles are typically continuous
tone emissions that may last for many seconds.
Calls,
simply put, are pulsed signals which have discrete patterns
that can be recognized by ear and by spectrogram. They are
the main component of the orca communication repertoire.
Dr. John Ford categorized the discrete call types for the
orcas of Washington State and British Columbia. He discovered
that each pod has its own collection of calls which he referred
to as their "dialect". He was then able to define
larger acoustic groups or "clans" by grouping
together pods which share common calls. Only pods which
share common calls are part of that clan. The Northern Resident
Community has three clans, whereas the Southern Resident
Community has just a single clan, as do the Transient orca
of this coast.There is variability within call types, even
for different maternal,groups within pods and clans. This
is a useful tool for identifying groups in the absence of
visual identification e.g. at night or from remote locations.
It has also been used to identify the pods and communities
of orcas captured in the 1960s and '70s. The differences
in vocal call types between clans does not seem to inhibit
the various maternal groups and pods within a community
from coming together and socializing.
The
role of these calls is not precisely known. However, the
different calls are certainly a way for the whales to keep
track of each other over large distances, in the dark, or
when large congregations occur. Though it has not been demonstrated,
there is certainly potential for communication of complex
specific information in calls. Sometimes groups are very
vocal and at other times the groups may be silent. The calls
are not necessarily modified in sound level to accommodate
whales travelling close together.
