The Northern Resident population of Orcas is well known for their strong family bonds and acoustic dialects that separate one pod from another. This community consists of over 200 whales and is growing. Within this community exist 3 separate clans. A clan most likely is a continuous lineage that long ago shared a common ancestral pod. The acoustic tradition of this pod has been passed on for generations and with each generation a slight acoustic variation would occur. A clan is then divided into different pods that share a number of calls. Most likely, the more closer related members of a pod are, or more time spent together the more calls they will share. Each pod has different matriline groups, which consists of a mother and her offspring. This family of whales will spend their entire lifetime together, especially sons and mothers.
This unique relationship is what separates this population of Orcas
from most other species on this planet, including humans. The daughters
and her offspring may form their own matriline taking with them the
acoustic tradition that was passed on to her by her mother. A matriline
group may add a slight variation to a call shared by other pods or
may develop a call used only by that family. This call-specific behavior
certainly aids researchers when trying to identify a specific group
of whales with the use of a hydrophone. All we need to do is listen,
and they will tell us who they are.
Northern Residents feed primarily on fish, their favorite being the largest species of salmon, the Chinook. During the early spring till late fall, family groups follow the salmon runs as they make their way towards northern then southern inlets along the coast.
They fish individually but family members may spread out to maximize feeding success and alert other members to the presence of fish in other locations. While this foraging occurs underwater you may hear a clicking sound. This "echolocation" produces an acoustic image which the whale can use to find food and for navigational purposes. The faster the clicks most likely the closer the object; slower clicks may be used for example to follow the ocean floor from above. When air is forced back and forth through the nasal cavities just below the blowhole sound is created. This sound can vary from clicks to whistles to loud complex calls that can be heard for miles underwater. Near the forehead of an orca is a body of fat referred to as a melon. Sound is able to pass through this melon to water easily because the acoustic coupling of these two mediums is perfect. The melon is able to change shape and send the sounds created in the nasal cavities into a directional beam ahead of the whale. This is a grand example of adaptation in a species, since the acoustic properties of water are much better than that of air, sound will travel four times faster underwater than above. Incoming sounds are received through the lower jaw then conducted to the middle ear.
During the spring to fall months there is the occasion where different pods from different clans will meet. There could be from 30 to over 100 whales. If one were to place a hydrophone under the water at this time they would listen to an orcrastra of different dialects and calls. At times the whales may be vocal all at once, other times one family may be silent while the other is vocal, as if taking turns to be heard. During this time it also becomes obvious just how social these whales are and the gentleness they display for one another could be an example for us all. Among resident Orcas there has never been any display of aggression amongst them. It is also believed that during these times when separate clans are together that breeding may occur. Most likely this vocal display becomes a means to choose a mate that sounds least like themselves to ensure interbreeding does not occur. Genetic studies have proven that the father and the mother of an offspring are from separate clans.
Orcas can travel at a speed of 3 to 12 knots. Mature male orcas can measure up to 10 meters and weigh up to 10,000 kilograms, the dorsal fin being as high as 6 feet! Females grow up to 8.5 meters and may weigh up to 7,000 kilograms; their dorsal fin is much smaller.
Most females give birth to a single offspring for the first time at 14-15 years of age. The gestation period is 15-17 months and may occur every 3 years until the age of 40. Females also live much longer than males; the maximum age estimated at 70-80 verses the male at about 40 years of age. The average life span for a female is 50, a male 29 years.
When you witness a family of Orcas moving through the water you are immediately aware of their connectedness. Whether they are side-by-side or apart, they are intensely aware of one another either by communication or touch.