Marine Science Chapters

5.5.4

Killer Whales

Reproduction



A baby killer whale surfaces to breathe as other members of its pod dive to feed Adult killer whales give birth to a single baby (only once were twins recorded) about every 3-10 years. They start breeding at about 14-15 years of age (the youngest known was only 11). Gestation is 16-17 months. Babies nurse for about one year. Almost half of all the babies die within their first year. Females only breed for about 25 years then they stop when they are about 40 years old. Thus, each female only produces about 4-6 surviving offspring in her life.
A baby killer whale (above), surfaces to breathe.


Killer Whale Pod
Male and female killer whales.

All individuals in the resident populations stay with their mother. Little is known of actual mating encounters but genetic evidence (DNA analysis) shows that there is no mating within the matrilineal group. This behavior prevents inbreeding. How it is accomplished is unknown. It may be by recognition of their dialects. Each of these matrilineal groups has its own dialect that changes from time to time but all of the whales within one matrilineal group use the same dialect. It would seem that mating may only occur between two individuals that had different dialects. This is only a theory but a plausible answer.


A Killer Whale Pod at Turning Point, San Juan Islands in the evening
A killer whale pod at 'Turning Point,' San Juan Islands, in the evening (above).

Females live an average life of 50 years, but there are some that are estimated to be over 90 years old. The whale K7 was probably born in 1910 and may be the oldest killer whale alive today. The whale named Granny (J2) was thought to have been born in 1911. She is the matriarch of the J pod [and probably the mother of Ruffles (J1) who was born in 1951]. Granny and Ruffles always travel together.


J Pod, Ruffles and his female relatives
J pod, Ruffles and his female relatives (above).

Males live an average life span of only 29 years, but some have lived to 50-60 years old. Male killer whales mature at about 12-14 years old. They reach full size at about 20 when the tall dorsal fin and droopy flukes become obvious. Before that, young males are hard to tell from young females unless they breach (to see the mammary slits) or display their penis (which they may do in play).


The San Juan Island resident orcas are divided into the J, K and L pods. The naming of the pods in the British Columbia/Washington area began with A. The naming system was at J, K, and L when it reached the San Juan Islands. Each individual is given a number and put in a catalogue with a picture of its dorsal fin and saddle patch. The catalogue is updated each year as the San Juan researchers census each pod and plot their daily activities every June. The J, K and L pods often join and intermingle for social activities. They spyhop, breach, tail lob, fin slap and generally appear to be playing with each other during these social interactions. In 2001 J pod had 20 individuals, K pod had 17, and L pod had 40. One source noted that in 2006 there were a total of 87 (up from the 2001 numbers) in these three pods combined and that it was thought that original numbers were close to 120. These three pods are some of the most studied orcas in the world.



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(Revised 23 June 2003)
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