K26 travels tight with new sibling K42 on the west side of San Juan Island, July 6, 2008 (Photo by Holly Fernbach)
Killer whales are polygamous, so they mate with more than one partner, and in this case the males do not have any known defined role to play in raising the calves they produce.
Instead, the adult males stay with their own mothers and help care for their siblings, nieces and nephews, who were sired by a different male. Similarly, their own calves are raised in a different maternal group, and any males in that family will help with raising the calves sired by the other males.
By all accounts, mating is a free-for-all between different pods, yet it is extremely rare for two members of the same family to mate together. Periodically the different pods hang out together, and occasionally all three of the southern resident pods - J,K,and L - meet in what the researchers call a "super pod". Vigorous interaction and mating can occur at these gatherings, but apparently the females only select males from outside of their own family group.
Young males from three pods traveling together: L78, J27 and K26 (Photo by Ken Balcomb)
It all sounds like a pretty sweet deal for the males - they live with their moms and frolic freely, not responsible for outcomes. 15 to 17 months later when the calves are born, the females are living with their own families. And it is - but it is a sweet deal for the whole clan, and may be key to why the orcas coexist so peacefully.
In this situation, male rivalry is minimized, plus they would seem to have a vested interest in insuring the well being of all calves since most likely they don't know which ones they might have fathered.
Young male J26 (Photo by Katie Jones)
J1, known for his wavy dorsal fin. (Photo by Emma Foster)
To account for this, scientists speculate that the orca's low genetic diversity might be the result of having gone through a genetic "bottleneck" about 130,000 years ago, during which time their population was drastically reduced, and is not just do to their tendency to mate with related individuals.
It may turn out that the orcas' reproductive strategy - though it creates or maintains a limited gene pool - enhances the success of the population as a whole. Their population is controlled by factors we don't quite understand, but it is closely tied to food abundance, and it may turn out that birth defects as a result of close inbreeding are naturally weeded out.
However indirectly, the dads play a key role in ensuring the success of the whole southern resident clan of orcas. And although orcas are deemed apex predators and appear to have no natural enemies, what that really means is that there are no successful natural predators. I imagine that the males are active and vigilant in protecting their families along with their involvement in the rearing of other males' offspring.
In the big picture, it works beautifully.
L41 traveling north through Haro Strait, August 10, 2008 (Photo by Dave Ellifrit)
From: January 2008 II-124 NMFS
" Resident killer whales display some of the most advanced social behavior of any nonhuman mammal, as evidenced by their highly stable social groupings, complex vocalization patterns, the presence of long-lived post-reproductive females, and behaviors such as cooperative foraging, food sharing, alloparental care, matriarchal leadership, and innovative learning. Maintenance of minimal group sizes is therefore probably necessary in preserving beneficial social interactions and in raising young."