The breath spray of a Southern Resident killer whale near its dorsal fin.
Photo courtesy of Sara Shimazu.

K21 Cappuccino was the oldest living male Southern Resident killer whale when he died recently, aged 35. A new study finds that the average lifespan for Southern Residents is mid-50s for females, and mid-30s for males. However, as with all average lifespans, humans included, some individuals will live beyond this, and in fact studies since 1976 show that 17 females have survived beyond 55, with 8 males over 35. The oldest known male J1 Ruffles lived to be 59, and fathered a calf at 58!

A 2011 paternity study shows that these older Southern Resident males are vitally important, as their reproductive success appears to increase with age, and body size. Although these males may be sexually mature from around age 11, the females seem to select the largest—and therefore older—males, those who have the largest fins, flippers and flukes!

Finding fathers

Researchers had DNA from 8 potential fathers, and then looked for any evidence of their paternity in 242 biological samples collected up to 2009. These came from a variety of sources: biopsies (33), necropsy (3), and fecal/mucus samples (206).

These samples were found to belong to 78 different whales, and 43 of these were known individuals—either previously identified, or the samples were collected from known whales or families.

Mega daddy

L41 Mega and J1 Ruffles were identified as fathering the most calves. In fact, when more recent samples are included, L41 has been identified as father to 19 calves. He was 37 when he fathered J53 Kiki, his last known calf, however, he lived another six years, so it is possible he fathered one or more of the 14 calves known born between 2015 & 2021, and for whom paternity is unknown.

J1 is known father to 14 calves, including 12 after he reached 35 years of age, and his last known calf, L53 Saturna was born in 2010, the year he died, aged 59.

A Southern Resident killer whale at the surface.
Photo courtesy of Stewart Macintyre.

J1, Ruffles, with his large distinctive dorsal fin.

Age matters

J1 and L41 were two of the three oldest males in the population in the study. Third oldest was L57 Faith, so-named when thought to be a girl in his early years! Born in 1977, and so the same age as L41, he’s identified as father to 3 calves.

Size matters

L41 was estimated—by aerial photography measurements—to be the largest living male at the time of the study, with J1 coming in at 3rd largest. L78 Gaia—though younger than both these males—was the 2nd largest, and identified as father to two calves. So in total, these four males —J1, L41, L57, and L78—were either the largest or oldest in the population in the last decade, and have fathered 38 out of the 42 calves where paternity has been identified.

Females prefer older, larger males

Resident females have many opportunities to choose a younger mate, as older males often forage at a distance from their pods. The choice then of these older, more mature males clearly shows their preference. In fact, J1 and L41 were in their mid-30s and beyond when they fathered 14 calves; demonstrating the significance of the recent loss of K21 Cappuccino at 35.

Who are the oldest males now?

Following the death of K21, the oldest living males today are J26 Mike, J27 Blackberry & L85 Mystery, all 30 years old. There are 7 males aged 28-30, but only 3—J26, K28 & L85—are known to have fathered calves,

Worryingly, there are no males in the age range 21-27, the next likely batch of potential fathers. There are 9 males aged between 16 and 20—who are of reproductive age—but unlikely to be selected by females to father their babies.

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Making males matter

In the last 5 years, the two oldest males —L41 and K21—have died, along with 5 other males aged from 18 to 29. However, a recent study shows that male transient killer whales, hunting marine mammals in these same waters, are living on average 10 years longer than male residents, likely due to their prey being more abundant. If well-fed, these endangered Southern Residents would be less susceptible to disease, and less impacted by vessels and chemicals in their environment and could live longer to father more calves.

It is essential that the Southern Residents have access now to sufficient Chinook salmon to ensure that the current generation of younger males are able to reach their maximum size, to be selected as fit fathers to the next generation.