0:00:09.898,0:00:13.228 Off the rugged coast [br]of the pacific northwest, 0:00:13.228,0:00:17.318 pods of killer whales [br]inhabit the frigid waters. 0:00:17.318,0:00:19.538 Each family is able to survive here 0:00:19.538,0:00:21.578 thanks mainly to one member, 0:00:21.578,0:00:23.598 its most knowledgeable hunter: 0:00:23.598,0:00:25.208 the grandmother. 0:00:25.208,0:00:28.418 These matriarchs can live eighty years [br]or more, 0:00:28.418,0:00:31.508 while most males die off [br]in their thirties. 0:00:31.508,0:00:34.608 Though killer whales inhabit [br]every major ocean, 0:00:34.608,0:00:37.658 until recently we knew [br]very little about them. 0:00:37.658,0:00:40.518 The details of their lives [br]eluded scientists 0:00:40.518,0:00:44.028 until an organization called [br]the Center for Whale Research 0:00:44.028,0:00:46.608 began studying a single population 0:00:46.608,0:00:51.378 near Washington State and [br]British Columbia in 1976. 0:00:51.378,0:00:52.978 Thanks to their ongoing work, 0:00:52.978,0:00:55.368 we’ve learned a great deal [br]about these whales, 0:00:55.368,0:00:57.768 known as the Southern Residents. 0:00:57.768,0:00:59.008 And the more we learn, 0:00:59.008,0:01:04.388 the more this population’s elders’ [br]vital role comes into focus. 0:01:04.388,0:01:07.072 Each grandmother starts her life as a calf 0:01:07.072,0:01:10.882 born into her mother’s family group, [br]or matriline. 0:01:10.882,0:01:12.942 The family does everything together, 0:01:12.942,0:01:18.202 hunting and playing, even communicating [br]through their own unique set of calls. 0:01:18.202,0:01:23.922 Both sons and daughters spend their entire[br]lives with their mothers’ families. 0:01:23.922,0:01:28.152 That doesn’t mean a young whale [br]only interacts with her relatives. 0:01:28.152,0:01:30.382 Besides their own special calls, 0:01:30.382,0:01:33.912 her matriline shares a dialect [br]with nearby families, 0:01:33.912,0:01:35.992 and they socialize regularly. 0:01:35.992,0:01:39.082 Once a female reaches age fifteen or so, 0:01:39.082,0:01:43.512 these meetings become opportunities [br]to mate with males from other groups. 0:01:43.512,0:01:46.432 The relationships don’t go much [br]beyond mating— 0:01:46.432,0:01:49.032 she and her calves stay with her family, 0:01:49.032,0:01:52.022 while the male returns to his own mother. 0:01:52.022,0:01:54.282 Until approximately age forty, 0:01:54.282,0:01:57.822 she gives birth every 6 years on average. 0:01:57.822,0:02:00.292 Then, she goes through menopause— 0:02:00.292,0:02:03.622 which is almost unheard of [br]in the animal kingdom. 0:02:03.622,0:02:07.242 In fact, humans, killer whales and [br]a few other whales 0:02:07.242,0:02:11.232 are the only species whose females [br]continue to live for years 0:02:11.232,0:02:14.002 after they stop reproducing. 0:02:14.002,0:02:15.232 After menopause, 0:02:15.232,0:02:18.452 grandmothers take the lead [br]hunting for salmon, 0:02:18.452,0:02:21.112 the Southern Residents’ main food source. 0:02:21.112,0:02:23.622 Most of the winter they forage offshore, 0:02:23.622,0:02:26.092 supplementing salmon with other fish. 0:02:26.092,0:02:30.312 But when the salmon head [br]towards shore in droves to spawn, 0:02:30.312,0:02:32.612 the killer whales follow. 0:02:32.612,0:02:34.752 The matriarch shows the younger whales 0:02:34.752,0:02:37.882 where to find the most fertile [br]fishing grounds. 0:02:37.882,0:02:42.772 She also shares up to 90% of [br]the salmon she catches. 0:02:42.772,0:02:44.242 With each passing year, 0:02:44.242,0:02:46.792 her contributions become more vital: 0:02:46.792,0:02:51.872 overfishing and habitat destruction have [br]decimated salmon populations, 0:02:51.872,0:02:56.152 putting the whales at near-constant [br]risk of starvation. 0:02:56.156,0:02:58.006 These grandmothers’ expertise 0:02:58.006,0:03:01.906 can mean the difference between [br]life and death for their families– 0:03:01.906,0:03:04.196 but why do they stop having calves? 0:03:04.196,0:03:08.656 It’s almost always advantageous for a[br]female to continue reproducing, 0:03:08.656,0:03:12.786 even if she also cares for her existing [br]children and grandchildren. 0:03:12.786,0:03:17.406 A couple unique circumstances [br]change this equation for killer whales. 0:03:17.406,0:03:20.416 The fact that neither sons or daughters 0:03:20.416,0:03:23.636 leave their families of origin [br]is extremely rare— 0:03:23.636,0:03:26.036 in almost all animal species, 0:03:26.036,0:03:28.786 one or both sexes disperse. 0:03:28.786,0:03:31.926 This means that as a female [br]killer whale ages, 0:03:31.926,0:03:33.886 a greater percentage of her family 0:03:33.886,0:03:36.596 consists of her children [br]and grandchildren, 0:03:36.596,0:03:39.416 while more distant relatives die off. 0:03:39.416,0:03:44.126 Because older females are more closely [br]related to the group than younger females, 0:03:44.126,0:03:47.511 they do best to invest in the family [br]as a whole, 0:03:47.511,0:03:51.231 whereas younger females should [br]invest in reproducing. 0:03:51.231,0:03:52.911 In the killer whale’s environment, 0:03:52.911,0:03:55.591 every new calf is another mouth to feed 0:03:55.591,0:03:58.301 on limited, shared resources. 0:03:58.301,0:04:02.581 An older female can further her genes[br]without burdening her family 0:04:02.581,0:04:04.761 by supporting her adult sons, 0:04:04.761,0:04:07.801 who sire calves other families will raise. 0:04:07.801,0:04:10.231 This might be why the females have evolved 0:04:10.231,0:04:14.321 to stop reproducing entirely [br]in middle age. 0:04:14.321,0:04:16.802 Even with the grandmothers’ contributions, 0:04:16.802,0:04:20.202 the Southern Resident killer whales [br]are critically endangered, 0:04:20.202,0:04:23.052 largely due to a decline in salmon. 0:04:23.052,0:04:26.562 We urgently need to invest in restoring [br]salmon populations 0:04:26.562,0:04:28.442 to save them from extinction. 0:04:28.442,0:04:32.742 In the long term, we’ll need more studies [br]like the Center for Whale Research’s. 0:04:32.742,0:04:34.982 What we’ve learned about [br]the Southern Residents 0:04:34.982,0:04:37.172 may not hold true for other groups. 0:04:37.172,0:04:39.612 By studying other populations closely, 0:04:39.612,0:04:42.602 we might uncover more [br]startling adaptations, 0:04:42.196,0:04:46.156 and anticipate their vulnerabilities [br]to human interference 0:04:46.156,0:04:49.306 before their survival is at risk.