SORROW A spate of new observations of grief in animals hints at why some species mourn and others do not

LAST JULY A FEMALE ORCA named J35 captured world-wide attention for her unprecedented vigil. J35, also known as Tahlequah, is a member of the closely monitored Southern Resident population of orcas in the Salish Sea, off the coast of Washington State and British Columbia. She had just given birth, following a nearly year-and-a-half-long gestation period. It was her second offspring, a daughter, and the first live birth in the declining Southern Resident community in three years. But 30 minutes after birth, the calf died. J35 would not let her baby go. With great effort, she swam with the tiny body on her head and made deep dives to retrieve it when it slipped off. Other members of her pod registered her distress: at one point, a group of females gathered in a tight circle around J35, an act of apparent emotional attunement that lasted at least two hours. Seventeen days and 1,000 miles passed before J35 finally released her daughter's corpse for good.