科学 · セミクジラの子クジラ遅れて見つかったセミクジラの子、シーズンの集計を24頭に引き上げ執筆 2026年11月6日 19:30 UTC視聴文字起こし0:07A previously uncounted right whale calf has lifted the season's birth tally to0:12twenty-four.0:13Around three hundred and eighty North Atlantic right whales remain, and this is0:17their strongest recorded calving season in seventeen years.0:21But their recovery depends on whether those calves survive, and whether births can0:25outpace deaths.0:27Researchers had already recorded twenty-three mother calf pears.0:30Adding this calf brings the tally to twenty-four, the fourth highest on record.0:36Aquarium scientists believe it was born during the winter calving season, months0:41before they identified it.0:42The New England Aquarium announced the identification on November2.0:46After analyzing photographs and citing data from Canada, the calf appeared alongside0:51its mother, Silt.0:53Researchers with the Mingan Islands Cetaceation Study, a non-profit based in0:57Quebec's Côte-Nord region, had photographed the pair off Antacosti Island in1:01September.1:02A September twenty-fifth photograph places Silt and her calf in the Jacques Cartier1:07Passage.1:08In the Gulf of Saint Lawrence, Mathilde Laverdier took the photograph for the Mingan1:13Islands Cetacean Study.1:15It documents the pair together in Canadian waters.1:18Silt is thirty-eight years old, and this is her sixth known calf.1:22Researchers track individual whales through an extensive photographic catalog,1:27giving them a way to follow mothers across sightings and breeding seasons.1:31Silt's calf hadn't previously appeared in this season's birth record, despite boat1:36and aerial surveys along the U.S.1:38East Coast through spring and summer.1:40Silt briefly visited the southeastern U.S.1:42calving grounds in February.1:44Researchers didn't document her with this calf there.1:47The September photograph and November announcement came much later, leaving1:52scientists to assess when the birth most likely happened.1:55Right whales usually give birth in winter off the southeastern United States.1:59They then travel north to feed in New England and Canadian waters.2:04That seasonal movement offers a plausible explanation for a calf appearing far from2:09the calving grounds.2:10Months after the winter surveys ended, aquarium scientist Amy Warren says Silt may2:15have given birth in the southeastern calving grounds and left before observers2:20documented them together.2:22Scientists consider a winter birth likely, but the calf's exact birth date and2:27birthplace are still uncertain.2:29Boat crews and aircraft can miss a mother and calf, even during months of2:33monitoring.2:34Unrecorded births are unusual because researchers catalogue these animals so2:39closely.2:40This identification shows how a later sighting can change the record of a breeding2:44season that has already ended.2:46Richard Sears, the founder and director of the Mingan Island Cetacean Study, put the2:52challenge this way: it just goes to show you how big the ocean is and how those2:57animals can get lost out there.2:59No right whale births were recorded in two thousand and eighteen.3:02Since two thousand and ten, annual documented births have exceeded twenty only a few3:07times, even before Silt's calf was identified.3:10The twenty-three recorded pairs had made this season the strongest since two3:16thousand nine.3:17The extra calf improves an already unusually productive season.3:21Only about seventy reproductively active females remain within a global population,3:26estimated at around three hundred and eighty.3:29That small breeding population makes each mother calf pair consequential.3:34Silt's sixth known calf adds another documented birth from a mother.3:39Researchers have followed for years.3:41The population lost roughly a quarter of its whales between2010 and2020, then3:46rebounded slightly.3:47The recent improvement follows a decade of substantial losses.3:51Ship collisions and entanglement in fishing gear remain severe dangers, while3:56warming ocean conditions have shifted whale movements beyond protected waters.4:00Silt herself has survived multiple fishing gear entanglements.4:04Her ability to produce another calf comes alongside that continuing exposure to4:09human-made hazards.4:10Conservationists have also criticized U.S.4:13government decisions to delay new protections for a decade to help commercial4:18fishing.4:18The revised tally counts documented births.4:21It doesn't tell us how many of the season's calves survive or how the whole4:25population changes after deaths.4:28Silt's calf was alive alongside her in September.4:31For that birth to contribute to recovery, the young whale has to survive the dangers4:36its mother has already faced.記事を読むストーリーの時系列HeyDex
