A bottlenose dolphin came up out of the water off Coronado, California and tapped the front of her handler’s boat with her snout.<\/p>\n
That is the signal, and it means she has found something on the bottom matching what she was taught to look for.<\/p>\n
Her handlers logged it as a false positive<\/strong> and carried on with the exercise.<\/p>\n A week later a second dolphin marked the same patch<\/strong> of sand.<\/p>\n What the divers eventually pulled out of it had been lying there for 112 years<\/strong>.<\/p>\n Because the animals are never shown a picture of a mine and sent out to match it.<\/p>\n They are trained on a set of criteria<\/strong> instead, a size, a shape, a density, a particular way an object answers a pulse of sound.<\/p>\n Anything down there that fits the description gets reported, whether or not anyone expected it.<\/p>\n Chris Harris, who supervises operations for the program, has described the work in exactly those terms, saying the job is to teach them to look for a specific set of criteria.<\/p>\n He also pointed at the reason the method holds up at all. Their sonar is so sensitive<\/strong>, and they are so well adapted to a highly cluttered environment.<\/p>\n Navy dolphins have been doing mine work since the 1960s, and the unit still operates out of San Diego with bottlenose dolphins and roughly 50 sea lions<\/strong>.<\/p>\n So a boat went back over the spot, and the second dolphin was sent down again carrying a marker to show the divers where to dig.<\/p>\n The object was almost entirely buried, which is why nothing with a screen had ever noticed it.<\/p>\n It ran about 11 feet long<\/strong> and 14 inches across, and it had weighed roughly 580 pounds with a warhead fitted.<\/p>\n The warhead was long gone and the thing was inert, but it still came up in two pieces.<\/p>\n Stamped into the casing was the detail that turned a curiosity into a record, a mark reading USN number 24<\/strong>.<\/p>\n More than 220 pounds<\/strong> of concretion and sediment then came off it by hand, first with pneumatic chisels and afterward by pulling the salt out electrically, a job that ran for 18 months.<\/p>\n And the reason a museum wanted the wreck of it has very little to do with its age.<\/p>\n Torpedoes of that period ran on compressed air, which meant they dragged a line of bubbles<\/strong> across the surface the whole way to the target.<\/p>\n A lookout could watch that track coming and the helm could turn out of its path, so the weapon announced itself.<\/p>\n John Howell put a 132 pound flywheel<\/strong> in the middle of the hull instead, spun up to 10,000 revolutions a minute on deck before the weapon went over the side.<\/p>\n That wheel drove the propellers and held the weapon steady on its heading at the same time, and it left no wake at all<\/strong> behind it.<\/p>\n Which made it the first torpedo able to hold a course without telling the ship ahead where it was coming from.<\/p>\n Then there is the paperwork, which makes the story checkable rather than merely charming.<\/p>\n The battleship Iowa spent a December day off southern California running torpedo practice, and the log for that day disposes of the loss in a single line<\/strong>.<\/p>\n Target practice with torpedoes, it reads, and then the number of the weapon that did not come back.<\/p>\n So the object two animals found in the sand is matched to a date<\/strong>, a ship and an exercise, which almost never happens with anything recovered from a seabed, as naval reporting<\/a> set out at the time.<\/p>\n Most of what comes off the bottom arrives with no name attached, whether it turns up under an offshore project<\/a> or beside a coastal solar site<\/a>.<\/p>\n This one surfaced with a paper trail<\/strong> already written for it, more than a hundred years in advance.<\/p>\n Which brings it round to the count, and the count is why anyone made a fuss.<\/p>\n Only 50 of these torpedoes were ever manufactured, across roughly two decades, before a competing design overtook the flywheel and the Navy stopped buying them.<\/p>\n Five are known to survive today, and two of those<\/strong> stand in one museum in Keyport, Washington, as the museum<\/a> lays out.<\/p>\n When this one came up, the reporting described a single known survivor<\/strong> elsewhere in the country, which is a fair measure of how thin the record was at the time.<\/p>\n The recovered weapon was cleaned, stabilized and handed to the naval history command at the Washington Navy Yard.<\/p>\n None of that was the point of the morning. Two animals were being asked to locate practice shapes<\/strong> on a flat sandy bottom.<\/p>\n They turned up a real one instead, and the only reason anybody went back to look was that a second dolphin refused to drop it.<\/p>\n","protected":false},"excerpt":{"rendered":" A bottlenose dolphin came up out of the water off Coronado, California and tapped the front of her handler’s boat with her snout. That is the signal, and it means she has found something on the bottom matching what she was taught to look for. Her handlers logged it as a false positive and carried on with … Read more<\/a><\/p>\n","protected":false},"author":28,"featured_media":31044,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"rank_math_focus_keyword":"dolphins","rank_math_title":"","rank_math_description":"","footnotes":""},"categories":[83],"tags":[],"class_list":["post-31043","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-earth"],"_links":{"self":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/31043","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/users\/28"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/comments?post=31043"}],"version-history":[{"count":0,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/posts\/31043\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media\/31044"}],"wp:attachment":[{"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/media?parent=31043"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/categories?post=31043"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ecoportal.net\/en\/wp-json\/wp\/v2\/tags?post=31043"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}How a dolphin is told what to find<\/h2>\n
What came up in two pieces<\/h2>\n
Why the design was worth keeping<\/h2>\n
How it ended up on the bottom<\/h2>\n
Fifty were built and five are left<\/h2>\n