<i>Updated:</i>Marine mammal researchers on Monday night euthanized a baby sperm whale that had stranded itself at a small island off the Upper Keys.</p><p>The 12- to 13-foot female sperm whale was not more than a week old and had a severly impaired immune system due to separation from its mother, according to officials with the rescue group Marine Mammal Conservancy.</p><p><hr size="1"><br> <table border="0"><tr><td align="center"> <a href="http://media.keysnet.com/smedia/2008/09/29/20/Sperm_Whale_LARGE.source.prod_affiliate.143.wmv"><img src="http://media.keysnet.com/smedia/2008/09/11/14/1-GREEN_Clapboard.standalone.prod_affiliate.143.jpg" alt="Video link"></a></td> <td align="center"><a href="http://media.keysnet.com/smedia/2008/09/29/20/Sperm_Whale_LARGE.source.prod_affiliate.143.wmv"><h5>Watch video of the rescue</h5></a></td></tr></table> </p><p><font size="-2">You need a video player or browser plugin that supports Windows movie files (.wmv), such as Windows Media Player (installed on most PCs). </font></p> <hr><br></p><p>A commercial fisherman reportedly located the whale in the mangroves of the westernmost islet of the Peterson Keys early Monday afternoon. The group of three islands is about five miles north of Lower Matecumbe Key, just inside the southeastern boundary of Everglades National Park.</p><p>However, rescuers said they heard reports of the whale since Saturday but could not locate it.</p><p>Marine Mammal Conservancy President Robert Lingenfelser said it’s unclear what caused the whale, which is commonly a deep-ocean species, to strand that far into Florida Bay.</p><p>“It’s very unusual to see them in the bay,” Lingenfelser said. “Normally they would strand on the oceanside. This is a deep-water animal.</p><p>“We believe there’s three matriarchal pods, resident pods, of sperm whales off of West Palm Beach,” he added. “This is also a transit point [for migration], but who knows. [There’s] no sign of any adults out there at all. They wouldn’t be able to swim in that shallow water anyway.”</p><p>Volunteers reportedly extracted the whale, which was about 20 feet up in the mangroves, and transferred it to a pontoon boat, according to Suzy Robeling, a volunteer stranding coordinator with the conservancy.</p><p>A Florida Fish and Wildlife Conservation Commission boat then towed the pontoon boat with the whale and three rescuers to the Indian Key Fill boat ramp between Upper and Lower Matecumbe keys.</p><p>After moving the pontoon boat onto a trailer, the whale was transferred into a moving truck and transported to the conservancy’s Key Largo facility for further diagnosis and treatment at about 4:30 P.M.</p><p>Once at the facility, Marine Mammal Conservancy officials saw that the whale had water in its lungs and exposed flesh where the umbilical cord attaches to the body. Normally, sperm whales stay with their mothers for up to eight years before venturing out on their own, officials said.