(AAron Ontiveroz, The Denver Post) 
 
 A 58-year-old hippopotamus who was the longest living animal resident at the Denver Zoo and one of its celebrities was euthanized Monday as his age left him in declining health. The oldest known hippo in the world, at least at accredited zoos, celebrated his amazing longevity with birthday cake and a large gathering of visitors on Thursday. After witnessing a significant decline in his quality of life due to his advanced age, staff made the difficult decision to humanely euthanize him on the morning of Monday, May 4 at Denver Zoo. “It’s a big deal for us today.” 
 
 Hippos tend to live 30 to 40 years in the wild and 40 to 45 years in captivity. Bertie's caretakers had kept an eye on him and as of late noted that his appetite level had decreased and he was less consistently interested in training sessions with zookeepers, the release said. "He became more reluctant to leave his pool and showed some difficulty walking," the zoo's release said. "Veterinarians were limited in how they could treat him as he had not responded well to medications." "This is never an easy decision, but it was the right one," Scott Larsen, the zoo's vice president of veterinary medicine, said in a statement. He arrived at the Zoo on December 16, 1958, from New York’s Central Park Zoo and was the first hippopotamus to ever reside at Denver Zoo. He was the first hippo ever housed at the Denver Zoo, and over his lifetime fathered 29 hippopotamuses. Bertie came to the zoo as a donation from Arthur and Helen Johnson, longtime zoo supporters, who bid on him in an auction and secured travel arrangements for him. Upon seeing young Bertie in New York, Mrs. Johnson said “he has a lot of personality and will make a fine addition to the City Park Zoo,” Denver Zoo’s name at the time. Throughout the years Bertie has been one of the most documented animals at Denver Zoo and has been featured in numerous stories in the daily papers. “He’s taking another bite!” a younger visitor exclaimed during Bert’s party, presumably impressed a hippo could eat that much. Advertisement 
 
 "In the last couple of years, the zoo even held special 'BertDay' celebrations in the days around his birthday, where countless guests signed his birthday cards and watched him eat his favorite treats," the release said. Bert, who’s lived at the zoo since donors Helen and Arthur Johnson brought him to Denver on a train in 1958, shares space with one other hippo, his son Mahali. Sean Andersen-Vie, a zoo spokesman, said goodbye cards and memorial boards have been placed outside the exhibit where Bertie lived so guests can remember the hippo.
– The oldest hippo in America—and possibly the world—has celebrated his last Bertday. Bertie, a 58-year-old male, was euthanized at Denver Zoo yesterday after keepers noticed a steep decline in the aging animal's quality of life, the Denver Post reports. Hippos don't usually make it much past 40 in the wild or 50 in captivity, the zoo says, and Bertie had been showing little interest in taking part in training sessions, leaving his pool, or even eating. Bertie had been at the zoo since the Eisenhower administration, having been transferred as a 2-year-old in 1958 from New York's Central Park Zoo. The zoo had long celebrated the hippo's "Bertday" with a party in August, and at last year's celebration, a keeper noted that "58 in hippo years is like a man being 110," CBS Denver reports. Bert had two mates over the decades and fathered a total of 29 hippos, including Mahali, a 12-year-old male who is now the zoo's only hippo. "This is a very sad loss for Denver Zoo and our community. Bert was a member of our family for more than 50 years," the zoo's president said in a statement. "He will be missed by all of us, including the many families and children who visited him and came to know his charismatic personality over the years." (Meanwhile, in Colombia, a drug lord's hippos are breeding out of control.)