DENVER (CBS4) – Happy “Bertday” to Bert, the Denver Zoo’s 58-year-old hippo. 
 
 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. 
 
 “Fifty-eight in hippo years is like a man being 110,” zookeeper and pachyderm expert Dave Johnson said. 
 
 PHOTO GALLERY: Bert Turns 58 
 
 On Tuesday, he chowed down on pounds of cake — or, at least, what is cake to a hippo: soaked grass-eater grain, soaked monkey chow, bananas and apple sauce mixed together. 
 
 The monkey chow is a juice-scented biscuit treat that “smells much better than it tastes,” Johnson laughs. “But the animals love them.” 
 
 Johnson decorated the cake with apple slices for candles and garnish. Bert consumed it in roughly eight bites over several minutes as Johnson tossed handfuls into the hippo’s gaping mouth. 
 
 “He’s taking another bite!” a younger visitor exclaimed during Bert’s party, presumably impressed a hippo could eat that much. 
 
 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. 
 
 “He has been with us for many years,” zoo spokeswoman Tiffany Barnhart said. “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. Johnson said the oldest hippo on record lived to be 61. Bert — one of the zoo’s resident geriatrics along with an 80-something-year-old alligator snapping turtle named Bob and a “really old” flamingo — has fathered 29 children with two females during his 56 years at the zoo. Not bad for a guy carrying approximately 5,000 pounds on his frame. 
 
 “He’s still getting around really well,” Johnson said. 
 
 Bert — or Bertie for those who know him well — now eats more alfalfa, grain and fatty foods to help him maintain his weight. Barnhart said the zoo used to treat him to real cake — angel food, for instance — but they’ve made the celebration healthier. 
 
 “You can’t live this old if you eat junk food,” Johnson said. 
 
 – Written by Tim Skillern for CBSDenver.com ||||| Hippo was Zoo’s longest resident and oldest hippo in accredited North American zoos 
 
 Denver Zoo is deeply saddened to announce the death of “Bertie,” a 58-year-old male hippopotamus. In addition to being the Zoo’s longest resident, Bert, as he was affectionately known, was the oldest hippo in accredited North American zoos. 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. Hippos live 30-40 years in the wild and usually up to about 50 years in zoos. 
 
 “This is a very sad loss for Denver Zoo and our community. Bert was a member of our family for more than 50 years,” says Denver Zoo’s President/CEO Shannon Block. “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.” 
 
 Bert’s caretakers had kept a close eye on him. Recently, his appetite level noticeably decreased and he was less consistently interested in training sessions with zookeepers. He became more reluctant to leave his pool and showed some difficulty walking. Veterinarians were limited in how they could treat him as he had not responded well to medications. Diagnosing problems in hippos is particularly difficult because of their size and anatomy, but all of Bert’s symptoms pointed to his severe old age. Ultimately, his caretakers knew his quality of life would not improve and made the difficult decision to humanely euthanize him. 
 
 “This is never an easy decision, but it was the right one. We’ll all miss him very much, but were glad he lived such a long, happy life here at the zoo,” says Denver Zoo Vice President of Veterinary Medicine Scott Larsen. 
 
 Bert had lived at Denver Zoo longer than any other animal resident. 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. Bert is the father of every hippo calf born at the zoo. He only had two mates his entire life, and he fathered 29 hippopotamuses! 
 
 Bertie came to Denver Zoo as a donation from Arthur and Helen Johnson. The Johnsons were pioneers in the development of Denver Zoo and long-time supporters. Helen Johnson was a former Denver Zoological Foundation Trustee and chaired its board from 1957 until her passing in 1978. The couple bid on Bertie in an auction and secured travel arrangements for him when he was two years old. 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. 
 
 A fine addition indeed - the young hippo was a media sensation and his arrival was greatly anticipated. 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. Bertie was one of Denver Zoo’s most well-known animals and a visitor favorite. In the last couple 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. 
 
 Denver Zoo is home to one other hippopotamus, Bertie’s 12-year-old son, Mahali. 
 
 Denver Zoo will have cards available for guests to sign at the hippo exhibit. ||||| Caroline Sullivan signs a card for Bertie the hippopotamus. Bertie, the oldest-living hippopotamus in North America, died at age 58 on Monday. (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. 
 
 Bertie, or Bert as he was known, was also the oldest hippo in accredited North American zoos. Hippos live 30 to 40 years in the wild and usually up to about 50 years in zoos. 
 
 "After witnessing a significant decline in his quality of life due to his advanced age, staff made the difficult decision to humanely euthanize him," the zoo said in a news release. 
 
 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." 
 
 Bertie came to Denver from New York City's Central Park Zoo on Dec. 16, 1958, when he was 2 years old. He was the first hippo ever housed at the Denver Zoo, and over his lifetime fathered 29 hippopotamuses. 
 
 "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. 
 
 The zoo said that throughout the years, Bertie had been one of the most documented and popular animals at the attraction. 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. 
 
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 "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. 
 
 The zoo is home to one other hippopotamus: Mahali, Bertie's 12-year-old son. 
 
 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. 
 
 Bertie's body will be sent to Colorado State University, where zoo staff and the college will perform a necropsy. From there, Bertie will be cremated and his bones donated to the Denver Museum of Nature and Science, according to Andersen-Vie. 
 
 Jesse Paul: 303-954-1733, jpaul@denverpost.com or twitter.com/JesseAPaul
– 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.)