Bert the hippo turns 58 this week, a remarkably old age for a hippopotamus.

(Photo: Courtesy Denver Zoo)
The Denver Zoo is celebrating the birthday of its oldest resident this week: Bert the hippo is turning 58.

That's remarkably old for a hippopotamus, but "Bertie" is still going strong.  

"Other than age-related issues he is unbelievably spry for an animal of his age,” Denver Zoo large animal curator Dale Leeds says.

The zoo is offering free admission from Aug. 21-24 to anyone with "Bert" in their name (so you're in luck, Roberta and Norbert).

Bert's been a fan-favorite since he arrived at the zoo in 1958. Leeds says he hears grandparents tell their grandkids about their visits to see Bert decades ago. 

“If you’re a Broncos fan, you’re never going to forget John Elway," Leeds says. "In the zoo community, at least for Denverites and people who come here frequently, he’s respected on that level.” 

Hippos can be territorial and aggressive if ther personal space is invaded. But Leeds says those days are behind Bert.  

“During the time I’ve known him, he’s been a dream to be around. When he was younger? I don’t know; he might have been a little bit of a tougher guy," Leeds says.

Video: Bert's 57th birthday celebration last year