The Houston Zoo's 18-year-old male lion has died Jonathan was a zoo favorite since arriving in 2006

On Wednesday, Sept. 14, 2016, the Houston Zoo announced that Jonathan, the zoo's 18-year-old male lion, had died after medical staff discovered a severe blood clotting issue and a low white blood cell count. He arrived at the zoo in 2006 and was a hit with patrons. less On Wednesday, Sept. 14, 2016, the Houston Zoo announced that Jonathan, the zoo's 18-year-old male lion, had died after medical staff discovered a severe blood clotting issue and a low white blood cell ... more Photo: Stephanie Adams/Houston Zoo Photo: Stephanie Adams/Houston Zoo Image 1 of / 44 Caption Close The Houston Zoo's 18-year-old male lion has died 1 / 44 Back to Gallery

The Houston Zoo has announced that Jonathan, its 18-year-old male lion, died early Wednesday morning after medical staff discovered a severe blood clotting issue and a low white blood cell count.

These issues appear to plague geriatric lions, according to the Houston Zoo staff. The lion spent the night in the zoo’s animal hospital under observation before dying, a news release said.

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The loss will be a great one to zoo staff and visitors.

“Jonathan spent the majority of his life at the Houston Zoo after being rescued from a private owner when he was just a few years old,” zoo staff said in the release. “Jonathan’s regal mane was identifiable to all who visited him at the Houston Zoo, and since his arrival in 2006, (he) has been a guest and keeper favorite.”

The elderly lion was frequently seen lounging in the sun, surrounded by a pride of three females.

“Jonathan’s impact on our keepers and guests will not be forgotten,” said Dr. Adrian Fowler, vice president of animal operations for the Houston Zoo, as news of the death was released. “Our team of keepers who have spent more than a decade caring and bonding with this incredible animal are grieving this loss, and we support them through this sad time.”

Brian Hill, who retired from the zoo in 2014 after 12 years as its director of public affairs, was on staff when Jonathan arrived in 2006. He has nothing but fond memories of the lion.

"Jonathan was a rock star from the minute he arrived. A beautiful guy. The term "sweetheart" is rarely applied to male African lions but I think it is truly appropriate for Jonathan,” Hill said Wednesday.

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If the zoo is a movie, think of Jonathan as one of its leading men. Hill said that the lion could always be seen interacting with his keepers at a special "lion training window" in his habitat.

"It's covered in a strong metal mesh and when he would stand up with his paws on the mesh you got a strong sense of his strength and power," Hill said.

"Zoo guests loved him. That love was exceeded only by the love his keepers had for him,” Hill said.

One of those keepers was Kathy Watkins, the carnivore supervisor at the zoo. She says that Jonathan had just celebrated 10 years at the zoo this past weekend. The big cat that she knew was expressive and endearing.

“He was one of our cats that had the most personality,” she says. “He definitely had his favorite keepers. “If he liked you he would moan a bit and rub on the inside of the bedroom area when he saw you.”

When the keepers would begin work at 6 a.m. and wake up the animals, his roar would usually signal the beginning of the day.

“He was the voice of the zoo,” Watkins says. For lions, roaring is sort of like marking territory. Anyone who heard it can tell you that it was imposing and awe-inspiring, maybe reminding our inner DNA of something in our primal past.

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His favorite treats were giant femur bones plus whole prey items like frozen goats, rabbits and chickens.

The three females he shared the habitat with – sisters Uzima, Mattie and Nimue – haven’t showed much emotion since he died. That's natural, though.

“Typical lion behavior means males coming in and out of their lives; they’re not monogamous,” says Watkins. For now there are no definitive plans to bring another male lion to the Houston Zoo, but one could come into the picture.

When any animal dies at the zoo, especially one as distinctive as Jonathan, there is a mourning period among the keepers.

“Their daily job includes interacting with the animals, cleaning their habitats, working every day including holidays, and spending at least eight hours a day with them,” Watkins says. “The animals become not just a part of their job but a part of their family.”

“We all have our favorites, the ones we bond to,” she says. “They also bond to us, too.”