New Zealand conservationist Pete Bethune in serious condition after snake attack in Costa Rica

New Zealand extreme adventurer and conservationist Pete Bethune is in a Costa Rican hospital after being bitten by a venomous snake.

Bethune, who's reported to be in a serious condition, was on patrol in the jungle when he was bitten on the leg by the deadly fer-de-lance snake, before facing a race against time to get medical care, a spokesperson for Earthrace Conservation said.

The New Zealander's condition quickly worsened and Bethune remained in a serious condition on Monday morning (NZ time), the spokesperson told Newshub.

Bethune reportedly crawled out of the jungle and navigated several waterfalls before being rushed to the hospital.

The spokesperson said he's said to be in severe pain with extreme swelling from the snakebite.

According to Anywhere, a travel website, the fer-de-lance is one of the most menacing animals in Latin America and the most threatening snake in Central America. 

"Venom from this species contains an anticoagulant and causes hemorrhaging," the website says. "It moves quickly when threatened.

"The full length of this snake can be more than 2m; females are able to reach slightly longer body lengths than males."

In 2017 Bethune, the captain of Earthrace Conservation, survived a stabbing attack in Brazil while on a mission to fight poachers and loggers.

"I really thought my number was up. I was battling for my life," Bethune told The Project at the time, describing attempts to shake off his attackers.