Pete Bethune's condition improving after deadly fer-de-lance attacked him in Costa Rica

Kiwi conservationist Pete Bethune is on the mend and feeling "very lucky" after being bitten by a fer-de-lance, the most deadly snake in Central America, while out in the Costa Rican wilderness.

Bethune was hospitalised in a serious condition on Monday morning (NZ time) - but now, the 55-year-old is feeling in much better spirits.

Speaking to Newshub on Tuesday afternoon, Bethune said the pain and swelling have subsided and his condition has stabilised.

"Today's been a much better day. Yesterday and the day before sucked, they were tough days," he said from his hospital bed.

"The doctors are saying I'm not entirely out of the woods - sometimes these things can progress and regress - but they're saying it certainly looks good for me. They think I'll be about another week here."

While Bethune doubts amputation will be necessary, he's expecting the bite will result in some permanent muscle damage.

"But I'll take that now, considering what I was looking at a couple of days ago. I honestly thought my number was up when that snake first bit me - we were such a long way from getting out of the jungle," he told Newshub.

It's been a tumultuous few days for the conservationist, who raced against the clock to battle his way out of the jungle after the venomous snake attacked. Navigating the treacherous terrain of waterfalls and rock faces became increasingly difficult for Bethune as his life hung in the balance.

"There was no way emergency services could get up to us there," he said. "I knew my only chance was to make it out."

He said his colleagues attempted to carry him, but they were using too much energy to navigate the difficult terrain while supporting his weight.

"They were falling over and tripping, and I kept getting my foot and calf bashed and sore - I sort of knew the clock was ticking so I wanted to keep going, but I also wanted to go to sleep.

"It was one crazy day."

Now recovering in a local hospital, Bethune appears to be in good hands. The father-of-two has praised the work of the local medics and emergency services who rushed to his aid.

"These guys know what they're doing," he said. "The emergency services were outstanding, they gave us some really good advice. The Coastguard was quick to respond.

"The doctors here know their s**t on snake bites. I've been very lucky, mate."

His daughter, Danielle, is busy fielding calls from concerned friends and relatives here in New Zealand - but is well-accustomed to her dad's dangerous lifestyle.

"I think in some regards I'm not the easiest dad to have. I've had a few of these types of things over the years. Poor old Danni, she said this morning, 'Dad, you keep ruining my holidays,'" he laughed. 

"I'm happy that I'm alive and I cherish every day I have on this earth."

Bethune's spirits have been bolstered by hundreds of messages of support, with people from around the world sending him their well-wishes.

"There's a lot of support out there. Conservation is a tough gig, you get the feeling often that people don't really care - something like this makes you realise that people do support your work. It's a very humbling experience actually."

The fer-de-lance is a highly venomous pit viper, considered the most deadly snake in Central America. Bethune, the founder of Earthrace Conservation, assists countries across Asia, Central America, and Africa with fisheries enforcement and anti-poaching efforts.

In 2017, Bethune had another brush with death when he survived a stabbing attack while on a mission to fight poachers and loggers in Brazil.

Watch the video above.