Naturalist and bear biologist Brad Josephs is no stranger to amazing ursine encounters. But even he was impressed by the arboreal acrobatics of the sun bears he filmed in Malaysian Borneo.

A long-time nature photographer and expedition leader for Natural Habitat Adventures, a travel outfitter and partner to the World Wildlife Fund, Josephs has seen (and captured) his share of wildlife behaviours, but the sun bears stood out. They loafed and played just like other animals do, with one key difference: they were several metres up in the air as they engaged in their friendly wrestling matches.

Image: Brad Josephs

"They are such amazing climbers and are so powerful for their size, I was simply awestruck while observing them," says Josephs, who captured the footage while volunteering at the Bornean Sun Bear Conservation Centre (BSBCC). "I honestly think they are the toughest mammals for their size on earth."

Sun bears are built for climbing. Image: Brad Josephs

The smallest bear species, the sun bear (Helarctos malayanus) is built for climbing, and those impressive, sickle-shaped claws help, too. The animals also have almost comically long tongues – up to 25 centimetres (almost ten inches) long! – which they use to extract honey and insects from the insides of trees. The namesake sun-like markings on their chests are all unique, too, ensuring that no two sun bears are exactly alike.

Long tongues come in handy for honey and insect retrieval. Image: Brad Josephs

Ranging from Bangladesh to Borneo, this is also one of the most threatened bear species in the world, classified as "Vulnerable" by the IUCN. Hunting the bears is illegal throughout their range, but poaching and capture for the black-market pet trade persist. Habitat destruction only compounds the problem.

"Climate change, which is upsetting the cycle of El Niño and La Niña, is affecting the natural patterns of fruiting fig trees, which sun bears rely on," adds Josephs. And unlike more iconic animals such as elephants, tigers, pandas and orangutans, he explains, the species doesn't get much time in the global media spotlight, so conservation funding is scarce. "It is such a grave situation."

Fortunately, some work is being done to both protect the bears and rehabilitate them when they clash with their encroaching human neighbours. The BSBCC, for example, recently managed to successfully re-release a captive sun bear back into the wild – only the second time this has ever been accomplished – and there are efforts underway to bring global awareness of the bears' plight, such as the Save the Sun Bear Campaign.

For Josephs, any effort to protect these small, remarkably acrobatic bears with ridiculously long tongues is welcome. "They are also incredibly intelligent, and hilariously cute at times," he says. "It didn't take very long for me to fall in love with them."