Camera traps in Sumatra's Bukit Barisan Selatan National Park have captured the rare moment that two critically endangered Sumatran tigers (Panthera tigris ssp. sumatrae) start to get their groove on. 

It might not look like much, but the tigress is giving signals to the male by lying down, explains WWF Tigers Alive biologist Joseph Vattakaven. "The noise she makes is a non-threatening nasal sound used in friendly tiger interactions. The scientific term is 'prusten' but it is informally referred to as 'chuffing'."

In the second video, we can also see what is known as a 'flehmen response' by the male (when he sticks out his tongue and bares his teeth). "He's [taking in] the scent and pheromones of the tigress," says Vattakaven. "This allows the scent to be taken to the olfactory organ on the roof of his palate to better ascertain her condition." 

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This isn't just any Sumatran tiger; the male, known locally as Riko, was captured by WWF's cameras in mid 2013, making this an exciting development. Pre-mating behaviour is a sign of a healthy tiger population, amazing given what these animals are up against. "In 2014 alone, we cleared 80 tiger snares and two illegal weapons from the park," says park-programme leader Yob Charles. "With just 450 left in the wild, this [should be a good motivator] for the government to maintain and increase protections within the National Park boundaries and its surroundings, to ensure the tiger population remains stable."  

Top header image: Mark Roche/Flickr