Viewers of Planet Earth used to epic tales of life and death among charismatic beasts will be met with a different kind of drama on Sunday: the sex life of a rare frog in Ecuador.
The last episode of the third series follows the search for a mate for “Sad Santiago”, the sole captive frog belonging to the species Atelopus halihelos, which is believed to number no more than 49 in the wild.
Jaime Culebras, a biologist who has dedicated his professional life to frog conservation, is seen hiking into the cloud forest of the Ecuadorian Andes to try to find a female partner for the morona-santiago harlequin frog.
In a race against time because Sad Santiago is very old, Mr Culebras spent sleepless nights searching in torrential rain for what was feared to be the last remaining female in the wild.
The crew hiked with mules and horses before camping for 10 days, searching during the day and at night, when there was more chance of finding one of the three-centimetre creatures.
“Many nights I didn’t sleep and searched right through to breakfast - I drank a lot of coffee,” Mr Culebras said. “There was a lot of rain and mud, and we only really stopped looking when the rains were so bad we were in danger from a killer flash flood.
‘You have to be careful where you put your hands’
“You look very slowly - you have to be careful where you put your hands because of dangers in the forest.”
Planet Earth viewers will see Mr Culebras’s hopes eventually raised by a sound - only for it to be a rare glass frog. But finally finds his quarry and exclaims: “I feel so happy - the first female. Santiago will be very, very, very happy because she seems very beautiful.”
The team on Sir David Attenborough’s BBC show filmed Mr Culebras in Ecuador, the only country the Atelopus halihelos is found after a producer was “blown away” by his story.
He features in the final episode of Planet Earth III, which is dedicated to conservation “heroes”.
The biologist, who says he’s been enthralled by frogs since he was four, has identified nine species of them and won court cases to prevent huge mining projects that threaten frogs.
He says the amphibians do not receive as much attention as at-risk mammals, even though 41 per cent of their species are threatened and they play a crucial role in the eco-system.
“In the 80s and 90s the Harlequin frogs were common in several areas of Ecuador, but a combination of fungal disease, climate change and destruction of habitat meant they’d virtually disappeared,” Mr Culebras said.
‘Being with him is not a normal relationship’
His girlfriend, Francesca Angiolani, a fellow frog scientist, said: “He can see frogs when he’s out that others can’t, from a distance away” and added: “Being with him isn’t a normal relationship.”
After filming, back at the research centre, scientists prepared a special humidity area and tried various foods, because there is limited knowledge of amphibian breeding programmes.
Santiago and his female clung to each other in the mating amplexus position for two months after the BBC crew had left, but there was no happy ending: Santiago died still embracing his partner.
The scientists were lucky enough to find another male and a female on a return trip to the stream and breeding attempts continue.
“We had to play Tinder again,” Mr Culebras joked. “But sometimes it can be years and years of a male and female trying without producing babies. In the end we were lucky after a year.
“The female releases hundreds of eggs. Some tadpoles die, but we ended up with dozens of small frogs.”
Although the frogs remain in captivity while further tests are carried out to ensure they can survive in the wild, scientists at the centre hope they will help keep the species alive.