A species of endangered toad endemic to Colombia鈥檚 Sierra Nevada de Santa Marta mountains is clinging on for dear life. The tiny Santa Marta harlequin toad (Atelopus laetissimus), which is just 4 centimetres long, can cling to the back of a female for five months without feeding until the pair are ready to mate.
The grasping behaviour, which is known as 鈥渁mplexus鈥�, is seen in many other animal species 鈥� but rarely continues for such a long period of time, says at the University of Magdalena, Colombia. In some cases, it can even prove fatal. But finding a female early in the breeding season and holding on for the long haul comes with big reproductive benefits, he adds.
鈥淚t鈥檚 very probable that the male will not find another female and have that chance again,鈥� says Rueda-Solano. 鈥淎nd the male who clasps the female first essentially wins access to her.鈥澛�
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The Santa Marta harlequin toad is only found in the north-west of Colombia鈥檚 isolated Sierra Nevada de Santa Marta mountains on the country鈥檚 Caribbean coast. The amphibians are in danger of extinction due to habitat loss. Many other species of harlequin toad across Latin America have already disappeared.
The Santa Marta harlequin probably developed its intense and protracted courting practices due to fierce competition, says Rueda-Solano. Males outnumber females three to one, so once a male sights a rare female, he attracts her with his mating call, hops onto her back, slips his front legs around her underbelly and clings on for dear life.
It matters little if the female isn鈥檛 ready to reproduce: the male can hang on for five months without feeding while he waits for the female to spawn eggs. The researchers were unable to track the toads for the entirety of the amplexus, so estimated its duration based on weight lost during mating.
The process of 鈥渕ate guarding鈥� is practised by many species of vertebrates and invertebrates, with male toads and frogs being among the most likely animals to on to the back of a female. But the behaviour usually continues for a matter of minutes, hours or occasionally a few days.聽
For A. laetissimus to cling on so long requires plenty of preparation. Males eat as much as they can to fatten up ahead of mating season. They can expect to lose up to 30 per cent of their body mass while clinging to females, and some die from starvation while doing so.
The practice doesn鈥檛 mean that only the strongest survive, however. Getting in early means that even the weediest toads face a chance against bulkier competitors. The researchers calculate that there is a less than 20 per cent chance of a male being able to dislodge another male once it is attached to a female.
They also concluded that male Santa Marta harlequins have evolved to have larger forearms, which make them harder to dislodge from females. Their strong hug has an average clasp force of 18.11 Newtons 鈥� equivalent to 52 times the male鈥檚 body weight, according to the team鈥檚 calculations. As well as using their tight grip to hold on, males fend off desperate challengers by kicking them away.
Researchers actively try not to anthropomorphise their subjects, but the parallels with a clingy, toxic relationship of 鈥減ossessive love鈥� have been clear for many Colombian couples, who have shared the study online with each other mockingly, says Rueda-Solano.
鈥溾�楾oxic鈥� could be one of the words of 2022, and the possessive love of these harlequin toads is seen by many as a reflection of that behaviour in people,鈥� he says.聽
Animal Behaviour
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