Frogs keep trying to mate with weird things – and have for millions of years

Male frogs often try to mate with different species, turtles, fish or dead partners – and may have been getting wrong for hundreds of millions of years.

When frogs mate, they go through a process known as amplexus. This involves the male frog gripping tightly to the female until the eggs are fertilised, which can take hours or even days.

However, there is no shortage of records of male frogs getting frisky with something other than a female, clinging on to all sorts – including inanimate objects. 

One reason for this bizarre behaviour may be the fact there are so many more female frogs out there than males, leaving some amorous amphibians without a mate, but still with the urge.

‘For a male facing huge competition with rivals to reproduce, it would be advantageous for males to arbitrarily be attracted to – and thus clasp – any female-looking object in order to increase mating probabilities,’ said herpetologist François Brischoux, from La Rochelle University in France.

However, despite the fact that not all frogs and toads mate in this way, the ‘misdirected amplexus’, also known as a very awkward sexual encounter, has been witnessed in a number of other species.

This suggests it may have been around since frogs first appeared on Earth.

To investigate, Mr Brischoux and his team delved back into the frog evolutionary tree, plotting all the close encounters by 159 frog species across their family history.

Using probability analysis to calculate when the behaviour first appeared, the study, published in the Biological journal, found a 97% chance that even the earliest frog species hopping around 220 million years ago were getting it wrong.

‘Our results suggest that the reproductive strategies promoting misdirected amplexus were possibly occurring early during [frog and toad] diversification,’ said Mr Brischoux, speaking to New Scientist.

However, while the behaviour appears to have been around for as long as frogs, records of misdirected amplexus has soared since the start of the century. Environmental changes caused by humans, including habitat modification and noise pollution, could be to blame.

‘The possibility that anthropogenic activities may promote the occurrence of this reproductive dead end is worrying at a time when amphibian populations are suffering a strong decline,’ said Mr Brischoux.

According to the International Union for the Conservation of Nature’s Red List of Threatened Species, amphibians are the most at risk vertebrate class on Earth, with 41% of species threatened with extinction.

In 2019, the Chiriquí harlequin frog was officially declared extinct, one of 90 species of frogs, toads and salamanders wiped off the planet due to the deadly fungal disease chytridiomycosis.

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