How One Fish Uses Sneak Attacks to Divebomb Potential Mates

It's one of the first times that scientists have filmed “sneaking” in the wild.

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Feb 10 2017, 11:00am

Image: Ronald Oldfield

It can't be easy to be a little fish. If you're unlucky enough to be a (metaphorical) shrimp pitted against (non-metaphorical) tuna, then you might have to get a bit creative when it comes to mating.

Scientists have video proof of a species of fish using the aptly-named reproductive strategy called 'sneaking.' Basically, it involves smaller fish passing on their DNA by swooping in on the private time of other couples.

Ron Oldfield, who studies the social behavior of fish at Case Western Reserve University in Ohio, taped the Mexican Cuatro Ciénegas cichlid exhibiting the behaviour, which is known to be used by just a few dozen fish among about 34,000 species, according to research published in Hydrobiologia in 2015. He recently released a video exhibiting the behaviour.

Video: Ronald Oldfield

"Sneaking has been recorded in diverse species, but overall it's uncommon throughout the animal kingdom, including fishes," Oldfield said in a press release, which noted that the video recordings were "among the first of sneaking behavior published for any species of animal."

There's usually no reason for so-called alternative reproduction techniques if there are enough female fish to mate with. But bigger male fish in some environments monopolize several partners, so smaller fish have to resort to other means.

For this reason, sneaking as an alternate reproductive strategy has occasionally been observed in different animals—often by smaller males who have to encroach on the territory of bigger ones, because their size puts them at a disadvantage for regular mating. This is the case with cichlids, the fish caught on video.

Read More: Scientists Used Fake Birds to Scare Sunfish and Filmed It With A GoPro

Like many species, the female fish lays her eggs on a rock, where they stick. The male's job is to release a cloud of his sperm over the eggs to add his DNA—leaving a small window for the sneaky fish, which lies in wait for this moment.

"As the female finished a pass, in a sudden burst, the small male dove to the rock, tilted his underside toward the eggs, and then leisurely swam away," Oldfield explained. 

He observed this behaviour in a large tank by his desk, where, presumably looking up from Facebook, he noticed some fish doin' it and whipped out the video camera. Whom among us, right?

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