Four reproductive tales from the animal kingdom, where sealing the deal doesn’t always turn out so great for one partner.

Come Valentine’s Day, some people may wonder to themselves, “Is this the only way to find a mate?” And the answer is no. There are many ways to find one.

But be careful what you wish for. Evolution has produced all manner of surprising interactions that enable reproduction in nature. Compared with these four unusual tales from the animal kingdom, being someone’s Valentine might sound pretty good.

Painted turtles

The way that male painted turtles entice females may sound almost romantic. The male faces the female, stretches out his long, dainty claws and strums the sides of her neck, head and face; this courtship gesture has been well documented since the days of Charles Darwin. But scientists recently documented another mating strategy, often deployed by the largest males, that is far less elegant.

At Canada’s Algonquin Wildlife Research Station, researchers noticed injury marks on the heads and necks of female painted turtles. Year after year, and often during breeding season, the wounds appeared fresh. The marks matched the shape of the spiky front of a male turtle’s shell and of sharp, toothlike structures on his beak.

Patrick Moldowan, a doctoral candidate in evolutionary biology at the University of Toronto, and his colleagues hypothesize that the males ram and grind the front portion of their shells on the soft head and neck tissues of the females to coerce them to submit.

The larger, possibly older males are more aggressive, and their “sexual weapons” are more developed, the researchers noted. The smaller males still rely on seducing the females with their claws, which appear more grandiose compared with the males’ bodies. That may prompt larger males to adopt more combative tactics.

Mr. Moldowan compared the situation with a small moose sporting a gigantic rack of antlers. On a larger male, the same antlers don’t look as impressive.

But which male — large or small — wins the race to father more painted turtle generations remains a mystery. Mr. Moldowan’s team is now conducting paternity tests to see if the large, mature and weaponized brutes sire more offspring each season than the younger males.

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