Wild Things

The weird and wonderful in the natural world

Sarah Zielinski

Wild Things


Wild Things

Sneaky male fiddler crabs entrap their mates

banana fiddler crab

A male banana fiddler crab raises his large claw to try to lure a female to mate. A new study finds that some males take a more sinister approach to mating and trap females in their burrows.

Sponsor Message

Among people, a man stepping aside to let a woman pass through a door first is seen as a gentlemanly — if a bit old-fashioned — act. Among banana fiddler crabs, though, this behavior is a trap — one that lets a male crab coerce a female into a mating she may not have preferred.

To catch the attention of a female and lure her into his burrow, a male banana fiddler crab stands outside the entrance to his cave and waves the larger of his two claws. A female will look him over and consider his size, the color of his claw and how he’s waving it. If she likes what she sees, she’ll approach him. She might decide to enter his burrow and check it out, and once inside, she might stick around for mating if she thinks that the burrow has the right conditions for rearing her embryos.

When a female approaches a male and his burrow, most males enter first, letting their potential mate follow him down. But many male crabs take another approach, stepping aside and following her into the lair — letting a male trap the female inside and mate with her, researchers report June 15 in PLOS ONE.

Christina Painting of the Australian National University in Canberra and colleagues observed banana fiddler crabs in Darwin, Australia, during two mating seasons, watching what happened as males waved their claws and females made their choice. When a female was interested in a male, the guys entered the burrow first 32 percent of the time. While females were more likely to enter a burrow if a male entered first (71 percent versus only 41 percent when the guy stepped aside), the trapping strategy was more successful in getting a mating out of the meeting. When the male followed the female in, 79 percent of females stuck around the mate. But waiting for her to follow resulted in a pairing only 54 percent of the time.

“The results strongly suggest that entering a male’s burrow first reduces the probability that a female will leave the burrow after sampling it since females are effectively trapped underground in the narrow burrow shaft when the male follows her in,” the researchers write.

So why would a female ever enter a burrow first if there were the possibility that she would be trapped inside and coerced into mating? Perhaps this might give the female a chance to test the male’s strength, the researchers suggest. If she can successfully fight her way out, then the male was obviously not worthy of her attention. Or it is possible that this is just a type of courtship behavior in which no coercion is actually happening. It’s difficult to know exactly what’s going on underground.

This isn’t the first time that the males of a fiddler crab species have been found behaving in what we might consider an ungentlemanly fashion. Males of other species have been found trapping, herding, startling and capturing females in their attempts to coerce a mating. And some male sand bubbler crabs, the researchers note, have even been found behaving somewhat like pirates of the sand-mud flats: Males have been spotted capturing female crabs, carrying them back to their burrows and forcing them into their underground lairs for mating.

Animals

Bacteria make male lacewings disappear

By Sarah Zielinski 10:00am, June 24, 2016
Scientists have tracked down why some green lacewings in Japan produce only female offspring: Bacteria kill off all the males early in life.
Animals,, Evolution

Three-toed sloths are even more slothful than two-toed sloths

By Sarah Zielinski 9:00am, June 20, 2016
The three-toed sloth Bradypus variegatus has the lowest field metabolic rate ever recorded, a new study finds.
Animals,, Conservation

That ‘Dory’ for sale may have been poisoned with cyanide

By Sarah Zielinski 3:00pm, June 16, 2016
Preliminary results from a new study show that over half of aquarium fish sold in the United States may have been caught with cyanide.

For harbor porpoises, the ocean is a 24-hour buffet

By Sarah Zielinski 7:00am, June 12, 2016
Scientists tagged harbor porpoises with monitoring equipment and found that the small cetaceans eat thousands of fish throughout the day.
Animals

Electric eels play defense with a mighty leap

By Sarah Zielinski 3:00pm, June 9, 2016
A biologist finds evidence that a 200-year-old report of electric eels attacking horses may be true.
Animals,, Oceans

Maximum size of giant squid remains a mystery

By Sarah Zielinski 12:03pm, June 3, 2016
A scientist has come up with a new estimate of the maximum size of giant squid. He says the animals could be as long as two public buses.
Animals

Animals get safe spots to cross the road — and car collisions drop

By Sarah Zielinski 12:00pm, May 31, 2016
Over- and underpasses built for wildlife in Wyoming proved a success for both the animals and the humans traveling the roads.
Animals,, Conservation

Counting cats is hard, but we know the numbers aren’t good

By Sarah Zielinski 9:03am, May 27, 2016
Recent studies highlight the difficulty of counting big cats, but even imperfect counts show that these species are in trouble.
Animals

For baby sea turtles, it helps to have a lot of siblings

By Sarah Zielinski 8:31am, May 23, 2016
After hatching, baby sea turtles must dig themselves out of their nest. This requires less energy if there are lots of siblings, a new study finds.
Animals

These mystery mounds are actually giant piles of earthworm poop

By Sarah Zielinski 8:33am, May 20, 2016
The grassy mounds that dot a watery landscape in South America are created by giant earthworms, a new study finds.
Subscribe to RSS - Wild Things