The Pickiest Creatures in the World
The Pickiest Creatures in the World
Most species, including humans, consider only a small group of potential mates before choosing one. However, female Uca crenulata fiddler crabs in California (USA) “inspect” up to 106 candidates before deciding to mate.
With this trait, female Uca crenulata crabs have earned the title of the “pickiest” animals in the world.
“As far as I know, no other species goes through such a large number of potential mates like the California fiddler crab,” said Catherine deRivera, the lead researcher.
“Most invertebrates, as well as some mammals, amphibians, and reptiles, mate with a neighbor or the first candidate they meet – or at least the first one to correctly perform courtship rituals,” she explained.
But California fiddler crabs are not so easily won over.
DeRivera and her colleagues observed a population of these crabs on a tidal flat near the Sweetwater River estuary in Chula Vista, California. Male crabs dig flat burrows, gather near their burrows, and signal to females by waving their large claws, essentially beckoning them to “come over here.” Female crabs, attracted by the calls, inspect the burrows, which reflect the size of the male.
Typically, a quick glance at a burrow is enough, and the female moves on to another male’s invitation. Sometimes, she even enters a burrow but leaves shortly after. A single female might repeat this process over 100 times before settling on the final burrow that best fits her size.
Once she makes her choice, either the male or the female seals the burrow entrance. Each burrow has multiple compartments, providing space for up to four females, meaning some males may attract a small “harem” to their homes.
Females remain in the burrow for 2 to 16 days, during which time they mate and lay eggs. The mother leaves before the larvae hatch, and the young crabs find their way to the water during high tide at night.
DeRivera believes that females are so selective because a burrow of the right size is more comfortable, retains heat better, and allows larvae to emerge more easily, reducing the risk of predation.
Tom Langen, an assistant professor of biology and psychology at Clarkson University, commented that this study highlights how creatures with small brains are not necessarily unintelligent.
