{"id":22639,"date":"2018-01-26T00:05:23","date_gmt":"2018-01-26T08:05:23","guid":{"rendered":"https:\/\/hakaimagazine.com\/?post_type=custom_news&p=22639"},"modified":"2018-01-25T14:25:33","modified_gmt":"2018-01-25T22:25:33","slug":"the-confusing-social-lives-of-fiddler-crabs","status":"publish","type":"custom_news","link":"https:\/\/hakaimagazine.com\/news\/the-confusing-social-lives-of-fiddler-crabs\/","title":{"rendered":"The Confusing Social Lives of Fiddler Crabs"},"content":{"rendered":"

Rising sea levels are pushing different species of fiddler crabs together, and their interactions may cost one species vital territory.<\/p>\n

Most fiddler crab species share similar lifestyles, but each has its own very particular tolerances for how long, how often, and how much its burrow floods during high tide. In the intertidal zone, a few centimeters can make a big difference, so each species sticks to a very narrow strip of habitat. Along the coast of Darwin Harbour in northern Australia, rising sea levels are sending two fiddler crab species, elegant fiddler crabs (Tubuca elegans)<\/em> and signaling fiddler crabs (Tubuca signata), <\/em>scurrying higher to seek less waterlogged homes.<\/p>\n

The problem is, they\u2019re moving into the habitat already occupied by the banana fiddler crab (Austruca mjoebergi<\/em>), which is having trouble adjusting to its new neighbors\u2014mostly because it\u2019s being too friendly, according to a new study<\/a>.<\/p>\n

Male fiddler crabs of all species stake out a territory, dig a burrow, and defend it against intruders. For two weeks during the summer, the females walk among the males’ burrows in search of mates, while the males stand outside and wave their large claws for attention. When there\u2019s just one species of fiddler crab in an area, the system works. But male banana fiddlers seem willing to wave at any female who wanders by, whether she\u2019s the right species or not.<\/p>\n

Sometimes they\u2019ll even leave their burrows to follow a passing female for a short distance, which leaves them exposed and easy targets for gulls, kingfishers, and shorebirds. If they\u2019re chasing a female crab of the same species, that\u2019s often worth the risk. But banana fiddler crabs can\u2019t mate with the newcomers, which leaves indiscriminate male crabs wasting time and energy\u2014and possibly risking their lives\u2014to court females incapable of bearing their offspring.<\/p>\n

Interactions with males of other species are even more complicated for banana fiddler crabs. Negotiating property lines is a violent business among fiddler crabs, and living with a neighbor you\u2019ve already worked things out with is easier than starting over with a new one. Males sometimes pitch in to help their smaller neighbors defend against intruders, but only if the odds of winning are good\u2014the bigger the intruder, the tougher the fight, and the more likely males are to think twice.<\/p>\n

\"two<\/a>

Elegant fiddler crabs like the ones shown here are scurrying into banana fiddler crab territory, creating confusing social situations. Photo by Pat Backwell<\/p><\/div>\n

Banana fiddler crabs tend to be smaller than elegant and signaling fiddlers. So when the bigger crabs show up, banana fiddler crabs are less likely to help each other fight them off. But it may be even worse. Because banana fiddler crabs do not always discriminate when it comes to their neighbors, study author F\u00e1bio Sanches, a biologist at S\u00e3o Paulo State University in Brazil, says it\u2019s possible that they might choose to help a neighbor of a different species and gang up on their own species.<\/p>\n

Losing a burrow is a tough break for an individual crab, but if enough banana fiddler crabs start losing territory to the newcomers, this population could end up losing its habitat.<\/p>\n

If sea level rise and habitat destruction keep squeezing species together in smaller habitats, those who don\u2019t adapt may lose out. \u201cIt is possible that some species will [face] a more negative impact,\u201d says Sanches.<\/p>\n

And the banana fiddler crabs have nowhere else to go. Construction, including buildings, roads, and levees along the upper edge of the intertidal zone, creates a barrier for species migrating uphill to flee rising waters.<\/p>\n

It\u2019s hard to predict how these three crab species will ultimately adjust to sharing space. \u201cFiddler crabs still have many strategies for species recognition,\u201d says Daniela Perez, a biologist at Australian National University, who was not associated with the study. In time, she says that the banana fiddler crabs may get better at telling the different species apart and it may be the females that save the day. Females seem to have an edge on identifying appropriate partners, and are better at recognizing the claw color and distinctive “wave” of potential mates.<\/p>\n

Taking a cue from courtship timing, for example, would be one survival strategy. The three species seem to mate at different times, Sanches explains. Since courtship is energetically demanding, male banana fiddler crabs may eventually wise up to the fact that displaying for any female fiddler crab that happens to wander by\u2014 regardless of her species\u2014is a distraction that doesn\u2019t serve them well.<\/p>\n

It may look like a tragedy in the making, but if male banana fiddler crabs can stay on task, there\u2019s hope that their story may play out more like a romantic comedy.<\/p>\n","protected":false},"excerpt":{"rendered":"

Rising sea levels are pushing different species of fiddler crabs together, and their interactions may cost one species vital territory. Most fiddler crab species share similar lifestyles, but each has its own very particular tolerances for how long, how often, <\/p>\n

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