Featured Research

from universities, journals, and other organizations

Hermit crabs socialize to evict their neighbors

Date:
October 26, 2012
Source:
University of California - Berkeley
Summary:
Social animals usually congregate for protection or mating or to capture bigger prey, but a biologist has found that the terrestrial hermit crab has a more self-serving social agenda: to kick another crab out of its shell and move into a larger home.

The terrestrial hermit crab Coenobita compressus lives inside a discarded snail shell and forages for plants and carrion along the Pacific coast from Mexico to Peru.
Credit: Photos by Mark Laidre, UC Berkeley

Social animals usually congregate for protection or mating or to capture bigger prey, but a University of California, Berkeley, biologist has found that the terrestrial hermit crab has a more self-serving social agenda: to kick another crab out of its shell and move into a larger home.

All hermit crabs appropriate abandoned snail shells for their homes, but the dozen or so species of land-based hermit crabs -- popular terrarium pets -- are the only ones that hollow out and remodel their shells, sometimes doubling the internal volume. This provides more room to grow, more room for eggs -- sometimes a thousand more eggs -- and a lighter home to lug around as they forage.

But empty snail shells are rare on land, so the best hope of moving to a new home is to kick others out of their remodeled shells, said Mark Laidre, a UC Berkeley Miller Post-Doctoral Fellow who reported this unusual behavior in this month's issue of the journal Current Biology.

When three or more terrestrial hermit crabs congregate, they quickly attract dozens of others eager to trade up. They typically form a conga line, smallest to largest, each holding onto the crab in front of it, and, once a hapless crab is wrenched from its shell, simultaneously move into larger shells.

"The one that gets yanked out of its shell is often left with the smallest shell, which it can't really protect itself with," said Laidre, who is in the Department of Integrative Biology. "Then it's liable to be eaten by anything. For hermit crabs, it's really their sociality that drives predation."

Laidre says the crabs' unusual behavior is a rare example of how evolving to take advantage of a specialized niche -- in this case, land versus ocean -- led to an unexpected byproduct: socialization in a typically solitary animal.

"No matter how exactly the hermit tenants modify their shellters, they exemplify an important, if obvious, evolutionary truth: living things have been altering and remodeling their surroundings throughout the history of life," wrote UC Davis evolutionary biologist Geerat J. Vermeij in a commentary in the same journal. For decades, Vermeij has studied how animals' behavior affects their own evolution -- what biologists term "niche construction" -- as opposed to the well-known Darwinian idea that the environment affects evolution through natural selection.

"Organisms are not just passive pawns subjected to the selective whims of enemies and allies, but active participants in creating and modifying their internal as well as their external conditions of life," Vermeij concluded.

Laidre conducted his studies on the Pacific shore of Costa Rica, where the hermit crab Coenobita compressus can be found by the millions along tropical beaches. He tethered individual crabs, the largest about three inches long, to a post and monitored the free-for-all that typically appeared within 10-15 minutes.

Most of the 800 or so species of hermit crab live in the ocean, where empty snail shells are common because of the prevalence of predators like shell-crushing crabs with wrench-like pincers, snail-eating puffer fish and stomatopods, which have the fastest and most destructive punch of any predator.

On land, however, the only shells available come from marine snails tossed ashore by waves. Their rarity and the fact that few land predators can break open these shells to get at the hermit crab may have led the crabs to remodel the shells to make them lighter and more spacious, Laidre said.

The importance of remodeled shells became evident after an experiment in which he pulled crabs from their homes and instead offered them newly vacated snail shells. None survived. Apparently, he said, only the smallest hermit crabs take advantage of new shells, since only the small hermit crabs can fit inside the unremodeled shells. Even if a crab can fit inside the shell, it still must expend time and energy to hollow it out, and this is something hermit crabs of all sizes would prefer to avoid if possible.

The work was funded by UC Berkeley's Miller Institute.


Story Source:

The above story is based on materials provided by University of California - Berkeley. The original article was written by Robert Sanders. Note: Materials may be edited for content and length.


Journal Reference:

  1. Mark E. Laidre. Niche construction drives social dependence in hermit crabs. Current Biology, 2012; 22 (20): R861 DOI: 10.1016/j.cub.2012.08.056

Cite This Page:

University of California - Berkeley. "Hermit crabs socialize to evict their neighbors." ScienceDaily. ScienceDaily, 26 October 2012. <www.sciencedaily.com/releases/2012/10/121026125131.htm>.
University of California - Berkeley. (2012, October 26). Hermit crabs socialize to evict their neighbors. ScienceDaily. Retrieved July 24, 2014 from www.sciencedaily.com/releases/2012/10/121026125131.htm
University of California - Berkeley. "Hermit crabs socialize to evict their neighbors." ScienceDaily. www.sciencedaily.com/releases/2012/10/121026125131.htm (accessed July 24, 2014).

Share This




More Plants & Animals News

Thursday, July 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Dogs Appear To Become Jealous Of Owners' Attention

Dogs Appear To Become Jealous Of Owners' Attention

Newsy (July 23, 2014) A U.C. San Diego researcher says jealousy isn't just a human trait, and dogs aren't the best at sharing the attention of humans with other dogs. Video provided by Newsy
Powered by NewsLook.com
Stone Fruit Listeria Scare Causes Sweeping Recall

Stone Fruit Listeria Scare Causes Sweeping Recall

Newsy (July 22, 2014) The Wawona Packing Company has issued a voluntary recall on the stone fruit it distributes due to a possible Listeria outbreak. Video provided by Newsy
Powered by NewsLook.com
Michigan Plant's Goal: Flower and Die

Michigan Plant's Goal: Flower and Die

AP (July 22, 2014) An 80-year-old agave plant, which is blooming for the first and only time at a University of Michigan conservatory, will die when it's done (July 22) Video provided by AP
Powered by NewsLook.com
Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Newsy (July 22, 2014) The 83 new genetic markers could open dozens of new avenues for schizophrenia treatment research. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins