Saturday, November 25, 2017

[Crustacea • 2017] Birgus latro • Ruler of the Atoll: the World's Largest Land Invertebrate

A coconut crab (Birgus latro) kills an adult red- footed booby (Sula sula) on Chagos Archipelago (British Indian Ocean Territory) 
 Laidre, 2017.   
 DOI: 10.1002/fee.1730  

Predation can exert life-or-death selection pressures on prey over evolutionary time. Even when the observed frequency of predation is low, predators may induce wide-spread avoidance behavior in prey, thereby creating “landscapes of fear” (Laundré et al. 2014), which indi-rectly transform species abundance and community composition. For some animals, especially in remote areas, we know little about their predatory capacities or their potential impact on communities.

The coconut crab (Birgus latro) inhabits remote coral atolls and is the world’s largest terrestrial invertebrate, growing to what Charles Darwin described as “a monstrous size” (Darwin 1845), with a leg span exceeding 1 m and a weight of up to 4 kg. Following a brief larval stage in the ocean, these crabs spend the rest of their life on land, first as juveniles wearing remodeled gastropod shells (Laidre 2012) – like their closest evolutionary relatives, the terrestrial hermit crabs (Laidre 2014) – and then as adults living shell- free. Historically, coconut crabs were distributed across the Indo- Pacific on islands that for millions of years lacked any human presence. However, due to anthropogenic impacts, especially harvesting by humans, coconut crabs have been driven to local extinc-tion in many parts of their original range. Few studies of this remarkable animal’s behavior have been undertaken since Darwin’s Beagle voyage, but anecdotes abound, including rumors that the crabs ate Amelia Earhart (Nuwer 2013; though see Krieger et al. 2016 for well- documented predation on invertebrates). A review of the biology of coconut crabs emphasized that “behavioral ecology studies are few” and stressed “the need for further systematic research” (Drew et al. 2010).


Figure 1. A coconut crab (Birgus latro) kills an adult red- footed booby (Sula sula) on Chagos Archipelago (British Indian Ocean Territory) 

Mark E Laidre. 2017. Ruler of the Atoll: the World's Largest Land Invertebrate. Frontiers in Ecology and the Environment. 15(9); 527–528.  DOI: 10.1002/fee.1730 

Giant coconut crab sneaks up on a sleeping bird and kills it

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