Coconut crabs were calculated to have one of the strongest pinching forces in the animal kingdom, exerting a force of over 3,300 newtons. Compared to the human bite, the pinch of the coconut crab is at least ten times stronger.
The discovery was noted by researchers from the Okinawa Churashima Foundation in Japan. Researchers pointed out that heavier animals produce stronger bites and pinches, which led to the question of how strong could a coconut crab pinch seeing that they can weigh over 3 kilos.
Go ahead and touch a coconut crab
The coconut crab, Birgus latro, is the largest land-living crustacean, and to date, its pinching force has not been recorded. Based on previous studies that analyzed the largest coconut crab, which weighed around 4 kilos or 8.8 pounds, it should be able to exert a pinching force of 3,300 newtons, exceeding the biting force of most land predators. Previous studies documented that the coconut crab can lift over 60 pounds.
“During our field study, obtaining data for analysis was challenging, as the large claws of this crab pinched us on multiple occasions,” reads the study.
Researchers measured the pinching force of 29 coconut crabs in the northern section of Okinawa Island in Southern Japan. The maximum pinching force exerted by the crabs stood at a 1,765.2 Newton mark. To draw the comparison to the largest coconut crab recorded, researchers analyzed the closer muscle fiber sarcomere length, present at the left claw of the crab. The force applied to the base of the dactyl was linked to the relationship of the crab’s strength, weight, and leverage. Although male and female coconut crab specimens differ in size and morphology, sexual dimorphism was not found to influence in the relation of body size to claw dimensions.
The coconut crab is closely related to the hermit crab, with the difference that the coconut crab does not rely on its shell for protection when it becomes an adult; instead, it develops a hard, calcified body which can keep growing, thus allowing it to rely on its claws for feeding and mating.
Early in life, coconut crabs do carry a shell for protection until they no longer need it. These crustaceans maintain a lonely life, seeing that they fight other animals and other coconut crabs for food and mates. Coherently, Birgus latro was named coconut crab thanks to their ability to open coconuts with their claws.
“The powerful claw provides some advantages to their terrestrial lifestyle. They can monopolize rigid terrestrial foods such as coconut, which are unavailable to other animals, and they can drive off predators and other competitors. Thus, the mighty claw is likely to be an adaptation to a terrestrial lifestyle and had been produced over the course of coconut crab evolution,” reads the study.
The coconut crab can take a coconut, cut it up, take it with its claw up a tree, and drop the nut to eat the insides then. After doing so, they tend to fall from the tree unhurt. This complicated process can take several days to be completed.
Coconut crabs live mostly in areas surrounding the Indian and the Pacific Ocean, coherently wherever there are coconut palms. These crabs are usually extirpated from populated areas, mainly from Australia and Madagascar. They are primarily red, but in some locations, they are predominantly blue to purple.
Since they are land crabs, coconut crabs cannot swim and can easily drown if submerged in water for a prolonged period. They have an intermediate organ between gills and lungs, which in the end serves to absorb oxygen from an air-predominant environment. Coconut crabs find their food mostly through their sense of smell and using their antennae to know where the smell comes from. This behavior has been compared to the one present in insects, being able to detect attractive odors in long distances, especially that of rotten fruit.
Coconut crabs population is not dense, seeing that the Christmas Island has the largest population of coconut crabs in the world and at the same time it is outnumbered by the Christmas Island red crab by about 50 times.
The existence of the coconut crab was noted by Charles Darwin on his travels, at first believing that it was endogenous to a coral island of the Society Islands.
Because coconut crabs are omnivorous, they can feed on fruits, seeds, and carcasses of small animals. This leads scientists to believe that coconut crabs may have eaten the remains of Amelia Earhart, near Nikumaroro, a small uninhabited island in the Pacific Republic of Kiribati.
Researchers only found a woman’s shoe, and empty bottle, and a sextant box whose serial numbers are consistent with the equipment that Earhart was carrying.
“The reason why they found a partial skeleton is that many of the bones had been carried off by giant coconut crabs. There is a remote chance that some of the bones might still survive deep in crab burrows,” stated British Colonial Service officer Gerald Gallagher, who recovered a partial skeleton on the island.
Source: PLOS One