Coconut crabs, known scientifically as Birgus latro, are remarkable inhabitants of tropical Indo-Pacific islands. They hold the distinction of being the largest land arthropods globally, capable of reaching impressive sizes. An adult coconut crab can span up to three feet across and weigh as much as nine pounds. These unique creatures have evolved to live almost entirely on land, showcasing significant adaptations to their terrestrial environment.
General Dietary Habits
Coconut crabs are omnivorous scavengers, consuming a wide array of organic matter found in their island habitats. Their diet primarily consists of fallen fruits, such as coconuts and pandanus, along with various nuts and seeds. They also consume decaying organic material, which forms a regular part of their foraging activities. Beyond plant matter, these opportunistic feeders will readily consume animal carcasses, including those of other crustaceans and even small mammals or birds. Larger food items are often dragged back to their burrows for more secure consumption and storage.
Bone Consumption: Evidence and Context
While not a primary food source, coconut crabs do consume bones, a behavior observed opportunistically and confirmed by scientific observations of their scavenging on skeletal remains. This includes carcasses found in their habitat, where they process and scatter bones. For example, experiments involving pig carcasses demonstrate that coconut crabs can strip flesh and rapidly remove bones within a couple of weeks. Historical accounts further support this, with reports from colonial officers noting small bones being removed by these crabs. Their powerful capabilities allow them to crush bone material during their scavenging activities.
Nutritional Drivers for Bone Consumption
The consumption of bones by coconut crabs is primarily driven by their need for specific nutrients, particularly calcium. This mineral is essential for the formation and hardening of their exoskeleton, especially after molting. Molting, the process of shedding their old shell to grow, requires significant calcium for a new, robust exoskeleton. Their exoskeleton is composed largely of chitin reinforced with calcium carbonate. By consuming bones or even their own shed exoskeletons, coconut crabs efficiently reclaim this calcium and other vital minerals. This strategy is resourceful for obtaining necessary materials in their resource-limited island environments.
Physical Adaptations for a Diverse Diet
Coconut crabs possess physical adaptations for their diverse diet, including the consumption of tough materials like bones. Their most notable feature is their powerful claws, also known as chelae. These claws generate up to 742 pounds of force, about 90 times their body weight, making them among the strongest of any crustacean and comparable to a lion’s bite. Beyond their formidable claws, coconut crabs have a highly developed sense of smell. Specialized antennules detect olfactory cues, allowing them to locate potential food sources from considerable distances. Their acute sense of smell is particularly attuned to odors such as rotting meat, bananas, and coconuts. This keen olfactory system, well-developed in their brain, contributes to their success as efficient scavengers.