Sea otters are among the few marine mammals known to use tools in the wild. How do they typically use them?
- They use kelp strands as fishing lines to snag small fish
- They build floating rafts of driftwood to rest on at night
- They crack open hard-shelled prey like clams and mussels by hammering them against a rock held on their chest
- They use sharp shells to dig burrows into muddy riverbanks
Why C? And why not the others?
Correct answer: C. They crack open hard-shelled prey like clams and mussels by hammering them against a rock held on their chest
A floating sea otter will often carry a favorite rock tucked in a loose pocket of skin under its forelimb, then repeatedly smash a hard-shelled clam, mussel, or crab against that rock balanced on its chest until the shell breaks — a genuine, learned tool-use behavior that has been documented and studied since the 1970s and appears to be passed down within otter populations. Sea otters do wrap themselves in strands of kelp to keep from drifting away while they sleep, but that is anchoring, not fishing, and does not involve using kelp as a line to catch anything. They do not build rafts of driftwood; that behavior belongs to beavers, which use wood for dams and lodges rather than resting platforms. Digging burrows into muddy riverbanks describes the denning habits of the North American river otter, a different species from the marine sea otter described here.
Source: Monterey Bay Aquarium & Smithsonian Institution: sea otter rock-and-chest tool-use behavior.