Hungry sea otters have come up with a solution when they want to open the shell of a crustacean without damaging their teeth: by using tools. The furry marine mammals are vital to California's kelp forests, and they can be eat 25 percent of their own body weight per day. They especially enjoy eating large abalones and sea urchins, and can prevent the urchins from taking over marine ecosystems. They will also switch to clams, clams, crabs and small sea snails when their preferred prey becomes exhausted.
Chewing on all those hard-shelled organisms can cause tooth damage, so sea otters – especially females – use tools to eat larger prey. The findings are described in a study published May 16 in the journal Science.
Southern sea otters are considered an endangered species only about 3,000 in California. Their main threats are prey, entanglement in commercial fishing gear, oil spills, disease and shark predation. according to the Marine Mammal Commission.
In the studya team from the University of Texas at Austin, the University of California, Santa Cruz and Monterey Bay Aquarium collaborated volunteer “otter spotters” to track 196 radio-tagged southern sea otters off the coast of California. They monitored how these endangered marine mammals use tools – including trash, shells and stones – to break open prey. They also made some connections with their diets and dental health.
“Tools allow otters to specialize in different diets (when preferred prey is limited) that they otherwise could not eat without the use of tools,” study co-author and UT Austin biologist Chris Wet tells PopSci. “This allows them to maintain their energetic needs even when their preferred prey is exhausted.”
When food supplies dwindle or disappear, feasting on crabs, clams, mussels and small sea snails with hard shells can damage their teeth when prying them open. Their dental condition is important for survival. If they become too worn or damaged, the otters can starve. The study found that female otters had less dental damage than male otters and used tools more often.
“Females raise young, that is [a] very energetically expensive to do. These results suggest that tool use allows female otters to overcome the mechanical limitations of processing harder prey associated with their smaller body size,” says Law. “We found that tool-using females consumed prey that was 21 to 35% harder compared to male tool users and non-tool users, despite their smaller heads and weaker biting skills compared to those of males.”
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Female bonobos, chimpanzeesAnd dolphins They are also known to use more tools than their male counterparts. Scientists suspect that this may also be due to the taxing work involved in raising offspring. Females are also often the ones to pass on tool-use behavior to their offspring.
In future studies, Law hopes to investigate whether individual otters who use tools also have greater reproductive success.
