By Stephen Beech via SWNS
Sea otters – especially females – use tools when feeding to help look after their teeth, reveals new research.
The cute marine mammals employ shells, rocks and even litter to open the mollusks they love to feed on, but which often have thick shells.
Using tools increases the otters’ foraging success and protects their teeth from damage by allowing them to eat prey that would otherwise be difficult to obtain, say scientists.
Their findings, published in the journal Science, suggest that using tools is a “necessity” for the survival of sea otters in environments where competition is high and their preferred prey is often in short supply.
Sea otters had previously been observed using rocks, shells, human litter, and even the hulls of boats to bash open hard prey – including marine snails, sea urchins and clams.
However, the new study is the first to link the use of tools with tooth protection.
Scientists say the threatened species generally prefer to forage on prey that is not only rich in energy but also easy to process.
But in areas where the animal occurs at high densities, competition can lead to easy-to-access prey becoming depleted, driving some otters to specialize in alternatives – which influences their reliance on tool use for foraging.
Using data from 196 radio-tagged southern sea otters off the coast of California, American scientists investigated whether tool use enhances their foraging success.
Researchers from The University of Texas at Austin, University of California, Santa Cruz, Monterey Bay Aquarium and other institutions monitored how the marine mammals used tools to break open prey and identified links to the animals’ dietary patterns and dental health.
The research team found that using tools enabled the otters to target a wider range of prey, which led to higher energy consumption rates and reduced tooth wear.
They also discovered that the more female otters relied on tools, the more often they processed harder prey, increasing their foraging success.
The team said their findings suggest that using tools is disproportionally more beneficial for females.
Study leader Dr. Chris Law said: “Sea otters vary in how often they use tools.
“The females are likely using tools to overcome their smaller body size and weaker biting ability in order to meet their calorie demands.
“Raising pups takes a lot of energy, and the females need to be efficient in their foraging.
“The study shows that tool use is an important behavior for survival.”
He said that, in the southern sea otter’s range off Central California, some of otters’ preferred prey – such as large abalone and sea urchins -are not difficult to break open.
But those food sources dwindle or disappear in many areas, leading otters to prey more often on crabs, clams, mussels and small marine snails whose hard shells can damage their teeth in the process of prying them open.
Dr. Law explained that tooth condition is important for survival because when an otter’s teeth become too worn or damaged, they could starve.
The study found that female otters were able to consume prey that were up to 35 percent harder compared with that of males that used tools.
Dr. Law said that female dolphins, chimps and bonobos are also known to use tools more than their male counterparts, probably for the same reasons.
He added that in those species females tend to raise offspring, and they are often the ones that pass down tool-use behaviour.
