What animal juggles pebbles or rocks?

Name an animal in the canine family that is monogamous.

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Sea otters. They lie back and juggle their favorite rock from one foot to the other and under their chin, as practice.

River otters, like we have, do the same, even though they don't use pebbles/rocks in the same way.

Also, sea otters find the perfect pebble for opening shell fish, and keep it in their "pebble pocket" for weeks, months, or over a year, in some cases.

Coyotes.