Peanut the squirrel was a leaper. He loved to leap. In videos of his seven happy years of domesticated cohabitation with a lively American family named the Longos, seldom was he seen to creep or scurry in the manner of duller, more earthbound rodents. Antic Peanut was always catching air. Down from the bookshelf and onto his master’s shoulders, from the top of the fridge to his master’s outstretched arm, his takeoffs showed total commitment to the arc, but his landings were always sure, as if he were possessed of Velcro feet. 

That Peanut became a star of social media, the world’s most famous squirrel with millions of followers, is no more surprising than Nureyev’s ascent to the top of the twentieth-century ballet scene. Peanut’s artistic medium was gravity, a mysterious force invisible to humans but readable to Peanut’s brain in much the way the ocean is to surfers. Kowabunga!

His early …