His independent White House campaign has fizzled, but the flow of bizarre stories of Robert F Kennedy Jr’s unorthodox handling of the carcasses of wild mammals has experienced no similar suspension.

An environmental group is calling for a federal investigation into the former presidential candidate for an episode in which he allegedly severed the head of a washed-up whale with a chainsaw – and drove home with it strapped to his car’s roof.

The episode has parallels with another extraordinary tale reported earlier in August in which Kennedy confessed to dumping a dead bear cub in New York’s Central Park and attempted to make it look like the animal was killed by a bicyclist.

The latest grisly revelation, about the whale head, is not particularly new – it stems from a 2012 interview Kennedy’s daughter Kick gave to Town & Country magazine, in which she talks about a visit to other family members of the political dynasty in Hyannis Port, Massachusetts, more than two decades prior.