The kitten is thought to have inherited his “polydactyl” trait from his father, Tiger, and uncle, Bowie, who both had extra toes.
Ann Manners, joint co-ordinator at the charity’s Taunton & Wellington branch, said: “Due to his extra toes, Fingle is very good at climbing up their tall scratching post.
“We just need to be careful about his bedding, as he gets his claws well and truly stuck in towels, so needs to have a soft fleece blanket.”
The kitten was born on February 4, along with two brothers and one sister.
“Fingle is the only polydactyl in the litter,” Ms Manners said.
“He is bigger than his siblings, and has been first to achieve most things, although walking was more by luck than judgment as he got his paws in the wrong order!
“The kittens all spend time stalking one another, followed by an airborne ambush and kitten play. They’re like lambs, jumping in the air and racing around for no apparent reason.”
Although the genetic condition is uncommon, polydactyl cats can be found across the globe, and in the majority of cases the cat’s extra digits are harmless.
Ms Manners said: “Fingle and his siblings are truly gorgeous, but he and his family all arrived in care because none of his relatives were neutered.
“There was in-breeding between the cats because, like so many people, his previous owners didn’t realise that not only can female cats become pregnant as young as four months old, but that unneutered family members will mate. The numbers simply got out of control.
“We’d invite anyone who is struggling to afford to get their cat neutered to reach out to us as in many occasions we can help.”
Fingle, his siblings and his mother have all been reserved, and will go to their new homes once they have been neutered.