Kittens sometimes suck their thumbs and before today I never had any idea that this happened. It looks strangely human. It’s interesting because it tells us about cat emotions. Thumb sucking is an extension of sucking at mother’s nipple. It is an intuitive behavior which can start in the womb.
For a weaned child thumb sucking is a source of pleasure and comfort i.e a ‘pacifier’. It is the emotional comfort element that interests me because if kittens sometimes suck their thumbs they are doing it for the same reason as humans. In which case the kitten feels the emotional comfort of thumb sucking. Perhaps we no longer need evidence that cats have quite complex emotions but this behavior confirms that cats feel anxiety and seek emotional comfort.
I’ll have to assume that kittens thumb suck for the same reason as humans. As they develop and are weaned off nutritional sucking they find alternative ways to find comfort and soothing experiences. For adult cats this might mean being in close contact with their human caretaker or with a cat or dog friend.
Sometimes when a cat is prematurely weaned they can develop behavior problems. A well-known issue is pica; eating non-food, non-nutritional objects. Pica affects cats and kids. There are adult cats who, for example, suck on the ear lobe of their owner. You’ll see Siamese cats wool-sucking. It is another variant of the same problem. It is thought that fabric chewing in cats is a variant of thumb sucking.
But I had never before realized that kittens sometimes suck their thumbs. For me it is a reminder that there are many areas of overlap between the cat and the human in terms of anatomy, behavior and psychologically.
Wikipedia states that thumb sucking is a form of behavior found in humans, chimpanzees and captive ring-tailed lemurs. They will have to amend their page and add cats.