Leopard geckos store most of their excess body fat in their chunky little tails. A fat (though obviously not too fat) tail is cute, but it’s also a sign that your gecko is healthy. A leopard gecko rapidly losing fat in its tail has Sick Tail, which can be caused by a number of different parasitic infections. The main one to watch out for is Cryptosporidium, which is highly deadly. Check out our full article for all the details on how to treat Sick Tail.