Can I use your disclaimer on all my future comments please ? <| sep |> Lol that ' s what commercials are for tho <| sep |> It is territorial behavior . Laying on top of the other one trying to force them out of the basking spot . I wouldnt do it as its very likely the larger one will start to bully the smaller one over food and heat . Unless you are keeping them in a very large tank with multiple basking spots to get away from each other , its more likely to cause both of them stress more than anything . At the very least try to feed them separately to make sure they both get ample food . How much bigger is yours than the new one ? If they are hungry enough they will consider anything smaller than them as potential food .