If animals can sue humans then this means that the opposite can also ring true, that being that humans can also sue animals.
Allow me to point out the following, animals should not have rights equal to humans (we are easily a superior species on the planet, we've earned the right to have rights through being dominant), there is no logic which supports the idea of giving animals legal representation.
What would an animal gain by suing a hunter that shot their reletive? Money? (how can they use it?) Justice? (I'm not sure that animals can grasp abstract ideals such as that) More rights? (we're going over the top as it is, why make the matter worse?)