Cats fur is getting short in certain spots... Ideas on problem and cure?

[Outdoorkls]

One of our cats has a weird problem with his fur mainly around his hind legs. I was wondering what may be causing it. Any cure ideas?

 

[Outdoorkls]

Here are more pictures of it.

 

[Peaches Lee]

Does he groom a lot there? Is he on any flea prevention?

 

[enola]

My cat does that when she has fleas.

 

[Outdoorkls]

Well he has had flea medicine a few times... And now that you mention it I think I have been seeing him groom there a lot. That it probably the problem... Fleas. Thanks for y'all's help!