Plastic crap behind my back seat???

So detailing my 2007 SR5 quad cab I was sweeping around the back seat and started getting a bunch of little black plastic chips. I haven't taken the seat out to see what it was from but I thought I would ask if anyone else had this problem??? I do have the sub behind the back passenger side seat. I'm not sure if it was from a part of that or what. Thanks for your help!!!

 

Left overs from a messy installer? Did they drill any holes?

 

Check the convoluted tubing that's wraps around your under seat wires. mice like to eat that suff

 

Well it's the factory sub so I don't think that's the issue

 

Ill take a look at it but it seems to clean to have ever had mice in it at least I hope there isn't mice in it! Lol

 

It also gets brittle with age. Check the wires to make sure nothing is wrong with them