paypal charges a fee for their service. Its up to a business to decide whether or not they want to accept the fee as a cost of doing business or not accept paypal at all. For the record, it IS against paypals TOS for a seller to charge more for an item because a buyer is using paypal.
I can see both sides of this. I take paypal because its easy and offers me some protection. I would also take personal checks.
OP, if you feel comfortable after doing some research on the seller go for it. If not, there are plenty of other rodent houses you can order from.