Rats that big are usually lone males that have gone 'walkabout' and so don't have the usual rat colony with them. With no dominant pack male to keep them in check, they eat anything and everything. 15 inches is pretty big, although our old arthritic Max cat brought in a very dead one that measured 18 inches. Seems the people over the back had been troubled by it so they put out some poison... Max cat just took the opportunity.

Check her carefully for rat bites, they can be nasty.

Why do cats always do this sort of thing on a Sunday morning when we're at our least dressed and most vulnerable?

LTS