"Yes, I imagine he became a dog for that unique feature, but you don't know what animal you'll turn into when you start the process of becoming an Animagus. Like you said, shapeshifters aren't affected by the infection that causes lycanthropy. In dog form, Sirius can be with me on full moons without risking infection."
This was quickly turning from a meeting about James to a lesson on what it meant to be a werewolf, but it was good for Remus. As he delved deeper into plans for legislation and action, he'd have to start admitting his condition to people. Tonks was a good start.
"The thing most people don't realize," he said honestly. "Is that it's incredibly painful to turn into a werewolf and then once you transform, if you don't have an outlet for hunting or running, you basically turn on yourself. When I was a child, my parents had to lock me in the root cellar and I'd basically tear myself to pieces once a month. With another animal present, I can direct my attention towards Sirius and he keeps me in check."
He sipped his tea thoughtfully and leaned forward.
"That's why I married him, you know," he teased. "He keeps me in line."
If only. It was almost always Remus Lupin keeping the eye on Sirius Black. Once a month was a nice role reversal.