A lot of this sort of magic in Harry Potter is closely connected to your personality - think the Patronus, or your sorting, or your wand. Similarly, your Animagi form is related:
Q: When you turn into an Animagus, can you choose what animal you become? Or does this get "assigned" to you?
JKR: No, you can't choose. You become the animal that suits you best. Imagine the humiliation when you finally transform after years of study and find that you most closely resemble a warthog.
JK Rowling's World Book Day Chat, March 4, 2004
Also consider Rowling's (not just magic's) tendency towards this sort of allusion - Snape's flower dialogue, the names of spells, names of chracters (Remus Lupin, as often pointed out, might as well be named Wolfy McWolf, and Sirus Black = dog star black = black dog) all point toward these sorts of things being very intentional because Rowling paid attention to that kind of thing.
Look at also at his nickname: Wormtail. One of the definitions for worm is "a weak or despicable person (often used as a general term of abuse)" - also probably intentional. Look also at the personality of Pettigrew when we finally meet him, and the characters' reaction to him - Harry
[threw] Pettigrew’s hands off him in disgust
Pettigrew was begging and groveling towards Harry and Ron, e.g., in
Kind boy ... kind master [...] I was your rat ... I was a good pet...
And of course there's
If you made a better rat than a human, it’s not much to boast about, Peter.
All of this seems to indicate that yes, Peter Pettigrew's Animagi form and what he did are quite related. Interesting end link - this essay; see the last section of the essay at the very bottom titled The Rat.