In the films, Hermione's Patronus is depicted as a European River Otter, and her Animagus form would most likely be the same animal, as confirmed by author J.K. Rowling.
A badger would be a great fit for Ron's Animagus form.
Otter (Hermione Granger)
Her Patronus, the otter, is a clever and dexterous animal; some have even been known to juggle small rocks. Otters have also featured in many classics of English literature such as Tarka the Otter, Ring of Bright Water and The Wind in the Willows.
Following both ordeals, Ginny grew into a confident young woman. Her and her friends followed in the footsteps of a previous generation, completely unbeknownst to them, and became Animagi at the age of fourteen, to support their best friend, Maisie Cattermole. Ginny took the form of a grey mare.
Transfiguration and Animagi are different
For example: if Viktor Krum can transfigure his head into a shark's, like he does in Goblet of Fire, that doesn't mean he is an Animagus. Transfiguration is a form of spell-casting, whereas becoming an Animagus is forever. And yes, he could turn into a falcon. Lucky.
Animagus. Lily's animagus form is a Doe, coupling with her husband, James Potter who is a Stag. Severus Snape's animagus is also a Doe.
Usually people turn into Animagi who match their Patronus, so it is safe to assume Snape would be a doe. But based on his morals qualities, I'd say maybe some kind of prey bird; a crow would be the perfect match.
And there is no question that Snape was a talented wizard, and that he could have become one if he had wanted to. But the fact is, there is not one single shred of evidence in Canon that Snape ever became an animagus.
Definition: An Animagus is a witch or wizard who can transform at will into an animal. In Harry Potter and the Prisoner of Azkaban, Remus Lupin shared that it took his fellow Marauders – James, Sirius and Peter – until their fifth year at Hogwarts to finally become Animagi and keep him company in his werewolf form.
Draco is not an animagus in the story. However, if he were to become one, I believe he would be a Siamese cat. His belief in his superiority and his snobbish manner line up with Siamese traits, but he, like the cats, loves his family deeply.
Mrs. Norris seems exceptionally smart for a cat, to the point that we might think her a cat / Kneazle cross like Crookshanks, an Animagus, or Filch's familiar, it those existed in this world. However, the author has stated that she is just a highly unpleasant cat.
Pettigrew's Animagus form was a rat, from which his nickname "Wormtail" was derived. The four friends called themselves the Marauders and designed a map to navigate Hogwarts.
Talbott Winger was a wizard who attended Hogwarts School of Witchcraft and Wizardry in 1984 and was Sorted into Ravenclaw house. He was also an Animagus and took the form of an Eagle.
Extremely intelligent, exceedingly talented and a "wicked" Animagus, it's no wonder Minerva McGonagall is Head of Gryffindor house.
Albus Dumbledore indirectly stated that the Marauders never revealed to anyone, the Order of the Phoenix included, that three of them became Animagi until mid-1994, when Sirius Black told the entire story to him.
Was Voldemort an Animagus? No, Voldemort was not an Animagus. He didn't see any reason to become an Animagus despite being a gifted wizard and knowing a lot of magic. This may simply be because his sole purpose was to obtain immortality and become the strongest wizard who could control the world around him.
Falco Aesalon — Falcon; the first recorded Animagus; the registration system was not in existence in his time. Morgan le Fay — Bird; the registration system was not in existence in her time. Minerva McGonagall — Tabby cat; registered. James Potter — Large stag; unregistered.
When she completed all the steps, her Animagus form turned out to be a silver tabby cat, with what appeared to be square spectacle markings around the eyes.
If Snape hadn't been in Slytherin, Voldemort would have still risen to power, yes. But Snape might well have been on the good side from the start, and wouldn't have betrayed Trelawney's prediction to Lord Voldemort. Maybe the first wizarding war would have ended differently.
He is seen in his animagus form by Lucius Malfoy while on Platform 9 3/4. Lucius, as a Death Eater, knows about Sirius' animagus form because Peter Pettigrew told the Death Eaters when he returned to their side after book 3.
James Potter
Werewolves might be dangerous to humans, but they don't attack other animals; so Lupin's friends found a way to stay together as a kind of pack. James's Animagus form was that of a stag, which earned him his nickname, Prongs.
Your animagus is not always your patronus. Both an animagus and a patronus are said to take on a form that reflects the caster's inner most personality traits, so it makes sense that they would be the same. An example of this is that James Potter transformed into a stag and also had a patronus that was a stag.
Being an animagus wasn't Dark magic, nor particularly useful for ruling over everyone, nor for genocide, nor for achieving immortality, nor for infamy, so Voldy never bothered to become an animagus.