Migration
The targets naturally take on animal forms most fitting their movement and environment. Each target gains a land, burrow, climb, fly, and swim Speed of 40 feet, and can transform into a Tiny or Small animal most appropriate for a given movement and environment. It also gains immunity to mild, severe, and extreme cold and heat, along with any other immunities common to the local wildlife, at the GM's discretion. In exploration mode, a target can move much faster, at a travel Speed of 20 miles per hour.
A target can't Strike, cast spells, or use most manipulate actions in animal form, but it can resume its normal shape by Sustaining the spell. It can Sustain the spell again to resume animal form.
Traits
An action with this trait requires a degree of mental concentration and discipline.
You must physically manipulate an item or make gestures to use an action with this trait. Creatures without a suitable appendage can't perform actions with this trait. Manipulate actions often trigger reactions.
These effects completely transform the target into a new form. A target can't be under the effect of more than one polymorph at a time. If it comes under the effect of another, the second effect attempts to counteract the first. If it succeeds, it takes effect, and if it fails, the spell has no effect on that target. Any Strikes granted by a polymorph effect are magical. Unless otherwise stated, polymorph spells don't allow the target to take on the appearance of a specific individual creature. If you take on a battle form with a polymorph spell, the special statistics can be adjusted only by circumstance bonuses, status bonuses, and penalties. Unless otherwise noted, the battle form prevents you from casting spells, speaking, and using most manipulate actions that require hands. (If there's doubt about whether you can use an action, the GM decides.) Your gear is absorbed into you; the constant abilities of your gear still function, but you can't activate any items. You lose your Speeds and gain those of the battle form. If a polymorph effect causes you to increase in size, you must have space to expand into or the effect is disrupted.