Tuckin (Mountain Form)
Due to changes in soil composition, its skin has taken on an orange-red hue after absorbing minerals from the Earth, also becoming thicker and more robust.
What the Mountain Form changes
Tuckin is Grass. This form adds Earth, so it answers to a different set of matchups from the one you learned on the basic form.
Where Tuckin (Mountain Form) spawns
This form has no wild spawn point of its own. It comes from an egg, an evolution or an event rather than from walking into the right weather.
Tuckin (Mountain Form) base stats
A form changes the look and the element, never the numbers. Every form of Tuckin shares one stat line.
HP
106
Attack
80
Defense
83
Magic attack
80
Magic defense
110
Break
100
EP regen
71
The full Tuckin page has the rankings, skills, talents, catch rate and evolutions.