Model is changed by animator without animation clips

When I hit play, the model goes from this (in scene)
to this (in game)


and I haven't added in animation clips or anything to make it move. I'm new to animating, so I don't know if this is just automatic and I have to add in an animation clip to get the model to the position I want it to be in at the start, or if something's wrong with the bones or... what.
Any help is appreciated, thanks!