Mont. Code Ann. § 27-17-403

In case such property, while in the possession of the party against whom such judgment shall be rendered or while unlawfully detained from the party entitled to the possession thereof, be materially injured or lessened in value by use or otherwise, then a return or offer to return shall not be deemed a compliance with the undertaking given for its return but an action may be maintained for the value thereof, as assessed by the jury or court, and damages for its detention.