Mateo suddenly stops transforming, and starts transforming into a wolf- much smaller, though still larger than a natural wolf- and faster. He leaps forward as he changes, hoping that the movement and decreased size causes the slippery pondweed to loose its grip. The sudden change has caused Mateo slight disorientation, especially as the change into bear wasn't complete. Therefore, his pounce might be off-target, but he's hoping to bound into the siren and clamp his lupine/ursine jaws around her throat and bite until he feels her spine crack.