Bush....that deer is at least 2.5 because the third cheek tooth (starting from the front) only has 2 cusps. A 1.5 yr old would have 3 cusps on the third cheek tooth. To determine if he is 3.5 you need to go to the 3rd cusp of the last cheek tooth. IF the back cusp is not flat then the deer is 2.5. If the last cusp is flat and shows any dentine (brown color) then he's at least 3.5.