This learning resource explores how biologists at Yellowstone National Park utilize mathematical concepts to monitor and manage bison populations. It starts by introducing vocabulary related to subtraction, such as 'difference', 'regroup', and 'standard algorithm', essential for understanding the mathematical operations involved. The resource presents a scenario where students are to determine how many more bison are in Yellowstone compared to a neighboring group, providing a practical context for the mathematics. Through a detailed step-by-step guide, students learn the process of regrouping when subtracting larger numbers and the importance of verifying their answers through addition. The resource includes guided practice problems and prompts for class discussion to solidify understanding, emphasizing the critical thinking needed in math and wildlife management.