Knowing ‘how many’ of any species is a challenge for researchers. In recent years satellites have been used, but there are so many pictures, we are asking classrooms to help. In this activity, students use satellite images taken over time, to see changes in the population of seals within and between seasons. There is background information on Weddell seals, a tutorial on how to count and a file of the images. New images posted every year provide a long-term data set on the Weddell Seal population in McMurdo Sound, Antarctica. Go here for the activity http://z.umn.edu/seals. When you class has finished send us your data.