Pacific walruses examined for body mass measurements with drone imagery

Walruses identified as being in an appropriate position for measurement from an image collected by a USGS survey drone on September 6, 2018, at a haulout near Point Lay, Alaska.  These images were used in a USGS study in collaboration with zoos and aquaria in the United States and western Europe for validating aerial imagery as a method for monitoring the body condition of reproductive females and their calves in the wild. The red dots (1) indicate single, non-calf walruses. Yellow dots (2) indicate females with calves.  White dots (3) indicate first year calves, and blue dots (4) indicate calves greater than 1 year old.