What are the difficulties in counting pinnipeds?
Because pinnipeds are usually counted on land, one difficulty with these counts is that large colonies have animals constantly coming and going. It becomes very difficult to account for all animals. One way that scientists address this problem is by tagging a small number of individuals and determining the fraction of time they spend ashore. Researchers estimate the total population from a count of animals on the shore (referred to as “hauled out”), and then correct the estimation for animals that are missed during the count because they were in the water. Often, pups are counted as an index of size of the colony, since when pups are small, they do not move in and out of the colony as the other animals do. What are the advantages in counting pinnipeds? Pinnipeds are usually easy to find because many breed repeatedly in the same locations; these are known as rookeries. Pinnipeds are counted on land because it is much easier and less expensive than trying to count animals in the water. W
