Kruuk et. al. (1989) used a stratified sample to estimate the number of otter dens along the 1400-km coastline of Shetland, UK. The coastline was divided into 242 5-km sections, and each section was assigned to the stratum whose terrain type predominated. Then sections were chosen randomly from the sections of each stratum. In each section chosen, the investigators counted the total number of dens in 110-m wide strip along the coast. The population sizes of strata are as follows.

Stratum 1: Cliffs over 10m 2: Agriculture 3: Not 1 or 2, peat 4: Not 1 or 2, non-peat Total Sections Sections counted 89 19 61 20 40 22 47 21