Noninvasive age estimation for wild Indo‐Pacific bottlenose dolphins (Tursiops aduncus) using speckle appearance based on quantification‐theory model I analysis

Abstract

AbstractAge is an important parameter for the study of ecology and population dynamics. Current methodologies for age estimation in cetaceans generally involve invasive or postmortem techniques. They are not suitable for wild marine mammals with small populations. Our previous study shows that in Indo‐Pacific bottlenose dolphins, both the number and size of body speckles increase with age. We observed speckles of 41 known‐age individuals (28 females and 13 males) between the ages of 7 and 25 years using underwater video data. The ages of individuals were obtained from a long‐term identification survey since 1994. Here, we created an age‐estimation model using quantification theory type I analysis. The model estimated the age accurately from speckle observation (R2 = 0.77, standard deviation of 2.58 years). We clarified the age of 89 individuals (64% of 139 unknown age individuals) near Mikura Island. This is the first study to use a noninvasive age estimation method to statistically verify its accuracy and revealed the age of the majority of the population.