Publications

Abstract

To study patterns in behavior, fitness, and population dynamics, estimating the age of the individuals is often a necessity. Specifically, age estimation of young animals is very important for animal rehabilitation centers because it may determine if the animal should be taken in and, if so, what care is optimal for its rehabilitation. Accurate age estimation is also important to determine the growth pattern of an individual, and it is needed to correctly interpret the influence of early body condition on its growth trajectories. The purpose of our study was to find body measurements that function as good age estimators in young (up to 3 months old) harbor seals (Phoca vitulina vitulina), placing emphasis on noninvasive techniques that can be used in the field. To meet this goal, body mass (BM), dorsal standard length (DSL), upper canine length (CL), body condition (BC), and sex were determined from 45 Harbor Seal pups of known age. Generalized additive mixed models were fitted to find how well these morphometric measures predicted age, and the results from the selected model were used to compute growth curves and to create a practical table to determine the age of young animals in the field. We found that both DSL and CL—and to some extent sex—were useful predictors for estimating age in young harbor seals and that the growth rate of pups raised in captivity is significantly lower than for those raised in the wild. In addition, we found no evidence for compensatory growth, given that animals that arrived at the center with a poor BM or BC continued to show lower BM or BC throughout almost the entire rehabilitation period.

Abstract

Rhythmic patterns in interactive contexts characterize human behaviours such as conversational turn-taking. These timed patterns are also present in other animals, and often described as rhythm. Understanding fine-grained temporal adjustments in interaction requires complementary quantitative methodologies. Here, we showcase how vocal interactive rhythmicity in a non-human animal can be quantified using a multi-method approach. We record vocal interactions in harbour seal pups (Phoca vitulina) under controlled conditions. We analyse these data by combining analytical approaches, namely categorical rhythm analysis, circular statistics and time series analyses. We test whether pups' vocal rhythmicity varies across behavioural contexts depending on the absence or presence of a calling partner. Four research questions illustrate which analytical approaches are complementary versus orthogonal. For our data, circular statistics and categorical rhythms suggest that a calling partner affects a pup's call timing. Granger causality suggests that pups predictively adjust their call timing when interacting with a real partner. Lastly, the ADaptation and Anticipation Model estimates statistical parameters for a potential mechanism of temporal adaptation and anticipation. Our analytical complementary approach constitutes a proof of concept; it shows feasibility in applying typically unrelated techniques to seals to quantify vocal rhythmic interactivity across behavioural contexts.