Growth in pinnipeds

Area of Science:

• Marine Mammal Biology
• Quantitative Ecology
• Zoology

Background:

• Pinniped growth patterns are complex and vary significantly across species and populations.
• Understanding these patterns is crucial for conservation and ecological assessments.
• Existing growth models may not adequately capture the nuances of pinniped development.

Purpose of the Study:

• To fit generalized von Bertalanffy (vB) and Gompertz growth curves to pinniped body length data.
• To assess the reliability of available data and present growth curve parameters for numerous species.
• To enable statistical comparisons of growth rates, sizes, and individual variability among pinniped populations.

Main Methods:

• Fitting generalized von Bertalanffy (vB) growth curves (Lx = L∞(1 - e^(a(x-x0)))b) to body length data.
• Utilizing Gompertz equations for polygynous species' males to account for accelerated pubertal growth.
• Analyzing growth-curve residuals to quantify individual variability and compare populations statistically.

Main Results:

• No single monotonic growth equation adequately describes pinniped length from birth to adulthood; linear growth precedes vB suitability.
• Gompertz equations are generally adequate for adult males of polygynous species.
• Specific findings include variations in walrus size by region, no significant size difference between male and female Weddell seals, amplified variability in male southern elephant seals, and differences in ringed seal asymptotic sizes based on breeding habitat.

Conclusions:

• Pinniped growth requires species- and sex-specific modeling, often necessitating multiple equations to capture developmental stages.
• The fitted growth curves provide a robust framework for comparative analyses of pinniped populations.
• The study highlights unique growth characteristics in several species, contributing to a more refined understanding of pinniped life history.