DOI: 10.5061/dryad.7d7wm388m
title: Sexual dimorphism of head, teeth, flipper, and body size in northern elephant seals (<em>Mirounga angustirostris</em>) throughout ontogeny

description: Sexual dimorphism, the difference in appearance between males and females
 of the same species, can shape physiology, behavior, and fitness. Yet, few
 species have age-and sex-specific data to characterize its development.
 Northern elephant seals (Mirounga angustirostris) are an extremely
 sexually dimorphic marine vertebrate for which detailed measurements are
 measured throughout life. To investigate the ontogeny of sexual dimorphism
 in juvenile elephant seals, we assessed differences in body size, tooth
 size, craniofacial and flipper morphology directly and photogrammetrically
 from 60 male and female seals ≤4 years old. Males and females maintained
 similar age-specific masses, but males grew in length more rapidly than
 females, with males growing 5.31 cm more than females each year based on
 model predictions. We found evidence of early onset sexual dimorphism in
 the snouts and flippers of juvenile seals, with males growing larger more
 quickly than females. Overall, we found that sexual dimorphism developed
 even earlier than sexual maturity in northern elephant seals. These
 results help explain differences in behavior and fitness between male and
 female juvenile elephant seals early in life, and highlight the importance
 of understanding the ontogeny of sexual dimorphism in large marine
 vertebrates.
description: # Sexual dimorphism of head, teeth, flipper, and body size in northern
 elephant seals (*Mirounga angustirostris*) throughout ontogeny Dataset
 DOI: [10.5061/dryad.7d7wm388m](https://doi.org/10.5061/dryad.7d7wm388m) ##
 Description of the data and file structure Sexual dimorphism is a
 highly-studied topic in marine mammals, especially in northern elephant
 seals. Described below are the data files used for analyses and figure
 generation for the associated manuscript. ### Files and variables ####
 File: Animal_Measurement_Data.csv **Description:**  .CSV file with animal
 and measurement data for 60 seals. ##### Variables * UniqueID: unique
 alpha-numeric identifier for each seal (character) * Year: year that
 morphometric measurements were obtained * Decimal_Age: Decimal age of
 seals assuming a population birth day of January 17. * Sex: seal sex (M)
 or (F) * StraightLength: straight length from tip of the noise to tip of
 the tail in centimeters * Mass: mass at time of handling (kg) *
 DorsalSnoutWidth: measured dorsal snout width using ImageJ photogrammetry
 (cm) * DorsalSnoutLength: measured dorsal snout length using ImageJ
 photogrammetry (cm) * DorsalFaceWidth: measured dorsal face width using
 ImageJ photogrammetry (cm) * LatSnoutLength: measured lateral snout length
 using ImageJ photogrammetry (cm) * LatSnoutHeight: measured lateral snout
 height using ImageJ photogrammetry (cm) * LatCranialHeight: measured
 lateral cranial height using ImageJ photogrammetry (cm) * LUCanine:
 measured left upper canine length using ImageJ photogrammetry (cm) *
 RUCanine: measured right upper canine length using ImageJ photogrammetry
 (cm) * LLCanine: measured left lower canine length using ImageJ
 photogrammetry (cm) * RLCanine: measured right lower canine length using
 ImageJ photogrammetry (cm) * FFLength: measured front flipper length using
 ImageJ photogrammetry (cm) * FFWidth: measured front flipper width using
 ImageJ photogrammetry (cm) * RFWidth: measured rear flipper width using
 ImageJ photogrammetry (cm) * RFLength: measured rear flipper width using
 ImageJ photogrammetry (cm) * Procedure: chemical immobilizations
 procedures to retrieve (Recovery) or deploy (Deployment) biologging tags
 #### File: Figures_Dryad.R **Description:** Code for creating final
 figures #### File: GLM_Dryad.R **Description:** Code for running main
 analyses ## Code/software All analyses were run using RStudio (RStudio
 Version 4.4.3) ## Access information Other publicly accessible locations
 of the data: * None Data was derived from the following sources: * None