Sexual Dimorphism and Foraging Trips of the Laysan Albatross (Phoebastria immutabilis) on Guadalupe Island.

Julio César Hernández Montoya,Alfonso Aguirre-Muñoz,Gustavo Arnaud,Evaristo Rojas-Mayoral,Eduardo Íñigo-Elias,Alfredo Ortega-Rubio,Maricela Juárez-Rodríguez,Patricia Galina-Tessaro,Federico Méndez-Sánchez

doi:10.3390/ani9060364

Abstract

Simple SummaryWe evaluated the existence of sexual dimorphism in Laysan albatross from Guadalupe Island. Males were larger than females across all the morphological variables analyzed. We created a sex predictor model for Laysan albatross individuals that requires a minimum number of input variables and will considerably reduce the handling times and field costs of future studies. Laysan albatross foraging trips were recorded during their breeding season over multiple years and no significant differences were found between the distances travelled by males versus females.Sexual dimorphism in the Laysan albatross (Phoebastria immutabilis) on Guadalupe Island was evaluated during the breeding seasons of 2015–2018 by measuring and comparing 10 morphological attributes: cranial length, bill length, nostril length, cranial width, bill height, bill width, tarsus length, closed wing length, opened wing length, and wingspan length in reproductive adults (n = 135). Males were larger than females across all traits (Student’s t-test, p < 0.05, p < 0.05). We created a logistic model using stepwise regression to predict sex based on morphological variables. This model indicated four significant morphological predictor variables (z < 0.05) and was able to successfully predict the sex of P. immutabilis individuals in more than 90% of the cases. Based on these predictor variables, a web app was developed to determine the sex of the Laysan albatross in the field, providing a non-invasive method for rapid data collection that reduces costs and handling times while improving conservation efforts. We tracked Laysan albatross (n = 36) during breeding seasons and found no significant differences between females and males for either trip length (GLMM, F = 0.017, DF = 1, 1, p = 0.917 > 0.05) or maximum trip distance (GLMM, F = 0.374, DF = 1, 1, p = 0.651 > 0.05). Our results suggest that both sexes show a strong preference to travel to highly productive coastal waters northeast of the breeding colony that are influenced by the California Current. The present research will serve to establish a baseline to protect this species on Guadalupe Island and highlights the importance of understanding sexual dimorphism in at-risk seabird species.

Highlights

Sexual dimorphism in vertebrates is a condition in which the sexes of the same species exhibit differences in size, color, markings, characteristics, or even behavior [1,2,3,4].These differences may be subtle or extreme and are subject to sexual selection
The existence of sexual dimorphism may appear less evident in monogamous species such as the Laysan albatross (Phoebastria immutabilis) [17,18], a species that is difficult to sex from field observations and exhibits bi-parental care, which likely contributes to the lack of sexual dimorphism observed [19]
Laysan albatross reproductive males on Guadalupe Island were significantly larger than reproductive females

Summary

Introduction

Sexual dimorphism in vertebrates is a condition in which the sexes (male and female) of the same species exhibit differences in size, color, markings, characteristics, or even behavior [1,2,3,4].These differences may be subtle or extreme and are subject to sexual selection. The Laysan albatross mostly in the Central Pacific (Northwestern Hawaiian Islands), this species colonized new sites in the eastern Pacific in 1983, Guadalupe Island, Alijos Island, and the Revillagigedo Archipelago (the islands of Roca Partida, San Benedicto, and Clarión) [20,21]. This expansion of the Laysan albatross breeding range resulted in high oceanic spatial segregation, reflected in differences between the two populations based on foraging habitat, behavior, and reproductive success [22]. Laysan albatross from the Hawaiian colonies forage in cold, subarctic waters and in the North Pacific Transition Zone [23], while albatross from the Eastern

Objectives

Methods

Results

Discussion

Conclusion