Date of Award

2012

Document Type

Thesis

Degree Name

Master of Science

School

College of Arts and Sciences

Program

Biology MS

First Advisor

James L. Hayward

Second Advisor

Shandelle M. Henson

Third Advisor

Gordon J. Atkins

Abstract

Galápagos marine iguanas (Amblyrhynchus cristatus) briefly forage in marine habitats but spend their remaining time hauled out on land. A wide range of diurnal activities, from social and thermoregulatory behaviors to sleep and food processing, occurs during haulout. To understand the dynamics of haulout and foraging in relation to environmental factors, I fit compartmental models derived from ordinary differential equations to field data collected daily from 30 April to 16 May 2011 at two sites—one Sandy and one Rocky—at Cabo Douglas, Isla Fernandina. The best model for haulout at the Sandy site accounts for 77–80% of observed variability and includes the environmental variables solar elevation, heat index, tide height, and relative humidity. Using only the predictable variables of solar elevation and tide height, the model still accounts for 72% of system variability. The best model for haulout at the Rocky site includes solar elevation, THW index, tide height, and hour of day, and accounts for 57% of observed variability. Using only solar elevation, tide height, and hour of day, the model still accounts for 51% of the variability. Poisson regression supports these results with few inconsistencies and provides further insight into system dynamics. Although the environmental variables that predict haulout are different across sites, the methodology is powerful and could benefit conservation measures developed for this endemic species.

Subject Area

Marine iguana--Galapagos Islands--Research; Marine iguana--Galapagos Islands--Hauling-out; Fernandina Island (Galapagos Islands)

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