Publication Date

Spring 2013

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Lynne Trulio


human disturbance, pacific pond turtle, recreational disturbance, reptile recreational disturbance, western pond turtle, wildlife behavior

Subject Areas

Wildlife conservation; Conservation biology; Environmental studies


The western pond turtle (Emys marmorata) is the only native freshwater turtle in California, and it is listed as a California Species of Special Concern. One population near Moffett Naval Air Station in Northern California uses a highly altered water channel along a recently opened section of the Bay Trail, exposing western pond turtles (WPT) to high rates of human activity through recreational trail use. This research assessed whether human recreational trail use had a measurable effect on WPT basking behavior. WPTs were also trapped and marked to collect data on the structure and stability of the current population.

The lengths of basking periods of WPTs, when disturbed by human activity, were significantly shorter than background basking periods. Shorter basking periods can cause aquatic turtles to forfeit proper thermoregulation, leading to a decline in their ability to carry out necessary behaviors and physiological processes. The rate at which WPTs were disturbed by pedestrian recreational trail use was very low (<7% of pedestrian events led to disturbance), while motor vehicles caused a much higher rate of basking abandonment (45.5% of motor vehicle events led to disturbance).

Eleven WPTs were trapped in 2012, of which 61.5% were adults and 38.5% were juveniles. The sex ratio was 3:1 male to female. These findings are similar to data collected by another investigator in 2006 at this location.