National Park Service

Gulf Coast Network (GULN)

Texas Tortoise Monitoring

Volunteer measuring a tortoise at Palo Alto Battlefield NHP Volunteer, Yadi Pink, processing a tortoise at Palo Alto Battlefield NHP

GULN Amphibian & Reptile Inventory Reports

There are currently no other documents or reports concerning this topic.

Importance

The Texas Tortoise, Gopherus berlandieri, is a key larger vertebrate species on PAAL and gains specific legal protection due to its listing as an endangered species by Texas, making this species a focal natural resource of specific interest to park management. The close association of tortoises with specific vegetation types and habitats is a key factor in the park’s development of comprehensive long-term vegetation and resource management plans. G. berlandieri distribution in the United States is limited to the lower Texas Plain extending south and east from below the Edwards Plateau. Historically noted as being substantially abundant and widespread within this area, this species is now considered to be in significant decline over much of its historic range due to habitat fragmentation and loss. PAAL provides a protected island of potential good habitat for this species within a region noted for increasing land-conversion and loss of habitat for many native species, and many casual staff and visitor observations and initial data collected by GULN between 2008 and 2011 strongly suggest that PAAL may support a sizable tortoise population and that this population may be viable and sustainable given the size and apparent quality of natural resources and habitat afforded permanent protection on the park.


Parks to be Monitored

  • Palo Alto Battlefield National Historical Park (PAAL)

Monitoring Objectives

  • Provide the park with a detailed annualized description of the adult tortoise population in terms of age-structure, sex-ratio, and size and weight distributions.
  • Provide annual estimates of adult tortoise population size and density within better-quality habitat on the park.
  • Provide estimation of tortoise home-ranges and movement on the park.
  • Develop long-term assessment of tortoise population changes and trends over time to better enable the park to effectively manage this key faunal resource.
  • Develop and verify a habitat model for Texas Tortoise based on PAAL vegetation types and their distribution.

Basic Approach

Texas Tortoise monitoring on PAAL is based upon intense visual-ground-search surveys performed in spring and fall of each year by experienced field teams in specified sampling areas to collect, assess and mark individuals in the context of a spatially-defined repeat-sampling based program. Sampling targets tortoises in their native habitats and normal activity, and does not rely on tortoises being mobile or otherwise active in any specific manner. Emphasis is placed on careful performance of detailed handling techniques coupled with specific prophylactic measures to support consistent collection of high quality data while ensuring both tortoise and personnel safety and well-being.


Key Standardized Sampling Methods

Tortoises are collected using a time-and-space-defined visual ground search survey.

Teams of 3-6 people visually search each assigned permanently-mapped sampling plot for designated time-periods of 1-2.5 hours duration.

Searchers encounter and collect tortoises. Each tortoise is immediately processed when and where collected. Tortoises are photographed, weighed, sexed, aged, measured for body size. Site photographs and GPS coordinates are taken at the time of collection. Each tortoise is immediately released back to its capture location following completion of processing and data-recording.

Each tortoise is assigned a unique ID number at time of first encounter. This number is permanently marked with a drilled code using marginal scute positions. This ID number facilitates repeated recapture ID for long-term movement monitoring.

Each tortoise encounter yields a time, date, and location record with logged GPS coordinates, and an observation record of tortoise ID, sex, weight, estimated age (scute annuli counts), body length, width and height, and observations on tortoise carapace and plastron condition. Photographs record the capture location, dorsal, ventral, anterior, posterior, and lateral L and R aspects of the individual, visible injuries and ID markings.

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Last Updated: May 17, 2017 Contact Webmaster