Research Plan for Gopherus polyphemus Study in the Christopher B. Smith Preserve 2012

Dated May 4, 2012

 

Project Title: Assessment of a Gopher Tortoise Aggregation in an Urbanized Area of Naples, Florida. Phase II: Resampling After Road Construction and Exotic Vegetation Removal. Principle Investigators: Jeffrey R. Schmid and Ian A. Bartoszek, Conservancy of Southwest Florida, 1450 Merrihue Dr., Naples, FL 34102 Need: The gopher tortoise (Gopherus polyphemus) was uplisted as “threatened” throughout its range in Florida. Urban and agricultural development of the upland areas used by the gopher tortoise has resulted in fragmented habitat and drastically reduced populations. Southwest Florida has experienced rapid population growth and subsequent development over the past 50 years, resulting in “islands” of gopher tortoises and their habitat in the urbanized landscape. The Conservancy purchased a 7 acre parcel adjacent to its facilities in Naples and efforts are underway to manage the property as a gopher tortoise preserve. Prior surveys of the parcel indicate there are approximately 100 active or inactive gopher tortoise burrows, and estimates of population size have ranged from 40-60 individuals based on burrow counts. Recent mark-recapture efforts resulted in the collection of 73 individuals from the property (Florida Fish and Wildlife Conservation Commission for Scientific Collecting Permit No. WV08253). Construction of an access road was completed and exotic vegetation was removed after these capture efforts. Continued surveys are needed to monitor the demographics, functionality, and viability of this tortoise aggregation in order to adequately manage the property as a gopher tortoise preserve. Objectives: The purpose of the proposed project is to provide detailed scientific information on gopher tortoises inhabiting a privately owned land parcel to aid the long-term management of the aggregation and habitat restoration efforts on this property. The objectives of this study are: (1) to determine the distribution of tortoises and the status of their burrows on the property, (2) to determine the population size, demographics (size classes and sex ratio for adults), feeding ecology, and health of the aggregation from field collections, (3) to identify the physical and biological factors influencing their distribution, and (4) to restore habitat characteristics on the parcel with regards to the needs of gopher tortoises. Expected Benefits: The proposed study will aid in the management of this threatened species by determining the distribution, population size, and demographics of gopher tortoises in an isolated parcel within an urbanized landscape, describing the habitats and forage essential to the viability of this aggregation, and identifying factors that may assist in improved conservation of the species and restoration of its habitat in urbanized areas. It is hoped that these efforts will be expanded to include other areas in Naples and Collier County to ensure the viability this and other fragmented tortoise aggregations. Study Area: The study area includes 7.54 acres of land in Naples, Collier County, Florida that is bounded by roadways (Goodlette-Frank Road and 14th Avenue N), a stormwater ditch, and residential and institutional development (including the Conservancy’s facilities). Historically, the land had been cleared and converted to a citrus grove in the 1950s and a small pond was excavated presumably for irrigation. This agricultural practice was abandoned by the 1980s and the natural vegetation reverted to scrubby flatwoods and scrub communities. Exotic vegetation also became established including dense stands of Brazilian pepper (Schinus terebinthifolius) in the former grove and Melaleuca trees (Melaleuca quinquenervia) in the artificial pond. The Conservancy purchased 6.56 acres of the study area in 2005 to construct an access road and prevent further development on the property. An additional 0.98 acre heavily wooded tract along 14th Ave. N was purchased in 2009. These contiguous properties were subsequently designated as a preserve area. Construction of the access road began in 2009, which included a wooden bridge to allow connectivity, as did removal of exotic vegetation and partial clearing of the heavily wooded area (Fig. 1). A tortoise barrier fence was installed on the west, south, and east boundaries of the property and the northern edge is bounded by a seasonally-flooded stormwater ditch. The artificial pond was converted to a depressional wetland/filter marsh. Any impacts to gopher tortoises during construction were covered under a FFWCC special relocation permit (GTRS-2009-4386 and subsequent amendment). Methodology: The entire parcel will be systematically surveyed for gopher tortoise burrows. Each burrow will be flagged and numbered. The width of each burrow will be measured with forester's caliper and the location recorded with a Global Positioning System (GPS). The status of each burrow will be determined as active (tracks or scrape-marks indicating recent tortoise activity), inactive (no observable activity), or abandoned (overgrown or damaged). Activity will also be determined by placing small sticks in the ground at the entrance to the burrow. A telescopic video camera may also be used to check burrow occupancy and the presence of burrow commensals. The distribution of burrows will be mapped and analyzed using geographic information system (GIS) software. Tortoises will be captured by hand and using bucket traps. Bucket traps will consist of 5 gal. buckets with drainage holes in the bottom and will be buried at the entrance of active burrows. Efforts will be made to limit disturbance to nests beneath the burrow apron and traps will not be used if a nest is detected. Buckets will be checked twice daily when trapping tortoises. Additionally, Sherman traps and screen funnel traps will be set near the entrances of burrows to document the presence of commensals. Trapping/collecting will be conducted intensively during the initial phase of the proposed study in order to capture all tortoises inhabiting the parcel, and then for one week each month thereafter when tortoises are active. Mr. Bartoszek has experience in collecting gopher tortoises, surveying gopher tortoise burrows, using fiber-optic scopes to verify burrow activity, and excavating tortoises for relocation into a tortoise preserve. Dr. Schmid has 26 years experience with collecting listed species of marine turtles and a similar meticulous protocol will be employed in the present study. Each tortoise will be measured (carapace length and width, plastron length, and gular projection length), weighed, sexed, and given an individual identification code by notching or drilling holes in the marginal scutes. Additionally, a temporary identification number will be painted on the carapace to aid the visual detection of individuals. Age will be estimated by counting plastral annuli and ventral and dorsal digital photographs will be taken of each animal. Food items will be identified by observation of tortoise feeding and the collection of fecal samples. Tortoises will be held 24-48 hours in shaded plastic bins at the Conservancy’s facilities for fecal sample collection. Standard protocols will be used to collect blood samples from a subsample of tortoises to test for Upper Respiratory Tract Disease. The Conservancy conducts wildlife rehabilitation, including gopher tortoises, and has a veterinarian available on site. After data collection, tortoises will be released at the site of capture. Capture and diet data will be analyzed with respect to body size, age, and sex classes. Data from recaptured tortoises will be used to calculate growth rates and to construct von Bertalanffy growth models. Growth models may be useful for aging older turtles where the method of counting annuli becomes less reliable. Mark-recapture efforts resulted in the collection of 73 individuals from the property.   This research was repeated again in 2018. Between 45 and 55 tortoises were estimated to be in the preserve. Although the same general method was used, the hunt for tortoises was not as aggressively performed as was done in the earlier year of the study.

© Photographs by Volunteer Susan Snyder in 2018; text by the Science Division of the Conservancy of Southwest Florida.

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