Species

Gopher tortoise (Gopherus polyphemus)

Principal Biologist(s)

Magnus McCaffery

Project Location

Nonami, GA
Avalon, FL

Conservation Problem

The primary threats to gopher tortoises are habitat destruction, fragmentation, and degradation. Populations have also been severely depleted by human predation.

Conservation Status

• State listed as threatened in Georgia and Florida
• Candidate species for listing under the federal ESA
• In the western portion of its range in Florida, the species is listed as threatened under the ESA

Project Goals

Our overarching goal is to restore robust and viable gopher tortoise populations to suitable habitat at Avalon.

Objectives

We will restore two viable gopher tortoise populations to suitable habitat (100 ha minimum size) on the Avalon property (one population on the Avalon Annex and one population on Avalon Proper) to restore eastern indigo snake winter habitat, advance gopher tortoise recovery, and serve as a model for conservation on private lands. These restored populations will ideally exhibit densities of 1 to 2 tortoises/ha (minimum of 0.4 tortoises/ha), will have positive population growth rates, and comprise a minimum of 250 adults (> 235 mm MCL), variability in size and age structure, a male to female ratio of approximately 1:1, and evidence of juvenile recruitment.

Supporting Rationale for Objectives

The importance of restoring robust gopher tortoise populations to Avalon is supported by ecological and conservation considerations. For instance, the gopher tortoise is a keystone species in Sandhill, longleaf pine, and shrub ecosystems. Their excavation of deep burrows provides habitat for approximately 60 vertebrate and 300 invertebrate commensal species, many of which are legally protected. Therefore, increasing gopher tortoise densities is expected to enhance local biodiversity, and improve the recovery prospects for other imperiled species that rely on tortoise burrows to meet their ecological requirements. Furthermore, gopher tortoise is state listed as threatened in Florida and is a candidate species for listing under the ESA. We aim to contribute to producing a level of benefit to the species that could preclude or remove any need to list the gopher tortoise under the Endangered Species Act in Florida.

Project Background

The Avalon property (12,584 ha) located near Tallahassee, Florida is principally managed for northern bobwhite quail recreational hunting as well as for ecological conservation. The property comprises extensive areas of quality gopher tortoise habitat, characterized by large tracts of suitable soil types combined with a pine/grassland vegetation structure that is maintained by frequent prescribed burns and hardwood mid-story control. Despite habitat conditions conducive to occupancy by large gopher tortoise populations, the species is only patchily distributed on the property and at relatively low densities. It is likely that gopher tortoises were historically distributed far more widely and in greater densities on the property. Reductions in both tortoise range and numbers are most likely due to anthropogenic pressures such as direct consumption of tortoises as food, ‘gassing’ of burrows for rattlesnake control, and tortoise collection, as well as habitat loss through historical land management practices.

Prior to 2008, no formal gopher tortoise surveys, projects, or studies had been conducted on the Avalon property, although tortoises were known to occur on the Avalon Annex portion of the property. In 2008, gopher tortoise burrow surveys were conducted in suitable habitat types on the Avalon Annex. Approximately 578 ha were surveyed and 257 burrows (both active and inactive) were located during this initial survey.

Five years later, in 2013, we examined the suitability of Avalon Proper for gopher tortoises. Soil type is one of the most important factors that determines habitat suitability, with tortoises requiring xeric, well-drained, sandy soils that facilitate burrow construction. We used data from the Natural Resources Conservation Service Web Soil Survey to evaluate Avalon’s soils profile. We classified soil as being acceptable for gopher tortoise occupancy based on the following characteristics: (1) moderately well-drained to excessively well-drained and (2) depth to water table of 45 cm or greater.

In October 2013, we searched Avalon for both active and inactive gopher tortoise burrows, with the goal of identifying tortoise locations beyond the Annex. We found that burrows were predominantly concentrated on the Annex (81 active and 44 inactive), but also identified nine previously unknown active burrows and eight inactive burrows on Avalon Proper.

We continued mapping gopher tortoise burrows in 2014–revisiting known locations and finding previously unknown burrows–and evaluated their occupancy status using a burrow scope. The total number of active and inactive burrows located by our surveys on the Annex was 223 and 81 respectively, while we had found 11 active and three inactive burrows on Avalon Proper. An assessment of the occupancy status of these burrows indicated that a minimum of 136 gopher tortoises occupied the Annex and at least eight tortoises were present on Avalon Proper.

We began to bolster the extant gopher tortoise population on the Annex in 2014, and in the process, we assisted with humane relocation of gopher tortoises from incidental take permitted (ITP) sites across Florida where tortoises were at risk of being entombed through development of their habitat. We worked in collaboration with FWC to delineate a 505-acre Unprotected Recipient Site on the Annex (“Annex Tortoise Recipient Site (TRA)”). Avalon staff built two temporary soft-release pens (“North Pen” and “South Pen”) within the Annex TRA, and we worked with SFGT to translocate 107 ITP tortoises into these acclimation pens. FWC requires that relocated tortoises remain in these temporary pens for 6 – 12 months before pens are removed and the animals are released.

In 2015, we continued with ITP tortoise translocations to the Annex TRA. We installed a 52-acre acclimation pen (“2015 Pen”) at the Annex recipient site and translocated 139 ITP tortoises to the site. On June 15th, we removed the two original acclimation pens used for ITP translocations in 2014, and we began to planning work for developing a new ITP recipient site on Avalon Proper.

In 2016, we carried out intensive surveys across 800-acres of Avalon Proper to determine extant tortoise populations levels. During this fine-scale survey work, we found 23 abandoned burrows and 20 potentially occupied burrows. This survey included a detailed examination of the 50-acre Nursery site which, in consultation with Avalon management, was selected as Avalon Proper’s first ITP tortoise recipient site. During the Nursery survey, we mapped the extent of potentially occupied and abandoned tortoise burrows. We then worked with FWC to designate this 50-acre Nursery area as an Unprotected Recipient Site for the relocation of ITP tortoises. With the help of Avalon staff, we constructed three soft-release pens, and translocated 142 tortoises to this site from 2016 to 2018. The integrity of each temporary pen was maintained for a year after its last tortoise was added, then removed.

With successful restoration of gopher tortoises to the Nursery area, we have made encouraging progress towards restoring the species to 1,000 acres of Avalon Proper, and rebuilding Avalon’s capacity to support indigo snakes. There are over 2,500 acres of dry uplands on Avalon Proper which already meet FWC’s criteria for desirable gopher tortoise habitat. This is therefore an exceptional area for restoring Avalon’s tortoise population that would contribute to the security of the species in Florida.

Proposed Future Activities

Our next step will be to work with Avalon’s managers to identify additional areas of Avalon Proper to reach our goal of a 1,000-acre tortoise restoration area on this part of the property. During planning work for expanding Avalon Proper’s gopher tortoises beyond the Nursery, we reviewed the various recipient site options. Our previous success with translocating ITP tortoises to the Annex and Nursery, and the ethical considerations of aiding in the rescue and relocation of these doomed ITP tortoises, mean that this strategy should play a role in expanding Avalon’s tortoise population. However, we suggest diversifying our approach to restore tortoises across 1,000 acres at a quicker pace. This could be achieved by supplementing the Unprotected Recipient Site/ITP model with the Long-Term Protected (LTP) Site approach, which has the capacity to translocate relatively more tortoises on an annual basis, thereby facilitating a more rapid restoration of indigo snake habitat. Our goal involves restoring tortoises to at least 1,000 acres of Avalon Proper, and we recommend implementing a combined ITP: LTP approach at a ratio of 1:4, in which 200 acres of Avalon Proper is designated as an ITP recipient site, and 800 acres as an LTP site. It is important to note that these ITP and LTP recipient sites need not be contiguous, and there is a great deal of flexibility in their placement within Avalon Proper’s 2,500 acres of potential tortoise habitat. Similarly, the arrangement of temporary soft-release pens used within these recipient sites to hold relocated tortoises for a 6-month period may be large or small, and would be positioned in consultation with Avalon managers to reduce interference with quail management operations.