Demographic Survey of Gopherus polyphemus (Gopher Tortoise) at the Abacoa Greenway by Tokio Sano A Thesis Submitted to the Faculty of The Wilkes Honors College in Partial Fulfillment of the Requirements for the Degree of Bachelor of Arts in Liberal Arts and Sciences with a Concentration in Biology Wilkes Honors College of Florida Atlantic University Jupiter, Florida May 2014
Demographic Survey of Gopherus polyphemus (Gopher Tortoise) at the Abacoa Greenway by Tokio Sano This thesis was prepared under the direction of the candidate s thesis advisor, Dr. Jon A. Moore, and has been approved by the members of her/his supervisory committee. It was submitted to the faculty of The Honors College and was accepted in partial fulfillment of the requirements for the degree of Bachelor of Arts in Liberal Arts and Sciences. SUPERVISORY COMMITTEE: Dr. Jon A. Moore Dr. James K. Wetterer Dean Jeffrey Buller, Wilkes Honors College Date ii
ABSTRACT Author: Tokio Sano Title: Institution: Demographic Survey of Gopherus polyphemus (Gopher Tortoise) at the Abacoa Greenway Wilkes Honors College of Florida Atlantic University Thesis Advisor: Dr. Jon A. Moore Degree: Bachelor of Arts in Liberal Arts and Sciences Concentration: Biology Year: 2014 The Abacoa Greenway reserve is a 105 ha preserve in Jupiter, Florida. We investigated the demographics of the gopher tortoise population and their burrow distributions in a 9 ha portion of the greenway (Range VIa) used for the relocation of gopher tortoises. Range VIa currently houses at least 90 tortoises. According to state guidelines this reserve is considered to be a support population with 250 individuals living in an area 100 ha. We found that the tortoises in the reserve are showing signs of maturity at a younger age (7-10 years) and a larger size (25-35 cm carapace length) compared to more northern populations. We hypothesize that this is due to the latitudinal climate effects and warm winters allowing year-round foraging. For the gopher tortoise burrow distribution, we found that many tortoises are creating new burrows on the periphery due to the overgrowth of the vegetation in the interior of the reserve and a reduction mowing is needed. iii
To Dr. Jon Moore and the gopher tortoises. To my family and friends for their support in all my endeavors. iv
Table of Contents Introduction... 1 Methods... 3 Study Sites... 3 Data Collection... 4 Data Analysis... 6 Results... 7 Discussion... 8 Literature Cited... 18 v
List of Illustrations Figure 1... 13 Figure 2... 14 Figure 3... 14 Figure 4... 15 Figure 5... 15 Figure 6... 16 Figure 7... 16 Figure 8... 17 Figure 9... 17 vi
Introduction Gopher tortoises, Gopherus polyphemus, are vital members of their ecosystem and provide benefits for other organisms. Gopher tortoises are ecosystem engineers (Kinlaw and Grasmueck 2012) because their burrows provide shelter for many species of organisms (Jackson and Milstrey 1989), including threatened species such as Eastern Indigo snake, Drymarchon corais couperi, Florida mouse, Podomys floridanus, and the Florida gopher frog, Rana capito aesopus (Kent and Snell 1994). Providing such a diverse array of animals with shelter makes the tortoises a keystone species (Eisenberg 1983). Keystone species are organisms that cater to many members of the ecosystem and the absence of the organism results in the destabilization of the ecosystem. Gopher tortoises are endemic to South-eastern United States and listed as federally threatened in Louisiana, western Alabama, and Mississippi (USFWS 1987). In Florida, eastern Alabama, Georgia and South Carolina, gopher tortoises are currently a candidate species for federal protection (USFWS 2011). In Florida this species is also listed as threatened by the state since 2007 (FWC 2014). The narrow range of habitation makes the tortoises more vulnerable to habitat loss and changes. Tortoises are in danger from human activity, juvenile predations by animals such as raccoons, and disease such as upper respiratory tract disease. They are mainly threatened by urban development and poaching (Diemer 1986). The development encroaches into the natural Floridian habitats such as scrub, xeric pine flatwoods, and pine flatwoods. Therefore, many populations in Florida are having difficulties even with the help of land set aside for relocation and protection (McCoy et al. 2006). The relocation efforts have provided the tortoises with alternative habitat sites (Burke 1989, Tuberville et al. 2008); however the sites of relocation are 1
sometimes far from optimal. As more data is collected for the conservation of the tortoises, better habitats can be found or sub-optimal land can be managed to provide more suitable ecosystems. Recent state guidelines for the minimum viable population for tortoises are 250 tortoises in an area of at least 100 hectares (GTC 2013). Another category, called support populations, calls for parameters of 50 to 250 individuals in an area less than 100 hectares (GTC 2013). With these parameters, researchers are able to correctly manage the gopher tortoise population. However, populations existing in these broad categories can show a significant amount of variation and sometimes support populations can exhibit signs of improved quality when compared to minimum viable populations. The types of natural habitats typically used by tortoises in our region of South Florida are pine flatwoods or scrub. These habitats are naturally maintained by frequent ground fires, renewing the low vegetation and allowing fire-dependent flora to once again prosper with a burn cycle of about 1-8 years for mesic flatwoods or scrubby/xeric flatwoods (Breininger et al. 2002) and 5-20 years for oak scrub or 15-100 years for rosemary scrub (Menges 1999). Contrary to the need for the continuation of the natural burn cycle, many new housing developments are very close to fire dependent ecosystems and this has incredibly decreased the amount of prescribed fires used to maintain the flatwoods and scrub habitats (Marti et al. 2005, Del Signore 2007). The lack of fire to renew the flora for the habitat has allowed for overgrowth of plant species such as the saw palmettos, Serenoa repens, and the gallberry trees, Ilex glabra. The overgrowth of the vegetation has decreased the open space available in the habitat, decreased low herbaceous plants and grasses as food for tortoises, and caused increased levels of litter 2
on the ground, which lowers the number of active burrows (McCoy and Mushinsky 1995). Del Signore (2007) found the litter and saw palmettos forced the majority of new tortoise burrows to be made on paths on the periphery of reserves. The litter also creates a fire hazard because they are fuel for natural occurring fires from sources such as lightning; however litter is not naturally depleted with the suppression of fires. Vincent Del Signore, was able to show and propose a method of maintaining the xeric pine flatwoods by reduction mowing the experiment site (Del Signore 2007). The reduction mowing showed positive effects on the tortoise population and the tortoises began making burrows in the interior of the reserve (Del Signore 2007). For this thesis, I conducted a demographic survey of the gopher tortoise population in range VIa of Abacoa in Jupiter, Florida. From August 2013 to April 2014. With the data gathered from the population I was able to investigate the status of the population and whether or not another reduction mowing was needed. Methods Study Sites The site used for this investigation is located in the Abacoa Greenway in Jupiter, Florida on Central Boulevard and Fredrick Small Road. Starting in 1998, the Abacoa Greenway was constructed as 150 hectares of pine flatwood habitat within the housing development for many purposes. The Greenway was incorporated into the town plans and provided a passageway for water to prevent flooding of the surrounding development, as well as land for the relocation of tortoises and a preserve for several other animals and plants. However, the greenway is highly fragmented by roads crossing the development. 3
The Study site range VIa, consists of 9.16 hectares of upland flatwoods and is surrounded by a trail for recreational use. Remnants of an old cattle range fence line create an eastwest path inside the reserve. Another path extends from southeast to northwest and intersects the cattle fence line. There is also a dry detention basin south of the upland area of the reserve (see Fig. 1 in Wetterer and Moore 2005). The elevated edges of the basin provide sloped areas that the tortoises used to avoid flooding conditions in the basin following heavy rains. The habitat is mostly xeric pine flatwoods with small areas of more mesic flatwood and oak habitats (Wetterer and Moore 2005). The reserve is mainly composed of an open canopy of slash pines (Pinus elliottii var. densa), a low to mid story of saw palmettos and gallberry, and an understory of wire grass (Aristida beyrichiana), gopher apples (Licania michauxii), and many other small herbaceous plants. Within the reserve, there are at least 90 individual gopher tortoises and many burrows densely populated on the periphery of the reserve along the paths and fence lines. The burrows in the interior of the reserve are located in close proximity to open areas used for foraging. Data Collection The gopher tortoises were surveyed by re-visiting the burrows and finding any tortoises either just inside the entrance or already outside of their burrow. The burrow locations were obtained from marked burrows and maps from previous experiments in the reserve. When a new burrow was encountered, GPS coordinates were taken and the burrow was given a unique number, marked with a pin flag, and recorded onto a printed map. The tortoises were captured by hand and were lured to the entrance of the burrow if they were initially found inside the burrow. 4
Once captured, the tortoise was checked with a chip reader for a subdermal RFID microchip (AVID Friendships with one-time use injectors). If the tortoise did not already have an ID chip and was more than 3 years old, a chip was inserted after measurements were taken. The tortoises were weighed using a hanging scale and plastic bags. The plastic bags were each only used once in order to prevent the spread of upper respiratory tract disease. Age of the tortoise was possible to determine from growth rings on the scutes, particularly the large scutes on the plastron (Aresco and Guyer 1998). Previous work on this site has determined that these growth rings are almost always annual rings (except in special cases where an individual was severely sick during the main growth season from March-December and resulted in two rings that year). Growth rings are only visible on tortoises that were typically less than 20 years old, after which time the plastron is generally worn smooth by abrasion. The dimensions of the tortoises shells were measured using a large tree caliper. The carapace, the upper shell, length was measured from the nuchal, the most anterior part of the carapace, to the most posterior part of the carapace. The plastron, the under shell, length was measured as the longest distance from the gular, the most anterior part of the plastron, to the tip of anal scute. The carapace width was measured across the plastron at the suture line between the pectoral and the abdominal scutes on the plastron. The shell height was measured using the same suture line to the top of the shell above the suture line. Then the tortoise was re-marked with a unique number over each leg, either with a yellow acrylic paint pen for subadults to adults or with a black permanent marker for juveniles in order to decrease conspicuousness of the juveniles. The tortoise was checked for signs of upper respiratory tract disease and any signs of damage or parasites. 5
After the measurements and re-markings the tortoise was released and followed, in order to find any new burrows. Data Analysis The measurements taken from each gopher tortoise were logged in the records and used to examine the size distributions of the gopher tortoise population in range VIa. The carapace length, weight, and ages were heavily focused on because these are the measures used by most other researchers. Juveniles were categorized as having a carapace length less than 13 cm, sub-adults had a carapace length from 13-22 cm, and adults had a carapace length above 22 cm (Landers et al 1982; Diemer 1992). Using this data, frequency distributions of carapace length, carapace length with respect to sex, weight, and weight with respect to sex were created. Carapace length versus age was also graphed to provide an age vs. growth curve. The gopher tortoise burrows were recorded on a map. The burrows were noted as active, inactive, or abandoned based on observations of the burrow apron, the sandy part of the entrance before the hole. Active burrows showed signs of tortoise footprints or plastron scuff marks on the apron or tunnel entrance. The presence of spiders in the entrance, lack of footprints on the apron, signs of a partial cave-in, and partial blockage of the entrance due to leaf litter or other debris were signs of inactive or abandoned burrows. Abandoned burrows typically were completely blocked in the entrance by roof collapse or a thick pile of debris. The burrow data was compared to the burrow distributions of Del Signore s (2007) honors thesis to see if another reduction mowing was needed. 6
Results We mapped a total of 200 gopher tortoise burrows in range VIa (Fig. 1 grey dots represent new burrows added from 5 August to 16 December 2013). An additional 22 burrows were located within the dry detention basin and its periphery. We recorded 43 new burrows during the investigation of range VIa. We found a high density of burrows in the exterior of the range and along the pathways. The burrows located in the interior of the range were adjacent to open areas for foraging and absent in areas overgrown with saw palmettos. During this investigation, 89 tortoises were encountered and measured. The carapace length distribution of the tortoises from the 2007 data was graphed (Fig. 2) from previously collected data by Dr. Jon Moore and the distribution of the tortoises from 2013 data was also graphed (Fig. 3). We found that carapace length leveled off at 9-10, indicating that the tortoises reached sexual maturity and stopped investing energy in growth (Fig. 4). It is possible that some 7 and 8 year old tortoises were sexually mature or just becoming mature. This is shown as the point where the growth in carapace length shows very little change, the plateau of the graph. Upon further data analysis, the smallest mature male on the plateau was 10 years old and smallest mature female was 9 years old, however there were larger females on the plateau at 7 or 8 years old. The distribution of the age of the tortoise was graphed (Fig. 5) and the graph shows an abundance of adults. The weights of the tortoises were graphed (Fig. 6) and the distribution showed a dominance of adult tortoises. The weight distribution was then further separated by sex. The weight distribution of the males lies mainly around 4.1 to 4.3 kg. (Fig. 7) and the female weight distribution lies in the range of 6.3 to 6.5 kg. (Fig. 8). 7
Discussion As in earlier studies in the Abacoa (e.g., Del Signore s 2007), we found higher densities of gopher tortoise burrows on the periphery. This suggests that the tortoises are being affected by the over growing vegetation in the interior of the range. The burrows in the interior of the range are almost always adjacent to open areas used for foraging. The open areas include wire grass and trails made by frequent usage by the tortoises. The last reduction mowing was conducted 7 years ago in October/November 2006 and this relates to the average burn cycle of xeric slash pine flatwoods which is about 5 to 20 years. The new burrow distributions indicate that another reduction mowing is needed soon in order to improve the lives of the tortoises. We predict that after the reduction mowing there will be another trend of the reoccupations of abandoned burrows and construction of new burrows towards the interior of the reserve. Reduction mowing is being used as an alternative to fire to manage the land because fire usage is suppressed by the nearby housing developments (Brose and Wade 2001). Reduction mowing is a viable alternative to the fires that the habitat depends heavily on; however, the mowing does not clear the leaf debris and pine needles, which remain as fuel for ground fire (Del Signore 2007). That mulch left on the ground also allows some invasive ants to spread (Jones 2013) and may also kill seed banks and suppress seedlings in the soil under the mulch as it decomposes (J. Moore, FAU, pers. obs.). Finally, mowing does not affect woody plants nearly as much as fire does and allows species such as gallberry and runner oak (Quercus minima) to proliferate (Tanner et al. 1988). Using fires not only allows for firedependent flora to grow, but also clears the land of fire fuel, eliminates invasive flora, and adds nutrients to the sandy soil (Drawe and Kattner 1978, Flynn et al. 2004, Menges 8
and Gordon 2010). Suppressing fires only allows for more fuel to accumulate and produces a very high risk of an uncontrollable wildfire. Another method, such as raking the potential fire fuel, in conjunction with reduction mowing that could clear the fuel would be beneficial for the wildlife and the people that live around the reserves. The size frequency results show unique characteristics of the gopher tortoise population at range VIa. The recruitment increase seen in 2013, compared to the 2007 carapace size frequency distribution, in Figure 2 shows that the population is doing well in terms of survival. We hypothesize that the increase, a near doubling, in the juvenile recruitment and survival of the juveniles correlates to the decrease in raccoon population in the past 4 years due to an outbreak of Rhabdoviridae lyssavirus, the rabies virus (J. Moore, FAU, pers. obs.). There was also a dominance of adult tortoises in both the 2007 and 2013 size frequency distributions for range VIa. Findings from northern populations of gopher tortoises show that most of the mortalities occur during the first year due to predation (Alford et al. 1980). Furthermore, the decrease in the number of adult sized tortoises in the 2013 population is due to poaching by a homeless man who lived in the reserve for a short time. He is suspected to have poached at least 9 tortoises and discriminated for size based on the remains of some of the largest tortoises found in the reserve. Large tortoises do not have natural predators and the knife marks on some of the skeletons discredits possible predation by coyote or raccoons which are the main predators of juvenile tortoises. Additionally, a number of tortoises originally marked in range VIa have moved to adjacent ranges within the Abacoa Greenway (J. Moore, FAU, pers. obs.). 9
The tortoises in range VIa in 2013 had 5-year old tortoises with 20 to 23 cm CL and 7-year old tortoises with 18.5 to 28.8 cm CL. The carapace length data from Covington County, south central Alabama had 5-year old tortoises with 9 to 14 cm and 7- year old tortoises with 11 to 16 cm (Aresco and Guyer 1999). This data shows the level of differences with northern populations. The tortoises of range VIa reach maturity around the ages of 7 to 10 years which is earlier when compared to populations in north Florida, but they were difficult to distinguish from large subadults and no mating behavior were observed for these young individuals. The gopher tortoises at Archbold Biological Station located in Venus, Florida (130 miles WNW of Jupiter, FL) reach maturity around 15 years old (B. Rothmerel, Archbold Biological, pers. comm.). The northern populations reach maturity around 10 to 15 years old (Iverson 1980). Also the tortoises of the northern populations hibernate during the winters and have less food resources due to seasonal constraints. The age versus carapace length data for our site also shows that the tortoises grow very slowly after 7 to 10 years, by which time they have reached at least 21 cm CL and in most cases exceeded 25 cm CL. The size of 25 cm CL is an important threshold, since this is the smallest length for a tortoise older than 10 years old (it was a 26 year old tortoise), signifying tortoises at this size are mature. This is similar in carapace length with northern populations, reaching sexual maturity around 23 cm (Landers et al. 1982). Taking 23 cm as the point in which sexual maturity is reached; there is at this size one subadult that is 5 years old and another that is 6 years old, plus what are likely two females at 7 and 8 years old. The maximum length for the carapace for a tortoise of 7 years of age is 29 cm in range VIa. We believe that this difference in maturation is due to 10
the year round foraging available to southern populations such as range VIa. According to the plant hardiness zone map (Fig. 9) by the US Department of Agriculture, the areas around Jupiter belong in northernmost tip of zone 10b because of climatic influence of the Gulf Stream. This allows for vegetation to grow year long and thus provides food for the tortoises all year, which more northern populations cannot have. The tortoises in range VIa do not hibernate as in northern populations, e.g. Georgia (Landers et al. 1982). These factors combine to allow the tortoises to reach large size and sexual maturity at earlier ages than the more northern populations. The weight distributions of the whole population do not provide enough insight about the population and only depicts the dominance of large adult tortoises. When analyzed further by sex, there is a distinct abundance of males in the range of 4.1 to 4.3 kg and females in the range of 6.3 to 6.5 kg. This shows the sexual dimorphism that exists between the sexes; females tend to be larger than males (Landers et. al 1982). The largest recorded male was 24 years old, weighed 6.62 kg, and measured 33 cm for CL. The largest female was 31 years old, weighed 7.85 kg, and measured 34 cm for CL. These results represent a healthy population even when faced with less than optimal conditions. However, recent state guidelines (GTC 2013) presented at the 35 th annual Gopher Tortoise Council states that: A minimum viable population (MVP) projected for 1,000 years is defined by having more than 250 individuals in an area larger than to 100 hectares and a support population is defined by a population of 50 to 250 individuals in an area 11
less than 100 hectares. The support population can be revived to a minimum viable population with the use of extensive land management. The guidelines label the population at range VIa as a support population. However, the population is sustaining with good recruitment. The population also reaches sexual maturity at a very young age and produces high clutch sizes. The state average clutch size is 5 to 7 eggs (Moore et al. 2009). The average clutch size is about 10.1 at range VIa (Moore et al. 2009). The population at range VIa had a female with a nest holding 18 eggs, over double the average clutch size (Moore et al. 2009). The demographics, age of sexual maturity, emigration from range VIa, and reproduction statistics show a prosperous population in range VIa. The guidelines help determine a very basal level of management awareness, but could be subject to a more case-by-case level of attention when assessing the status of the gopher tortoise populations. The population showed signs of improvement and recruitment above projection of recent state guidelines and therefore merits closer investigation as to why it is doing better than other support populations. The protection and management of gopher tortoises are crucial to not only preserving the biodiversity of the world, but maintaining the ecosystems of natural Florida. 12
Figure 1. The gopher tortoise distribution map. The grey dots represent the new burrows added from 5 th of August to 16 th of December in 2013. 13
Number of Tortoise Number of Tortoise 2007 Carapace Length Distribution 14 12 10 8 6 4 2 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 CL (cm) Figure 2. Carapace length distribution from 2007. 14 2013 Carapace Length Distribution 12 10 8 6 4 2 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 CL (cm) Figure 3. Carapace length distribution from 2013. 14
Percent of Gopher Tortoise CL (cm) Age versus Carapace Length Plot 40 35 30 25 20 15 10 5 0 0 5 10 15 20 25 30 35 40 Age (years) Figure 4. Scatter plot of age versus carapace length of tortoises in 2013. 100 90 Age Distribution of Gopherus polyphemus 80 70 60 50 40 30 20 10 0 Juvenile Subadult Adult Age Category Figure 5. Distribution of age in the tortoise population. 15
Number of Tortoise Number of Tortoise 12 2013 Weight Distribution 10 8 6 4 2 0 Weight (kg) Figure 6. Weight distribution of the tortoises from 2013. 7 Adult Male Weight Distribution 6 5 4 3 2 1 0 Weight (kg) Figure 7. The 2013 distribution of adult male weights. 16
Number of Tortoise 7 Adult Female Weight Distributions 6 5 4 3 2 1 0 Weight (kg) Figure 8. The 2013 distribution of adult female weights. Figure 9. Plant hardiness map from US Department of Agriculture (2012). 17
Literature Cited Alford, R. A. 1980. Population Structure of Gopherus polyphemus in Northern Florida. Journal of Herpetology, Vol. 14, No. 2, pp. 177-182. Aresco, M. J. and Guyer, C. 1998. Efficacy of Using Scute Annuli to Determine Growth Histories and Age of Gopherus polyphemus in Southern Alabama. Copeia 1998, Vol. 4, pp. 1094-1100. Aresco, M. J. and Guyer, C. 1999. Growth of the Tortoise Gopherus polyphemus in Slash Pine Plantations of Southcentral Alabama. Herpetologica, Vol. 55, No. 4, pp.499-506. Breininger, D. R., Duncan, B. W., and Dominy, N. J. (2002). Relationships Between Fire Frequency and Vegetation Type in Pine Flatwoods of East-central Florida, USA. Natural Areas Journal, Vol. 22, No. 3, pp. 186-193. Brose, P. and D. Wade. 2001. Potential Fire Behavior on Pine Flatwood Forests Following Three Different Fuel Reduction Techniques. Forest Ecology and Management, 163:71-84. Burke, R. L. 1989. Florida Gopher Tortoise Relocation: Overview and Case Study.Biological Conservation, Vol. 48, No. 4, pp. 295-309. Del Signore, V. 2007. The Effects of Reduction Mowing on Gopher Tortoises (Gopherus polyphemus). Undergraduate Thesis, Wilkes Honors College of Florida Atlantic University. Diemer, J. E. 1986. The Ecology and Management of the Gopher Tortoise in the Southeastern United States. Herpetologica, Vol. 42, No. 1, pp. 125-133. Diemer, J. E. 1992. Demography of the Tortoise Gopherus polyphemus in Northern Florida. Journal of Herpetology, Vol. 26, No. 3, pp. 281-289. Drawe, D. L. and Kattner, K. R. 1978. Effect of Burning and Mowing On Vegetation of Padre Island. Southwestern Naturalist, 23:273-278. Eisenberg, J. F. 1983. The Gopher Tortoise as a Keystone Species. In Proceedings of the 4th Annual Meeting of the Gopher Tortoise Council, Vol. 4, pp. 1-4. Flynn, R. S., C. D. Craig, and T. Edwards, Jr. 2004. Effect of Burning and Mowing on Grass and Forb Diversity in a Long-term Grassland Experiment. Applied Vegetation Science, 7:1-10. FWC (2014) Gopher Tortoise Management Plan. Available at (http://myfwc.com/wildlifehabitats/managed/gopher-tortoise/management-plan/). 18
Gopher Tortoise Council (GTC). 2013. Gopher Tortoise Minimum Viable Population and Minimum Reserve Size. Working group report. Available at (http://www.gophertortoisecouncil.org/conservation/minimum-viable-population). 7 pp. Iverson, J. B. 1980. The Reproductive Biology of Gopherus polyphemus (Chelonia: Testudinidae). American Midland Naturalist, Vol. 103, No. 2, pp. 353-359. Jackson, D. R. and Milstrey, E. G. 1989. The Fauna of Gopher Tortoise Burrows, p. 86-98. In: J. E. Diemer, D. R. Jackson, J. L. Landers, J. N. Layne and D. A. Wood (eds.). Gopher Tortoise Relocation Symposium Proceedings. Fla. Game and Fresh Water Fish Comm. Nongame Wildl. Prog. Tech. Rep. No. 5, Tallahassee. 109 p. Jones, R. C. 2013. Undergraduate Thesis, Wilkes Honors College of Florida Atlantic University. Kent, D. M., and Snell, E. 1994. Vertebrates Associated with Gopher Tortoise Burrows in Orange County, Florida. Florida Field Naturalist, Vol. 22, No. 1, pp. 8-10. Kinlaw, A. and Grasmueck, M. 2012. Evidence for and Geomorphologic Consequences of a Reptilian Ecosystem Engineer: The Burrowing Cascade Initiated by the Gopher Tortoise. Geomorphology, Vol. 157-158, pp. 108-121. Landers, L. J., McRae, A. W., and Garner, J. A. 1982. Growth and Maturity of the Gopher Tortoise in Southwestern Georgia. Bulletin of the Florida State Museum, Biological Sciences, Vol. 27, pp. 81-110. Marti, D., W. O Brien, H. Smith, J. Moore, and S. Fitchett. Endangered Species, Prescribed Fires, and Public Resistance in a Florida Scrub Community. Endangered Species Update Vol. 22, No. 1, pp. 18-28. McCoy, E. D. and Mushinsky, H.R. 1995. The demography of Gopherus polyphemus (Daudin) in relation to size of available habitat. Fla. Game and Fresh Water Fish Comm. Nongame Wildlife Program Project Rep. 71pp + viii. Tallahassee, Fla. McCoy, E. D., Mushinsky, H. R., & Lindzey, J. 2006. Declines of the Gopher Tortoise on Protected Lands. Biological Conservation, Vol. 128, No. 1, pp. 120-127. Menges, E. S. 1999. Ecology and Conservation of Florida Scrub. Pages 7 22 in R. C. Anderson, J. S. Fralish, and J. M. Baskin, editors. Savannas, barrens and outcrop plant communities of North America. Cambridge University Press, Cambridge, United Kingdom. Menges, E. S. and D. R. Gordon. 2010. Should Mechanical Treatments and Herbicides Be Used as Fire Surrogates to Manage Florida s Uplands? A review. Florida Scientist, Vol. 73, No. 2, pp. 147-174. Moore, J. A., Strattan, M., and Szabo, V. 2009. Evidence for Year-round Reproduction in the Gopher Tortoise (Gopherus polyphemus) in Southeastern Florida. Bulletin of the Peabody Museum of Natural History, Vol. 50, No. 2, pp. 387-392. 19
Tanner, G. W., J. M. Wood, R. S. Kalmbacher, and F. G. Martin. 1988. MEchanica Shrub Control on Flatwoods Range in South Florida. Journal of Range Management, 41:245-248. Tuberville, T. D., Norton, T. M., Todd, B. D., & Spratt, J. S. 2008. Long-term Apparent Survival of Translocated Gopher Tortoises: A Comparison of Newly Released and Previously Established Animals. Biological conservation, Vol. 141, No. 11, pp. 2690-2697. USDA. 2012. Plant Hardiness Zone Map. Agricultural Research Services. Available at (http://planthardiness.ars.usda.gov/phzmweb/). USFWS. 1987. Endangered and Threatened Wildlife and Plants; Determination of Threatened Status for the Gopher Tortoise (Gopherus polyphemus). Federal Register 52: 25376 25380. USFWS. 2011. Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition to List the Gopher Tortoise as Threatened in the Eastern Portion of its Range. Federal Register 76: 45130 45158. Wetterer, J.K. and Moore, J.A. 2005. Red Imported Fire Ants (Hymenoptera:formicidae) at Gopher Tortoise (Testudines: Testudinidae) Burrows. Florida Entomologist, Vol. 88, No. 4, pp. 349-354. 20