Estimating Occupancy of Gopher Tortoise (Gopherus polyphemus) Burrows in Coastal Scrub and Slash Pine Flatwoods

Breininger, David R.; Schmalzer, Paul A.; Hinkle, C. Ross

doi:10.2307/1564590

Cited by 31 publications

(20 citation statements)

References 1 publication

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“…When burrows flood during heavy rains (Breininger, Schmalzer & Hinkle, 1991), the tortoises usually do not leave the burrows (Diemer, 1992), and the water will soon drain from them. However, in the clayey soils typical of Georgia, burrows tend to be shorter (Ultsch & Anderson, 1986) and water drains from them much more slowly.…”

Section: (3 ) Gopher Tortoise (Gopherus Polyphemus)mentioning

confidence: 99%

The ecology of overwintering among turtles: where turtles overwinter and its consequences

2006

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Turtles are a small taxon that has nevertheless attracted much attention from biologists for centuries. However, a major portion of their life cycle has received relatively little attention until recently - namely what turtles are doing, and how they are doing it, during the winter. In the northern parts of their ranges in North America, turtles may spend more than half of their lives in an overwintering state. In this review, I emphasise the ecological aspects of overwintering among turtles, and consider how overwintering stresses affect the physiology, behaviour, distributions, and life histories of various species. Sea turtles are the only group of turtles that migrate extensively, and can therefore avoid northern winters. Nevertheless, each year a number of turtles, largely juveniles, are killed when trapped by cold fronts before they move to safer waters. Evidently this risk is an acceptable trade-off for the benefits to a population of inhabiting northern developmental habitats during the summer. Terrestrial turtles pass the winter underground, either in burrows that they excavate or that are preformed. These refugia must provide protection against desiccation and lethal freezing levels. Some burrows are extensive (tortoise genus Gopherus), while others are shallow, or the turtles may simply dig into the ground to a safe depth (turtle genus Terrapene). In the latter genus, freeze tolerance may play an adaptive role. Most non-marine aquatic turtles overwinter underwater, although Clemmys (Actinemys) marmorata routinely overwinters on land when it occurs in riverine habitats, Kinosternon subrubrum often overwinters on land, and several others may overwinter terrestrially on occasion, especially in more southern climates. For northern species that overwinter underwater, there are two physiological groupings, those that are anoxia-tolerant and those that are relatively anoxia-intolerant. All species fare well physiologically in water with a high partial pressure of oxygen (PO2). A lack of anoxia tolerance limits the types of habitats that a freshwater turtle may live in, since unlike sea turtles, they cannot travel long distances to hibernate. Hatchlings of some species of turtles spend their first winter in or below the nest cavity, while hatchlings of other species in the same area, including northern areas, emerge in the autumn and presumably hibernate underwater. All hatchlings are relatively anoxia-intolerant, and there are no studies to date of where hatchling turtles that do not overwinter in or below the nest cavity spend their first winter. Equally little is known of the ontogeny of anoxia tolerance, other than that adults of all species are more anoxia-tolerant than their hatchlings, probably because of their better ossified shells, which provide adults with more buffer reserves and a larger site in which to sequester lactate. The northern limits of turtles are most likely determined by reproductive limitations (time for egg-laying, incubation, and hatching) than by the rigors of hibernation. Mortalit...

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Section: (3 ) Gopher Tortoise (Gopherus Polyphemus)mentioning

confidence: 99%

The ecology of overwintering among turtles: where turtles overwinter and its consequences

2006

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“…Individuals rarely occupy burrows simultaneously, but not all burrows are occupied at any particular time; therefore, the number of burrows exceeds the number of tortoises (Breininger et al 1991, Witz et al 1991, McCoy and Mushinsky 1992, Eubanks et al 2003. Individuals rarely occupy burrows simultaneously, but not all burrows are occupied at any particular time; therefore, the number of burrows exceeds the number of tortoises (Breininger et al 1991, Witz et al 1991, McCoy and Mushinsky 1992, Eubanks et al 2003.…”

Section: Study Speciesmentioning

confidence: 99%

Estimates of Minimum Patch Size Depend on the Method of Estimation and the Condition of the Habitat

McCoy

Mushinsky

2007

Ecology

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Minimum patch size for a viable population can be estimated in several ways. The density-area method estimates minimum patch size as the smallest area in which no new individuals are encountered as one extends the arbitrary boundaries of a study area outward. The density-area method eliminates the assumption of no variation in density with size of habitat area that accompanies other methods, but it is untested in situations in which habitat loss has confined populations to small areas. We used a variant of the density area method to study the minimum patch size for the gopher tortoise (Gopherus polyphemus) in Florida, USA, where this keystone species is being confined to ever smaller habitat fragments. The variant was based on the premise that individuals within populations are likely to occur at unusually high densities when confined to small areas, and it estimated minimum patch size as the smallest area beyond which density plateaus. The data for our study came from detailed surveys of 38 populations of the tortoise. For all 38 populations, the areas occupied were determined empirically, and for 19 of them, duplicate surveys were undertaken about a decade apart. We found that a consistent inverse density area relationship was present over smaller areas. The minimum patch size estimated from the density-area relationship was at least 100 ha, which is substantially larger than previous estimates. The relative abundance of juveniles was inversely related to population density for sites with relatively poor habitat quality, indicating that the estimated minimum patch size could represent an extinction threshold. We concluded that a negative density area relationship may be an inevitable consequence of excessive habitat loss. We also concluded that any detrimental effects of an inverse density area relationship may be exacerbated by the deterioration in habitat quality that often accompanies habitat loss. Finally, we concluded that the value of any estimate of minimum patch size as a conservation tool is compromised by excessive habitat loss.

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“…Burrow entrances can provide evidence of occupancy by fossorial and semi‐fossorial species. Counts of burrow entrances also have been used to estimate abundance for several obligate burrowing species, including ground squirrels ( Spermophilus townsendii , Van Horne et al 1997; S. columbianus , Weddell 1989), prairie dogs ( Cynomys ludovicianus , Biggins et al 1993, Powell et al 1994, Severson and Plumb 1998, Johnson and Collinge 2004), kangaroo rats ( Dipodomys stephensi , O'Farrel 1992, Brock and Kelt 2004), pocket gophers ( Thomomys talpoides , Reid et al 1966), European rabbits ( Oryctolagus cuniculus , Parer and Wood 1986, Palomares 2001, Ballinger and Morgan 2002), badgers ( Meles meles , Wilson et al 2003), and gopher tortoises ( Gopherus polyphemus , Breininger et al 1991). Several studies have documented positive and significant relationships between burrow counts and species abundance (Parer 1982, Biggins et al 1993, Vreeland and Tietje 1999, Ballinger and Morgan 2002, Johnson and Collinge 2004), whereas others identified no significant relationship between the 2 parameters (Powell et al 1994, Van Horne et al 1997, Severson and Plumb 1998, Palomares 2002).…”

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confidence: 99%

Development of an index of abundance for pygmy rabbit populations

Price

Rachlow

2011

J Wildl Manag

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The pygmy rabbit (Brachylagus idahoensis) is a cryptic, burrowing lagomorph of conservation concern for which an efficient method to monitor populations is needed for conservation planning. We developed an index of abundance based on density of active burrow systems at 7 sites (57.2–118.5 ha) in east central Idaho. We conducted censuses of burrow systems and used mark‐resight surveys of 80 radio‐collared individuals to estimate density of rabbits. At 5 sites, we also used a second method to estimate rabbit numbers based on presence of tracks in snow around burrow systems. We evaluated patterns of burrow use by individuals and examined the relationship between vegetation structure and density of rabbits. Density of active burrow systems varied from 0.19 to 3.46 per ha, and density of rabbits ranged from 0.02 to 0.46 per ha. Number of burrow systems used by individuals increased with density of available burrows, which supported a nonlinear relationship between abundance of burrows and rabbits. Population density increased curvilinearly with density of active burrows accounting for >75% of the variation (r2 = 0.79) in population estimates across sites. We documented a positive relationship between visual obstruction of vegetation and density of rabbits across 6 of the study sites. Our results suggest that density of burrows can serve as an index for monitoring changes in abundance of pygmy rabbits in east central Idaho and that this index also might be useful for monitoring changes in relative abundance over time at other locations. To assess abundance at larger spatial scales or across different regions, the index should be calibrated under regional conditions and site‐level covariates should be evaluated. © 2011 The Wildlife Society.

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Estimating Occupancy of Gopher Tortoise (Gopherus polyphemus) Burrows in Coastal Scrub and Slash Pine Flatwoods

Cited by 31 publications

References 1 publication

The ecology of overwintering among turtles: where turtles overwinter and its consequences

The ecology of overwintering among turtles: where turtles overwinter and its consequences

Estimates of Minimum Patch Size Depend on the Method of Estimation and the Condition of the Habitat

Development of an index of abundance for pygmy rabbit populations

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