METHODS

Study Site: Ordway–Swisher Biological Station. — The Ordway–Swisher Biological Station consists of ca. 3800 ha of sandhills and wetlands located southeast of Melrose in Putnam County, Florida. Habitats on the station include large communities of xeric sandhill uplands consisting of Longleaf Pine (Pinus palustris), Turkey Oak (Quercus laevis), and Wiregrass (Aristida beyrichiana), xeric oak (Sand Live Oak, Quercus geminata and Laurel Oak, Quercus hemisphaerica) hammocks, temporary ponds and clear-water lakes, swamp forests, and dark-water (tannin-stained) ponds, lakes, and prairie marshes. The dark-water habitats are connected through intermittent Mill Creek and form a permanent water flow that eventually reaches the Etoniah–Rice Creek drainage and thence into the St Johns River. The open-canopied sandhill lakes and ponds are mostly isolated from one another. Eisenberg and Franz (1995) provide an introduction to the station with a detailed map of its ponds and wetlands.

Study Site: Breezeway Pond. — We collected field data from 2 February to 12 April 1985 and from 1 October 1985 to 30 September 1990 at Breezeway Pond, a 0.16-ha temporary depression marsh located in a shallow 1.3-ha basin on the Ordway–Swisher Biological Station, Putnam County, Florida (lat 29°41′N, long 82°00′W). The pond is located in xeric sandhill uplands near the ecotone between a Longleaf Pine–Turkey Oak–Wiregrass community and a xeric oak (Sand Live Oak and Laurel Oak) hammock community. To the immediate south and west (at angles 72° to 298° from the center of the pond basin), Longleaf Pine sandhills predominated; to the north (at angles 299° to 360°, and 0° to 27°), xeric oak hammocks predominated; to the northeast, a small grassland dominated by Maidencane (Panicum hemitomon) was found at angles 28° to 71° from the center of the pond basin. The distance from the drift fence to the nearest forested plant association was generally 20 m but extended to about 50 m behind the Panicum meadow. Additional physical and vegetative details concerning the site are in Dodd (1992, 1993), LaClaire (1992), and Dodd and Anderson (2018). The pond held water for 2 yrs prior to the study, but a severe drought resulted in an intermittent hydroperiod from October 1985 to December 1988, with no standing water after 23 December 1988 (see Dodd 1992, fig. 1).

The nearest water bodies to Breezeway Pond were Smith Lake (350 m to the north of Breezeway Pond) and 3 small temporary ponds, all located generally north or northeast of Breezeway Pond: Pine Lodge Pond (minimum 180 m distant), Smith Lake Pond (450 m distant), and Breezeway Sandhills Pond (400 m distant). All temporary ponds within 1 km of Breezeway Pond dried completely by late 1989 and remained dry throughout the remainder of the sampling period. This was approximately 1 yr after the last standing water was recorded in Breezeway Pond (Dodd 1992). Drought reduced Smith Lake from 7.55 ha surface area in 1985 to approximately 0.75 ha in 1989.The lake dried completely in May 1990.

Sampling Procedure. — Turtles were captured opportunistically as we traveled to and from Breezeway Pond from the entrance gate to the station. Turtles were processed immediately in the field and released unless retained for a brief radio-tracking study (see below).

The Breezeway Pond basin was encircled by a 230-m drift fence made of galvanized metal flashing (36 cm above ground, 10–15 cm below the surface). Twenty-three pairs of pitfall traps (19-l black plastic buckets, 36 cm deep) were sunk into the ground at 10-m intervals, with 1 trap on each side of the pitfall at each position. The pitfalls were partially shaded to minimize the effects of the direct sun. We placed wet sponges in the buckets at all times and cover boards flat across the openings when pitfalls were not checked to prevent desiccation. We checked pitfalls 5 d per week between 0700 and 0900 hrs, depending on season (corresponding to approximately 1 hr after sunrise), from 1 October 1985 through 30 September 1990 (1825 d; 83,950 bucket-nights). We obtained compass directions by standing in the center of the pond basin and measuring the angle to each pair of pitfall traps, with 0° indicating due north.

We examined captured turtles in the field and recorded a variety of measurements and environmental data, including straight-line carapace (CL) and plastron length (PL) (using a digital caliper to 0.1 mm), weight (to 0.1 g), location on the station if not at Breezeway Pond, buckets where turtles were captured, pond and air temperature at capture using a digital thermometer, and air and pond maximum and minimum temperatures since the previous day using in-place max-min thermometers. Juvenile turtles were individually V-notched using a fingernail clipper; adults were notched with a small triangular file. Turtles were considered adults if > 60 mm CL (Ernst et al. 1973); males have a longer tail than females and have a sharp point on the tip.

Telemetry. — Two male Florida Mud Turtles were captured leaving Breezeway Pond on 28 August 1989, fitted with LF-1 transmitters (Custom Electronics, Urbana, IL), and released on 29 August. Turtles were followed incidental to other research on the station. Turtle 4590 (110 mm CL, 168 g) was followed until 19 October 1989 (37 times tracked); turtle 4589 (96 mm CL, 123 g) was followed until 13 October 1989 (33 times tracked). A female (4513, 103 mm CL, 170.4 g) captured at Breezeway Pond on 16 April 1987 was tracked until 22 June 1987 (59 times tracked). Another female (4521, 93 mm CL, 121 g) was tracked from 29 November 1988 to 23 December (19 times tracked) when the transmitter fell off. She was again captured on 25 June 1990 leaving the pond basin and later followed from 4 July 1990 to 3 September. All turtles were released when transmitters failed.

RESULTS

Six adult males were captured during sampling, 1 (4518) of which was captured 3 times. All males were captured at Breezeway Pond. Exclusive of the multiple captures, males were 76 to 110 mm CL (mean = 89 mm), 61 to 78 mm PL (mean = 68.2 mm), and weighed 67 to 168 g (mean = 109 g). Turtle 4518, first recorded as a subadult, grew from 63 mm CL, 52 mm PL, and 47 g on 25 November 1985 to 76 mm CL, 62 mm PL, and 73.5 g on 20 June 1989, by then clearly an adult male. From 25 November 1985 to 26 March 1987, the male showed no change in CL or PL, but actually lost 4.2 g in weight. Males were captured at air temperatures of 19°C to 27°C when pond temperatures were 18°C to 25°C. Males were captured departing the encircled pond basin in May, June, August, October, and November; the May, June, and August departures coincided with the worsening drought in 1988 and 1989. Males entered the pond basin in March (1987) and August (1986).

Four females were captured during sampling, 2 of which were captured 3 times, all at Breezeway Pond. Two females were captured incidentally, 1 on the steps of a storage pole barn in the middle of a field in late September (air temperature 25°C), and the other crossing a road at 1200 hrs in January (air temperature 19°C). Exclusive of the multiple captures, females were 93 to 103 mm CL (mean = 97 mm), 78 to 88 mm PL (mean = 82.3 mm), and weighed 104 to 200 g (mean = 144.3 g). Turtle 4513 grew from 99 mm CL, 81 mm PL, and 200 g on 28 October 1985 to 103 mm CL and 82 mm PL, but lost weight to 170.4 g on 16 April 1987. From 16 April to 8 May, this female showed no change in CL or PL, but regained 19.6 g in weight to 190 g. Turtle 4521 never showed any change in CL (93 mm) or PL (78 mm) from 14 March 1986 to 25 June 1990. However, this female’s weight dropped from 131 g to 121 g over the course of this period. Females were captured at air temperatures of 17°C to 26°C when pond temperatures were 18°C to 25°C. Turtle 4513 entered the pond basin in April (1987), and was found leaving the pond in October (1985) and May (1987); note that the female likely entered the pond while the drift fence was opened and not being checked from mid-April to late September 1985. Turtle 4521 entered the pond basin in March (1986) and exited in November (1988) and June (1990), suggesting an ability to trespass the fence.

There were 2 size classes of juvenile turtles. The first consisted of recent hatchlings: 20 to 24.4 mm CL (mean = 22.5 mm, n = 33); 17 to 20.7 mm PL (mean = 18.6 mm, n = 33); 2.1 to 3.5 g (mean = 2.8 g, n = 32). Of the 31 hatchlings in buckets, 5 were on the inside of the fence and 26 were on the outside; an additional hatchling was found walking towards the fence, and another hatchling was found in a distant field not in proximity to Breezeway Pond. Hatchlings were captured as follows: February 1988 (4), February 1989 (1), February 1990 (1), March 1985 (6), March 1986 (1), March 1987 (6), March 1988 (5), March 1989 (1), April 1988 (3), and December 1986 (5). Hatchlings to 24.4 mm CL still had a caruncle (“egg tooth”) present. Seven hatchlings were recaptured once each with 1.5 mo of previous capture: February 1987 (1), March 1988 (4), April 1988 (2). None showed appreciable changes in CL, PL, or weight. At time of bucket sampling, air temperatures were 6°C to 28°C (24-hr max 18°C to 35°C) and pond temperatures were 11°C to 21°C.

Six additional subadults were captured at Breezeway Pond: 40.2 to 55 mm CL; 32.7 to 46 mm PL; 11 to 31.7 g weight. Five captures occurred inside the fence (March 1985, May 1988, August 1988, May 1989, September 1989) and 1 outside the fence (March 1985). A seventh turtle (GS6) was originally captured as a hatchling on 9 March 1987 entering the pond basin and recaptured on 25 May 1988 leaving the basin. In 14 mo, it grew 13.6 mm in CL, 12.8 mm in PL, and gained 5.0 g weight.

Telemetry, Turtle 4513 (Figs. 1–3). — From 17 April through 7 May, female 4513 remained within Breezeway Pond, moving continuously throughout the wetland. Daily movements were 1 to 28 m in water 18 to 50 cm at maximum pond depth. During this period, maximum air temperatures were 26°C to 35°C; pond maximums were 22°C to 28°C, with pond minimums at 16°C to 22°C. On 8 May, this female departed the pond basin and made a direct movement of 240 m before stopping at Pine Lodge Pond northeast of Breezeway. The turtle appeared to use the Panicum grass corridor to travel between the 2 ponds. From 10 May until 16 June, it remained at Pine Lodge Pond, frequently moving around its margins (daily movements between tracking events were 4 to 40 m, mean = 22.7 m). Water depth at the turtle’s location was 22 cm to > 1 m. Water temperatures were 25°C to 35°C maximum and 19°C to 23°C minimum during the tracking period. On 16 June, the turtle moved 61 m directly west of Pine Lodge Pond and buried in leaf litter in a xeric oak hammock. At the time of movement, water depth along the margins of the pond had begun falling and maximum water temperatures had increased substantially (to 39°C) at the edge of the pond, although the center of the pond still contained deeper cooler water. Tracking was then discontinued.

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Telemetry, Turtle 4521 (Figs. 1, 2). — This female spent her entire first tracking session within Breezeway Pond. During this time, it moved very little (twice, 3 and 5 m) and buried into the aquatic pond vegetation or substrate. Pond temperatures ranged from 6°C to 12°C, air temperatures from 2°C to 17°C, and pond depth ranged from 45 to 240 cm at its deepest point. Between tracking periods, the turtle did not grow, but increased in weight by 8 g. Upon rerelease on 4 July, it traveled < 10 m from the pond and buried itself under thick leaf litter in a nearby xeric oak hammock. The female remained there until tracking ended on 3 September. It was found buried 30 cm below the surface, alert but dehydrated, having lost 13 g in body weight. This turtle was then reburied in the cavity under the leaf litter.

Telemetry, Turtle 4589 (Figs. 1, 4). — Adult male 4589 was released at Breezeway Pond at 0740 hrs on 29 August 1989; by 1125 hrs, the turtle had traveled 72 m in a direct line toward Breezeway Sandhill Pond to the east-northeast of Breezeway Pond. On 1 September, it was in Breezeway Sandhill Pond, having traveled a further 324 m. This male remained in Breezeway Sandhill Pond until tracking ceased on 13 October when the transmitter detached. Turtle 4589 avoided deep water, preferring the shallow grassy margins of the pond. Water depth at capture was 7.8 to 43 cm (mean = 19.3 cm); water temperatures were 20°C to 33°C (mean = 26.7°C). Movements between tracking events at the pond were 1 to 110 m (n = 27; mean = 28.5 m; median 21.5 m). During this period, turtle 4589 neither gained nor lost appreciable weight.

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Telemetry, Turtle 4590 (Figs. 1, 5). — Adult male 4590 was also released at Breezeway Pond on 29 August 1989 at 0740 hrs; by 1125 hrs, it had traveled 34 m in a direct line toward Pine Lodge Pond to the northeast of Breezeway Pond. On 4 September, the male was in Pine Lodge Pond, having traveled a further 114 m. Turtle 4590 remained in Pine Lodge Pond frequenting the grassy shallow margins of the pond until 18 October when it traveled 52 m west of Pine Lodge Pond and buried into the leaf litter in a xeric oak hammock. Turtle 4590 also avoided deep water, preferring the western and southwestern margins of the pond. Water depth at capture was 6.0 to 48 cm (mean = 24.6 cm); water temperatures were 23°C to 33°C (mean = 26.5°C). Movements between tracking events at the pond were 0 to 39.3 m (n = 30; mean = 6.3 m; median 5.7 m). During this period, turtle 4590 neither gained nor lost appreciable weight.

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DISCUSSION

Activity and Movements. — Hatchling K. steindachneri were caught in buckets surrounding Breezeway Pond. The buckets were checked shortly after dawn, and turtles were released under nearby vegetation or in the pond depending on whether they were captured immigrating to or emigrating from the pond basin. Hatchling movements likely occurred after dark, as they would have had to cross unvegetated, white, often very hot sand in direct sunlight for a considerable distance before reaching the fence, whether immigrating or emigrating. This would have left the small black hatchlings exposed to predators, heat stress, and dehydration for an extended amount of time. Movement at night would reduce these adverse effects. Two hatchlings, however, were observed during bucket checking as they walked along the fence shortly after dawn on 28 March (entering) and 2 September (leaving), indicating at least some activity during very early morning hours.

Adults were not tracked at night, but they clearly made long-distance terrestrial movements during daylight hours and were active in the ponds throughout the day. Activity of this species occurs year round in north Florida, but adults bury in leaf litter under nearby vegetation during periods of high temperatures and drought and when ponds and lakes dry. Iverson (1979) noted only 5 of 62 K. steindachneri examined in north and central Florida were collected between 15 June and 15 August during peak summer temperatures. Activity and movements of the 4 telemetered adult turtles agree with previous observations suggesting a period of midsummer dormancy under certain environmental conditions. At large Lake Conway, however, turtles were active year round in shallow littoral habitats (Bancroft et al. 1983). The size of the habitat and availability of water likely influence whether turtles will leave a wetland and seek terrestrial refugia.

In a study of an extensive urban lake (Lake Conway, 743 ha) in central Florida, Bancroft et al. (1983) never observed terrestrial activity by this species. They recorded the farthest distance between resighted individuals as 132 m (mean = 32.8 m). The home range was considered small, but movement between isolated ponds and terrestrial activity were not included in their study. In aquatic Breezeway Sandhills Pond, turtle 4590 traversed the entire pond area, the extent of which was > 110 m in a somewhat oblong shape. As at Lake Conway, it seems likely that Florida Mud Turtles would traverse greater distances if the habitat was available in shallow ponds and marshes. Movements among the other Florida Mud Turtles tracked were short (and likely their aquatic home ranges small) because their isolated ponds were small.

Although K. steindachneri has been characterized as mostly aquatic and rarely seen on land, this perception likely results from a lack of detailed studies of this species. Both K. subrubrum and Kinosternon baurii are well known to move overland in response to drought, to seek terrestrial habitats for dormancy, and to nest (reviewed by Meshaka and Gibbons 2006; Harden et al. 2009; Stemle et al. 2019). The fact that K. steindachneri on the Ordway Biological Station quickly moved up to 400 m between ponds through sandy terrestrial habitats, and that 3 of 4 turtles buried in shallow leaf litter within 61 m of a pond, suggests that this species has similar habits as those at the Savannah River Site in South Carolina. In north Florida, none of these movements was associated with rainfall.

Reproduction. — In Florida, nesting occurs from October to June (Iverson 2022). After incubation for ca. 100 d, hatchlings are 18 to 23 mm (Iverson 1979). These data suggest that the very small turtles at Breezeway Pond hatched rather recently, from late December through April, corroborating Iverson (1979) but with slightly larger hatchlings, especially since one had a caruncle still attached at 24.4 mm CL. The fact that most recent hatchlings were found entering the pond indicates that nesting occurred around the pond margins and that the hatchlings traveled downslope to the lower-elevation pond basin. In north Florida, the mean clutch size is 3.58 (Iverson 1977, 1979, 2022), thus the 1 to 6 hatchlings found in any one season could have resulted from 1 or 2 females. If hatchlings initially grow at a rate of 11 mm/yr (Ernst et al. 1973), the subadults observed at Breezeway Pond could be approximately 3.5 to 5 yrs of age. In Florida, Ernst et al. (1973) estimated that males reached maturity at 4 to 5 yrs (53 to 60 mm PL) and females at 6 to 8 yrs (66 to 75 mm PL). However, Iverson (2022) found the smallest Florida adult female to be 90 mm CL, but at an estimated 5 yrs of age. Isolated ponds could serve as important developmental habitat for this species.

Management Implications. — Whereas the life history information gathered at Breezeway Pond corroborates previous observations, the telemetry data suggest that K. steindachneri likely uses terrestrial habitats more frequently than heretofore recognized. In this, the species behaves much like K. subrubrum to the north. In small isolated seasonal wetlands, Florida turtles left drying wetlands and summer heat and moved up to 60 m from the pond before burying into leaf litter. For K. subrubrum, terrestrial dormancy has been reported for up to 170 d (Bennett et al. 1970; Buhlmann and Gibbons 2001), and it seems likely K. steindachneri exhibits similar behavior.

In a similar note, K. steindachneri will move considerable distances across terrestrial habit to move to more favorable wetlands when necessary. Lardie (1975) also noted a hatchling ca. 200 m from the nearest water body, presumably from a long-distance nesting foray. Such movements may occur rapidly. These directed movements may be more prevalent when seasonal wetlands are patchily distributed across a landscape, and singular moving turtles may easily go unnoticed. In much larger permanent wetlands, Florida Mud Turtles might remain in place among shallow littoral vegetation and thus give the appearance of being more stationary and aquatic than other Kinosternon. In South Carolina, Burke and Gibbons (1995) noted that a 275-m buffer zone protected 100% of nesting and dormancy sites of a K. subrubrum population; even a 73-m buffer zone protected 90% of the turtles. Extensive buffer zones for K. steindachneri, with protection for movement corridors, will likely be of similar dimensions, but more extensive data among different landscape configurations would be desirable before making site-specific recommendations. In rapidly developing central and north Florida, protecting K. steindachneri populations outside of protected areas may prove to be a daunting challenge. Although the life histories of K. steindachneri and K. subrubrum are frequently compared, it appears that there are important differences between them (Iverson 2022).