Taxonomic Notes
Hybridization occurs with Graptemys ernsti in the Choctawhatchee River drainage of Alabama and Florida (Godwin et al. 2014).
Justification
Graptemys barbouri is assessed as Near Threatened based on an estimated population decline of ca 25% over the last three generations of ca 60–75 yrs, nearly qualifying as Vulnerable under criteria A2bcde. The previous Red List assessment (van Dijk 2011) determined the species to be Vulnerable at that time, but the global population has appeared to stabilize somewhat since then. The global population is now estimated to be >10,000 adult individuals, but this is distributed among only three watersheds with a maximum of 20 subpopulations (likely less due to linear connectivity). Previously inferred population declines resulting from overharvesting have been mostly mitigated, though habitat degradation, predation, and disease still pose threats, especially given the limited range. Catastrophic events such as tropical storms or chemical spills have the potential to greatly impact a high percentage of the population due to negative impacts to nesting sites, basking areas, specialized gastropod and bivalve food sources, and water quality. Graptemys barbouri has been described as reasonably abundant in parts of its range but rare in others. Long-term population comparisons may be interpreted as indicating stable or declining populations, but the large numbers historically collected are no longer encountered. Nevertheless, more robust population estimates along with genetic assessments comparing river drainages are needed.
Geographic Range Information
Graptemys barbouri inhabits the Apalachicola River and adjacent systems of Florida, Georgia, and Alabama in the southeastern United States, including the Chattahoochee River system as far north as Muscogee County, Georgia, the Flint River north to Meriwether County, Georgia, the Chipola River, the Choctawhatchee and Pea River systems as far as Geneva County, Alabama, and the Ochlockonee River in Florida below the Shaw Creek confluence (Iverson 1992, Bonin et al. 2006, Ewert et al. 2006; Hepler et al. 2015, Mays and Hill 2020, TTWG 2021). There are two documented occurrences of G. barbouri from the Wacissa River in the Aucilla River drainage of Florida, though it is uncertain if a population is present (Jackson 2003, Mays and Hill 2020). Fossil material from the Suwannee River drainage of north central Florida is morphologically and geographically similar to G. barbouri but was described by Ehret and Bourque (2011) as the extinct species G. kerneri
Population Information
Graptemys barbouri was considered the fourth rarest Graptemys based on extensive basking surveys (P.V. Lindeman pers. comm. 2009). The population of G. barbouri was estimated to range between 1,000 and 10,000 individuals, found in 1–20 subpopulations (NatureServe 2014). This species is reportedly abundant in parts of its range, such as the Chipola, Apalachicola, and Flint rivers, while it is scarce in others. NatureServe (2014) describes the population's short-term trend as “decline of <30% to relatively stable”.
Moler (1986), who found an average of 2.6 turtles/river kilometre (rkm), compared his population survey along the upper Chipola River to Carr's (1952) observations and concluded that population trends in the 45 years since the observations by Carr were as compatible with a stable population as with a decline. However, compared to encounter rates of 68.3 turtles/rkm by Sanderson (1992) in 1974 during repeated sampling of a 5.65 km section (total of 386 individuals), sighting rates of 2.64 (average) to 5.66 turtles/rkm by 1986 suggest a decline, at least locally. Cagle (1952) collected 393 individuals from an unspecified section of this river, and Chaney and Smith hand captured 397 individuals over a three-night period that Lindeman (2013) calculated as 62 turtles/rkm.
Ruhl (1991) reported 0.8 G. barbouri/rkm along the lower Apalachicola River but high-water levels during the surveys likely impeded detection. Stewart's surveys on the Apalachicola River (1992) tallied 5–8 G. barbouri/rkm along four separate stretches of the upper and middle sections. Basking surveys conducted between 2010–2014 within the Apalachicola River Wildlife and Environmental Area averaged 25.6, 6.1, and 6.0 map turtles/rkm along the (lower) Chipola, Apalachicola, and Brothers rivers, respectively (Ricketts 2014).
Enge and Wallace (2008) reported 2.0 G. barbouri/rkm along a 145.2-km stretch of the Choctawhatchee River, with the highest densities, 5–7 turtles/rkm, seen in the river’s upper reaches north of Caryville. The same study documented only four G. barbouri along a 162-km stretch of the Ochlockonee River.
More recently, Hepler et al. (2015) used basking surveys to target G. barbouri along the Chattahoochee and Flint rivers and major tributaries. The highest density reported was 9.7 map turtles/rkm along the Flint River where it was the most common turtle observed, with 3,323 individuals. However, on the Chattahoochee River, only 731 G. barbouri were observed (2.4 map turtles/rkm).
Mays and Hill (2020) surveyed the entire known range of G. barbouri in Florida and observed 5,917 individuals during single-pass surveys across 502 rkm. The Apalachicola River yielded the most G. barbouri observations, with 3,779 individuals observed (21.8 turtles/rkm), followed by the Choctawhatchee, with 1,245 (10.6 turtles/rkm), the Chipola, with 826 (7.1 turtles/rkm), and the Ochlockonee, with 67 (0.7 turtles/rkm). Multiple-pass basking surveys and N-mixture modelling were also used in sections of the Apalachicola and Ochlockonee rivers to estimate detectability and abundance: 2079 G. barbouri along six 2-km sections (12 km total) of the Apalachicola River (173.3 turtles/rkm) with an estimated 21–32% daily detection rate, and 292 G. barbouri along five 5-km sections (25 km total) of the Ochlockonee River (11.7 turtles/rkm) with an estimated 32–51% daily detection rate. The most cautious interpretation of these estimates would be to view the observed 5,917 individual G. barbouri as a minimum count, while acknowledging that the overall Florida population could be as high as 11,601–28,176 map turtles (23–56 turtles/rkm), if the range of detection estimates reflect all rivers surveyed. Overall, the Florida population appears secure with evidence of expansion in both the Choctawhatchee and Ochlockonee drainages.
A summary of the number of individuals recorded per river kilometre is presented in Table S1 (see Supplementary Information).
Habitat and Ecology Information
Graptemys barbouri inhabits free-flowing rivers and streams which support populations of freshwater molluscs (Ewert
et al. 2006). Both limestone-bottomed and sandy-bottomed alluvial streams and rivers are utilized, provided there are ample basking sites consisting of snags and fallen trees (Ernst and Lovich 2009, Sterrett
et al. 2015). Juveniles and males feed on a variety of insects and small snails, whereas larger females shift to a specialized diet of freshwater gastropods and bivalve molluscs (Ewert
et al. 2006, Sterrett
et al. 2020). While
G. barbouri was historically absent from blackwater rivers, the introduced Asian clam
Corbicula may be driving the recent expansion in Florida's Ochlockonee River watershed (Enge and Wallace 2008, Mays and Hill 2020).
Corbicula spp. are a potential food source for other megacephalic map turtles (Aresco and Shealy 2006, Selman and Lindeman 2015) and were first detected in the Ochlockonee River during the 1960s (J. Williams pers. comm.).
Females require as many as 14–20 years to reach maturity at 20 cm carapace length (CL) and 1 kg weight; males mature in three to four years at about 8 cm CL. Females reach their maximum size (largest recorded – 330 mm CL, 3.3 kg) by the age of about 24 years. Generation time for the species is about 20–25 yrs. Males may reach a maximum recorded size of 130 mm CL at about 200 g. Hatchlings measure 30–38 mm and weigh up to 13 g (Ewert
et al. 2006). Females have a prolonged nesting season (late April to early August) with a rather small clutch size (usually 7–10 eggs/clutch, extremes 3–15) and may produce three to five clutches per year, for an annual reproductive output of 25–40 eggs (Ewert
et al. 2006). Nest predation rates are substantial, mainly by raccoons but also crows (Ewert
et al. 2006).
Threats Information
Graptemys barbouri is threatened by habitat degradation, illegal collection, and predation by predators (e.g., raccoons and crows). Local harvesting was previously a concern along the Chipola River, along with “plinking” (i.e., shooting for target practice) (Ewert et al. 2006), but recent evidence is lacking and may indicate that these behaviours have waned. Channel modification, dredging, barge traffic, and pollution threaten its riverine habitat. Upland nesting habitat is also threatened, both by negative impacts of increased ATV use, along with overgrowth caused by varying flood modification devices (e.g., dams). “Deadheading” or removal of dead trees along with channelization has negatively impacted basking sites (Ewert et al. 2006). Demand for water (including both irrigation and drinking) from the rivers G. barbouri inhabit is substantial and likely to increase in the future. A few polluted (EPA “superfund”) sites are located within or immediately connected to G. barbouri habitat along with several major highway crossings, thus the potential of a major industrial spill affecting a significant section of the total population of G. barbouri cannot be discounted (Ewert et al. 2006). Eggs and young are heavily predated by raccoons and crows, affecting recruitment. Raccoons also kill nesting adult females, and to what extent raccoon and crow populations near the nesting sites of G. barbouri are being subsidized by humans remains unknown but is likely increasing (Ewert et al. 2006).
Parts of the Flint River population have been affected by a potentially fatal disease of unknown etiology. The effects of altered flows from increased demand for water and periodic releases from dams on the Flint River and its tributaries (Rugel et al. 2012) on G. barbouri is unknown; the latter has the potential to affect nesting beaches. In upstream reaches of the Choctawhatchee River system there is indication of introgressive hybridization with G. ernsti, which could locally deplete G. barbouri as a pure form (Ewert et al. 2006).
Use and Trade Information
As of 2023, Graptemys barbouri is included in CITES Appendix II, and was previously listed since 2006 in Appendix III (USA). It is in some demand in the global pet trade and persistent collection could impact the species significantly.
Conservation Actions Information
Previously Graptemys barbouri was assessed by IUCN in 1996 as LC/nt under Red List categories and Criteria ver, 2.3, but uplisted to VU in 2011 using version 3.1 (van Dijk 2011). It was listed as G2 (Imperiled) by NatureServe in 2014. At the State Natural Heritage Program level, G. barbouri is S2 (Imperiled) in Alabama and Florida, S3 (Vulnerable) in Georgia. The species is listed ‘State Threatened’ in Florida and Georgia, and of ‘High Conservation Concern’ in Alabama. As of 2023, G. barbouri is included in CITES Appendix II; it was previously in Appendix III (USA) since 2006. Graptemys barbouri is prohibited from most forms of commercial exploitation in Alabama, Florida (prohibits take and possession for commercial or personal use), and Georgia. Following a Species Status Assessment (SSA) as part of a 12-month petition finding, USFWS (2017) found that listing this species under the Endangered Species Act (ESA) was not warranted at this time. However, due to similarity of appearance with Graptemys pearlensis, USFWS (2021) has more recently proposed to list G. barbouri as federally threatened, along with others of the Graptemys pulchra group.
Future river management, including commercial barge traffic, recreational boating, snag removal, sand dredging, water usage, and waterfront residential developments are generally beyond the scope of turtle conservation, but turtles should at least be integrated into management plans and practices, and a few specific sites warrant protected status (Ewert et al. 2006). Continued research and long-term monitoring of G. barbouri populations should continue to establish baseline levels and provide early detection of potential decline.