Where are the turtles? Looking for Western Chicken Turtles, Deirochelys reticularia miaria, in Mississippi

Turtles are among the world’s most threatened vertebrates, with roughly two-thirds of species listed as threatened or endangered (Buhlmann et al., 2009). Factors such as habitat loss, overharvesting, poaching, disease, and climate change are driving these declines (Stanford et al., 2020), and it is imperative that we carefully monitor turtle populations to determine the extent of declines and prioritize conservation actions for threatened species. Western Chicken Turtles (Deirochelys reticularia miaria Schwartz, 1956) are among the turtles that appear to be experiencing rapid declines. This subspecies is distinct from the other subspecies in morphology (Schwartz, 1956), diet (McKnight et al., 2015c), nesting season (McKnight et al., 2015a, 2018; Carr and Tolson, 2018), and activity season (McKnight et al., 2015a; Bowers 2020). Genetic comparisons are currently limited, but available data also suggest a deep phylogenetic split between the Eastern Chicken Turtle, D. r. reticularia, (Latreille, 1801) and D. r. miaria Schwart, 1956 (Walker and Avise 1998; Hilzinger 2009). Historically, D. r. miaria occurs in Missouri, Oklahoma, Arkansas, Louisiana, Texas, and a small portion of western Mississippi, and the ranges of D. r. miaria and D. r. reticularia are primarily divided by the Mississippi River, which likely acts as a strong barrier to interbreeding

Learned avoidance of trap locations in freshwater turtles

Context. Understanding the effects that learned responses to being captured have on subsequent recapture rates and associated abundance estimates is important for developing accurate descriptions of populations and communities. Although variation in the willingness of individual turtles to be trapped is commonly mentioned in the literature, few studies have experimentally tested learned trap avoidance (or fondness) in turtles. Aims. To determine whether turtles learn to avoid traps, whether repositioning traps will lead to increased capture rates, whether this effect varies among species, and whether such relocations yield more accurate depictions of community structure. Methods. We studied a community of turtles in a small lake in southeastern Kansas that included populations of red-eared slider turtles (Trachemys scripta elegans) and common musk turtles (Sternotherus odoratus). We trapped the lake for 35 consecutive days by using two concurrently deployed groups of traps. One group remained stationary for the duration of the study, whereas traps comprising the other group were moved to new locations on Day 14 and returned to their original locations on Day 28, thus dividing the trapping season into three periods. Key results. For both species, capture rates declined over time. However, traps in the moved group captured more T. s. elegans than did those in the stationary group during the second period and more S. odoratus during the third period. Traps in the moved group also had higher recapture rates in the second period. Population abundance estimates based on captures from the moved group, the stationary group, and the pool of all captures were similar for T. s. elegans, but for S. odoratus the stationary group of traps produced an abundance estimate much lower than those generated from the moved group and the pool of all captures. Conclusions. Both species exhibited learned avoidance of trap locations, but relocating traps had distinct effects on different species, and the accuracy of the observed community structure was improved by relocating traps. Implications. The movement patterns and catchability of individuals of different species within a community must be taken into consideration when developing trapping protocols. Even high-intensity trapping over a long period may not generate an accurate sample of the community if different species use the spatial environment in substantially different ways and learn to avoid trap locations

Good vibrations: A novel method for sexing turtles

The ability to accurately determine the sex of individuals is important for research and conservation efforts. While most species of turtle exhibit secondary sexual dimorphisms that can be used to reliably infer sex, there are some species that are very difficult to sex, and even within many dimorphic species, it is not uncommon to encounter individuals that appear to exhibit both male and female secondary sex characteristics. Therefore, we tested the novel method of using a vibrator to sex turtles by stimulating male turtles to evert their penises. We tested this method on males of four species (three families) with known sexual dimorphisms: spiny softshell turtles (Apalone spinifera; n = 14), western chicken turtles (Deirochelys reticularia miaria; n = 17), Mississippi mud turtles (Kinosternon subrubrum hippocrepis; n = 10), and common musk turtles (Sternotherus odoratus; n = 9). The method accurately sexed 100% of A. spinifera, 64.7% of D. r. miaria, 80.0% of K. s. hippocrepis, and 55.6% of S. odoratus. Despite the low success rates in some species, there are situations in which this method will be useful for researchers working with species that are difficult to sex using external morphological characteristics

Good vibrations: a novel method for sexing turtles

The ability to accurately determine the sex of individuals is important for research and conservation efforts. While most species of turtle exhibit secondary sexual dimorphisms that can be used to reliably infer sex, there are some species that are very difficult to sex, and even within many dimorphic species, it is not uncommon to encounter individuals that appear to exhibit both male and female secondary sex characteristics. Therefore, we tested the novel method of using a vibrator to sex turtles by stimulating male turtles to evert their penises. We tested this method on males of four species (three families) with known sexual dimorphisms: spiny softshell turtles (Apalone spinifera; n = 14), western chicken turtles (Deirochelys reticularia miaria; n = 17), Mississippi mud turtles (Kinosternon subrubrum hippocrepis; n = 10), and common musk turtles (Sternotherus odoratus; n = 9). The method accurately sexed 100% of A. spinifera, 64.7% of D. r. miaria, 80.0% of K. s. hippocrepis, and 55.6% of S.odoratus. Despite the low success rates in some species, there are situations in which this method will be useful for researchers working with species that are difficult to sex using external morphological characteristics

Egg and clutch sizes of western chicken turtles (Deirochelys reticularia miaria)

Chicken turtles (Deirochelys reticularia) are generally characterized as having atypical reproductive characteristics relative to other sympatric emydids. However, the comparatively understudied western chicken turtle (D. r. miaria) has been shown to exhibit some reproductive characteristics that differ from the other subspecies. Therefore, we examined clutch and egg sizes from six D. r. miaria (13 clutches) in Oklahoma and compared the results to values that have been reported for the other two subspecies. Females nested up to three times per year, with clutches ranging from 8-13 eggs per clutch (mean = 10.9). The eggs were 19.4-25.3 mm wide (mean = 22.2 mm). These values are greater than the means reported for the other subspecies, but the differences were not statistically significant

Good vibrations: a novel method for sexing turtles

The ability to accurately determine the sex of individuals is important for research and conservation efforts. While most species of turtle exhibit secondary sexual dimorphisms that can be used to reliably infer sex, there are some species that are very difficult to sex, and even within many dimorphic species, it is not uncommon to encounter individuals that appear to exhibit both male and female secondary sex characteristics. Therefore, we tested the novel method of using a vibrator to sex turtles by stimulating male turtles to evert their penises. We tested this method on males of four species (three families) with known sexual dimorphisms: spiny softshell turtles (Apalone spinifera; n = 14), western chicken turtles (Deirochelys reticularia miaria; n = 17), Mississippi mud turtles (Kinosternon subrubrum hippocrepis; n = 10), and common musk turtles (Sternotherus odoratus; n = 9). The method accurately sexed 100% of A. spinifera, 64.7% of D. r. miaria, 80.0% of K. s. hippocrepis, and 55.6% of S. odoratus. Despite the low success rates in some species, there are situations in which this method will be useful for researchers working with species that are difficult to sex using external morphological characteristics

Nocturnal basking in freshwater turtles: A global assessment

Diurnal basking (“sunning”) is common in many ectotherms and is generally thought to be a behavioural mechanism for thermoregulation. Recent studies have reported the occurrence of nocturnal basking in a few distantly-related species of freshwater turtles, but the true extent of this behaviour is unknown, and it may be underreported due to sampling biases (e.g., not surveying for turtles at night). Therefore, we initiated a global, collaborative effort to systematically document and quantify basking activity (diurnal and nocturnal) across a wide range of freshwater turtle species and locations. We conducted camera trap or manual surveys in North America, the Caribbean, Europe, Asia, Africa, the Seychelles, and Australia. We collected 873,111 trail camera photographs (25,273 hrs of search effort) and obtained data on 29 freshwater turtle species from seven families. Nocturnal basking was documented in 13 species, representing six families (Chelidae, Emydidae, Geoemydidae, Kinosternidae, Pelomedusidae, and Trionychidae), including representatives in Central America, Trinidad and Tobago, Africa, the Seychelles, Asia, and Australia. Nocturnal basking was restricted to tropical and sub-tropical locations, suggesting that environmental temperature plays a role in this behaviour. However, the primary factors driving nocturnal basking are yet to be determined and may vary geographically and by species. The frequency and duration of nocturnal basking varied among species and seasons, but nocturnal basking events were often substantially longer than diurnal events. This is the first study to document a widespread occurrence of nocturnal basking, and our results suggest that nocturnal basking may be a common, although overlooked, aspect of many species’ ecology