Rarely naturalized, but widespread and even invasive: the paradox of a popular pet terrapin expansion in Eurasia

Abstract

The North American terrapin, the red-eared slider, has globally recognized invasive status. We built a new extensive database using our own original and literature data on the ecology of this reptile, representing information on 1477 water bodies throughout Eurasia over the last 50 years. The analysis reveals regions of earliest introductions and long-term spatio-temporal dynamics of the expansion covering now 68 Eurasian countries, including eight countries reported here for the first time. We established also long-term trends in terms of numbers of terrapins per aquatic site, habitat occupation, and reproduction success. Our investigation has revealed differences in the ecology of the red-eared slider in different parts of Eurasia. The most prominent expression of diverse signs of invasion success (higher portion of inhabited natural water bodies, higher number of individuals per water body, successful overwintering, occurrence of juvenile individuals, successful reproduction, and establishment of populations) are typical for Europe, West Asia and East Asia and tend to be restricted to coastal regions and islands. Reproduction records coincide well with the predicted potential range based on climatic requirements but records of successful wintering have a wider distribution. This invader provides an excellent and possibly unique (among animals) example of wide alien distribution, without the establishment of reproducing populations, but through the recruitment of new individuals to rising pseudopopulations due to additional releases. Therefore, alongside the potential reproduction range, a cost-effective strategy for population control must take in account the geographical area of successful wintering.

Modelling the Distribution of Three Invasive Freshwater Turtles in Mainland Guadeloupe: Analysis of Their Presence, Abundance and Co-Occurrence

“…Indeed, Breuil [16] suggested that Trachemys species do not reproduce on mainland Guadeloupe. However, local climatic conditions in Guadeloupe fit particularly well with those associated with reproduction records of invasive populations of T. scripta [74]. In addition, observations of Trachemys in full courtship in the urban area of Les Abymes (Grande-Terre; see Video S1, Supplementary Materials) and regular observations of various ontogenic stages, including juveniles, are strongly suggestive that the Guadeloupe populations are reproducing.…”

“…Third, both Trachemys species, and possibly P. castaneus, might be well adapted today to the local environment in Guadeloupe and be self-sustainable without additional introductions. The wide alien distribution of freshwater turtles may not necessarily imply the establishment of reproducing populations but may in some areas be explained by the recruitment of new individuals through regular additional releases [74]. Indeed, Breuil [16] suggested that Trachemys species do not reproduce on mainland Guadeloupe.…”

Reproductive Output in the Pond Slider, Trachemys scripta, in Arkansas, USA, with Range-Wide Comparisons

“…Thus, the reproductive output of T. s. elegans (as measured by RCM per clutch) is more than twice that of T. s. scripta (see also Moll and Moll 1990), despite apparently similar nesting season lengths (Ernst and Lovich 2009:459) and annual clutch frequencies (Table 3), and much greater known longevity (47 yrs in T. s. elegans , Ernst and Lovich 2009; 25 yrs in T. s. scripta Gibbons 1987). The reason that T. s. elegans evolved such high reproductive output over a longer life compared with T. s. scripta is not yet clear, but no doubt contributes to its success as an invasive taxon around the world (Lowe et al 2000; Reshetnikov et al 2023).…”

“…Trachemys scripta is one of the most prolific turtles in North America, producing up to 30 eggs/clutch and depositing up to 5 clutches/yr (Ernst and Lovich 2009), contributing to its success as one of the most invasive species on the planet (Lowe et al 2000;Reshetnikov et al 2023). The species has wide distribution and abundance; therefore, data on reproductive output are available for .40 populations within the native range (Table 1), although very few data are available from the southwestern part of the species' range (particularly in and near Arkansas).…”