The pet trade is one of the main introduction pathways of invasive alien species. Exotic freshwater turtles are a worldwide paradigm of invasion from imported pets that are later abandoned into aquatic ecosystems by their owners or escape confinement (Lockwood et al., 2019). In Spain, alien turtles outcompete the native endangered terrapins: the European pond turtle, Emys orbicularis (Linnaeus, 1758), and the Spanish terrapin, Mauremys leprosa (Schweigger, 1812) (Polo-Cavia et al., 2010a, 2010b, 2011). The trade of red-eared slider Trachemys scripta subsp. elegans (Wied, 1838) was banned in Europe in 1997 following salmonellosis outbreaks in children and biodiversity concerns (Woodward et al., 1997). However, other freshwater turtle species such as Chrysemys picta (Schneider, 1783), Graptemys spp., Macrochelys temminckii Troost, 1835, alien Mauremys spp., Pelomedusa subrufa (Bonnaterre, 1789), Pelusios spp., or even a subspecies of the banned taxon (Trachemys scripta subsp. scripta (Thunberg, 1792)) have been imported into Spain (Cites Trade Database, 2020) although they may also be reservoirs of pathogens and invade aquatic ecosystems (e.g., Martínez-Silvestre et al., 2015; Sancho et al., 2015; Back et al., 2016). In 2013, the Spanish legislation (Royal Decree 613/2013) banned the trade of Trachemys scripta (Thunberg in Schoepff, 1792), Chrysemys picta and Pseudemys peninsularis Carr, 1938. Three years later, the list of invasive alien species of Union concern also banned Trachemys scripta according to the Commission implementing regulation 2016/1141. Despite these regulation advances, many unbanned pond turtle species have been imported in the last two decades, including some dangerous species such as the snapping turtle Chelydra serpentina (Linnaeus, 1758) (Cites Trade Database, 2020). To date, up to 21 freshwater alien chelonian taxa have been reported in Spanish natural, seminatural or artificial wetlands: Apalone ferox (Schneider, 1783), Chrysemys picta, Chelydra serpentina, Graptemys ouachitensis (Cagle, 1953), Graptemys pseudogeographica (Gray, 1831), Macrochelys temminckii, Mauremys mutica (Cantor, 1842), Mauremys reevesii (Gray, 1831), Mauremys sinensis (Gray, 1834), Pseudemys concinna (Le Conte, 1830), Pseudemys nelsoni Carr, 1938, Pseudemys rubriventris (Le Conte, 1830), Pelodiscus sinensis (Wiegmann, 1835), Pelomedusa subrufa, Trachemys decussata (Gray, 1831), Trachemys emolli (Legler, 1990), Trachemys ornata (Gray, 1831), Trachemys scripta subsp. elegans, Trachemys scripta subsp. scripta, Trachemys scripta elegans x Trachemys scripta scripta, and Trachemys scripta subsp. troostii (Holbrook, 1836) (Mateo et al., 2011; Balmori, 2014 and references therein; Campos-Such et al., 2015; Cruz et al., 2015; Martínez-Silvestre et al., 2015; Poch et al., 2020).

The case of alien taxa of the genus Mauremys is of particular concern due to their ability to hybridise with the native species Mauremys leprosa (Nickl, 2015; Sancho et al., 2020). Between 2006 and 2019, 55,825 live individuals of Reeves‘ pond turtle Mauremys reevesii and 45,320 live individuals of the Chinese stripe-necked turtle Mauremys sinensis have been imported into Spain, mainly from China, Hong Kong, Taiwan and Japan (Cites Trade Database, 2020). Although these species have been imported more recently and in much smaller quantities than Trachemys scripta elegans (up to 900,068 individuals until the year 2000; Cites Trade Database, 2020), their eventual release into the natural environment represents a conservation concern, particularly for the native Mauremys leprosa. Until now, the presence of naturalised specimens of M. sinensis was documented in the regions of Valencia and Catalonia (Campos-Such et al., 2015; Martínez-Silvestre et al., 2015, 2019), whereas M. reevesii was cited in Galicia (Ayres, 2016) and Catalonia (Poch et al., 2020).

Considering that early detection is an essential tool for efficient management, new citations of Mauremys reevesii and Mauremys sinensis from southern Spain were compiled from different sources (mainly naturalists, amateurs or nature managers) between 2009 and 2020. All records were georeferenced, using the UTM projection and the ETRS1989 reference system, in extended zone 30, in accordance with European standards. Only those citations that could be validated through photographs or captured specimens were included. In total, 15 new validated records were collected: seven records corresponded to M. reevesii and eight records to M. sinensis (Table 1; Fig. 1). All M. reevesii records showed the characteristic yellowish striping and blotching extending down the neck from the snout, whereas M. sinensis showed the characteristic parallel, narrow yellow stripes on their heads, necks and parts of their legs (Fig. 1).

Fig. 1.— Specimens of Mauremys reevesii observed in Málaga (left) and Mauremys sinensis found in Laguna del Portil Natural Reserve, Huelva (right). Photos by Juan Pablo González de la Vega©. Fig. 1.— Ejemplares de Mauremys reevesii observados en Málaga (izquierda) y Mauremys sinensis encontrado en la Reserva Natural Laguna del Portil, Huelva (derecha). Fotos de Juan Pablo González de la Vega©.

In sum, the new records included five of the eight provinces of Andalusia. Most of them (12/15) were found in artificial lakes, while the rest were found in protected areas (the ‘Arroyo Negro’ and ‘Laguna del Portil’ natural reserves), sharing the habitat with natural populations of M. leprosa. All locations were adjacent to urban centres, which may favour the reception of abandoned pets. Both species constitute new records to Andalusia.

The results suggest that the introduction of Mauremys reevesii and M. sinensis is not an anecdotal fact, but rather reproduces the ‘sale-release-naturalisation-invasion’ process that has already occurred with other exotic freshwater turtles marketed as pets and other regions (Sancho & Lacomba, 2016; Poch et al., 2020). There are several limitations for a new record to be reported: (i) the taxon must ‘cross’ a person’s view or be captured, and detectability decreases at low population size (Metha et al., 2007). In fact, the M. sinensis specimen found at ‘Laguna del Portil’ Natural Reserve was captured after six days of an alien turtle control campaign that used six baited fyke nets per day (lake surface = 12 ha). (ii) The taxon must be differentiated from a native taxon and be correctly identified. For this purpose, a high-quality picture or a captured specimen is needed, as well as certain expertise. (iii) The new record must be published. As a consequence, the current abundance of alien Mauremys spp. in the field may be much higher than documented in publications (García-de-Lomas et al., 2016; Vall-llosera & Cassey, 2017). Therefore, further surveillance of aquatic ecosystems is recommended to detect the presence of alien Mauremys species early and to implement rapid response actions.

Moreover, the increasing records of alien Mauremys spp. in Spain provides further evidence that all the turtle taxa marketed as pets are prone to be released and become a conservation threat. This fact suggests that banning particular species in the form of ‘blacklists’, far from solving the problem, may favour the trade of unbanned species (García-de-Lomas & Vilà, 2015). Thus, banning the movement and sale of all freshwater alien turtles apart from specifically permitted non-invasive, non-harmful species (in the form of a ‘white’ list) could help reverse the current trend of naturalisation and invasion.