NOTEWORTHY RECORDS OF FRESHWATER TURTLES IN OAXACA, MEXICO

— Freshwater turtles represent a diverse group of reptiles in Mexico, with the highest diversity being distributed mostly in the southern tropical states. Unfortunately, knowledge regarding their ecology, behavior, cultural importance, and reliable geographic distribution is still scarce; consequently, preventing in-depth spatial analyses that aim to provide a set of conservation plans that effectively shield them from high risks of extinction. Herein, we provide additional geographic records for four endangered species of freshwater turtles in the state of Oaxaca. These records not only expand their distribution range, but also provide information on habitat, and possible environmental threats. Importantly, the record of Chelydra rossignonii confirms its presence in the Papaloapan river basin; and the records of Dermatemys mawii and Claudius angustatus are among the first for the state. Furthermore, we provide an additional locality for Staurotypus triporcatus in Oaxaca.

Mexico is the second richest country with respect to freshwater turtles (van Dijk et al., 2014;Macip-Ríos et al., 2015). However, knowledge on ecology, natural history, and geographic distribution is still incipient for most species (Macip-Ríos et al., 2015). Unfortunately, this group of vertebrates currently faces a set of serious environmental threats, such as habitat loss and overexploitation. Consequently, this has resulted in 64% of these species to be categorized as threatened by the Mexican government (SEMARNAT, 2019), 60% included in the IUCN red list (IUCN, 2021), and on average 30% of these species are considered with high environmental vulnerability by the EVS system (Wilson et al., 2013;Macip-Ríos et al., 2015).
Currently, 15 species of freshwater turtles are known to occur in the state of Oaxaca (Mata-Silva et al., 2015). Of those, the distribution of Chelydra rossignonii, Dermatemys mawii, Staurotypus triporcatus, and Claudius angustatus still remain poorly known (Mata-Silva et al., 2015). For instance, before 2015 the presence of C. rossignonii was still uncertain. To this respect, Ramírez-González and Canseco-Márquez (2015) commented on a record provided by Pérez-Higareda (1978) that was regarded as dubious by Legler and Vogt (2013). This individual was collected in Laguna La Campana, 7 km west of Valle Nacional, and transported and kept at the "Estación de Biología Tropical de Los Tuxtlas, Veracruz". Then, Ramírez-González and Canseco-Márquez (2015) provided photographic evidence of C. rossignonii in semi evergreen tropical forest in the municipality of Santa María Guienagati, in the southeastern extreme of the Sierra Madre de Oaxaca physiographic region (Mata-Silva et al., 2015).
Reliable knowledge on species geographic distribution and especially on those regarded as endangered is among  the first valuable tools for the design and eventual execution of conservation plans. With that in mind, our purpose of this contribution is to document the presence of freshwater turtles in the state of Oaxaca. As it has been demonstrated, geographic records improve the modeling and interpretation of actual distributions of species (Berriozabal-Islas et al., 2020). Furthermore, these records also augment information concerning ecology, behavior, and potential threats, among others. Photo vouchers were deposited in The University of Texas at El Paso (UTEP) Biodiversity Collections (UTEPObs: Herp).  Fig. 7a). The length of the plastral forelobe of this species usually is less than 40% of carapace length, and the dorsal surface of the neck is covered with pointed tubercles (Gibbons et al., 1988). After being photographed, the specimen was left undisturbed at the original site. The locality is surrounded by plantain (Musa paradisiaca), and grazing fields (Brachiaria spp.). The area includes many permanent water bodies that are fed by the Papaloapan River when overflowing events occur. According to several local villagers, this species is captured in the region using fishing line with chicken guts as bait.  Fig. 7a), in the Sierra Madre de Chiapas physiographic region. According to the house owner, this individual, which was kept as a pet, was found at a small river named Escolapa. The vegetation at the site is represented by a mix of medium evergreen forest and riparian vegetation.  199) crossing the state road La Granja-Temascal, near Ejido Chichizapa, municipality of San Miguel Soyaltepec (18.29123° N, 96.35205° W, 50 m a.s.l.; Fig. 7b). This site is surrounded by sugarcane fields. It is worth mentioning that the day before this observation took place, some sugarcane fields had been burned for subsequent cutting and harvesting. The turtle was immediately removed from the road, and then released in a pond near the reported locality but away from the sugarcane fields.          Fig. 7c). The specimen had been kept alive for eventual consumption. Arroyo Santa Ursula is presently embedded in fields with sugarcane. The arboreal vegetation along this creek is dominated mostly by Pachira aquatica, Guazuma ulmifolia, Ochroma pyramidale, and Ceiba pentandra. According to the collector, this species used to be relatively common in the area, but currently individuals are rarely seen.   These records increase our knowledge regarding the current geographic distribution of four species of turtles for the state of Oaxaca, Mexico. We add two important records for Chelydra rossignonii to those already reported by Pérez-Higareda (1978), and Ramírez-González and Canseco-Márquez (2015). We also identified three more records of this species in Global Biodiversity Information Facility (GBIF, 2020a), with two of them reported in 2017 at a locality approximately 30 km west of that reported by Ramírez-González and Canseco-Márquez (2015), (Fig. 7a). The third record is from an arroyo that feeds the Yosocuta reservoir in the Mixteca region. Given the characteristics of the known habitat and elevation range of C. rossignonii, we do not think this locality is part of its natural distribution.
Field observations indicate that fishing of freshwater turtles, at least for Dermatemys mawii and Chelydra rossignonii, is still a relatively common practice by local communities in northern Oaxaca. Even though it seems that turtles have been resilient to the significant agricultural activities in the region, their populations are likely being affected by all kinds of waste that end up in the Papalopan River. For instance, in Arroyo Sal, Santa Úrsula, where Dermatemys mawii was recorded, we observed a significant loss of native vegetation cover and habitat pollution. Furthermore, serious threats to the site increased temporarily in 2008, when a hydroelectric power plant was planned to be built; however, this project did not prosper as the local communities strongly opposed this construction citing lack of consultation and violation of their land rights.
As noted earlier, currently freshwater turtles face numerous environmental threats, and consequently are regarded as a group with high extinction risk (Macip-Ríos et al., 2015). Among the species reported herein, the conservation status for Chelydra rossignonii has not been determined by the Mexican environmental laws (SEMARNAT, 2019), and this is likely in part because until recently this species was considered a subspecies of C. serpentina, which is considered as under Special Protection (Sujeta a Protección Especial). On the other hand, the IUCN red list places this species in the category of Vulnerable due to the development of urban settlements and hunting . More recently, using the EVS system, C. rossignonnii was determined to be a species with high environmental vulnerability (EVS = 17; Wilson et al., 2013).
Dermatemys mawii is known to be facing serious conservation problems, so that is listed as a high risk by national and international conservation assessment systems. Currently, it is classified as Endangered (En Peligro) by SEMARNAT (2019), as Critically Endangered by IUCN, it is included in appendix II of CITES (https://checklist.cites.org), and considered with high environmental vulnerability (EVS = 17) by the EVS system (Wilson et al., 2013). This large turtle is primarily threatened by activities such as agriculture, aquaculture, fishing, hunting, and habitat pollution (Vogt et al., 2006).
Regarding Staurotypus triporcatus, this species is listed as Threatened (Amenazada) and Claudius angustatus is listed as Threatened (En Peligro) (SEMARNAT, 2019). Both of these species are listed as Nearly Threatened by IUCN, with scarce information on their threats (Tortoise andFreshwater Turtle Specialist Group 1996a, 1996b). Furthermore, these two species are considered with high environmental vulnerability (EVS = 14) by Wilson et al. (2013).
Given the current situation of these species on their viability, their exploitation is only allowed with limited and required permits; thereof, the information provided herein is vital for the effective assessment of their populations and the steps that need to be taken to ensure their presence.