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Detailed studies on the natural history of snakes are essential for ecological hypothesis-driven research and effective conservation. Herein, we studied the diet composition and morphology of Yucatecan Cantils (Agkistrodon russeolusGloyd 1972 [Serpentes: Viperidae]), an understudied viperid species endemic to the Yucatán Peninsula. We collected data from live free-ranging snakes; freshly road-killed snakes and snakes deliberately killed by local villagers; and museum specimens and literature sources. We compared their age classes, sexes, and color morphs. Data came from snakes from Yucatán, Quintana Roo, and Campeche in Mexico, and two records were from northern Belize, comprising most of the species' distribution range. Examination of 76 individuals resulted in 77 prey items from 68 snakes. Results indicated that A. russeolus is a generalist-opportunistic predator that feeds on a wide variety of vertebrates, but primarily on lizards and small mammals and less frequently on birds, snakes, and anurans. Geographic patterns in the diet and morphology of A. russeolus were evident: snakes from the coastal region were smaller in body size and less heavy bodied and with a heavily lizard-based diet, whereas snakes from both dry and moist forest regions were larger and heavier and their diet was primarily mammal based. We did not detect differences in diet composition among age classes because lizards and mammals were eaten at all stages of life, but an “ontogenetic telescope” was evident; that is, the importance of mammals increases with snake body size and the spectrum of prey types consumed also broadens. Males had longer tails than females, and females were light colored more often than males, but other morphological characteristics were similar between the sexes. The sexes and color morphs did not differ in diet composition. We did not detect dietary composition variations between seasons, and our data indicate that this species can feed year-round opportunistically. Because of increasing environmental pressures within its range, studies are urgently needed to elucidate other critical aspects of the ecology of this viperid species.

The known distribution of Bothriechis aurifer (Salvin, 1860) is outdated, which impedes an accurate evaluation of its conservation status. Here, we clarify the locality-level distribution of B. aurifer and announce a 101-km range extension. Based on this and other data, we recommend its recategorization as Endangered under the International Union for Conservation of Nature's Red List of Threatened Species, and its addition to Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora. We also discuss problematic previous records and offer conservation recommendations. A complete Spanish translation of this paper is available in the Supplemental Data. Una traducción completa al español de este artículo está disponible en los Datos Suplementarios.

The Tehuantepec Isthmus rattlesnake (Crotalus ehecatl) is a poorly known species endemic to Mexico. We describe its diet, morphological variation, life history traits and activity patterns based on data from field encounters, museum specimens, and published data. Its diet consists almost exclusively of mammals, with no detected ontogenetic shift or sexual differences in prey type, and with feeding happening mainly in the rainy season. As the first detailed study on the feeding ecology of C. ehecatl, it adds six new prey species and suggests a homogeneous diet among age classes and sexes, but not among seasons. Crotalus ehecatl does not present sexual dimorphism in snout-vent length, head length or total length, but males have significantly longer tails than females, possess fewer ventral scales, more subcaudal and anterior intersupraocular scales. Crotalus ehecatl showed a unimodal activity pattern with peak activity in the summer, with crepuscular and nocturnal activity during the warmer months, and diurnal activity during the cooler months. The timing of C. ehecatl reproductive events, is similar to other rattlesnakes from temperate and tropical zones. Additional studies on this and related species would help to understand how the ecology of Neotropical rattlesnakes differs from rattlesnakes of more temperate zones.

The male of Craugastor yucatanensis (Lynch, 1965) is described for the first time, as the original description was based on four females. The advertisement call is described and additional morphological data on females are presented. Also, information is provided on the sexual dimorphism and natural history of the species.

The helminth and pentastomid fauna of 50 specimens of Crotalus tzabcan from the Yucatán Peninsula, Mexico is documented. The examination revealed the presence of three nematode species ( Hastospiculum onchocercum , Hexametra boddaertii , and Travassosascaris araujoi ), and one pentastomid ( Porocephalus crotali ). The threee nematode species had the same prevalence (2%), while the pentastomid had a higher prevalence (8%). The pentastomid P. crotali was the most abundant and intense parasite, although it was only found in four snake hosts. Crotalus tzabcan acts as definitive host for the adult helminths and pentastomids, with rodents as the probable intermediate hosts. This work represents the first systematic survey on the parasitic helminth and pentastomid fauna of C. tzabcan , and includes four new geographical records. Additionally, a checklist of helminths and pentastomids reported for Crotalus and Sistrurus is provided. To date, a total of 32 helminth and 7 pentastomid species have been recorded as parasites of rattlesnakes. Nematoda possessed the highest species richness. The genera with the highest number of host species were Mesocestoides and Hexametra , followed by Kalicephalus . The rattlesnake species with the highest number of reported parasites was C. durissus (18 nematodes and 2 pentastomids).

Sentinel species such as crocodilians are used to monitor the health of ecosystems. However, few studies have documented the presence of zoonotic diseases in wild populations of these reptiles. Herein we analyzed 48 serum samples from Crocodylus acutus ( n  = 34) and C. moreletii ( n  = 14) from different sites in the state of Quintana Roo (Mexico) to detect antibodies to Leptospira interrogans by means of a microscopic agglutination test (MAT). Crocodylus acutus and C. moreletii tested positive to 11 and 9 serovars, respectively, with Grippotyphosa being the serovar with the highest prevalence in Cozumel island (100%), Banco Chinchorro Biosphere Reserve (70.6%), and Río Hondo (100%), while in Chichankanab Lake, it was Bratislava (75%). Titers ranged from 1:50 to 1:3200, and the most frequent was 1:50 in all study sites. Leptospira is present in fresh and saltwater individuals due to the resistance of the bacterium in both environments. Cases of infected people involved with crocodile handling and egg collection suggest that these reptiles could play an important role in the transmission of leptospirosis. Preventive medicine programs should consider the monitoring of reptiles, and testing the soil and water, to prevent outbreaks of leptospirosis in facilities containing crocodiles.

Micrurus apiatus es una serpiente de coral poco conocida que se distribuye desde el este del Istmo de Tehuantepec, México hasta el oeste de Honduras, incluyendo la Península de Yucatán. Describimos su dieta, variación morfológica y patrones de actividad basados en datos de 107 especímenes de museos provenientes de los estados de Campeche, Quintana Roo y Yucatán, así como datos publicados. Su dieta consiste principalmente de otras serpientes, no fueron encontradas preferencias en el tipo de presa entre sexos, edades o estaciones; su alimentación ocurre a lo largo del año, observándose un ligero aumento en la temporada de lluvias. Agregamos ocho presas nuevas, incluyendo a Adelphicos visoninum, que representa un nuevo registro geográfico para Campeche, y sugerimos una dieta homogénea entre clases de edad, sexos y estaciones. Micrurus apiatus presenta dimorfismo sexual en longitud hocico-cloaca, longitud total, largo de la cabeza, escamas ventrales (mayor en hembras), longitud de cola y escamas subcaudales (mayor en machos). Micrurus apiatus mostró actividad durante todo el año, con un patrón de actividad aparentemente bimodal, con un pico de actividad a fines del invierno y primavera y el otro pico a mediados de verano y otoño. El momento de los eventos reproductivos de M. apiatus es similar al de otras serpientes de coral con patrón de color de anillos negros dispuestos en mónadas. Estudios adicionales sobre esta especie y otras relacionadas aumentará nuestra comprensión sobre cómo su ecología difiere de aquellas especies con un patrón de anillos negros dispuestos en tríadas y bicolores.

The variation in temperament among animals has consequences for evolution and ecology. One of the primary effects of consistent behavioral differences is on reproduction. In chelonians some authors have focused on the study of temperament using different methods. In our research our first aim was i) establish a methodology to determine the degree of boldness among individuals Rhinoclemmys areolata . Our second aim was to ii) determine the role boldness plays during reproduction, with emphasis on courtship and copulation, considering a) the interactions between males and females, and b) competition between males. We used 16 sexually mature individuals of each sex. Males were observed in four different situations and 17 behavioral traits were recorded. We selected 12 traits that allowed us distinguish between the bolder and the shier individuals and found that five behavioral traits were specific for bolder individuals and five others for shier individuals. In a second step, we observed a male in presence of a female and recorded courtship behaviors and breeding attempts. Bolder individuals did not display courtship behaviors and just attempted to copulate. Shier individuals displayed courtship behaviors and copulation attempts were rarely observed. Finally, in the simulations that compared two males in the presence of a female we noticed that bolder individuals displayed courtship behaviors while the shier ones simply ignored the female. Our results first allowed us to determine which methodology is the best to determine temperament in turtles. Secondly, temperament seems to be an important factor in modulating interaction between males and females. Bolder individuals have an advantage during competition and display courtship behaviours only if other males are present. Shier males displayed courtship behaviors and only try to copulate when no competitors were present. These two different temperament-dependant strategies are discussed in terms of ecology, evolution and management.

We rescued 22 Crocodylus moreletii adult individuals from an area designated to become a theme park in the Riviera Maya tourist corridor in Quintana Roo, Mexico. They were translocated between January and February 2018 to Río Yalikín stream located in the wildlife sanctuary Área de Protección de Flora y Fauna Yum Balam. Our goal was to evaluate the survival and dispersal of the translocated specimens, and to measure their possible impact on the local crocodile populations (C. moreletii, C. acutus, and possible hybrids) already established in the Yum Balam Protected Area. We conducted diurnal and nocturnal field surveys from January to June 2019 to search for translocated crocodiles, and to estimate abundance, size class structure, and sex ratio of the population (local and translocated crocodiles). Ten of the translocated crocodiles (five females and five males) were tagged with very high frequency (VHF) radiotransmitters with global positioning system datalogger. After spending 36 h at a fixed-point location and utilizing a boat to track animals (2,748 km traveled and 254 h expended), we did not recapture any of the translocated crocodiles, and we failed to detect individuals with radiotransmitters. We detected, however, VHF signals from three individuals outside of Río Yalikín area during an aerial survey. The spatial distribution of all crocodiles was aggregated with possible segregations as they moved away from the stream's delta. The estimated total abundance was 26 crocodiles with an encounter rate of 3.64 individuals/km. The population structure by size classes consisted of yearlings (1.14%), juveniles (9.66%), subadults (11.36%), adults (13.64%), and large adults (5.68%). An important fraction of sightings (58.52%) was assigned to the “Eyes Only” category. Twenty-six crocodiles were captured (12 C. moreletii and 14 C. acutus). The observed sex ratio for both species was 1:1 during our study. Our results concerning the dynamics of the local population and the possible impacts of the introduced individuals provide relevant information to determine the best practices that wildlife managers should pursue to achieve sustainable management and conservation of crocodiles. Rescatamos 22 individuos adultos de Crocodylus moreletii de un área designada para convertirse en un parque temático en el corredor turístico de la Riviera Maya en Quintana Roo, México. Estos individuos fueron translocados entre enero y febrero de 2018 al arroyo Río Yalikín ubicado en el santuario de vida silvestre Área de Protección de Flora y Fauna Yum Balam. Nuestro objetivo era evaluar la supervivencia y la dispersión de los ejemplares translocados y medir su posible impacto en la población local de cocodrilos (C. moreletii, C. acutus y posibles híbridos) ya establecida en el Área Protegida de Yum Balam. Realizamos muestreos de campo diurnos y nocturnos de enero a junio de 2019 para ubicar cocodrilos translocados y estimar la abundancia, la estructura de clases de tamaño y la proporción de sexos de la población (cocodrilos locales y translocados). Diez de los cocodrilos translocados (5 hembras y 5 machos) fueron marcados con radiotransmisores de frecuencia muy alta (VHF) con registrador de datos de sistema de geoposicionamiento global. Después de pasar 36 horas en un punto fijo y de utilizar una embarcación para rastrear a los animales (2,748 km recorridos y 254 horas empleadas), no recapturamos a ninguno de los cocodrilos translocados y no detectamos individuos con radiotransmisores. Sin embargo, detectamos señales VHF de tres individuos fuera del área de Río Yalikín durante un muestreo aéreo. La distribución espacial de todos los cocodrilos fue agregada con posibles segregaciones a medida que se alejaban del delta del arroyo. La abundancia total estimada fue de 26 cocodrilos con una tasa de encuentro de 3.64 individuos/km. La estructura de la población por clases de tamaño consistió en crías (1.14%), juveniles (9.66%), subadultos (11.36%), adultos (13.64%) y adultos grandes (5.68%). Una fracción importante de los avistamientos (58.52%) se asignó a la categoría “Sólo Ojos.” Se capturaron 26 cocodrilos (12 C. moreletii y 14 C. acutus). La proporción de sexos observada para ambas especies fue de 1:1 durante nuestro estudio. Nuestros resultados sobre la dinámica de la población local y los posibles impactos de los ejemplares introducidos aportan información relevante para determinar las mejores prácticas que los administradores de la fauna silvestre deben seguir para lograr un manejo sostenible y la conservación de los cocodrilos.