Rattlesnake (Crotalus spp.) distribution and diversity in Zacatecas, Mexico

Abstract

Mexico is home to a large number of reptile species and has one of the greatest diversities of venomous snakes, among which the rattlesnakes pertaining to the Crotalus genus stand out. Out of more than 40 species in the country, nine are found in Zacatecas: C. aquilus, C. atrox, C. basiliscus, C. lepidus, C. molossus, C. polystictus, C. pricei, C. scutulatus and C. willardi. Although these reptiles are important, due to their relevance in terms of ecology, cultural use and public health, their conservation is impacted by multiple factors, such as habitat fragmentation and indiscriminate killing. Thus, most species within this genus are found in some type of risk category at both the national and international level. The purpose of this study was to determine the potential distribution and diversity of rattlesnakes at the municipal level in the understudied state of Zacatecas. To do this, we analyzed and described the global distribution of nine rattlesnake species by building species distribution models, which determined their potential distribution based on a set of ecological variables and presence records. The resulting models were used to assess the diversity of rattlesnake species potentially present in each municipality within the state. Thirty-nine (67.24 %) out of fifty-eight municipalities registered at least one rattlesnake species. Fresnillo, Sombrerete and Valparaíso were some of the municipalities showing greatest diversity. Moreover, C. atrox, C. lepidus, C. molossus and C. scutulatus were the most widely found species in the state. On the other hand, C. basiliscus, C. polystictus, C. pricei and C. willardi were rarely spotted and so, information on their distribution patterns within Zacatecas is limited. Finally, the areas having the largest potential for the distribution of these species were defined. These findings should make field work much more time- and cost-effective, facilitating the collection of in situ data that are useful for management and conservation plans of these species in Zacatecas.

Potential Distribution of the Long-tailed Rattlesnake, <em>Crotalus stejnegeri </em>Dunn 1919 (Squamata: Viperidae): A Rare and Under-sampled Species

“…These results are consistent with those obtained for other rattlesnake species where temperature and precipitation ranges are important environmental factors in their distribution (Sunny et al, 2019;Lara-Galván et al 2020). Although it has also been suggested that these factors go beyond influencing physiological aspects of the species such as reproductive activity, they also influence other aspects related to their survival such as densities of predators, prey and competitors, weed cover and relative humidity (Yañez-Arenas et al 2020).…”

“…This observation aligns with Robert Meidinger's comment (in Uetz et al 2023), questioning the altitudinal range of 1,780 m asl as being too high for C. stejnegeri, as evident by the low habitat suitability around Yamiroba in the municipality of San Dimas, Durango (Figures 2 and 3). This is consistent with the altitudinal preferences of rattlesnake species (Lara-Galván et al 2020;Serna-Lagunes et al 2020), highly adapted to their elevation ranges to develop their physiological activities. On the other hand, Reyes-Velasco et al (2013) suggested that C. stejnegeri could also be found in Nayarit, Sonora, and Chihuahua, although Figure 3 shows a high suitability of the habitat for the species in the north of Nayarit and southwest of Sonora, the state of Chihuahua does not present a marked suitability environment for the species.…”

“…However, the significant variability in this relationship is less consistent or more variable in specific areas. The results obtained by Lara-Galván et al (2020) for C. basiliscus in the Mexican state of Zacatecas are similar to those presented here for C. stejnegeri, but differ in the annual range temperature (Bio7) for C. basiliscus and mean temperature of the driest quarter (Bio9) for C. stejnegeri. This suggests that C. stejnegeri may be more adapted to warm and dry climates, C. basiliscus may show a preference for cooler and wetter climatic conditions.…”

Addressing the global snakebite crisis with geo-spatial analyses – Recent advances and future direction

“…Just as snakebite risk and incidence change with season, weather and time of day depending on human and snake activity patterns, they also show long-term temporal trends based on changes in climate, weather anomalies ( Ediriweera et al, 2018 ) and human land use. Notably, this is not only of medical relevance, but also poses important challenges to conservation ( Lara-Galván et al, 2020 ). As with other human-wildlife conflicts, the general public usually perceives snakes as a threat, but is less aware that they themselves also pose a threat to wildlife ( Nyhus, 2016 ).…”