Academic editor: R. Jadin
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
Lara-Galván JL, Martínez-Montoya JF, Sigala-Rodríguez JJ, Esparza-Estrada CE, Rosas-Rosas OC, Ávila-Herrera L, Barbosa AM (2020) Rattlesnake (
Mexico is home to a great diversity of reptile species, including a large number of endemics, with 864 different species having been reported by 2014 (
Another problem that Zacatecas faces is the lack of publications on regional or municipal studies with venomous snakes and herpetofauna in general. There are only specific notes recorded on the state rattlesnake species of the
In general, the studies on Mexican rattlesnakes have focused on their distribution at a large scale or on a single species. An example of this is the study by
One way to determine distribution patterns is using species distribution modeling techniques (
Due to the lack of information on rattlesnakes of Zacatecas, their local importance and the concern by state agencies, we launched a study on the distribution patterns of the nine species of rattlesnakes in Zacatecas to be used in rattlesnake management and conservation in the state. The aim of this paper is to combine the literature, field work and Species Distribution Models or
The state of Zacatecas is located in Mexico’s central northern region (Figure
Location of the state of Zacatecas and their climate types (modified from
Location of Zacatecas in central-northern Mexico and Physiographic Provinces in which this state is situated (map based on
To determine the potential distribution of rattlesnakes in Zacatecas, we gathered records on their global presence. In order to do this, we conducted queries in the databases of the Global Biodiversity Information Facility:
Number of presence records shown by species of the
Group Studied | Species | Total occurrence records | Records pertaining to Zacatecas |
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Endemic to Mexico |
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127 | 7 |
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115 | 3 | |
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90 | 14 | |
Non-endemic to Mexico |
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999 | 39 |
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375 | 52 | |
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494 | 67 | |
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117 | 2 | |
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1,011 | 61 | |
|
84 | 3 |
According to
We prepared distribution models using package
We utilized a set of environmental variables that are typically associated with the presence of the species, the 19 bioclimatic variables from the WorldClim, version 2.0 database (
Regarding variable selection (Table
Variables selected by the
Group Studied | Species | Variables used in |
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Endemic |
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Non-Endemic |
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Model evaluation was based on the criterion of area under the curve (
To determine the rattlesnake number at the municipal level, we used the available presence records and prepared a list of the species observed at each municipality. Likewise, the list included the results of potential distribution models (Figures
Presence and global potential distribution of
Based on the potential distribution models for each rattlesnake species found in Zacatecas, two localities per municipality were selected (three in the case of the Pinos, Loreto and Valparaíso municipalities). Thus, the field work in this study comprised a total of 48 localities throughout 22 municipalities within the state. These 22 municipalities were chosen randomly to include various regions throughout the state. Moreover, in these municipalities, we selected localities situated within the areas of greatest suitability as predicted by the models. A map of Mexican localities was overlapped to the potential distribution maps to conduct this geographical selection (
There was significant variation on the number of records for the rattlesnakes present in Zacatecas, ranging from 1,011 records for
In the species distribution modeling, the most informative environmental variables for the models were
In Zacatecas, the potential areas for the distribution of
The western diamondback rattlesnake,
Presence and global potential distribution of
The known distribution of
Presence and global potential distribution of
The rock rattlesnake
Presence and global potential distribution of
The black-tailed rattlesnake (
Presence and global potential distribution of
In the case of
Presence and global potential distribution of
Regarding its global distribution, it extends from Zacatecas to Mexico City and it is similarly reported in the states of Aguascalientes, Jalisco, Guanajuato, Michoacán, Querétaro and the State of Mexico, all of them exhibiting a significant number of records. In the southwestern portion of its known distribution, the record which is found closest to Colima was in the municipality of Tuxpan in Jalisco. Several authors mentioned that this species
Unlike other species with a greater number of records, there were only two presence records of
Presence and global potential distribution of
During the field work, no direct observations or skin sheddings were identified for this species, although there are two records a few kilometers from the Zacatecas border. One of them is located in the municipality of Mezquitic, Durango (
Presence and global potential distribution of
Finally, the occurrence data and the potential distribution map of
Presence and global potential distribution of
Thirty-nine (67.24 %) out of the fifty-eight municipalities (Table
Rattlesnake diversity per municipality in Zacatecas, Mexico, based on published records, collection records and field work
Municipality |
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Species |
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Apozol | – | |||||||||
Apulco | – | |||||||||
Atolinga | x | 1 | ||||||||
Benito Juárez | – | |||||||||
Calera de Víctor Rosales | x | 1 | ||||||||
Cañitas de Felipe Pescador | x | x | 2 | |||||||
Concepción del Oro | x | x | x | x | 4 | |||||
Cuauhtémoc | x | 1 | ||||||||
Chalchihuites | x | x | x | x | 4 | |||||
El Plateado de Joaquín Amaro | x | x | x | x | 4 | |||||
El Salvador | – | |||||||||
Fresnillo | x | x | x | x | x | 5 | ||||
Genaro Codina | x | x | x | x | 4 | |||||
General Enrique Estrada | – | |||||||||
General Francisco R. Murguía | x | x | 2 | |||||||
General Pánfilo Natera | x | 1 | ||||||||
Guadalupe | x | x | x | x | 4 | |||||
Huanusco | x | x | x | 3 | ||||||
Jalpa | x | x | 2 | |||||||
Jerez | x | x | 2 | |||||||
Jiménez del Téul | x | x | 2 | |||||||
Juan Aldama | – | |||||||||
Juchipila | – | |||||||||
Loreto | x | 1 | ||||||||
Luis Moya | x | 1 | ||||||||
Mazapil | x | x | x | x | 4 | |||||
Melchor Ocampo | x | x | x | 3 | ||||||
Mezquital del Oro | – | |||||||||
Miguel Auza | – | |||||||||
Momax | – | |||||||||
Monte Escobedo | x | x | x | x | 4 | |||||
Morelos | x | x | 2 | |||||||
Moyahua de Estrada | x | 1 | ||||||||
Nochistlán de Mejía | x | x | x | 3 | ||||||
Noria de Ángeles | – | |||||||||
Ojocaliente | x | x | x | 3 | ||||||
Pánuco | x | x | 2 | |||||||
Pinos | x | x | x | x | 4 | |||||
Río Grande | x | x | 2 | |||||||
Santa María de la Paz | – | |||||||||
Sain Alto | x | x | 2 | |||||||
Sombrerete | x | x | x | x | x | x | 6 | |||
Susticacán | – | |||||||||
Tabasco | x | 1 | ||||||||
Tepechitlán | – | |||||||||
Tepetongo | – | |||||||||
Teúl de González Ortega | x | 1 | ||||||||
Tlaltenago de Sánchez Román | x | x | 2 | |||||||
Trancoso | x | x | 2 | |||||||
Trinidad García de la Cadena | – | |||||||||
Valparaíso | x | x | x | x | x | x | 6 | |||
Vetagrande | x | 1 | ||||||||
Villa de Cos | x | x | x | 3 | ||||||
Villa García | – | |||||||||
Villa González Ortega | – | |||||||||
Villa Hidalgo | – | |||||||||
Villanueva | x | x | x | 3 | ||||||
Zacatecas | x | x | x | 3 | ||||||
Total municipalities with presence per species: | 3 | 12 | 3 | 23 | 24 | 10 | 2 | 23 | 2 |
The model building area spanned the entire known distribution range of these species, so as to cover all possible habitats where the species might be found (
During our post-modelling field work, further occurrence records were collected. Moreover, when interviews were applied to individuals from different communities,
Human influence was one of the most widely used variables for the construction of potential distribution models for
Records of
No specimens were recorded for
There are no occurrence records for any rattlesnake species in 19 of the municipalities in Zacatecas (Table
Based on the obtained records and the field work, the distribution of nine rattlesnake species (
We recommend applying greater field work efforts in areas where no occurrence records have yet been identified for these species, as well as for organisms that showed the lowest number of records, particularly in the areas with a higher potential for presence. Likewise, we strongly advise conducting field work during the July-October period, since this will increase the sighting probability. We also suggest updating models once additional occurrence records have been registered.
Results obtained from the distribution modeling of these species generally agree with field work verification, making it possible to prioritize field efforts more effectively in different localities. During field work verification, multiple night sightings of rattlesnakes were noted, both alive or run over by vehicles on the roads, being the latter one of the major causes of death of these species in the state. This piece of information was merely gathered for
This paper represents substantial contribution to the knowledge on rattlesnakes in Zacatecas. Their occurrence records are shown and zones with greatest diversity within the state are inferred. Moreover, this study indicates the potential distribution areas of these organisms. This material will be of major help for the implementation of strategies on public health issues, as well as for the proposal of management and conservation plans for these species.
We believe that this study could be used by individuals wishing to conduct future projects related to rattlesnake conservation in Zacatecas. We also encourage the publication and incorporation of new occurrence records that contribute to gather further information on these organisms in the state.
All authors thank the reviewers, whose comments and suggestions provided great input and enriched this manuscript.
J.L.L.G. would like to thank the National Science, Technology and Innovation Council for the grant awarded to study the Graduate Degree in Natural Resource Management Innovation, from which this research arose. I similarly thank Jorge Bañuelos-Alamillo for having provided occurrence records. Further, to Iván Ahumada Carrillo and Joseph E. Forks for the outstanding photographs included within this manuscript; to Eric Centenero Alcalá for generously lending valuable photographic material that was used in the catalog during the interviews and a special thanks to Xabier Herrero for helping to improve the translation of this document.
A.M.B. was funded by Fundação para a Ciência e a Tecnologia, Portugal (Contract No. IF/00266/2013 related to the exploratory project CP1168/CT0001).
J.J.S.R. was funded by PRODEP-SEP and by institutional resources, initially from Universidad Autónoma de Zacatecas and currently from the Universidad Autónoma de Aguascalientes.
Finally, the authors would like to thank Jesús Lara Rayos, Paulo Sergio Haro Galván, Mónica Díaz Teniente, Emmeth Rodríguez Pérez, Guillermo Alatorre de Alba, Delia Hernández Juárez, Rodolfo Zacarías Alvarado, Jorge Bañuelos Alamillo, Violeta Bañuelos Frías, as well as the individuals from the various localities visited, for their field work collaboration aiming at the verification of the
Collecting permits needed to conduct field work were issued to Jesús Sigala-Rodríguez: SGPA/DGVS/ 06292/06, SGPA/DGVS/ 09453/14, SGPA/DGVS/ 05874/17, and scientific collector permit FAUT-0110 SGPA/DGVS/ 04324 and to David Lazcano-Villarreal SGPA/DGVS/ 011906/17.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.
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Global model of potential distribution.