Análisis de algunos parámetros ecológicos de 2 vertebrados indicadores de conservación en el monte Tláloc

Existen varias especies de animales vertebrados que por sus características biológicas son más propensos a extinguirse localmente cuando los ambientes son perturbados o modificados por el hombre (Primack 1995). Algunas de estas características que comparten Ambystoma leorae y Lynx rufus son: requerimientos específicos de hábitat (alimento, espacio), baja proporción de individuos reproductivos, ambos son capturados o cazados por el hombre. Cuando éste último irrumpe en el ambiente natural, transforma características de los ambientes acuáticos como el ph, la materia orgánica (cantidad y calidad) y esto modifica las condiciones que necesita A. leorae. Por otro lado, la deforestación provoca que disminuya la cobertura forestal así como las presas de L. rufus; de tal manera que la abundancia y densidad de ambas especies se modifican con la presencia del hombre en los ecosistemas naturales

Distribución regional y abundancia del lince (Linx rufus escuinape) y el coyote (Canis latrans cagottis) por medio de estaciones olfativas: un enfoque espacial

Abstract. This paper examines the frequency of presence of bobcats and coyotes in six vegetation units in the southern region of the Valley of Mexico, as indicated by scent stations. The bobcat was recorded with more frequency than anticipated in pine forests, fir forests and bush/grasslands. The coyote was present most frequently in pine forest, fir forest and mixed forest. The results have been formulated into spatial distribution models for the bobcat and the coyote, that can aid in formulating conservation and management actions for the study area

Top-down and bottom-up control on cougar and its prey in a central Mexican natural reserve

Top-down and bottom-up controls are hypothe sized to regulate population structures in many ecosystems. However, few studies have had the opportunity to analyzeboth processes in the natural environment, especially on largecarnivores like the cougar (Puma concolor). Previously, studies show that cougar diet in the Sierra Nanchititla NaturalReserve (SNNR), central Mexico, is mainly armadillo, coati, and white-tailed deer. We assess whether top-down and/or bottom-up control regulate this endangered food web: (a) wepredicted that seasonal per capita changes in abundance (pca) of cougar will be positively affected by the abundance of their main prey; (b) primary productivity in SNNR will affect the pca of prey species, driving bottom-up control; and (c) armadillo, coati, and white-tailed deer pca will be affected by the abundance of cougar, generating top-down control. Using 15 camera traps for 6 years in the SNNR, we calculated a relative abundance index (RAI) and pca for cougar and each of the focal prey, and we used the normalized difference vegetation index (NDVI) as a proxy of primary productivity. We constructed multiple regression models and selected the best linear models based on ranking the AICc values. Our analysis suggests that P. concolor pca is best explained by bottom-up control and intraspecific feedback. White-tailed deer and armadillo pca were both significantly affected by cougar abundance, indicating top-down control for these prey species, but NDVI was not retained in any of the models selected for prey pca. Our results indicate that both bottom-up and top-down control are involved in regulating this endangered food web in the SNNR, Mexico

Functional responses of cougars (Puma concolor) in a multiple prey-species system

The study of predator-prey interactions is commonly analyzed using functional responses to gain an understanding of predation patterns and the impact they have on prey populations. Despite this, little is known about predator-prey systems with multiple prey species in sites near the equator. Here we studied the functional response of cougars (Puma concolor) in Sierra Nanchititla Natural Reserve (Mexico), in relation to their main prey, armadillo (Dasypus novemcinctus), coati (Nasua narica) and white-tailed deer (Odocoileus virginianus). Between 2004 and 2010, cougar scats were collected along five transects to estimate the consumption of different prey species. A relative abundance index (RAI) was calculated for each prey species and cougar using 18 camera traps. We compared Holling type I, II and III functional response models to determine patterns in prey consumption based on the relative abundance and biomass of each prey species consumed. The three main prey species comprised 55% (armadillo), 17% (coati) and 8% (white-tailed deer) of the diet. Type I and II functional responses described consumption of the two most common prey species armadillos and coati similarly well, while a type I response best characterized consumption of white-tailed deer. A negative correlation between the proportions of armadillo versus coati and white-tailed deer biomass in cougar scats suggests switching to consume alternative prey, confirming high foraging plasticity of this carnivore. This work represents one of the few studies to compare functional responses across multiple prey species, combined with evidence for prey switching at low densities of preferred prey

Caracterización de sitios potenciales para reintroducción de Romerolagus diazi en el Área de Protección de Flora y Fauna Nevado de Toluca, México

Se realizó un muestreo intensivo en el APFF Nevado de Toluca (1807 UM), el 2.27% de las UM (41) mostraron evidencia de Romerolagus diazi. Se generó un mapa con sitios georreferenciados de excretas de R. diazi que, junto con las variables bióticas asociadas a la especie, se describió su hábitat: R. diazi se asocia a la comunidad Pinus hartwegii - Festuca spp. - Senecio cinerarioides, entre los 3500 a 3700 m de altitud. Se encontró que el afloramiento rocoso y una cobertura herbácea por encima del 70% favorecen la presencia de R. diazi, en contraste, el pastoreo determina la ausencia de la especie. Los resultados, evidencian un nuevo registro para su área de distribución además, para una posible reintroducción de la especie en dicha área

Nesting ecology of the American crocodile in La Encrucijada Biosphere Reserve, Mexico

Nesting of the American crocodile (Crocodylus acutus) is affected by natural and anthropogenic processes. In Mexico, few studies exist on reproductive traits of wild populations. We assessed the key reproductive characteristics of C. acutus in the La Encrucijada biosphere reserve and the environmental and anthropogenic factors that influence them. From February to June 2014, we searched for nests in the reserve. Clutch incubation temperature was recorded by data loggers and climatic variables were obtained from La Encrucijada meteorological station. Additionally, outside the study area, net primary productivity was obtained for different sites in Mexico to relate it to clutch characteristics. We found 34 nests in nine nesting areas. Egg laying occurred in March, and hatching took place from mid-May to early June. Mean clutch and eggs characteristics are among the higher reported for C. acutus. Some egg attributes had a relationship with the net primary productivity. There was no relation between hatching success and external and internal characteristics of the nest. A high percentage of nests was poached (50%) mainly for egg consumption and fear of crocodiles, and the nests closer to the river, trees or human settlements are more likely to be poached

Joint ecological, geographical and cultural approach to identify territories of opportunity for large vertebrates conservation in Mexico

The objective of the present paper is to provide a holistic framework to delineate ‘‘territories of opportunity’’ where agrarian communities can manage areas to enhance the conservation of large vertebrates. The study was conducted Mexico, which is sociologically, culturally and ecologically complex, similar to other ‘‘megadiverse’’ countries. We conducted ensemble niche modeling of endangered top predators to define a set of large vertebrate species. Environmental attributes were used to perform three distance-based and two artificial intelligence-based algorithms. Socio-cultural attributes were included to depict agricultural communities with strong social government schemes and clear evidence of well-managed natural resources. Other socio-economic attributes such as land acquisition cost, human agglomeration and anthropogenic land use were included in the analysis. Scenarios were computed and displayed cartographically with the aid of a geographic information system. Results showed that the largest concentration of biodiversity converges on regions with large land cover persistence and high local governance, defined as potential willingness to engage in conservation actions. The cartographic areas identified overlapped with current Mexican protected areas in only 2.7% of the country. Thus, conservation law enforcement in most of the country seems to be ineffective. Here we show that, in a number of territories, agrarian communities that have coexisted for millennia with umbrella species can be regarded as allies in biodiversity conservation. Results are discussed in the light of their relevance for future niche modeling, environmental policy design and implications for climate change.Conacy

Conociendo al lagarto escorpión: leyendas, realidad y potencial de una rareza biológica

A pesar de ser uno de los reptiles más esquivos en México, el lagarto escorpión es al mismo tiempo uno de los más famosos debido a sus peculiaridades, como la presencia de glándulas de veneno y una apariencia sumamente llamativa. Se recopila la literatura publicada sobre uno de los reptiles míticos de nuestro país para fomentar su protección a través de la divulgación científica. La literatura muestra un avance significativo en el conocimiento del lagarto escorpión, pero también evidencia la necesidad de investigar aspectos clave para su conservación: sensibilidad a las perturbaciones ambientales y requerimientos de hábitat, dinámica de interacción con las personas, aplicaciones medicinales y variabilidad genética.UAEMéx

Potential distribution and habitat connectivity of Crotalus triseriatus in Central Mexico

The dusky rattlesnake, Crotalus triseriatus, used to be very abundant in many parts of the highlands of central Mexico, but with the increasing human population and associated activities, the rattlesnake habitats and populations have suffered drastic reductions and fragmentation. At the moment, the most important habitat features, associated with the presence of C. triseriatus, the current potential distribution and the landscape connectivity amongst the populations of the State of Mexico and Mexico City, are unknown. Therefore, we used the maximum entropy modelling software (MAXENT) to analyse the current potential distribution and most important habitat features, associated with the presence of the species. The variables with the highest contribution to the model were: proportion of Abies forest, minimum temperature of coldest month, maximum temperature of the warmest month, proportion of Pinus forest and annual precipitation. Furthermore, we found connectivity corridors only within mountain chains. Our results highlight the necessity for conserving the patches of Abies forest and preserving the populations of C. triseriatus and the connectivity of the landscape

EVALUACIÓN DEL NICHO ECOLÓGICO EN UN GREMIO DE CARNÍVOROS DEL PARQUE NATURAL SIERRA NANCHITITLA, MÉXICO

La evaluación de las relaciones entre depredadores, sus presas, el ambiente y los recursos usados es importante para entender los mecanismos que influyen en la estructura de la comunidad. Es común realizar éstos análisis congregando especies dentro de grupos que explotan el mismo tipo de recursos de forma similar, conocidos como gremios. De esta manera, los organismos sobreviven a través del tiempo tanto como puedan competir exitosamente por recursos y lleven a cabo estrategias de repartición. De acuerdo a la estrategia de repartición de recursos entre especies para coexistir y al tamaño corporal como un factor importante en el uso de recursos, en este estudio se prueba la hipótesis de que existirá una mayor sobreposición de los recursos utilizados, entre especies de tamaño y hábitos similares, manteniendo 3 subgrupos: depredadores tope (Puma concolor y Panthera onca), mesodepredadores carnívoros (Leopardus pardalis, Leopardus wiedii y Puma yagouaroundi) y mesodepredadores omnívoros (Nasua narica y Urocyon cinereoargenteus). En este estudio, se analizaron las tres dimensiones del nicho ecológico (trófica, espacial y temporal), para lo cual, se colectaron excrementos de manera oportuna a lo largo de diferentes trayectos (30 km), y fueron identificados a través de perfiles de ácidos biliares. Se ubicaron trampas cámara para registrar la actividad de las especies y determinar su asociación con diferentes eco-variables (vegetación, pendiente, distancia a ríos, caminos, poblados etc.) que explican el hábitat usado. Los resultados demuestran la existencia de tres grupos de depredadores. Lo cual indica una repartición estratégica de los recursos usados que disminuye la competencia y favorece la coexistencia de estos depredadores. El análisis en conjunto de las dimensiones del nicho permite obtener una evaluación más completa del nicho ecológico, más aún cuando se aborda a nivel de gremios