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Accueil du site → Doctorat → Mexique → Factores ecológicos y antropogénicos que influyen en el estatus del berrendo peninsular (Antilocapra americana peninsularis) : La estrategia para su recuperación

Centro de Investigaciones Biológicas del Noroeste (CIBNOR) 2005

Factores ecológicos y antropogénicos que influyen en el estatus del berrendo peninsular (Antilocapra americana peninsularis) : La estrategia para su recuperación

Cancino Hernández, Jorge de Jesús

Titre : Factores ecológicos y antropogénicos que influyen en el estatus del berrendo peninsular (Antilocapra americana peninsularis) : La estrategia para su recuperación

Auteur : Cancino Hernández, Jorge de Jesús

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Doctorado en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2005

As a case study, the peninsular pronghorn (Antilocapra americana peninsularis), this dissertation addresses the problem of small populations with restricted distribution and affectation of its habitat. Small populations have high probabilities of extinction due to unbalances in their demographic and genetic parameters. Deterministic and stochastic factors have a more significant effect on small populations. In addition to the demographic parameters, it is necessary to consider changes caused by the space and time variations in the populations, and fluctuations resulting from environmental variables. Deterministic changes due to human activities and their interaction with stochastic factors also play an important role in determining population trends. The effect of several factors can be additive or synergic. Nevertheless, there are specific factors that can have a greater effect on small populations such as catastrophes and genetic diversity. The size of the peninsular pronghorn population is less than 250 individuals. The World Conservation Union (IUCN) categorizes a species as having "critical risk" status at that population size, as well as having a restricted distribution and extreme fluctuations in the number of adults. Based on the need to evaluate the extinction risk of the peninsular pronghorn and the trend of its population, the VORTEX simulation model was used to evaluate demographic and deterministic factors and changes caused by human activities on this subspecies. The concept of "supportive breeding”, defined as supporting weak wild populations through the release of conspecifics reproduced in captivity, is also used in this study. Management of captive peninsular pronghorn began in 1998 in the El Vizcaino Desert, Baja California Sur. By 2000, 22 founders were gathered. The questions addressed in this work are : How have human activities affected the original distribution of the peninsular pronghorn ? What is the risk of extinction to the wild population of peninsular pronghorn ? What effect did the removal of the 22 founders have on the wild population ? Can the management of captive peninsular pronghorn reduce the extinction prospects of the wild population ? Former range of the subspecies was estimated in 40,000 km2 and reduced by almost 90%, to 5,000 km2. The main causes are related with human activities ; habitat changes and poaching. The first results of the simulations indicate that the peninsular pronghorn small population is endangered, if the wild population is less than 100 animals the growth rate is negative (r=-0.037). The survival of fawns is one of most important factors. A change from 70% to 80% in the fawn mortality results in a negative growth rate (r=-0.103) an the extinction probability is high, P(E)=0.84. Changes in the adult female mortality was important also, at 15%, the extinction probability was P(E)=0.572. The drought effect was included in the reproductive female rate. When the scenario was without drought the population trend was to growth with P(E)=0.002. When three factors were evaluated the extinction trend was high up 96%. There was a clear correspondence between the captive population model and its real growth rate. Simulation with a “new wild population” generated by the release of a group from the captive population shows positive results because of this could be a stable population or growing. The study suggests that supplementing wild population will be beneficial. The study also indicates that the risk of extinction can be reduced with "supportive breeding". Captive breeding that avoids human impression on the animals, and periodic releases can be important factors in precluding the extinction of peninsular pronghorn.

Mots Clés : Berrendo peninsular ; Antilocarpa americana peninsularis ; habitat ; población ; modelación


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