RESUMO
Land use changes by human activities have been the main causes of habitats and wildlife population degradation. In the Tehuantepec Isthmus in Oaxaca, the tropical habitat of the porcupine Sphiggurus mexicanus has been subject to vegetation and land use changes, causing its reduction and fragmentation. In this study, we estimated vegetation cover and land use (δn) change rates and assessed habitat availability and potential corridors for possible porcupine movements to avoid its isolation. In the study area, the type of vegetation with the most change rate value was the savanna (δn=-2.9), transformed into induced grasslands. Additionally, we have observed the porcupine (since 2011) in semi-deciduous (δn=-0.87) and tropical dry (δn=-0.89) forests that have been transformed in temporal agriculture and mesquite and induced grasslands. The vegetation inhabited by the porcupine resulted in recording a total of 64 plant species (44 trees, nine vines, seven herbs, four shrubs), of which the vine Bunchosia lanceolata showed the highest importance value (41.85) followed by the trees Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), and Enterolobium cyclocarpum (17.02). The habitat evaluation and potential corridor analysis showed that only 1 501.93ha could be considered as suitable habitats with optimum structural conditions (coverage, surface, and distances to transformed areas) to maintain viable populations of S. mexicanus, and 293.6ha as corridors. An increasing destruction of the porcupines habitat has been observed in the study area due to excessive logging, and actions for this species and its habitat conservation and management have to be taken urgently. Rev. Biol. Trop. 62 (4): 1481-1494. Epub 2014 December 01.
Los cambios de uso del suelo por actividades humanas, han sido de las principales causas de la degradación, reducción y fragmentación de los hábitats y poblaciones de fauna silvestre. En el Istmo de Tehuantepec, Oaxaca, el hábitat del puercoespín tropical Sphiggurus mexicanus, se encuentra sometido a cambios de cobertura vegetal y uso del suelo, que están causando la reducción y fragmentación de su hábitat. Debido a ello, estimamos las tasas de cambio de la cobertura vegetal y uso del suelo (δn), y evaluamos la disponibilidad del hábitat y de corredores vegetales potenciales para los posibles movimientos del puercoespín tropical y evitar su aislamiento. En el área de estudio el tipo de vegetación con mayor valor de tasa de cambio fue la sabana (δn=-2.9), transformado en pastizal inducido. Adicionalmente, observamos puercoespínes (desde 2011) en selva mediana subperennifolia (δn=-0.87) y selva baja caducifolia (δn=-0.89), los cuales han sido transformados en áreas de cultivo, selva baja espinosa y pastizal inducido. Caracterizamos la vegetación del hábitat del puercoespín, registrando un total de 64 especies vegetales (44 árboles, nueve bejucos, siete hierbas y cuatro arbustos), de los cuales, el bejuco Bunchosia lanceolata, presentó los valores más altos de importancia (41.85), seguidos por los árboles Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), y Enterolobium cyclocarpum (17.02). El análisis de evaluación de hábitat y corredores potenciales mostró que solo 1 501.93ha pueden considerarse como hábitats adecuados con condiciones estructurales (de cobertura, superficie y distancias a áreas transformadas) para mantener poblaciones viables de S. mexicanus; y 293.6ha como corredores. La destrucción del hábitat del puerco espín en el área de estudio está incrementándose por la tala excesiva, por lo tanto, es prioritario emprender acciones para la conservación y manejo del taxón y su hábitat.
Assuntos
Animais , Ecossistema , Porcos-Espinhos/classificação , Conservação dos Recursos Naturais , México , Dinâmica Populacional , Porcos-Espinhos/fisiologiaRESUMO
Land use changes by human activities have been the main causes of habitats and wildlife population degradation. In the Tehuantepec Isthmus in Oaxaca, the tropical habitat of the porcupine Sphiggurus mexicanus has been subject to vegetation and land use changes, causing its reduction and fragmentation. In this study, we estimated vegetation cover and land use (δn) change rates and assessed habitat availability and potential cor- ridors for possible porcupine movements to avoid its isolation. In the study area, the type of vegetation with the most change rate value was the savanna (δn = -2.9), transformed into induced grasslands. Additionally, we have observed the porcupine (since 2011) in semi-deciduous (δn = -0.87) and tropical dry (δn = -0.89) forests that have been transformed in temporal agriculture and mesquite and induced grasslands. The vegetation inhabited by the porcupine resulted in recording a total of 64 plant species (44 trees, nine vines, seven herbs, four shrubs), of which the vine Bunchosia lanceolata showed the highest importance value (41.85) followed by the trees Guazuma ulmifolia (22.71), Dalbergia glabra (18.05), and Enterolobium cyclocarpum (17.02). The habitat evaluation and potential corridor analysis showed that only 1 501.93ha could be considered as suitable habitats with optimum structural conditions (coverage, surface, and distances to transformed areas) to maintain viable populations of S. mexicanus, and 293.6 ha as corridors. An increasing destruction of the porcupines' habitat has been observed in the study area due to excessive logging, and actions for this species and its habitat conserva- tion and management have to be taken urgently.
Assuntos
Ecossistema , Porcos-Espinhos/classificação , Animais , Conservação dos Recursos Naturais , México , Dinâmica Populacional , Porcos-Espinhos/fisiologiaRESUMO
Functional analysis of the limb bones of the erethizontid Steiromys duplicatus, one of the most abundant Miocene porcupines from Patagonia, provides evidence to infer their locomotor behavior. Remains of the giant Neosteiromys pattoni (Late Miocene of Northeast Argentina) are also analyzed. Osteological and myological features of extant porcupines were evaluated and used as a model to interpret the functional significance of Miocene species' limbs. Several features in erethizontids are compatible with the ability to climb: the low humeral tuberosities indicate a mobile gleno-humeral joint; the prominent and distally extended deltopectoral crest indicates a powerful pectoral muscle, which is particularly active when climbing; the humero-ulnar and humero-radial joints are indicative of pronation-supination movements; the well-developed lateral epicondylar ridge and the medially protruding entepicondyle are in agreement with an important development of the brachioradialis, supinator, flexor digitorum profundus, and pronator teres muscles, acting in climbing and grasping functions; the mechanical advantage of the biceps brachii would be emphasized because of its distal attachment on the bicipital tuberosity. As with extant porcupines, in Miocene species, the large femoral head would have permitted a broad range of abduction of the femur, and the medially protruding lesser trochanter would have emphasized the abduction and outward rotation of the femur by the action of the ilio-psoas complex. In S. duplicatus, the shape of the hip, knee, and cruro-astragalar, calcaneo-astragalar, and astragalo-navicular joints would have allowed lateral and rotational movements, although probably to a lesser degree than in extant porcupines. Foot features of S. duplicatus (e.g., great medial sesamoid bone, medial astragalar head, complete hallux) indicate that this species would have had grasping ability, but would not have achieved the high degree of specialization of Coendou. Steiromys duplicatus would have been a semiarboreal dweller, resembling Erethizon dorsatum.