Home About us Contact
|
Home About us Contact | ||
|
|
||
Forest Mammals (forest + mammal)
Selected AbstractsPatch Occupancy and Potential Metapopulation Dynamics of Three Forest Mammals in Fragmented Afromontane Forest in South AfricaCONSERVATION BIOLOGY, Issue 4 2000Michael J. Lawes We recorded patch occupancy of blue duiker ( Philantomba monticola), tree hyrax ( Dendrohyrax arboreus), and samango monkey (Cercopithecus mitis labiatus) in 199 forest patches. Their rarity is ascribed to the fragmentation and destruction of their forest habitat. Incidence functions, derived from presence and absence data, were formulated as generalized linear models, and environmental effects were included in the fitted logistic models. The small and mostly solitary hyrax and duiker persisted in smaller patches than the large and social monkey. Although this result follows expectations based on relative home-range sizes of each species, the incidence probability of the samango monkey was invariant with increasing isolation, whereas a gradual decrease with increasing isolation was observed for the hyrax and duiker. Group dynamics may inhibit dispersal and increase the isolation effect in social species such as samango monkeys. A mainland-island metapopulation model adequately describes patterns of patch occupancy by the hyrax and duiker, but the monkeys' poor dispersal ability and obvious area-dependent extirpation suggest that they exist in transient, nonequilibrium (declining) metapopulations. Through identification of large forest patches for careful protection and management, the survival of all three species,especially the monkey,could be prolonged. Because no functional metapopulation may exist for the monkey, however, this is an emergency measure. For the duiker and hyrax, larger patches should form part of a network of smaller and closer patches in a natural matrix. Resumen: Investigamos la persistencia de tres mamíferos forestales raros de tamaño mediano (2,9 kg) en los bosques fragmentados de cinturón de niebla Podocarpus en la región central de la provincia KwaZulu-Natal, Sudáfrica. Registramos la ocupación del duiker azul ( Philantomba monticola), el hyrax arborícola ( Dendrohyrax arboreus) y el mono samango (Cercopithecus mitis labiatus) en 199 parches forestales. Su rareza se atribuye a la fragmentación y destrucción de su hábitat forestal. Las funciones de incidencia, derivadas de datos de presencia y ausencia, fueron formuladas como modelos lineales generalizados, y los efectos ambientales fueron incluidos en los modelos logísticos ajustados. Los pequeños y mayormente solitarios hyrax y duiker persistieron en parches más pequeños que los monos, que son más grandes y más sociables. A pesar de que este resultado obedece a expectativas basadas en tamaños de rango de hogar relativos de cada especie, la probabilidad de incidencia del mono samango no cambió con un incremento en el aislamiento, mientras que una disminución gradual al crecer el aislamiento se observó en hyrax y duiker. Las dinámicas de grupos podrían inhibir la dispersión e incrementar el efecto de aislamiento en especies sociables como lo es el mono samango. Un modelo de metapoblación continente-isla describe adecuadamente los patrones de la ocupación de parches por hyrax y duiker; sin embargo, la pobre capacidad de dispersión de los monos y la obvia extirpación área-dependente sugiere que estos existen en metapoblaciones transitorias, desequilibradas (en disminución). Mediante la identificación de parches forestales grandes para la protección y manejo cuidadosos, la supervivencia de las tres especies ( pero especialmente la de los monos) podría ser prolongada. Sin embargo, debido a que no existen metapoblaciones funcionales de monos, esta es una medida de emergencia. Para el duiker y el hyrax, los parches grandes deberán formar parte de una red de parches más pequeños y más cercanos en una matriz natural. [source] Differential Use of Trails by Forest Mammals and the Implications for Camera-Trap Studies: A Case Study from BelizeBIOTROPICA, Issue 1 2010Bart J. Harmsen ABSTRACT Relative abundance indices are often used to compare species abundance between sites. The indices assume that species have similar detection probabilities, or that differences between detection probabilities are known and can be corrected for. Indices often consist of encounter frequencies of footprints, burrows, markings or photo captures along trails or transect lines, but the assumption of equal detection probabilities is rarely validated. This study analyzes detection probabilities of a range of Neotropical mammals on trails in dense secondary forests, using camera-trap and track data. Photo captures of the two large cats, jaguars (Panthera onca) and pumas (Puma concolor), were correlated solely with trail variables, while photo captures of their potential prey species had no correlation or negative correlation with trail variables. The Neotropical mammals varied greatly in their tendency to follow or cross trails based on footprints surveys. This indicates that camera locations on trails will have varying detection probability for these Neotropical mammals. Even the two similar-sized jaguars and pumas, occupying relatively similar niches, differed subtly in their use of trails. Pumas followed trails more completely while jaguars were more likely to deviate from trails. The ecological significance of these findings is that jaguars seem to be more willing to use the forest matrix away from trails than do pumas. We conclude that trail-based indices, such as photographic captures or tracks along trails, are not appropriate for comparison between Neotropical species, and not even between relatively similar species like jaguars and pumas. [source] Habitat assessment for a rare, arboreal forest mammal, the tree hyrax Dendrohyrax arboreusAFRICAN JOURNAL OF ECOLOGY, Issue 2 2001A. Gaylard Abstract Recent findings have suggested that there has been a change in the structural nature of forests in the Eastern Cape, South Africa, which explains decreases in forest fauna. One of these (rare) forest species is the tree hyrax Dendrohyrax arboreus, a nocturnal, arboreal folivore, which makes use of cavity-bearing trees as dens. However, a conflict exists between the use of forest resources and in protecting habitats for the tree hyrax. In order to design appropriate management strategies, conservation authorities and forest managers require information regarding the specific habitat requirements of fauna in their forest, particularly those that are already threatened by resource use. The aims of this study were thus: (i) to characterise the den trees of D. arboreus, (ii) to determine whether D. arboreus selects for certain den tree characteristics (i.e. relative to the abundance of that characteristic); and (iii) to develop a habitat assessment model for D. arboreus. The tree hydrax was found to select for den trees with particular characteristics: seven tree species were selected as den trees, which were usually the tallest trees in the canopy (4,8 m). Den trees were usually only partly decayed, with multiple cavity entrances and trunk angles of between 45° and 68°. Cavity entrance and orientation did not appear to play a role in den tree selection by D. arboreus. A function which discriminated between den trees and non-den trees was calculated, and can be used to determine the suitability of a tree as a den for a tree hyrax (and thus to prevent it from being removed during commercial logging operations), or to assess the suitability of an area for habitation by tree hyraxes. This model can therefore help to alleviate the conflict between forest conservation managers and resource users in the Eastern Cape. Résumé Des découvertes récentes laissent entendre qu'il y a eu des changements dans la nature structurelle des forêts du Cap oriental, en Afrique du Sud, qui expliquent le déclin de la faune forestière. Une de ces (rares) espèces forestières est le daman des arbres, Dendrohyrax arboreus, un nocturne arboricole, mangeur de feuilles, qui utilise les cavités dans les arbres comme terriers. Cependant, il existe un conflit entre l'utilisation des ressources forestières et la protection de l'habitat des damans des arbres. Afin de concevoir une stratégie de gestion adéquate, les autorités de la conservation et les gestionnaires forestiers ont besoin d'informations sur les exigences spécifiques en matière d'habitat de la faune de leurs forêts et particulièrement des espèces qui sont déjà menacées par l'utilisation des ressources. Les buts de cette étude étaient donc : (i) de caractériser les arbres qui servent de refuge àD. arboreus, (ii) de déterminer si D .arboreus choisit certaines caractéristiques des arbres qui lui servent d'abris (i.e. en fonction de l'abondance de cette caractéristique) et (iii) de mettre au point un modèle d'évaluation de l'habitat pour D. arboreus. On a découvert que le daman choisissait comme refuge des arbres qui avaient certaines caractéristiques : sept espèces d'arbres étaient choisies comme abris, qui étaient d'habitude les plus hauts arbres de la canopée (4 ,,8 m). Les arbres choisis n'étaient d'habitude que partiellement abîmés, avec des nombreuses entrées vers des creux et des troncs formant un angle compris entre 45° et 68°. L'entrée et l'orientation de la cavité ne semblaient pas jouer un rôle dans le choix de l'arbre par D. arboreus. On a calculé une fonction qui faisait la distinction entre les arbres qui servaient d'abris et les autres et qui peut servir à déterminer si un arbre convient pour servir d'abri à un daman des arbres (et donc à empêcher de le supprimer lors des opérations d'abattage commercial), ou àévaluer si une zone convient comme habitat pour les damans des arbres. Ce modèle peut donc aider à réduire les conflits entre les responsables de la conservation des forêts et ceux qui veulent en utiliser les ressources au Cap oriental. [source] Habitat use by forest mammals in Dzanga-Ndoki National Park, Central Africa RepublicAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Mario Melletti First page of article [source] | ||||||||||