a1 Museo di Storia Naturale e del Territorio, Centro Interdipartimentale, Università di Pisa, Via Roma, 79, 56011, Calci (PI), Italy
a2 Unit of Cognitive Primatology and Primate Center, Institute of Cognitive Sciences and Technologies, CNR, Rome, Italy
The increasing proportion of the landscape used by humans has led, and is still leading, to the conversion of the original habitat into numerous small patches, often separated by a matrix of inhospitable land-uses. This habitat fragmentation is a major threat to biological diversity and is considered to be the primary cause of the present species extinction crisis (Aurambout et al. 2005). Survival in fragments is related to both intrinsic factors, such as abundance and sex ratio, and extrinsic factors related to patch quality (Ramanamanjato & Ganzhorn 2001, Rovero & Struhsaker 2007). At first, the fragmentation process can randomly distribute animals among forest patches and across fragmented habitat and surrounding matrix (Marsh 2003, Tischendorf et al. 2005). Local populations can survive only if the colonized forest remnants are adequate and/or dispersal is possible (Marsh 2003). Subsequently, a non-random distribution can result from local populations either remaining connected but distinct (metapopulation) or merging into a single large but patchy population (Harrison & Taylor 1997). Such distribution can be dictated by different aspects of fragment quality, including size and vegetation variables (e.g. tree species diversity, large-tree abundance and food plant availability) (Ramanamanjato & Ganzhorn 2001, Rovero & Struhsaker 2007). The mutual relationship among variables and their linkage to animal abundance have proven difficult to disentangle and mammals largely diverge in their response to different fragment quality aspects (Irwin 2008, Ramanamanjato & Ganzhorn 2001, Rovero & Struhsaker 2007).
(Accepted August 20 2010)