Biological Correlates of Extinction and Persistence of Primates in Small Forest Fragments: A Global Analysis

Abstract

Habitat loss and fragmentation are two of the main threats facing wildlife. The species at risk in small fragments are not a random subset of the original community. Understanding the biology behind the distinction between species at risk and more persistent species should help inform conservation efforts. We attempted to identify risky traits in a well-known taxon, the primates, by asking which traits distinguished taxa that differed in the size of the smallest fragment in which they were recorded. We assumed that taxa that could persist in smaller fragments were at less risk of extinction than those that needed larger fragments. The traits investigated are indicative of amount of habitat needed, reproductive rate, and specialization. We obtained from the literature information on the presence-absence of 68 primate species of 36 genera in forest fragments of less than 100 km 2 . Association between size of smallest fragment and biology was tested with regressions, Spearman correlations, two-sample t tests, and non-parametric Wilcoxon tests. We found no significant relationships between area of smallest fragment in which species or genera persisted and any of the biological parameters. We suggest that the most likely explanation for this unexpected finding is that the smallest fragments in which primates are currently studied are usually so small that all primate species in them are doomed in the long-term and therefore, no biological traits distinguish taxa at risk. The finding implies that conservation research and efforts should be directed at assessing the efficacy of forest fragments and small biological preserves in conserving primate species.

Habitat selection and use in the Critically Endangered Sahamalaza sportive lemur Lepilemur sahamalazensis in altered habitat

“…Strictly arboreal species such as sportive lemurs, which are unable to cross the nonforest matrix within their distribution range, will eventually become extinct when their habitat patches get too small and disconnected to support a viable gene pool/flow (Frankham et al 2002, Fahrig 2003. The smallest forest fragment with confirmed sportive lemur persistence has been found to be 6 ha for the red-tailed sportive lemur (Ganzhorn et al 2000, Gibbons & Harcourt 2009) and 5.4 ha for the Milne-Edwards' sportive lemur (Craul et al 2009). The smallest fragment where Sahamalaza sportive lemurs were found in this study measured 10 ha.…”

Ecological and Behavioural Factors Influencing Territorial Call Rates for the Bolivian Titi Monkeys, Plecturocebus modestus and Plecturocebus olallae

“…As a response, some species simply leave the less suitable areas, while others try to adapt in reduced available forest areas, temporarily increasing their densities [Gibbons and Harcourt, 2009]. This reaction was observed in howler (Alouatta palliata) , capuchin (Sapajus apella) and titi (Plecturocebus donacophilus) monkeys in response to forest fragmentation [Pyritz et al, 2010;Arroyo-Rodríguez et al, 2013].…”

“…Apart from determining daily call rates for each species that will be useful for future population density estimations, we also assessed variations in call emission rates according to habitat type, group location within the territory, the vocal activity of neighbouring groups, and seasonality. Given the links between territorial call rates and neighbouring group interactions [Robinson, 1979;Robinson et al, 1987;Isabirye-Basuta and Lwanga, 2008;Gibbons and Harcourt, 2009], we expected higher territorial call rates and more emissions at territory boundaries in less fragmented forests. Also, overall higher territorial call rates were expected during the dry season due to increased interactions between groups provoked by a reduction of food resources.…”

The Influence of Seasonal Variation on Chimpanzee (Pan troglodytes schweinfurthii) Fallback Food Consumption, Nest Group Size, and Habitat Use in Gishwati, a Montane Rain Forest Fragment in Rwanda

“…Forest fragmentation due to anthropogenic activities is an increasing threat to primate populations (Chapman and Peres 2001;Gibbons and Harcourt 2009;Marsh 2003). Because most tropical forests are not legally protected, many populations will increasingly depend on fragmented forests to sustain them (Baranga et al 2009;Oates 1996;Redford 1992).…”