Mammal species richness and habitat use in rainforest and abandoned agricultural fields in Chiapas, Mexico.
The potential of small, isolated maize fields embedded in a large forest matrix (average canopy height 30 m, dominant trees Dialium guianense, Licania platypus, Vatairea lundelii, Talauma mexicana, Guarea glabra, Brosimum alicastrum, Pouteria spp., and Nectandra spp.) was investigated as an appropriate compromise between nature conservation and sustainable development. The relationship between habitat structure and habitat diversity with overall mammal species richness and abundance of six common small mammals was investigated in four 6-year-old abandoned maize fields (old fields) and four continuous rain forest sites in the most species-rich region in Mexico, the Selva Lacandon, Chiapas. Species richness did not differ between forests and old fields, indicating that forest-dependent mammals penetrated old fields of size 0.9-2.9 ha, presumably because forest cover and resources are nearby. Even species which strongly selected forest habitat, such as Heteromys desmarestianus and D. marsupialis [Didelphis marsupialis], were present in old fields, and only the latter showed a significant decline in the number of captures as a function of distance from forest edge. It is suggested that the Lacandon Indian use of the land for agriculture in the form of small (<3 ha) agricultural plots embedded in a large forest matrix increases spatial heterogeneity and promotes mammal diversity. Those small plots (in agricultural production terms) were considered intermediate in size when the whole continuum of the local natural and anthropogenic disturbance sizes are considered; more common are the extensive clearings for agriculture or cattle ranching, whereas the most common forest disturbance is tree fall gaps, at least 20-fold smaller than old fields. It is suggested that the use of plots <3 ha should be considered as an important, appropriate productive element when decisions are made about managing nature reserves and pursuing sustainable development.