Large-vertebrate assemblages of primary and secondary forests in the Brazilian Amazon

Abstract

Secondary forests account for 40% of all tropical forests yet little is known regarding their suitability as habitat for diurnal large mammals and game birds. This is especially so for second-growth that develops on large areas of degraded land. We address this by investigating assemblages of large-bodied birds and mammals in extensive patches of secondary forest in the Jarí region of the north-eastern Brazilian Amazon, comparing species richness and abundance against that of adjacent undisturbed primary forests. We conducted 184 km of line-transect censuses over a period of 3 mo, and found that although primary and secondary forests held a similar abundance of large vertebrates, the species composition was very different. Secondary forests supported a high abundance of ungulate browsers (0.85 vs 0.44 indiv. per 10 km) and smaller-bodied primates (15.6 vs 4.6 indiv. per 10 km) compared with primary forests. However, large prehensile-tailed primates were absent (black spider monkey Ateles paniscus) or at very low abundance (Guyanan red howler monkey Alouatta macconelli) in secondary forest. The abundance of large frugivorous/granivorous birds was also low in secondary forests compared with primary forests (22.6 vs 37.1 individuals per 10 km, respectively). Faunal assemblages appear to reflect food resource availability. Concurrent vegetation surveys indicated that secondary forests had high levels of terrestrial and understorey browse. Fruit production was largely restricted to pioneer trees such as Bellucia and Inga spp. Although these regenerating forests were an important habitat for large mammals and birds, they were limited in terms of faunal richness, particularly dispersers of large-seeded plants.