Abstract:
Seeds dispersed by fruigivorous mammals like gibbons were found to be positively affected by dung beetles (Coleoptera: Scarabaeidae). They incidentally remove seeds while feeding and removing feces, to be used for brooding. The study was done between Jan.Dec., 2000, in a primary rain forest at Khao Yai National Park, Thailand, to provide a basic knowledge of ecological interactions between these beetles and the seeds dispersed in feces of white-handed gibbons (Hylobates lar). A total of 3,809 seeds of 42 species (27 families) were recovered from 157 samples of gibbon feces. These seeds ranged 0.530 mm in length. From 288 pitfall traps and 49 direct observations of post-seed dispersal, 2,194 beetles of 53 species (9 genera) were collected. Beetles were caught more from night traps than day traps and more during
the beginning of the rainy season (Apr.Jun.) than in other seasons. However, beetles were equally abundant in valley and hill habitats. According to their dung processing and nest constructing methods, dung beetles are classified into three functional groups; tunnelers (86% of 1,818 beetles from traps), rollers (3%), and dwellers (11%). All tunnelers and rollers removed small seeds from their original positions while dwellers did not. From 49 observations, 10% (range 0100%) of large seeds were removed by 9% (075%) of dung beetles that visited dung. Tunnelers of eight species (526 mm in length) moved those seeds into their tunnels under or short distances from dung piles with an average of 14.9 cm (range 0105, N=32) and buried them 2.7 cm (range 07, N=32) under the soil. Each tunneler transported a single or two seeds during each observation. Large rollers (26 mm) removed 48 large seeds (mean 6.3, N=3) in their balls while dung balls of two small roller species (4 and 7 mm) contained only small seeds. These rollers rolled their balls an average of 62.8 cm away (range 5150 cm, N=24) and buried them an average of 5.2 cm (range 07, N=21). Considering these removal distances and burial depths, seeds are most likely to be given the advantages of escaping from clumping and avoiding predator attraction and have a greater possibility of germinating