ABSTRACT
At two temperate pasturelands in northern Mexico, we explored possible competition for food and space under pats during the simultaneous nesting periods of the univoltine species Dichotomius colonicus (Say), Phanaeus quadridens (Say), and Copris sierrensis Matthews. To simulate unlimited resources, 50 5-kg cow dung pats were placed at regular distance intervals in each pastureland. After building trenches around the pats, the number and depth of each nest, as well as larval development status, were documented once for a period of 1-8 mo. Analyses of variance and association tests were used to make a between-site comparison of dung pat occupation, nests occupied per species, nests per dung pat, and nest depth below each pat. The proportion of pats occupied by each species differed significantly between sites. C. sierrensis colonizing most pats at one site and D. colonicus at the other. There were no differences between sites in the frequency of pats occupied by more than one species. The association test and Ochiai index showed that each species colonized dung pats independently. The results suggest that pat occupation depended on their location by beetles and the relative abundance of each species. The species tended to dig nests at different depths, possibly reducing interspecific competition for space. It can therefore be concluded that, when food resources seem to be unlimited, they are shared following a "lottery dynamic" model if there is spatial differentiation among species.
Subject(s)
Coleoptera , Competitive Behavior , Ecosystem , Nesting Behavior , Animals , Feeding Behavior , Female , Larva , Male , Mexico , Pupa , ReproductionABSTRACT
The dung incorporation activity of three species of coprophagous beetle macrofauna (Coleoptera: Scarabaeidae: Scarabaeinae), Dichotomius colonicus (Say), Phanaeus quadridens (Say), and Copris klugi sierrensis Matthews, was studied on a hectare of pastureland on "La Michilía" Biosphere Reserve. In total, 223 specimens of the three species were recorded. On the basis of abundance, the dominant species was D. colonicus. A substantial percentage (31% in September and 51% in October) of dung pats remained on the surface, untouched by beetles. Most of the specimens observed (92%) were found amassing dung in galleries. The dung accumulation capacity of D. colonicus varied from 5 to 135 g of dung (dry weight)/pair, whereas C. klugi sierrensis amassed an average of 24.3 +/- 8.5 g/pair and P. quadridens amassed an average of 12 +/- 2.5 g/pair. Based on dung burying efficiency, D. colonicus was considered the most beneficial of the three species in the study area. It dug deeper, wider galleries and incorporated the largest amount of dung into the soil.
