Daily and seasonal activities of a guild of the coprophagous, burrowing beetle (Coleoptera Scarabaeidae Scarabaeinae) in tropical grassland

Daily and annual activity rhythms of a guild of burrowing beetles (Scarabaeinae) were quantified for beetles found on dung in induced pastures on the Coastal Plains of the Gulf of Mexico in the State of Veracruz, Mexico. Comparing collections from 1991–1992 with those of 1972–1973, a notable difference was observed: the presence of Digitonthophagus gazella (Fabricius 1787). This Indoafrican species has a wide environmental tolerance, and was introduced to Texas in 1972. In the study area it has excluded Onthophagus batesi Howden & Cartwright 1963, from the pasture, which is now only found in marginal habitats. The results of this study allow an interpretation of the coexistence of the species that form the nucleus of the guild as dependent on daily and annual segregation. Differences in the daily pattern of activity, as well as the differences in the yearly activity peaks, tend to decrease competition while allowing different species the possibility of being the first colonizer. Evidence of the role of this segregation in a guild dependent on an ephemeral resource (i.e. dung) is the reduced colonizer success of diurnal and crepuscular-nocturnal species on dung pats which have been on the ground for 12 hr, and therefore have been attacked by species of a group with a different time strategy.