Suspected side effects of a herbicide on dung beetle populations (Coleoptera : Scarabaeidae)

This paper addresses the association between use of a herbicide and anecdot al reports of reduced dung degradation and dung beetle populations. Dung be etles were monthly collected at two adjacent ranches in Mexico. Ranches wer e similar in area, elevation, exposition, soil, and vegetation, but differe d in weed control. Ranch A controlled weeds manually, and ranch B controlle d unwanted vegetation with applications of the herbicide Tordon(R)101M. The main species recovered on each ranch (Ataenius apicalis) was significantly more abundant at ranch A than at ranch B. Conversely, similar numbers of a second species, Ataenius sculptor, were recovered from both ranches. Three lines of evidence support the tentative conclusion that herbicide applicat ions may be causing a decline in populations of A. apicalis on ranch B. Fir st, the greatest reductions of A. apicalis were observed during periods of herbicide application. Second, A. sculptor, apparently little affected by t hese same herbicide applications, is active primarily during months without herbicide applications. Third, preliminary results of laboratory studies s how that exposure to herbicide can impair reproductive function of the dung beetle Canthon cyanellus. (C) 2001 Academie des Sciences/Editions scientif iques et medicales Elsevier SAS.