The Role of Canthon humectus hidalgoensis (Bates) (Coleoptera: Scarabaeidae) in Dung Removal from a Cattle Pasture

Centro de Investigaciones Biologicas, Instituto de Ciencias Basicas e IngenieriaUniversidad Autonoma del Estado de Hidalgo. Carretera Pachuca-Tulancingo km 4.5C.P. 42184, Mineral de la Reforma, Hidalgo, MEXICOcmoreno@uaeh.edu.mxAs rearing livestock spread in Mexico, cattledung became the main alternative food source fordung beetles in pastures (Amezquita and Favila2010). The role of these beetles is fundamental toecosystem functioning and recovery, given theircontribution to several ecological processes includ-ing dung removal, nutrient cycling, secondary seeddispersal, and soil aeration (Nichols et al. 2008). Inthe cattle pastures of the state of Hidalgo, Mexico,Canthon humectus(Say)isoneofthemostcommondung beetle species. In the Barranca de MeztitlanBiosphereReserve,thesubspecies Canthonhumectushidalgoensis (Bates) is a generalist dung feeder thatrepresents up to 94% of the total number of dungbeetles(Verduetal.2007),sostudyingthebehaviorof this beetle will allow us to describe its possibleimpact on ecological processes, especially that ofdung removal in pastures.Canthonhumectushidalgoensisisadiurnalbeetlethat makes dung balls and rolls them from the cowpat to another site. Lone beetles do this to feed andmatingpairsdoitfornesting.Fornesting,theballisrolled by the male who pulls the ball with his hindlegs. Thefemale isattractedby hispheromones andtakes her place atop the ball to help the male roll it.The male buries the dung ball in the nesting site,and the female transforms it into a brood ball(Moron 2004). This species is common in xerophi-lous scrublands, in forests ranging from 1,400 to2,000 m above sea level, as well as in open and iso-lated livestock areas (Halffter et al. 2011).The purposeofthisstudy was todescribe someofthe characteristics of the dung removal process per-formed by individuals and pairs (male and female)of C. humectus hidalgoensis. We measured: 1) thelinear distance (m) from the source and duration(minutes) of dung rolling; 2) the size (mm) andweight (g) of the dung ball; and 3) the abundanceand density of this species in order to estimate itsimpact on the ecosystem. The study was done innorthern Hidalgo, Mexico, in the vicinity of Jacala(21°1′1.17″ N 99°12′2.35″ W). The area is locatedin the Sierra Madre Oriental mountain range, at1,376 m elevation. Native vegetation is temperatemixed forest dominated byJuniperus flaccidaSchltdl., Juniperus deppeana Steud., and Cupressussp. (all Cupressaceae). Mean annual temperature is17.8 °C, and the rainy season occurs from June toSeptember. The study site is a 44.37-ha ranch, ofwhich 60% preserves temperate forest remnants.The rest of the property has been induced pasturefor livestock for at least the last 38 years. During thesampling period, there were approximately 20 headof cattle and 65 sheep on the property. We stud-ied the dung relocation behavior of C. humectushidalgoensis in the cattle pasture during 10 daysin July 2010. At this site, the mean length ofC. humectus hidalgoensis was 10.11 mm (n =50,range = 7.8–16.1 mm) and mean weight was 0.18 g(n = 50, range = 0.06–0.8 g).To determine the linear displacement of dungand the total rolling time, we followed individualsfrom the source cow pat to the burying site. Displa-cement trajectories were complex, changing direc-tions, but mean linear distance from the source tothe burying site was 2.6 m (n = 24, range = 0.28–9.65 m). Ball rolling lasted on average 23.6 minfrom departure from the cow pat until the buryingprocessbegan(n=25,range=5–65minutes;Fig.1a).This suggests that this beetle species may be remov-ing each dung pat, which is approximately 0.10 m