Potential impact of neonicotinoid use on Northern bobwhite (Colinus virginianus) in Texas: A historical analysis.

The widespread use of neonicotinoid insecticides in recent years has led to increasing environmental concern, including impacts to avian populations. In Texas and across their range, Northern bobwhite (Colinus virginianus) habitat frequently overlaps cultivated cropland protected by neonicotinoids. To address the effects of neonicotinoid use on bobwhites in Texas, we conducted a historical analysis from 1978-2012 in Texas' ecological regions using quail count data collected from North American Breeding Bird Survey and Texas Parks and Wildlife Department, and neonicotinoid use data from the U.S. Geological Survey. We considered bobwhite abundance, neonicotinoid use, climate, and land-use variables in our analysis. Neonicotinoid use was significantly (p<0.05) negatively associated with bobwhite abundance in the High Plains, Rolling Plains, Gulf Coast Prairies & Marshes, Edwards Plateau, and South Texas Plains ecological regions in the time periods following neonicotinoid introduction (1994-2003) or after their widespread use (2004-2012). Our analyses suggest that the use of neonicotinoid insecticides may negatively affect bobwhite populations in crop-producing regions of Texas.

Dung removal by dung beetles (Coleoptera: Scarabaeidae) and macrocyclic lactone use on cattle ranches of Yucatan, Mexico / Remoción de estiércol por escarabajos estercoleros (Coleoptera: Scarabaeinae) y uso de lactonas macrocíclicas en ranchos ganaderos de Yucatán, México

Abstract:The expanded use of macrocyclic lactones (ML) to treat endo- and ectoparasites in cattle in tropical regions, can reduce dung beetle populations, and thus interrupt the dung removal process in cattle pasture ecosystems. During the reproductive period (the rainy season) of two functional groups of dung beetles (paracoprid and telocoprid Scarabaeinae), we compared dung removal amount in ranches where ML are and are not used in Yucatan, Mexico, through exclusion traps baited with 500 g of ML-free cow dung. On each ranch, two transects (separated by 500 m) with six traps each, were set up for 24 hours. After this time, all the dung remnants in each trap were obtained and weighed in order to record the dung removal. Results showed that dung removal amounts were similar in ranches with and without ML use. Dung beetles removed 40.1 % of all cow dung weighed. Paracoprids removed 87.46 % and telocoprids 12.54 % of all the dung that was removed. Our results indicated that the ecological function of dung beetles in the pastures studied, does not seem to be affected by the ML use, and that paracoprid species removed most of the dung. For both types of ranch, further studies that take into account the population dynamics and movement of the most important dung beetle species in the region are required, coupled with laboratory studies evaluating the effect of ML on their reproductive success. This could give some light on the effect of ML on the ecological function of this important insect group in the sustainability of cattle production systems. Rev. Biol. Trop. 64 (3): 945-954. Epub 2016 September 01.

ResumenLa expansión en el uso de lactonas macrocíclicas (LM) para el tratamiento de endo y ectoparásitos del ganado en las regiones tropicales puede reducir las poblaciones de escarabajos del estiércol, interrumpiendo así el proceso de eliminación de estiércol de ganado en los pastizales. Durante el período reproductivo (época de lluvias) de dos grupos funcionales de escarabajos coprófagos (paracópridos y telecópridos), se comparó la cantidad removida de estiércol usando trampas de exclusión cebadas con 500 g de estiércol de vaca libre de LM en dos ranchos donde se usan y en dos donde no se usan LM, en la península de Yucatán, México. En cada rancho se establecieron dos transectos (separados por 500 m) con seis trampas cada uno, las cuales estuvieron activas durante 24 horas. Después de este tiempo, todos los restos de estiércol en cada trampa se pesaron para registrar la remoción. Los resultados mostraron que las cantidades de remoción fueron similares en ranchos con y sin uso de LM. Los escarabajos estercoleros removieron 40.1 % del peso total del excremento. Los paracópridos removieron 87.46 % y los telecópridos 12.54 % del total de excremento removido. Los resultados indican que la función ecológica de los escarabajos estercoleros en los potreros estudiados no parece verse afectada por el uso de LM y que las especies paracórpidas remueven la mayor parte del excremento. Se requiere hacer más estudios en ambos tipos de ranchos, en los que se tome en cuenta la dinámica poblacional y el movimiento de las especies más importantes de la región, acoplados a estudios de laboratorio que evalúen el efecto de las LM sobre el éxito reproductivo, y de esta manera esclarecer el efecto de las LM sobre la función ecológica de este grupo de insectos tan importante para la sustentabilidad de los sistemas ganaderos.

Dung removal by dung beetles (Coleoptera: Scarabaeidae) and macrocyclic lactone use on cattle ranches of Yucatan, Mexico.

The expanded use of macrocyclic lactones (ML) to treat endo- and ectoparasites in cattle in tropical regions, can reduce dung beetle populations, and thus interrupt the dung removal process in cattle pasture ecosystems. During the reproductive period (the rainy season) of two functional groups of dung beetles (paracoprid and telocoprid Scarabaeinae), we compared dung removal amount in ranches where ML are and are not used in Yucatan, Mexico, through exclusion traps baited with 500 g of ML-free cow dung. On each ranch, two transects (separated by 500 m) with six traps each, were set up for 24 hours. After this time, all the dung remnants in each trap were obtained and weighed in order to record the dung removal. Results showed that dung removal amounts were similar in ranches with and without ML use. Dung beetles removed 40.1 % of all cow dung weighed. Paracoprids removed 87.46 % and telocoprids 12.54 % of all the dung that was removed. Our results indicated that the ecological function of dung beetles in the pastures studied, does not seem to be affected by the ML use, and that paracoprid species removed most of the dung. For both types of ranch, further studies that take into account the population dynamics and movement of the most important dung beetle species in the region are required, coupled with laboratory studies evaluating the effect of ML on their reproductive success. This could give some light on the effect of ML on the ecological function of this important insect group in the sustainability of cattle production systems.