Impact of locust control on harvester termites and endemic vertebrate predators in Madagascar.
Abstract
Between 1997 and 2000 a plague of migratory locust in Madagascar triggered large-scale control operations. The widespread use of insecticides in a biodiversity hot-spot raised concern about hazards to wildlife. The aim of this study was to inform locust control policy by monitoring the effects of insecticides on key non-target organisms. The focus was on the harvester termite Coarctotermes clepsydra and its vertebrate predators. Effects on Coarctotermes clepsydra were studied in two areas. At Ankazoabo in 1998, we monitored rainy season barrier treatments with fipronil and triflumuron. At Malaimbandy in 2000, we monitored early dry season, full-cover sprays with fipronil and deltamethrin and also studied effects on the lizards Chalarodon madagascariensis and Mabuya elegans, the lesser hedgehog tenrec Echinops telfairi and their non-termite arthropod prey. At both sites, fipronil caused a strong reduction of the activity of Coarctotermes clepsydra colonies, culminating in high mortality. At Ankazoabo 10 months post-spray, colony mortality was 44.9%, 7.7% and 4.7%, respectively, in fipronil, triflumuron and unsprayed sites. Mortality within spray barriers was 90.7% and 10.8% for fipronil and triflumuron, respectively. Similar results were obtained at Malaimbandy 6 months post-spray, where fipronil caused 80.5% colony mortality, compared with 3.5% and 3.7% in unsprayed and deltamethrin plots. We observed a significant decline in the relative abundance of Chalarodon madagascariensis and Mabuya elegans in fipronil plots at Malaimbandy, with effective reductions (compared with pre-spray levels) of 52.7% and 45.2%, respectively. Echinops telfairi was not found in fipronil plots, while being frequent in unsprayed and deltamethrin plots. Termites proved to be important dietary components of all vertebrates studied, especially during the dry season. Echinops telfairi, the large-eared tenrec Geogale aurita and Mabuya elegans were more termite-specialized than Chalarodon madagascariensis. The abundance of lizards and Echinops telfairi was positively correlated with the density of live Coarctotermes clepsydra colonies. This suggests that reduced abundance of these insectivorous species in fipronil plots resulted from deprivation of their principal prey. Synthesis and applications. The present study provides evidence of food chain perturbations induced by fipronil. This has important implications for the management of locusts in Madagascar and other locust-affected countries. In recognition of the precautionary principle, we recommend that fipronil be withheld from full-cover spraying to ensure that locust control does not lead to biodiversity loss. Its use in barrier spraying requires further investigation of the long-term ecological effects, in particular with respect to the consequences of substantial termite mortality, before its environmental acceptability can be determined.