PS 59-7
Ecosystem services of bats in California agriculture; their role in agroecosystem management, crop protection, and farmer perceptions

Friday, August 15, 2014
Exhibit Hall, Sacramento Convention Center
Katherine P. Ingram, Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA
Background/Question/Methods

Agricultural pesticide use is a major source of environmental contamination and poses a health risk to society. Practices that increase the abundance of natural insect predators such as bats can reduce pesticide use and save farmers money. However, the adoption of such practices, while obviously beneficial, can be slow, and the reasons for lack of adoption are not well-understood. The goals of the present study are to (1) assess the ecosystem service provided by bats in California’s Central Valley, (2) quantify pest consumption by bats to create an economic model of costs and benefits for farmers, and (3) evaluate the factors that influence the willingness of farmers to adopt techniques that encourage bat residency on farms. The data presented here address the first goal of this study. To assess the role of bats in California walnut orchards, bat activity was measured using acoustic survey on 16 walnut orchards in central California allocated equally to four treatments (with 4 replicates per treatment).  These treatments included farming practices (organic vs. conventional) and husbandry for bats (active support vs. no such support; active husbandry is defined by the presence of bat houses or other artificial roosting structures).

Results/Conclusions

Preliminary results from this study indicate that at least 11 bat species occur in California walnut orchards, and that 5 of these actively forage in orchards, suggesting a potential role of bat-aided pest control in conventional as well as organic agriculture. The most abundant bat species occurring in walnut is the Mexican free-tailed bat (Tadarida brasiliensis), a known moth-specialist. Over 40,000 individual call sequences  from bats were recorded over a two and a half month time period. Of these calls, over half were T. brasiliensis. Additionally, qualitative comparisons between organic and conventional groves indicate that organic orchards support a higher diversity of bat species. I can infer from these preliminary results that bats are an abundant component of orchard agroecosystems. Moreover, the activity level of T. brasiliensis suggests that moth consumption, particularly that of slow-flying codling moth, may be high on walnut orchards.