Examining the role of bats in pest management in agroecosystems of south Texas

View the project final report

Commodities

Practices

• Education and Training: on-farm/ranch research
• Natural Resources/Environment: biodiversity, habitat enhancement, wildlife

Land use conversion to agriculture and urbanization impacts dynamics of flora and fauna, often negatively. With the use of acoustic recordings, this study estimates the potential impact of urbanization and agriculture on bat species diversity and abundance. We also examined the influence of land cover features such as tree canopy, impervious surfaces, and other features that might drive abundance of bats across 19 sites in the Lower Rio Grande Valley of south Texas. To achieve the research objectives bats were monitored from sunset to sunrise with acoustic surveys in sites spread across four general land use types: agricultural, peri urban, urban, and natural areas. A total of 14,614 distinct calls were detected over 114 observations during the period of 1 May to 15 August 2017. These calls corresponded to nine distinct species of bats, all of which were detected in all of land use types.  Results from this study indicate that there were no significant differences in bat abundance or diversity in the four different habitats, although we found a general trend of increasing abundance and decreasing diversity in urban and peri-urban sites. Brazilian free tail bats were the most commonly detected (representing 30.7% of all recordings), and were particularly dominant in both peri-urban sites and urban sites representing 45.5% and 37.8% of all recorded calls, respectively. A closer analysis of land cover features revealed that species evenness increased with tree canopy, and decreased with an increase of nearby area covered in impervious surfaces. Certain bat species were more closely associated with landscapes dominated by soil (such as the cave myotis), while others seemed to avoid urbanized areas entirely. This study highlights that changes in land use can affect bat diversity in somewhat predictable ways. Findings from this study may justify efforts to include urban forests in the design of urban landscapes, especially for flying organisms like bats and birds.

Objectives of this project were to:

1) Acoustically record echolocation calls of local chiropterans in four distinctive land uses: natural, agriculture, urban-suburban and urban-metropolitan. This objective was modified from the original proposal -- we were unable to find comparable areas that were considered organic agriculture vs. conventional agroecosystems.  

2) Determine what kind of landscape variables that may influence specific chiropteran species such as edge lines and bodies of water.