Moth munchers: limited intraspecific variation in summer diet of the endangered Florida Bonneted Bat (Eumops floridanus)

Abstract

Urbanization drives biodiversity loss for many taxa, including arthropods, which serve as the foundation for terrestrial food webs worldwide. Understanding variation in diet among and within wildlife populations across a range of urbanization is especially important for endangered species that often face habitat loss and threats to their prey base. Here, we used molecular metabarcoding of feces to examine geographic and individual variation in the diet of endangered Florida Bonneted Bats, Eumops floridanus, a species whose range is constricted by rapid urban development and whose harem social structure may confer demographic differences in foraging. We used 2 primer sets to amplify insect prey from fecal samples collected from bats in 3 study regions that spanned an urbanization gradient and corresponded to genetically distinct populations. All samples tested contained Lepidoptera, Coleoptera, and Orthoptera-with an especially high diversity of lepidopteran taxa including many large tympanate moths and agricultural pests. In contrast to our predictions, there was no clear influence of urbanization on diet nor marked differences between demographic groups apart from some subtle differences in diet composition and diversity. Instead, our results indicate that distinct populations of E. floridanus preyed on similar insect taxa across their range, with nearly half of identified prey genera being consumed by bats across all 3 regions. Bats from the moderately urban region with the greatest landscape heterogeneity did differ in diet composition and consumed a greater diversity of prey than bats from the urban region, suggesting some influence of landscape composition on foraging. The high overlap in insect prey consumed by E. floridanus across regions suggests that available prey is similar among regions or that the species may select similar resources across the range regardless of availability.

Keywords: Chiroptera; conservation; geographic variation; insect prey, molecular diet analysis; niche breadth; niche overlap.

Fig. 1.

Map of Florida, USA, showing the area designated by the U.S. Fish and Wildlife Service as the consultation area for Eumops floridanus (hatched area indicates the presumed geographic range of the species) and the location of 3 regions where guano was collected from bats from May to July 2017 across an urbanization gradient: the Greater Miami Area (GMA)–high urban; Fred C. Babcock-Cecil M. Webb Wildlife Management Area (BWWMA)—moderate urban; Avon Park Air Force Range (APAFR)–low urban.

Fig. 2.

Frequency of occurrence (FOO) of the most commonly consumed taxa by Eumops floridanus across all 3 regions: Avon Park Air Force Range (APAFR); Babcock-Webb WMA (BWWMA); Greater Miami Area (GMA). Includes prey items detected in > 60% of all samples tested (Total FOO, dotted black line) and FOO for detection within samples from each region (colored bars). Asterisks indicate prey items considered an agricultural or forest pest species. More details on insect habitat associations and natural history are in Supplementary Data SD3.

Fig. 3.

Relative abundance of operational taxonomic units (OTUs) identified to at least family (outer circle) and order (inner circle) using 2 primer sets (ANML, ZBJ) in fecal samples collected from Eumops floridanus in 3 geographic regions varying in level of urbanization May–July 2017: A) low urban–Avon Park Air Force Range (APAFR; n = 14 samples, 1,497 OTUs); B) moderate urban–Fred C. Babcock-Cecil M. Webb Wildlife Management Area (BWWMA; n = 18 samples, 2,556 OTUs); C) high urban Greater Miami Area (GMA; n = 10 samples, 1,122 OTUs), and D) all samples from the 3 study regions combined.

Fig. 4.

Non-metric multidimensional scaling (NMDS) showing diet composition of Eumops floridanus at the resolution of insect genera occurrence partitioned according to geographic region: low urban–Avon Park Air Force Range (APAFR); moderate urban–Fred C. Babcock-Cecil M. Webb Wildlife Management Area (BWWMA); and high urban–Greater Miami Area (GMA).

Fig. 5.

Extrapolated prey accumulation curves comparing richness of insect genera detected in the diet of Eumops floridanus at 3 geographic locations: low urban–Avon Park Air Force Range (APAFR); moderate urban–Fred C. Babcock-Cecil M. Webb Wildlife Management Area (BWWMA); and the high urban–Greater Miami Area (GMA). Shaded areas represent 95% confidence intervals.