Rapid increases in bat activity and diversity after wetland construction in an urban ecosystem

Abstract

Wetland construction can mitigate the biodiversity and water quality losses associated with reduced natural wetland coverage. While beneficial effects of wetland construction for bats have been observed in natural and rural settings, the effects of wetland construction on bats in an urban ecosystem are less understood. We used passive acoustic monitoring to measure bat activity levels and diversity at two constructed wetlands and two control sites on the University of North Carolina Greensboro campus, in Greensboro, North Carolina, USA. We monitored all 4 sites before and after wetland construction. Pre-wetland construction, there were few differences in bat activity and community structure at our sites. After wetland construction, we observed greater activity, attributable to all species we recorded, at wetland sites compared to control sites. Species diversity and species richness were also higher at wetland sites compared to control sites. When comparing the same sites before and after wetland construction, both bat activity and species richness increased after construction, but the effects were seen in Winter and not Spring. Our results demonstrate that bats use constructed wetlands in urban ecosystems similarly to other habitat settings. Increases in bat activity, diversity, and species richness occurred within one year of wetland construction.

Keywords: Bioindicators; Chiroptera; Conservation; Eptesicus fuscus; Fresh Water; Management; Piedmont; Spring; Winter.

Figure 1:

Total bat activity (number of passes per night) in control and proposed wetland sites before the wetland construction (November 19^th, 2016–March 14^th, 2017) and in control and wetland sites after the construction (March 15^th, 2017–March 28^th, 2018) at the Peabody Park at the University of North Carolina Greensboro. Total bat activity was not different between sites before the construction (p = 0.407, n = 177, Wilcoxon rank sum test) and was higher at wetland than control sites after the construction (p < 0.001, n = 691, Wilcoxon rank sum test).

Figure 2:

Species specific bat activity (number of passes per night) in control and proposed wetland sites before the wetland construction (November 19^th, 2016–March 14^th, 2017) and in control and wetland sites after the construction (March 15^th, 2017-March 28^th, 2018) at the Peabody Park at the University of North Carolina Greensboro. Species abbreviations are: (Eptesicus fuscus (EPTFUS), Lasiurus borealis (LASBOR), Lasiurus cinereus (LASCIN), Lasionycteris noctivagans (LASNOC), Nycticeius humeralis (NYCHUM), Perimyotis subflavus (PERSUB), and Tadarida brasiliensis (TADBRA). Before the wetland construction, LASBOR, LASCIN, and PERSUB activity was higher at the proposed wetland sites than the control (all p < 0.050, n = 177, Wilcoxon rank sum test). After the construction, all 7 species had higher activity at the wetland sites than the control (all p < 0.050, n = 691, Wilcoxon rank sum test).

Figure 3:

Total bat activity (number of passes per night) in control and proposed wetland sites before the wetland construction in the Winter (November 19^th, 2016–January 31^st, 2017) and Spring (February 1^st, 2017–March 14^th, 2017) and in control and wetland sites after the construction in the Winter (November 19^th, 2017–January 31^st, 2018) and Spring (February 1^st, 2018–March 14^th, 2018) at the Peabody Park at the University of North Carolina Greensboro. After the wetland construction, total bat activity was higher at both control and wetland sites as compared to control and proposed wetland sites respectively in the Winter (control p=0.004, n = 107, proposed wetland/wetland p = 0.013, n = 105, Wilcoxon rank sum test). No difference was found in the Spring (both p >0.050, n = 70 for control, n = 72 for proposed wetland/wetland, Wilcoxon rank sum test).

Figure 4:

Species specific bat activity (number of passes per night) in control and proposed wetland sites before the wetland construction in the Winter (November 19^th, 2016–January 31^st, 2017) and Spring (February 1^st, 2017–March 14^th, 2017) and in control and wetland sites after the construction in the Winter (November 19^th, 2017–January 31^st, 2018) and Spring (February 1^st, 2018–March 14^th, 2018) at the Peabody Park at the University of North Carolina Greensboro.Species abbreviations are: (Eptesicus fuscus (EPTFUS), Lasiurus borealis (LASBOR), Lasiurus cinereus (LASCIN), Lasionycteris noctivagans (LASNOC), Nycticeius humeralis (NYCHUM), Perimyotis subflavus (PERSUB), and Tadarida brasiliensis (TADBRA). In the Winter, LASCIN activity significantly increased at the control sites (p = 0.002, n = 107, Wilcoxon rank sum test) and NYCHUM activity increased at the wetland sites after the wetland construction (p = 0.016, n = 105, Wilcoxon rank sum test). In the Spring, only PERSUB activity increased at the wetland sites as compared to the proposed wetland sites (p = 0.004, n = 72, Wilcoxon rank sum test).