The Effects of Urbanization on Prairie Bats

(Uploaded by Plazi for the Bat Literature Project) My thesis addresses three key gaps in urban-ecology research, which lacks sufficient attention to (1) grassland biomes, (2) individual- and population-level effects, and (3) nonavian vertebrates. I hypothesized that in the fairly flat, homogeneous Prairies, the city (Calgary, Alberta) is like a structurally complex island, with increased availability of roosts and prey. Along with the urban heat island, these features of the urban environment would benefit Prairie bats, producing increased bat abundance, diversity and fitness in the city relative to outside. I acoustically monitored bat activity and captured bats in mist nets, and found that although urban bats were more abundant, they were not more diverse. Myotis lucifugus dominated bat assemblages throughout my study area, but nowhere more so than in Calgary. It appears that urbanization in the Prairies may create attractive habitat for one synanthropic species (M. lucifugus) but have the opposite effect for others. I sampled nocturnal insects to assess the potential availability of prey to bats, and acoustically monitored their foraging activity. Contrary to my predictions, neither insect abundance nor insect diversity was maximized in the city, and urban bats did not forage more than non-urban bats did. Thus, increased numbers of M. lucifugus in Calgary do not seem linked to an urban increase in prey availability. I assessed body condition, reproductive rates, spermatogenesis, production of juveniles, post-natal growth and population age structure in M. lucifugus. I found no support for predictions that urban bats have enhanced fitness relative to non-urban conspecifics. Instead, it appears that increased population density in the city may be detrimental to bats, perhaps by increasing intraspecific competition for food. Finally, I assessed the ectoparasite loads of urban and non-urban bats. The effects of urbanization in terms of modulating ectoparasitism were dependent on the bat species, bat group and parasite type, with no consistent pattern. Ultimately, I reject my overall hypothesis. Rather than benefitting Prairie bats, urbanization may be detrimental to them. This may reflect a more general negative effect of increased bat density and/or larger group size in the city.