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Effects of biosolids on a grassland community of rodents and birds of prey in British Columbia

University of British Columbia

Grasslands around the world are becoming degraded due to human causes. In British Columbia, Canada, grasslands cover only ~1% of the landmass, yet 20% of species listed as “at-risk” of extinction in British Columbia occupy grasslands. Grassland restoration is therefore important to managing imperiled species. Biosolids (post-treatment sewage) are being used to increase forage for livestock grazing in some areas. These grasslands appear to support high densities of insects and small mammal prey, potentially enhancing populations of owls and raptors. To examine impacts of biosolids on populations of prey and predators, I studied small mammals, raptors, and owls at the OK Ranch, a cattle ranch near Clinton, British Columbia. I quantified differences in North American deermouse (Peromyscus maniculatus) populations on biosolids and control pastures and studied populations of Short-eared Owls (Asio flammeus), Long-eared Owls (Asio otus), and American Kestrels (Falco sparverius), comparing yearly abundance, habitat use, and diet within this biosolids-influenced ecosystem. Deermouse populations were smaller in pastures with biosolids, likely due to an increase in grass cover in these areas, thus indicating these pastures may be being restored. American Kestrels and Short-eared Owls used biosolids pastures over control pastures disproportionate to availability. American Kestrels ate prey that were most abundant each year. When present on the study area, Short-eared and Long-eared Owls primarily ate voles, however Short-eared Owls diversified their diets more in 2019, when vole populations were low. This research has expanded our knowledge about how biosolids can impact small mammal populations and raptor and owl habitat use. These results suggest biosolids could be used in an explicit conservation capacity to help restore wildlife populations on degraded grasslands.

Text

2020-10-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/76323

Biology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/