TY - JOUR
T1 - Population changes and limitation in the montane vole (Microtus montanus) in perennial old-field grasslands
T2 - Insights from a long-term study
AU - Sullivan, Thomas P.
AU - Sullivan, Druscilla S.
AU - Boonstra, Rudy
AU - Krebs, Charles J.
N1 - Funding Information:
We thank the Natural Sciences and Engineering Research Council of Canada, Research Branch of Agriculture Canada, Silviculture Branch, British Columbia Ministry of Forests, Victoria, British Columbia, the Canada-British Columbia Partnership Agreement on Forest Resource Development (FRDA II), Forest Renewal BC, and the Applied Mammal Research Institute for financial support. We thank the Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, for the use of study areas and logistical support. We greatly appreciate the assistance of H. Sullivan and several other technical staff for help with the fieldwork. We thank the two reviewers of the manuscript for their incisive comments.
Publisher Copyright:
© 2021 The Author(s) 2021. Published by Oxford University Press on behalf of the American Society of Mammalogists, www.mammalogy.org.
PY - 2021/4/1
Y1 - 2021/4/1
N2 - We livetrapped populations of Microtus montanus from 1982 to 2003 in semiarid perennial old-field grasslands of southern British Columbia. We evaluated two, nonmutually exclusive hypotheses (H) to explain their population dynamics: first (H1), that extended breeding during the summer or winter will drive the increase phase of population fluctuations; and second (H2), that density-dependent depression of juvenile survival will be reflected in poor early juvenile survival during high populations. Populations on 2-3 grids of 1 ha were livetrapped at 3- to 8-week intervals in summer and winter except in 5 years of very low populations. Densities ranged from 10/ha to 250/ha. Peak densities occurred in 6 years and an extended low phase occurred from 1999 to 2003. Fluctuations of 3-4 years appeared in our populations but were not always present. Breeding occurred both in summer and winter, and the best predictor of the population growth rate was the fraction of adult females lactating in summer or winter, thereby supporting H1. Juvenile production (number of juveniles/lactating female) varied greatly among years with the mean being over two times higher in low (2.41) than high (1.08) years, thereby supporting H2. There was no clear correlation between population changes and either seasonal temperatures or rainfall, or any combination of these two variables, and no obvious cause of the prolonged low from 1999 to 2003. Thus, both female reproduction and juvenile production drive montane vole dynamics demographically, similar to what is found in other vole species. However, the ultimate cause of these changes remains to be tackled experimentally.
AB - We livetrapped populations of Microtus montanus from 1982 to 2003 in semiarid perennial old-field grasslands of southern British Columbia. We evaluated two, nonmutually exclusive hypotheses (H) to explain their population dynamics: first (H1), that extended breeding during the summer or winter will drive the increase phase of population fluctuations; and second (H2), that density-dependent depression of juvenile survival will be reflected in poor early juvenile survival during high populations. Populations on 2-3 grids of 1 ha were livetrapped at 3- to 8-week intervals in summer and winter except in 5 years of very low populations. Densities ranged from 10/ha to 250/ha. Peak densities occurred in 6 years and an extended low phase occurred from 1999 to 2003. Fluctuations of 3-4 years appeared in our populations but were not always present. Breeding occurred both in summer and winter, and the best predictor of the population growth rate was the fraction of adult females lactating in summer or winter, thereby supporting H1. Juvenile production (number of juveniles/lactating female) varied greatly among years with the mean being over two times higher in low (2.41) than high (1.08) years, thereby supporting H2. There was no clear correlation between population changes and either seasonal temperatures or rainfall, or any combination of these two variables, and no obvious cause of the prolonged low from 1999 to 2003. Thus, both female reproduction and juvenile production drive montane vole dynamics demographically, similar to what is found in other vole species. However, the ultimate cause of these changes remains to be tackled experimentally.
KW - Arid grasslands
KW - Demographic changes
KW - Population cycles
KW - Population regulation and limitation
KW - Small mammals
UR - http://www.scopus.com/inward/record.url?scp=85108167282&partnerID=8YFLogxK
U2 - 10.1093/jmammal/gyaa155
DO - 10.1093/jmammal/gyaa155
M3 - Article
AN - SCOPUS:85108167282
SN - 0022-2372
VL - 102
SP - 404
EP - 415
JO - Journal of Mammalogy
JF - Journal of Mammalogy
IS - 2
ER -