Comparing survey and multiple recruitment–mortality models to assess growth rates and population projections

William J. Severud, Glenn D. DelGiudice, Joseph K. Bump

Research output: Contribution to journalArticlepeer-review

Abstract

Estimation of population trends and demographic parameters is important to our understanding of fundamental ecology and species management, yet these data are often difficult to obtain without the use of data from population surveys or marking animals. The northeastern Minnesota moose (Alces alces Linnaeus, 1758) population declined 58% during 2006–2017, yet aerial surveys indicated stability during 2012–2017. In response to the decline, the Minnesota Department of Natural Resources (MNDNR) initiated studies of adult and calf survival to better understand cause-specific mortality, calf recruitment, and factors influencing the population trajectory. We estimated population growth rate (λ) using adult survival and calf recruitment data from demographic studies and the recruitment–mortality (R-M) Equation and compared these estimates to those calculated using data from aerial surveys. We then projected population dynamics 50 years using each resulting λ and used a stochastic model to project population dynamics 30 years using data from the MNDNR's studies. Calculations of λ derived from 2012 to 2017 survey data, and the R-M Equation indicated growth (1.02 ± 0.16 [SE] and 1.01 ± 0.04, respectively). However, the stochastic model indicated a decline in the population over 30 years (λ = 0.91 ± 0.004; 2014–2044). The R-M Equation has utility for estimating λ, and the supporting information from demographic collaring studies also helps to better address management questions. Furthermore, estimates of λ calculated using collaring data were more certain and reflective of current conditions. Long-term monitoring using collars would better inform population performance predictions and demographic responses to environmental variability.

Original languageEnglish (US)
Pages (from-to)12613-12622
Number of pages10
JournalEcology and Evolution
Volume9
Issue number22
DOIs
StatePublished - Nov 1 2019

Bibliographical note

Funding Information:
Author would like to thank T. Obermoller, K. Foshay, T. Enright, R. Ryan, B. Smith, T. Arnold, J. Forester, L. D. Mech, R. Wright, V. St-Louis, G. Street, the adult moose mortality study team (M. Carstensen, M. Dexter, E. Hildebrand, C. Jennelle, and D. Plattner), N. Hansen, D. Ingebrigtsen, A. Wuenschmann, A. Armien, J. Giudice, M. Schrage for technical and other assistance, and to MNDNR pilots B. Maas and J. Heineman. We are grateful to the volunteers who spent hours in the field: L. Ross, M. Haas, B. Betterly, J. (Lodel) Miedke, A. Jones, K. Miedke, J. Goethlich, and R. Willaert. This study was funded in part by the Minnesota Environmental and Natural Resources Trust Fund (ENRTF), the Wildlife Restoration (Pittman-Robertson) Program, and MNDNR Section of Wildlife's Wildlife Populations and Research Unit, with supplemental support from the Minnesota Deer Hunters Association. W.J.S. was also supported by the Albert W. Franzmann and Distinguished Colleagues Memorial Award and the University of Minnesota's Doctoral Dissertation Fellowship. The University of Minnesota's Department of Fisheries, Wildlife, and Conservation Biology provided technical and other support. J.K.B. was supported by grants NSF ID#1545611 and NSF ID#1556676.

Funding Information:
Author would like to thank T. Obermoller, K. Foshay, T. Enright, R. Ryan, B. Smith, T. Arnold, J. Forester, L. D. Mech, R. Wright, V. St‐Louis, G. Street, the adult moose mortality study team (M. Carstensen, M. Dexter, E. Hildebrand, C. Jennelle, and D. Plattner), N. Hansen, D. Ingebrigtsen, A. Wuenschmann, A. Armien, J. Giudice, M. Schrage for technical and other assistance, and to MNDNR pilots B. Maas and J. Heineman. We are grateful to the volunteers who spent hours in the field: L. Ross, M. Haas, B. Betterly, J. (Lodel) Miedke, A. Jones, K. Miedke, J. Goethlich, and R. Willaert. This study was funded in part by the Minnesota Environmental and Natural Resources Trust Fund (ENRTF), the Wildlife Restoration (Pittman‐Robertson) Program, and MNDNR Section of Wildlife's Wildlife Populations and Research Unit, with supplemental support from the Minnesota Deer Hunters Association. W.J.S. was also supported by the Albert W. Franzmann and Distinguished Colleagues Memorial Award and the University of Minnesota's Doctoral Dissertation Fellowship. The University of Minnesota's Department of Fisheries, Wildlife, and Conservation Biology provided technical and other support. J.K.B. was supported by grants NSF ID#1545611 and NSF ID#1556676.

Publisher Copyright:
© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.

Keywords

  • Alces alces
  • aerial survey
  • moose
  • population growth
  • recruitment–mortality Equation
  • survival

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