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Estimating ungulate recruitment and growth rates using age ratios
Author(s) -
DeCesare Nicholas J.,
Hebblewhite Mark,
Bradley Mark,
Smith Kirby G.,
Hervieux David,
Neufeld Lalenia
Publication year - 2012
Publication title -
the journal of wildlife management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.94
H-Index - 111
eISSN - 1937-2817
pISSN - 0022-541X
DOI - 10.1002/jwmg.244
Subject(s) - ungulate , vital rates , population growth , population , woodland , demography , biology , wildlife , mark and recapture , woodland caribou , ecology , sociology
Trends in population growth can be monitored with data for key vital rates without knowledge of abundance. Although adult female survival has the highest elasticity for ungulate population dynamics, the more variable recruitment rates are commonly monitored to track local variation in growth rates. Specifically, recruitment is often measured using late winter young:adult age ratios, though these age ratios are difficult to reliably interpret given the contribution of multiple vital rates to annual ratios. We show that the supplementation of age ratio data with concurrent radio‐telemetry monitoring of adult female survival allows both retrospective estimation of empirical population growth rates and the decomposition of recruitment‐specific vital rates. We demonstrate the estimation of recruitment and population growth rates for 1 woodland caribou population using these methods, including elasticity and life‐stage simulation analysis of the relative contribution of adult female survival and recruitment rates to variation in population growth. We show, for this woodland caribou population, that adult female survival and recruitment rates were nearly equivalent drivers of population growth. We recommend the concurrent monitoring of adult female survival to reliably interpret age ratios when managing caribou and other ungulates. © 2011 The Wildlife Society.