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Left truncation criteria for survival analysis of white‐tailed deer
Author(s) -
Norton Andrew S.,
Storm Daniel J.,
Watt Michael A.,
Jacques Christopher N.,
Martin Karl,
Van Deelen Timothy R.
Publication year - 2016
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.21110
Subject(s) - odocoileus , truncation (statistics) , hunting season , wildlife , population , demography , statistics , zoology , biology , geography , ecology , mathematics , sociology
Survival estimates are commonly obtained by physically capturing wildlife and marking or affixing a transmitter to a representative sample of the population. Bias induced by capture stress can occur for white‐tailed deer ( Odocoileus virginianus ) if capture influences the probability of mortality. To mitigate this bias, researchers often left truncate data for a threshold number of days (14–28 days for deer) after capture. Potential costs of left truncation include reduced sample size and reduced inference. Costs associated with capture and monitoring of deer are substantial, and defining a truncation period is usually arbitrary or ad hoc. Hence, researchers need to evaluate objectively the effects of left truncation. We analyzed time‐to‐event data from 1,001 radio‐collared white‐tailed deer from northern forests and eastern farmlands of Wisconsin, USA in 2011–2014 to evaluate justification for using a 2‐week truncation period by comparing the probability of mortality for deer <2 weeks post‐capture and deer ≥2 weeks post‐capture. We found little support for a difference in mortality between the groups. Results accounting for time of year, study area, and age suggested a 0.69 probability that deer ≥2 weeks post‐ capture had a lower mortality rate than deer <2 weeks post‐capture. Using a reference group of 6–10 ‐month‐old deer in the eastern farmlands in 2011, cumulative capture season mortality was 0.102 (50% CI = 0.075–0.125; SE = 0.037) for deer <2 weeks post‐capture and 0.114 (50% CI = 0.087–0.138; SE = 0.037) for deer ≥2 weeks post‐capture. Our results suggested that when a careful review of cause‐specific mortality is considered for each deer, and presumed capture‐related mortalities are removed from the sample, a 2‐week truncation period is unnecessary. © 2016 The Wildlife Society.