Data from: Re-evaluating neonatal-age models for ungulates: does model choice affect survival estimates?

New-hoof growth is regarded as the most reliable metric for predicting age
of newborn ungulates, but variation in estimated age among hoof-growth
equations that have been developed may affect estimates of survival in
staggered-entry models. We used known-age newborns to evaluate variation
in age estimates among existing hoof-growth equations and to determine the
consequences of that variation on survival estimates. During 2001–2009, we
captured and radiocollared 174 newborn (≤24-hrs old) ungulates: 76
white-tailed deer (Odocoileus virginianus) in Minnesota and South Dakota,
61 mule deer (O. hemionus) in California, and 37 pronghorn (Antilocapra
americana) in South Dakota. Estimated age of known-age newborns differed
among hoof-growth models and varied by >15 days for white-tailed
deer, >20 days for mule deer, and >10 days for pronghorn.
Accuracy (i.e., the proportion of neonates assigned to the correct age) in
aging newborns using published equations ranged from 0.0% to 39.4% in
white-tailed deer, 0.0% to 3.3% in mule deer, and was 0.0% for pronghorns.
Results of survival modeling indicated that variability in estimates of
age-at-capture affected short-term estimates of survival (i.e., 30 days)
for white-tailed deer and mule deer, and survival estimates over a longer
time frame (i.e., 120 days) for mule deer. Conversely, survival estimates
for pronghorn were not affected by estimates of age. Our analyses indicate
that modeling survival in daily intervals is too fine a temporal scale
when age-at-capture is unknown given the potential inaccuracies among
equations used to estimate age of neonates. Instead, weekly survival
intervals are more appropriate because most models accurately predicted
ages within 1 week of the known age. Variation among results of
neonatal-age models on short- and long-term estimates of survival for
known-age young emphasizes the importance of selecting an appropriate
hoof-growth equation and appropriately defining intervals (i.e., weekly
versus daily) for estimating survival.