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

Area of Science:

• Wildlife Ecology
• Population Dynamics
• Mammalian Biology

Background:

• New-hoof growth is a primary metric for aging newborn ungulates.
• Existing hoof-growth equations exhibit variability, potentially biasing survival estimates in population models.

Purpose of the Study:

• To evaluate age estimation discrepancies among current hoof-growth equations for newborn ungulates.
• To assess the impact of age estimation variability on survival estimates in staggered-entry models.

Main Methods:

• Radiocollared 174 known-age newborn ungulates (white-tailed deer, mule deer, pronghorn) from 2001-2009.
• Compared age estimates from existing hoof-growth equations against known ages.
• Analyzed the effect of age estimation variance on short-term (30-day) and long-term (120-day) survival estimates.

Main Results:

• Age estimation varied significantly among models, with differences exceeding 10-20 days for deer and pronghorn.
• Accuracy in aging newborns using published equations was low, ranging from 0% to 39.4%.
• Age estimation variability affected survival estimates for white-tailed and mule deer, but not pronghorn.

Conclusions:

• Daily survival modeling intervals are too fine when neonatal age-at-capture is uncertain due to equation inaccuracies.
• Weekly survival intervals are more appropriate for modeling survival when age is estimated.
• Selecting appropriate hoof-growth equations and survival intervals is crucial for accurate population assessments.