Recruitment estimates are critical for making wildlife harvest decisions. Lactation rate is used to estimate recruitment in monotocous species and as a recruitment index for polytocous species such as white‐tailed deer (Odocoileus virginianus). However, the relationship between lactation and recruitment has never been formally tested, and the suitability of the lactation index as a management tool for deer has been assumed rather than confirmed. We simulated the response of lactation rates to variation in fawn recruitment stemming from changes in fecundity and neonatal mortality. Additionally, we examined effects of sample size on precision of lactation rate estimates. The relationship between recruitment and lactation rate was nearly linear when fecundity = 1.0, but became progressively less so as fecundity increased. Fawn mortality and herd fecundity explained 99% of the variability in lactation rate, and fawn mortality explained five times more variability than fecundity. Precision of lactation rate was highly affected by sample size, greatly reducing the quality of information available from small samples. Confidently assessing recruitment trends in moderately to highly productive populations may commonly require sample sizes unavailable on small properties. Biologists on properties with limited sample size should seek other, unrelated measures of recruitment to supplement or replace lactation rate. © 2018 The Wildlife Society.

Recruitment estimates are critical for making wildlife harvest decisions. White-tailed deer (Odocoileus virginianus) lactation rates are often used to estimate fawn recruitment. Relatively long hunting seasons in the southern United States commonly include the period when females cease lactating, with concomitant reduction in the detection of lactation by hunters. We used 1,587 site-and year-specific lactation rates from 383 deer populations in Mississippi, Alabama, and Virginia, USA, to model the rate of decline in lactation detection across the hunting season. For each population, we calculated distance of mean female harvest date from median parturition date, and included linear, quadratic, and cubic functions of mean harvest day as potential explanatory variables. We grouped populations into 18 regions based on median conception date and tested 12 models using year and region as possible random effects. Mean female harvest occurred 92.5-210.7 days past median parturition date ( x ¼ 148.4 days, SE ¼ 0.5). Seasonal decline in lactation detection followed a linear trend with a daily decline of 0.25%. Given that our data contained properties where mean female harvest date varied by up to 81 days across years, this equates to a potential change in lactation index of 20% attributable only to differential detection. Adjusting hunter-estimated lactation indices should dampen variability of annual lactation indices simply associated with harvest date of females and clarify spatial and temporal trends in recruitment needed to advise wildlife managers. Ó 2016 The Wildlife Society.