Productivity Measures of White-Tailed Deer in New Hampshire: Assessing Reduced Recruitment

Effective management of white-tailed deer (Odocoileus virginianus) populations requires reliable estimates of demographic parameters. New Hampshire's deer population has increased substantially since the 1980s, while recruitment rates based on indices from harvested deer have steadily declined since the mid-1990s. To better understand the reasons for such decline, we assessed the current reproductive attributes of New Hampshire's deer herd through measurement of ovulation rate, pregnancy rate, and fetal counts from winter mortalities during 2011-2013 and compared these data with similar data collected in New Hampshire, USA, during 1972-1987. Pregnancy rates were 97% and 100% in the adult and yearling age classes, respectively, but few (8%) fawns bred. All pregnant fawns carried single fetuses, while yearlings averaged 1.72 fetuses and adults 1.95. Peak breeding for adults and yearlings occurred during the third week of November; fawns bred 4 weeks later. Pregnancy rate and fecundity of older deer were unchanged since the 1980s; fawn pregnancy rate declined but was always relatively low. Productivity of the population increased due to a greater proportion of adults in 2011-2013, suggesting that declining recruitment may be due to increased summer fawn mortality. Additional research is needed to provide more accurate estimates of recruitment and to identify the specific causes of summer fawn mortality; however, in New Hampshire and other northern deer populations limited by severe winters, lower recruitment rates may render local population goals unachievable. (C) 2015 The Wildlife Society.