Abstract

Title:  Long-term trends in white-tailed deer reproductive rates from eastern south Texas
Author(s): Mickey W. Hellickson
Year: 2009
Abstract: Annual and long-term trends in white-tailed deer (Odocoileus virginianus) reproductive rates are important considerations when establishing harvest quotas, especially for the female segment of the herd. We have monitored reproductive rates on the 825,000-acre King Ranch in eastern south Texas since 1999, annually collecting 70-300 females during late January-February. Annual fetus counts averaged 1.48 fetuses per female (N=1,582; range=1.06 to 1.63) and were correlated with January rainfall (r=0.516). Highest fetus counts occurred in 2.5- to 6.5-year-old females (1.5-1.6 fetuses/female); lowest counts were observed in yearling (1.0) and old (1.1) females. Mean date of conception was 18 December (range=27 Oct. thru 18 Jan.); 80% of conceptions occurred during December. Mean date of conception was earliest for old females (15 Dec.) and latest for yearling females (21 Dec.). Highest conception rates occurred in 2.5- to 6.5-year-old females (87-92%); lowest rates were displayed by old (8.5+ years old; 69%) and yearling (72%) females. On average, 14% of adult females were not pregnant, 24% carried singletons, 62% carried twins, and 0.7% carried triplets. None of 13 fawns collected was pregnant. Average annual conception rate varied (x=85%; range=66-93%) and was correlated with January rainfall (r=0.425). Conception rates of yearling females were correlated to body size (r=0.325), whereas conception rates of old females were correlated to kidney fat index (KFI; r=0.318). KFI was highest in 2.5-year-old females (54%) and lowest in female fawns (21%) and old females (28%). Average annual KFI varied (30-61%) and was correlated with rainfall during December (r=0.820). Yearling females had the highest ratio of male offspring (80%), followed by old females (64%).

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