REPRODUCTIVE-PERFORMANCE OF FEMALE SIKA-DEER IN MARYLAND

Because captive and free-ranging populations of sika deer (Cervus nippon) are increasing in the United States, with potential adverse effects on native cervids, a better understanding of the reproductive traits of this exotic species is needed to assess its population dynamics. Thus, we analyzed reproductive tracts of 15 calf, 25 yearling, and 54 adult female sika deer collected in Dorchester County, Maryland, during 1991-92 hunting seasons. Ninety-four percent of the adults and all yearlings had corpora lutea of pregnancy or estrus; 40 adults and 14 yearlings carried visible fetuses. Eight calves had ovulated as determined by the presence of corpora hemorrhagica; 4 of these had blastocyst-stage embryos. Adults bred earlier than yearlings, on the basis of corpora lutea (P = 0.02) and fetus size (P = 0.07), and both age groups bred before calves. However, for yearlings and adults there was no relationship between maternal body mass and fetus size (P = 0.85). Although twins have not been reported for free-ranging sika deer, 1 adult carried 2 healthy fetuses. The reproductive potential of introduced sika deer populations may be greater than previously reported because sika deer are capable of becoming pregnant as calves.