REPRODUCTIVE-PERFORMANCE OF FEMALE SIKA-DEER IN MARYLAND

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