In the European roe deer (Capreolus capreolus), implantation of embryos after breeding is delayed. The deer breed in July or August but do not give birth until the following May or
June. From summer to late December, the embryo rests in a state of dormancy as a 30-cell
blastocyst. In late December or early January, the embryo sends a signal that causes the
female to release hormones, allowing the embryo to continue to develop normally.