Chicago\'s Brookfield Zoo announced a 31-year-old dolphin gave birth to a calf, causing a temporary end to the facility\'s Dolphin Presentations. The Chicago Zoological Society, which manages the zoo, said mother Tapeko, gave birth Thursday to a calf weighing about 40 pounds and measuring 3.5 feet long. The society said the zoo\'s Dolphin Presentations are being put on hold for a time to allow Tapeko to bond with her calf and introduce it to the other dolphins in her group. \"We know that the first 30 days are extremely critical in the calf\'s life,\" said Rita Stacey, marine mammal curator for the Chicago Zoological Society. Tapeko has previously reared four calves, including one grandson. \"This is an important time for our breeding group of females,\" Stacey said. \"As an experienced mom, Tapeko is able to demonstrate to the younger females how to care for a newborn calf.\"