When the female bat is pregnant, however, she cannot be as relaxed about it as human beings with their nine-month gestation period; she must fly when heavily pregnant, search for food, sleep upside down, fight against gravity--it is really tough.
但雌蝠懷孕時，可不比懷胎十月的人類輕鬆，它們必需大腹便便，負擔胎兒的重量飛行、覓食，還要倒吊著入眠，與地心引力「抗衡」，極為艱辛。