Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that o...Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that of Neophocaena 0.2--0.5 sec. In Lipotes,a short divewould take 10--20 sec and a long dive up to 1--2 min (average value being 31 sec). InNeophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec.Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eyemuscles and nerves and the position of the eyes in the head correspond with the physical con-ditions of the environments so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direc-tion under water. With the Baiji this would occasionally cause fatal injuries by thepropeller of the ship. Such a case seems much less often with Neophocaena. The populationof Lipotes is at present very small.In the stretch of the river (between Nanjing andTaiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. Thecause for its scarcity is mostly due to accidents or wounds caused by propellers.展开更多
文摘Lipotes usually occurs in pairs or in small loose groups. The calves are born in March-April.The Finless porpoises are usually seen in groups of five or six individuals.The blowof Lipotes lasts 0.2--0.6 sec and that of Neophocaena 0.2--0.5 sec. In Lipotes,a short divewould take 10--20 sec and a long dive up to 1--2 min (average value being 31 sec). InNeophocaena a long dive would reach a maximum of 65 sec with an average of 17.5 sec.Lipotes has a pair of functional eyes. The selective secondary atrophy of a number of eyemuscles and nerves and the position of the eyes in the head correspond with the physical con-ditions of the environments so that the field of vision is directed forwards and upwards. When pursued by motor boat, both species react with a long dive and a change of direc-tion under water. With the Baiji this would occasionally cause fatal injuries by thepropeller of the ship. Such a case seems much less often with Neophocaena. The populationof Lipotes is at present very small.In the stretch of the river (between Nanjing andTaiyangzhou) under exploration, we found scarcely more than one dolphin per 4 km. Thecause for its scarcity is mostly due to accidents or wounds caused by propellers.
