AN INTRODUCTION TO RIVER DOLPHIN SPECIES - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 3

species are commonly the top predators in their habitats. Unfortunately, river dolphins are
extremely sensitive to environmental change, either natural or anthropogenic (Da Silva,
1995). The apparent extinction of the baiji, (see Wang & Zhao's and Turner chapters;
chapters 19 and 20) the Chinese river dolphin, has been a wake up call for much of the
general public as well as the scientific community and has intensified man's interest in these
incredible and intelligent creatures. Much of our biological knowledge of river dolphins is
based on a text published 20 years ago (Perrin et al., 1989). At that time, the major part of the
biological knowledge concerning these animals was limited to basic ecological and census
studies and some morphological and physiological data relating to taxonomy. But in the last
20 years, genetics and molecular biology have revolutionized our understanding of biology
and evolution. Now for the first time, revolutionary molecular techniques are being applied to
answer evolutionary reconstruction questions of many animals, including river dolphins
(Cassens et al., 2000; Hamilton et al., 2001; Banguera-Hinestroza et al., 2002; Yang et al.,
2002, 2005; Verma et al., 2004; Cunha et al., 2005; Caballero et al., 2007; Ruiz-García, 2007;
Ruiz-García et al., 2007, 2008 and many chapters included in this topic). In addition, new
paleontological records are dramatically changing our perspective about the relationships of
these dolphins with each other and with other cetaceans and yet, no topic has incorporated
these fascinating new discoveries (see the Cozzuol and Barnes et al., chapters; chapters 10
and 23). To meet this informational gap, we contacted the world's premier river dolphin
specialists from Columbia, Brazil, Bolivia, Argentina, New Zealand, The United States of
America, China, England, and India and asked them to contribute chapters to this updated
river dolphin topic. Moreover, this topic provides new census information and important
ecological characteristics of the river dolphins Inia , Sotalia , Pontoporia , and Lipotes and
presents molecular and genetics results of these dolphin species. A compilation of these data
is essential if we are to present a strategic conservation plan for these animals. Upon being
informed of critical evolutionary history data, conservation biologists will be able to tailor
their conservation efforts for each threatened river dolphin species. Additionally, new
morphological data and the new discoveries in the fossil record for river dolphins are
presented in this topic that graduate students, professors, scientists, evolutionary ecologists,
aquatic mammalogists, population ecologists, conservation ecologists, and marine biologists
should find valuable for the foreseeable future. Introductory descriptions of each of the
species covered in this topic, along with field photos taken by the topic's authors are provided
in the following sections. We, the Authors and Editors, hope that you utilize the provided
data, and, if not already, become active members in the conservation of river dolphin species.
Neophocaena phocaenoides asiaeorientalis (Finless Porpoise)
As its name states the finless porpoise does not possess a dorsal fin, but instead has a
series of tubercles (Figure 1). Their flippers are relatively large and their overall body color is
dark grey to black. It is also one of the smallest odontocetes with a maximum length for males
of 1.9 m with males being slightly longer than females. Average adult weight ranges from
around 30 to 45 kg (Wang et al., 2005). The subspecies of the finless porpoise in China
( Neophocaena phocaenoides asiaeorientalis ) is only found in the Main channel of the
Yangtze River and Poyang Lake. Until recently, it seemed to prefer the confluence area of the
Yangtze River and Poyang Lake where it historically had congregated in relatively large