POPULATION STATUS AND CONSERVATION OF THE GANGES RIVER DOLPHIN (PLATANISTA GANGETICA GANGETICA) IN THE INDIAN SUBCONTINENT - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 421

continues to be a threat (Sinha, 2006). Depletion of big size and major carp fishery in the
rivers over the years has resulted in greater exploitation of smaller fishes, which are
considered main prey of dolphins (Sinha, 2006; Choudhary et al., 2006). Conservation efforts
across India, Nepal and Bangladesh have mainly focused on sensitizing fishermen to stop the
killing of dolphins, seeking people's co-operation for prevention of illegal hunting and
creating awareness about the adverse effects of dams and barrages on river flows and
catchments (Smith et al., 1998; Sinha, 2006; WWF, 2006; Choudhary et al., 2006). Apart
from population surveys and threat mitigation measures, the detailed, scientific ecological
knowledge about the species is still bereft of empirical information. Considering the high
human impacts on the river systems the species inhabits, information regarding population
size, space use, and habitat preferences that influence distribution and survival is required to
systematically plan conservation strategies.
Most of the Ganges' major tributaries originate in the Himalayas and merge with the
Ganges in the state of Bihar and almost one-half of the total dolphin populations are expected
to survive in the Bihar stretch of the Ganges and its tributaries. The present study is based on
the surveys conducted during post-monsoon (November-December), winter (February-
March) and summer (May-June) of 2005-2007. It also includes information on biology
including origin, evolution and phylogenetic position of the species, as well as habitats
(different rivers / stretch of the rivers), threats and conservation efforts made to save the
animal from extinction.
Origin of Cetacea
Phylogenetic analyses of molecular data on extant animals strongly support the notion
that hippopotamids are the closest relatives of cetaceans (Millinkovitch et al., 1998; Nikaido
et al., 1999; Gatesy & O'Leary, 2001). In spite of this, it is unlikely that the two groups are
closely related when extant and extinct artiodactyls are analyzed, for the simple reason that
cetaceans originated about 50 million years ago in south Asia, whereas the family
Hippopotamidae is only 15 million year old, and the first hippopotamids to be recorded in
Asia are only 6 million year old (Boisserie et al., 2005). The middle Eocene artiodactyl family
Raoellidae is broadly coeval with the earliest cetaceans, and both are endemic to south Asia.
Thewissen et al. (2007) studied new dental, cranial and postcranial material for Indohyus , a
middle Eocene raoellid artiodactyl from Kashmir, India. Their analysis identifies raoellid as
the sister group to cetaceans and bridges the morphological divide that separated early
cetaceans from artiodactyls. Bajpai et al. (2009) reviewed the first steps of whale evolution,
i.e. the transition from a land mammal to obligate marine predators, documented by the
Eocene cetacean families of the Indian subcontinent: Pakicetidae, Ambulocetidae,
Remingtonocetidae, Protocetidae, and Basilosauridae, as well as their artiodactyl sister group,
the Raoellidae and concluded that the Eocene origin and evolution of whales is one of the best
documented examples of macroevolutionary change.
Indohyus was a small, stocky artiodactyl, roughly the size of the racoon Procyon lotor . It
was not an adept swimmer; instead it waded in shallow water and may have fed on land,
although a specialized aquatic diet is also possible. It probably spent a considerably greater
amount of time in the water either for protection or when feeding. As indicated by the
evidence from stable isotopes, Indohyus spent most of its time in the water and either came