Indian Gharial

 

 

Kingdom                                  ANIMALIA

Phylum                                    CHORDATA

Class                                        REPTILIA

Order                                       CROCODYLIA

Family                                     GAVIALIDAE

 

Common Names                        FISH-EATING CROCODILE (Eng)
GAVIAL (Eng)
GHARIAL (Eng)
INDIAN GAVIAL (Eng)
INDIAN GHARIAL (Eng)
LONG-NOSED CROCODILE (Eng)
GAVIAL DU GANGE (Fre)
GAVIAL DEL GANGES (Spa)

 

Year Assessed: 2007

Assessor/s:                               Choudhury, B.C., Singh, L.A.K., Rao, R.J., Basu, D., Sharma, R.K., Hussain, S.A., Andrews, H.V., Whitaker, N., Whitaker, R., Lenin, J., Maskey, T., Cadi, A., Rashid, S.M.A., Choudhury, A.A., Dahal, B., Win Ko Ko, U., Thorbjarnarson, J & Ross, J.P.

 

Assessment Information

Evaluator/s:                              Fergusson, R., Elsey, R., Velasco, A. & Dacey, T. (Crocodile Red List Authority)

 

Justification

 

Criterion A: Gharial qualify for Critically Endangered (CR) listing under criterion A2 ("reduction in population size based on an observed, estimated, inferred or suspected population size reduction of ≥80% over the last 10 years or three generations, whichever is the longer, where the reduction or its causes may not have ceased OR may not be understood OR may not be reversible"), based on (b) an index of abundance appropriate to the taxon and (c) a decline in area of occupancy, extent of occurrence and/or quality of habitat). Very conservative estimates of population decline over a three-generation period (from 1946 to 2006) indicate there has been a 96 to 98% population decline (see details below), and the once widespread population has been reduced to a very small number of widely spaced subpopulations.

Criterion C: The Gharial also qualified for CR listing under criterion C1 - ("population size estimated to number fewer than 250 mature individuals and an estimated continuing decline of at least 25% within three years or one generation"). Estimates of adult population size indicate that there has been a decline from 436 adult gharials in 1997 to 182 in 2006. This represents a 58% drop across its range over a period of nine years, well within the span of one generation (see details below).

Rationale for Criterion A:

The generation length for the species is 20 years (the age at which 50% of total reproductive output is achieved) (Rao et al. 1995). The Red List Criteria require "declines measured over the longer of 10 years or 3 generations", in this case the population decline since 1946.

Early Records:

The early records for the gharial are mainly subjective and rarely quantitative. Old references indicate the gharial's abundance in the past: Common in the Indus River in Pakistan (Francis 1910, Rao 1933); Gandak River in Nepal (I.A.K. 1921); Jumuna River in Uttar Pradesh (Hornaday 1885), Kosi river in Bihar (Shortt 1921). Several authors mention seeing groups basking together and in 1885 Hornaday wrote that he could count 64 gharials in two hours on the banks of the Jamuna. Andrew Leith Adams (1867) wrote: "abounds in all the great rivers of Northern India…Ten or twenty may be frequently seen together". "Hundreds of Gharial were observed on the Narayani River (Nepal) prior to the construction of the Gandak barrage…in 1964 and in the early 1950s about 235 Gharial were counted along the Narayani river between Narayanghat and Tribeni" (Maskey 1999). With an estimated 11,000 river kilometers of habitat over a geographic area of over 20,000 square kilometers (much of the northern mass of the Indian subcontinent form the Indus river system in the West to the Irrawaddy in the East) the Gharial had a conservatively inferred population of 5,000 to 10,000.

Current population status:

By 1976, the estimated total population of wild Gharial in the world had declined from what is thought to have been 5,000 to 10,000 in the 1940s to less than 200 (Whitaker et al. 1974), a decline of about 96%. In 2006, the mature Gharial population in India stands at a similar figure, less than 200 (Andrews 2006, Sharma and Basu, 2004) and less than 35 adults for Nepal (T. Maskey pers. comm. 2006). The species is virtually extinct in Pakistan (Whitaker and Basu 1983), Bangladesh (Whitaker 1976, Khan 1979, Faizuddin 1985) and Bhutan (Singh 1991). Only two records for the species were recorded from Myanmar in 1927 (Thorbjarnarson et al. in press) and it is presumed long extinct.

The drastic decline in the Gharial population over the last 60 years (three generations for the gharial) can be attributed to a variety of causes including over-hunting for skins and trophies, egg collection for consumption, killing for indigenous medicine, and killing by fishermen (for example: Biswas 1970 and Whitaker 1975). While hunting is no longer considered to be a significant threat, the construction of dams, barrages, irrigation canals, siltation, changes in river course, artificial embankments, sand-mining, riparian agriculture, and domestic and feral livestock have combined to cause an extreme limitation to gharial range due to this excessive, irreversible loss of riverine habitat. For instance, Hussain (2001) documents plans for 276 irrigation projects in the Chambal River basin alone. These threats have not ceased, indeed have increased and continue to compromise the survival of the species. Gharial decline has gone hand in hand with the decline of other riverine taxa once reportedly abundant and now endangered including the Ganges River Dolphin (Platanista gangetica) and the Mugger crocodile (Crocodylus palustris) as well as numerous waterfowl and well known game and edible fish species including the Mahseer (Tor sp.) and Hilsa (Hilsa illisha).

Based on the above, the Gharial qualifies for CR under Criterion A2bc. However, the lack of quantitative population estimates for three generations in the past makes the calculation of exact rates of decline over the period problematic (see Table 1 in the attached PDF for further information on how the reduction was calculated).

Rationale for Criterion C:

Once thought to be relatively stable or even increasing, the wild population of gharials has undergone a drastic decline over the last nine years. This decline, as outlined below, qualifies it for Critically Endangered listing.

The mature Gharial population was estimated by using gharial nest counts as they are easily visible and can be counted at well known locations that have been monitored for decades. This is also a more accurate assessment for numbers of mature animals because of the unknown number of immature males (which take five or more years longer to mature than do females) that are routinely counted as 'adults'. Using the only published data on ratios of males in the mature Gharial population (Hussain 1999), it can be inferred that 14% of all 'adults' reported in Gharial censuses are actually subadult males.

The Chambal River holds by far the largest breeding subpopulation with an estimated 48% of the total population. The total number of nests found in the Chambal Sanctuary in 2006 was 68. The only other large breeding population of gharial in India is in the Katerniaghat Wildlife Sanctuary where 20 nests were found in 2006. The one other known breeding population in India is the Son River Sanctuary where two nests were found in 2006 (Andrews 2006).

Since most female Gharial nest every year in captivity, it is reasonable to assume that the above cited nest counts indicate the presence of 90 reproducing female Gharial in India. Assuming that the sex ratio reported by Hussain (1999) in the Chambal of 14% males is the same in Katerniaghat and Son, there would be an inferred total of 13 mature male gharials throughout India. Considering the reported paucity of mature males (being very conspicuous with their gharas) on the Chambal in the surveys of 2005 and 2006, it is likely that there are extremely few mature males in that river (Andrews 2006, R.J. Rao pers. comm.). Along with a total of 20 nesting females, six mature male Gharial were counted by independent observers in 2006 (B.C. Choudhury, H.V. Andrews, R. Whitaker, pers. obs.). The total estimated number of mature Gharial in the three remaining wild breeding subpopulations in India is therefore 107 based on observed nest numbers and inferred numbers of mature males.

Other crocodilians are reported to nest less frequently than every year. Estimates of reproductive frequency (% females laying per year) range from 10% to 90% with a median value of 63% (Thorbjarnarson 1996). Although we believe that most gharials nest annually, some females may have migrated downriver away from where the few males still exist. Applying this median crocodilian value to our estimate and adding the estimates for all Indian and Nepal subpopulations would only increase it to 220, still below the numerical threshold for Critically Endangered using criterion C.

There are two other small, non-reproducing populations of Gharial in India (Ken River in Madhya Pradesh and Mahanadi River in Orissa) and three in Nepal (Kosi, Karnali and Babai Rivers) which have been supplemented by the reintroduction of captive bred stock (as in all present Gharial locations). There may also still be a few scattered Gharial in the Brahmaputra River of Northeast India but there have been no confirmed sightings since 1993 (Choudhury 1997). These other subpopulations of Gharial in India contain a total estimated 40 mature animals (no mature males reported). It is extinct in the Indus (Pakistan/India) and Irrawaddy (Myanmar) river systems.

In Nepal six nests were counted in 2006 and the total mature gharial in all subpopulations in that country is estimated at 35 animals (Maskey 1999 and pers. comm. 2006).

Based on these estimates the number of wild, mature gharials across the species' range (presently only India and Nepal) is 182 in about eight non-contiguous, fragmented habitats (but until further research tells us otherwise, note that 14% of these 'adults' can be inferred to actually be subadult males bringing the total figure down to 157).

In 1997, the peak year with the highest number of wild mature gharials and nests recorded in the last 30 years, 226 mature animals and 81 nests were recorded in the Chambal (Sharma and Basu 2004). There were no nests in the Son, where there were about 10 adults and no nest data for Katerniaghat where an estimated 30 adults were present. No nesting data from Nepal exist for this period, but Maskey (1999) estimated 36 adults present. Based on the available data (Maskey 1999, Sharma and Basu 2004), and adding the 1997 estimated numbers of non-breeding mature animals (in small subpopulations outside of the three Indian and one Nepali breeding subpopulations - a total of 50 animals), the estimated total mature gharial population throughout its present range (India and Nepal) in 1997 was 436.

The decline from an estimated 436 adult gharials in 1997 to 182 in 2006 represents a 58% drop across its range. This drastic decline has happened with a period of nine years, well within the span of one generation, qualifying the Gharial, under criterion C1, to be listed as Critically Endangered. Using the highly conservative estimate of 220 (based on only 63% of the adult females nesting annually) this is a 36% decline, still well within the 25% decline criteria for Critically Endangered (see Table 2 in the attached PDF for details of declines by subpopulation).

Conclusion:
The Gharial has undergone both chronic long term and a rapid short-term declines. The use of Criterion A illustrates the long term decline, which was in part addressed during conservation efforts for this species in India and Nepal during the 1970s and 1980s. However, a more recent, very rapid decline has been taking place in the last surviving subpopulations and is cause for considerable alarm. The use of criterion C here, effectively demonstrates that the gharial qualifies for a listing of Critically Endangered, which we think will be an important first step towards galvanizing renewed conservation efforts for this unique species.