Gharials and mugger crocodiles coexist by separating resources
Updated : April 29, 2019 04:40 PM IST
Gharials more vulnerable, muggers thriving This study seems to suggest that “gharials are specialists in selecting basking and nesting sites, while muggers are generalists,” said Choudhary, adding that “because of this, gharials are more vulnerable to any changes in habitat.” To reduce competition between the two crocodilian species, the researchers suggest that conservation efforts should pay attention to gharials in north Indian rivers while in peninsular rivers, muggers should be the focus. Choudhary warned that “de-siltation of the river or deepening of the river” could lead to the elimination of mid-river islands” or affect the course of the river, which can, in turn, have an impact on gharial nesting sites. “This is an interesting study that separates habitat requirements of gharial and mugger in the same habitat,” said Lala A.K. Singh, former officer-in-charge of the Government of India CCBMTI (Central Crocodile Breeding and Management Training Institute), who was not involved in the study. “They have quantified it to a certain extent,” he said, adding that “this will guide the managers and researchers” when incorporated with his past findings. In a 1991 report from the Mahanadi, he observed that “with disturbance, gharial, may desert a place but mugger may thrive and ‘prosper’.” Additionally, Singh pointed out a recent concerning trend he has observed: mugger populations are increasing in some gharial habitats. In a 2015 study he co-authored with Rishikesh K. Sharma from the National Chambal Gharial Wildlife Sanctuary, which houses the country’s largest population of gharials, Singh noted that over a period of 30 years from 1984, mugger sightings have shot up “more than 10 times from 33 and their spatial distribution has expanded to the entire river.” But during the same time period, “sighting of gharial has increased less than two-fold from 605,” he revealed. “Gharials have specific habitat requirements; so they do not leave perennial river habitats,” explained Singh. “In the long past, mugger could have taken over some habitats completely—in south / central India (Narmada river, is one example); Mahanadi is the recent example. Chambal appears to be going that way.”
Researchers found that gharials preferred basking on mid-river islands and on gentler slopes and lower heights, compared with the basking sites of muggers.
For nesting, gharials selected nest sites closer to the water whereas muggers chose sites farther away from the water.