Mugger crocodile

Etymology

The Hindi word मगर or मगरमच्छ (Hindi pronunciation:) means crocodile. The Sanskrit word मकर makar refers to both Capricornus, crocodile and a mythical crocodile-like animal.

In Balochi language, it is called Gando.

Taxonomy

Crocodilus palustris was the scientific name proposed by René Lesson in 1831 who described the type specimen from the Gangetic plains. In subsequent years, several naturalists and curators of natural history museums described zoological specimens and proposed different names, including:

• C. bombifrons by John Edward Gray in 1844 for a specimen sent by the Museum of the Royal Asiatic Society of Bengal to the British Museum of Natural History.
• C. trigonops also by Gray in 1844 for a young mugger specimen from India.

Characteristics

Mugger crocodile hatchlings are pale olive with black spots. Adults are dark olive to grey or brown. The head is rough without any ridges and large scutes around the neck that is well separated from the back. Scutes usually form four, rarely six longitudinal series and 16 or 17 transverse series. The limbs have keeled scales with serrated fringes on outer edges, and outer toes are extensively webbed. The snout is slightly longer than broad with 19 upper teeth on each side. The symphysis of the lower jaw extends to the level of the fourth or fifth tooth. The premaxillary suture on the palate is nearly straight or curved forwards, and the nasal bones separate the premaxilla above.

The mugger crocodile is considered a medium-sized crocodilian, but has the broadest snout among living crocodilians. It has a powerful tail and webbed feet. Its visual, hearing and smelling senses are acute. Adult female muggers are 2 to 2.5 m (6 ft 7 in to 8 ft 2 in) on average, and male muggers 3 to 3.5 m (9 ft 10 in to 11 ft 6 in). They rarely grow up to 5 m (16 ft 5 in). The largest known muggers measured 5.63 m (18 ft 6 in). The largest zoological specimen in the British Museum of Natural History measures 3.7 m (12 ft 2 in). One male mugger caught in Pakistan of about 3 m (9 ft 10 in) weighed 195 kg (430 lb).

Distribution and habitat

The mugger crocodile occurs in southern Iran, Pakistan, Nepal, India and Sri Lanka, but is probably extinct in Bangladesh. It inhabits freshwater lakes, rivers and marshes, and prefers slow-moving, shallow water bodies. It is also known to thrive in artificial reservoirs and irrigation canals.

In Iran, the mugger occurs along rivers in Sistan and Baluchestan Provinces along the Iran–Pakistan border. On the Iranian Makran coast near Chabahar lives a population of around 200 mugger crocodiles. Due to human activity and a long drought in the late 1990s and early 2000s, it had been pushed to the brink of extinction. Following several tropical cyclones in 2007 and 2010, much of the habitat of the mugger crocodiles has been restored as formerly dry lakes and hamuns were flooded again.

In Pakistan, a small population lives in 21 ponds around Dasht River; in the winter of 2007–08, 99 individuals were counted. By 2017, the population had declined to 25 individuals. In Sindh Province, small mugger populations occur in wetlands of Deh Akro 2 and Nara Desert Wildlife Sanctuaries, near Chotiari Dam, in the Nara Canal and around Haleji lake.

In Nepal's Terai, it occurs in wetlands of Shuklaphanta, Bardia National Parks, Ghodaghodi Tal and Chitwan National Parks, and in Koshi Tappu Wildlife Reserve.

In India, it occurs in:

• Rajasthan along the Chambal, Ken and Son Rivers, and in Ranthambore National Park
• Gujarat along the Vishwamitri River
• Madhya Pradesh's National Chambal Sanctuary
• Uttarakhand's Rajaji National Park, Corbett Tiger Reserve and Lansdowne Forest Division
• Uttar Pradesh's Katarniaghat and Kishanpur Wildlife Sanctuaries
• Odisha's Simlipal National Park and along Mahanadi and Sabari Rivers
• Telangana's Manjira Wildlife Sanctuary
• Maharashtra's Kadavi and Warna Rivers
• Goa's Salaulim Reservoir, Zuari River and in small lakes
• Karnakata along Kaveri and Kabini Rivers, in the Ranganthittu Bird Sanctuary, Nagarhole National Park and Tungabhadra Reservoir
• Kerala's Parambikulam Reservoir and Neyyar Wildlife Sanctuary
• Tamil Nadu's Moyar River and Amaravathi Reservoir

In Sri Lanka, it occurs in several national parks such as Wilpattu, Yala and Bundala National Parks. Between 1991 and 1996, it has been recorded in another 102 localities.

Behaviour and ecology

The mugger crocodile is a powerful swimmer that uses its tail and hind feet to move forward, change direction and submerge. It belly-walks, with its belly touching ground, at the bottom of waterbodies and on land. During the hot dry season, it walks over land at night to find suitable wetlands and spends most of the day submerged in water. During the cold season it basks on riverbanks, individuals are tolerant of others during this period. Territorial behaviour increases during the mating season.

Like all crocodilians, the mugger crocodile is a thermoconformer and has an optimal body temperature of 30 to 35 °C (86 to 95 °F) and risks dying of freezing or hyperthermia when exposed to temperatures below 5 °C (41 °F) or above 38 °C (100 °F), respectively. It digs burrows to retreat from extreme temperatures and other harsh climatic conditions.Burrows are between 0.6 and 6 m (2.0 and 19.7 ft) deep, with entrances above the water level and a chamber at the end that is big enough to allow the mugger to turn around. Temperatures inside remains constant at 19.2 to 29 °C (66.6 to 84.2 °F), depending on region.

Hunting and diet

The mugger crocodile preys on fish, snakes, turtles, birds and mammals including monkeys, squirrels, rodents, otters and dogs. It also scavenges on dead animals. During dry seasons, muggers walk many kilometers over land in search of water and prey. Hatchlings feed mainly on insects such as beetles, but also on crabs and shrimp and on vertebrates later on. Subadult and adult muggers favour fish, but also prey on small to medium-sized ungulates up to the size of chital (Axis axis). In Bardia National Park, a mugger was observed caching a chital kill beneath the roots of a tree and returning to its basking site. A part of the deer was still wedged among the roots on the next day. They seize and drag potential prey approaching watersides into the water, when the opportunity arises. Adult muggers also feed on turtles and tortoises. Muggers have also been observed while preying and feeding on a python. In Yala National Park, a mugger was observed killing a large Indian pangolin (Manis crassicaudata), of which it devoured pieces over several hours.

Tool use

Mugger crocodiles have been documented using lures to hunt birds. This means they are among the first reptiles recorded to use tools. By balancing sticks and branches on their heads, they lure birds that are looking for nesting material. This strategy is particularly effective during the nesting season.

Reproduction

Female muggers obtain sexual maturity at a body length of around 1.8–2.2 m (5.9–7.2 ft) at the age of about 6.5 years, and males at around 2.6 m (8 ft 6 in) body length. The reproduction cycle starts earliest in November at the onset of the cold season with courtship and mating. Between February and June, females dig 35–56 cm (1.15–1.84 ft) deep holes for nesting between 1 and 2,000 m (3.3 and 6,561.7 ft) away from the waterside. They lay up to two clutches with 8 to 46 eggs each. Eggs weigh 128 g (4.5 oz) on average. Laying of one clutch usually takes less than half an hour. Thereafter, females scrape sand over the nest to close it. Males have been observed to assist females in digging and protecting nest sites. Hatchling season is two months later, between April and June in South India, and in Sri Lanka between August and September. Then females excavate the young, pick them up in their snouts and take them to the water. Both females and males protect the young for up to one year.

Healthy hatchlings develop at a temperature range of 28–33 °C (82–91 °F). Sex ratio of hatched eggs depends on incubation temperature and exposure of nests to sunshine. Only females develop at constant temperatures of 28–31 °C (82–88 °F), and only males at 32.5 °C (90.5 °F). Percentage of females in a clutch decreases at constant temperatures between 32.6 and 33 °C (90.7 and 91.4 °F), and of males between 31 and 32.4 °C (87.8 and 90.3 °F). Temperature in natural nests is not constant but varies between nights and days. Foremost females hatch in natural early nests when initial temperature inside nests ranges between 26.4 and 28.9 °C (79.5 and 84.0 °F). The percentage of male hatchlings increases in late nests located in sunny sites. Hatchlings are 26–31 cm (10–12 in) long and weigh 75 g (2.6 oz) on average when one month old. They grow about 4.25 cm (1.67 in) per month and reach a body length of 90–170 cm (35–67 in) when two years old.

Sympatric predators

The mugger crocodile is sympatric with the gharial in the river systems of the Ganges, Chambal, Son, Ramganga, Girwa and eastern Mahanadi, as well as in the Rapti and Narayani Rivers. In a few coastal areas, its distribution overlaps with that of the saltwater crocodile, but it barely enters brackish water and prefers shallow waterways.

Other sympatric predators of the mugger crocodile include Asiatic lion, dhole, Indian python as well as Burmese and reticulated python in the far eastern parts of the mugger crocodile's range. The Bengal tiger is the only carnivore known to fight mugger crocodiles off prey and even, rarely and if extremely hungry, endeavor to prey upon mugger crocodile adults, such as in Ranthambore National Park. There is also evidence of lion predation on crocodiles on the banks of the Kamleshwar Dam in Gir National Park, during dry, hot months.

Attacks on humans

The mugger crocodile is potentially dangerous to humans. Fatal attacks have been reported, though less frequently than by saltwater and Nile crocodiles. Human victims are dragged into the water and drowned, but are rarely consumed. In the 1990s, several fatal attacks of muggers on humans have been reported in Gujarat, India.

Since large muggers occasionally take livestock, this leads to conflict with local people living close to mugger habitat. In Maharashtra, local people are compensated for loss of close relatives and livestock.

Threats

The mugger crocodile is threatened by habitat destruction because of conversion of natural habitats for agricultural and industrial use. As humans encroach into their habitat the incidents of conflict increase. Muggers are entangled in fishing equipment and drown, and are killed in areas where fishermen perceive them as competition.

In Gujarat, two muggers were found killed, one in 2015 with the tail cut off and internal organs missing; the other in 2017, also with the tail cut off. The missing body parts indicate that the crocodiles were sacrificed in superstitious practices or used as aphrodisiacs. Between 2005 and 2018, 38 mugger crocodiles were victims of traffic accidents on roads and railway tracks in Gujarat; 32 died, and five were treated and returned to the wild.

Conservation

The mugger crocodile is listed in CITES Appendix I, hence export of wild-caught specimens is banned. The mugger is protected under Indian law vide the Wildlife Protection Act, 1972 of India, which lists the mugger in Schedule I (as serial 1D of Part II Amphibians and Reptiles).

In captivity

In India, a total of 1,193 captive bred muggers were released to restock populations in 28 protected areas between 1978 and 1992. Production of new offspring was halted by the Indian Government in 1994.