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Mugger crocodile

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Mugger crocodile
Mugger crocodile Crocodylus palustris (2155269175).jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Family: Crocodylidae
Subfamily: Crocodylinae
Genus: Crocodylus
Species: C. palustris
Binomial name
Crocodylus palustris
Lesson, 1831[1]
Crocodylus palustris Distribution.png
Distribution of mugger crocodile

The mugger crocodile (Crocodylus palustris), also called marsh crocodile, broad-snouted crocodile and mugger is a crocodilian native to freshwater habitats from southern Iran and Pakistan to the Indian subcontinent and Sri Lanka. It is extinct in Bhutan and Myanmar and has been listed as Vulnerable on the IUCN Red List since 1982.[1]

It is a medium-sized crocodile that inhabits lakes, rivers, marshes and artificial ponds. Both young and adult mugger crocodiles dig burrows where they retreat when temperature drops below 5 °C (41 °F) or exceeds 38 °C (100 °F). Females dig holes in the sand as nesting sites and lay up to 46 eggs during the dry season.[2][3][4] Sex of hatchlings depends on temperature during incubation.[5] It preys on fish, reptiles, birds and mammals. Young feed on insects.[6][7]

It is one of three crocodilians in India, apart from gharial and saltwater crocodile.[8]

Characteristics

Illustration of mugger crocodile skull
Illustration of mugger dentition

The mugger crocodile is considered a medium-sized crocodilian, but has the broadest snout among living crocodilians.[4] It has a powerful tail and webbed feet. Its visual, hearing and smelling senses are acute.[2]

It is a heavily armored species with enlarged scutes around the neck. Adults are dark grey or brown, while hatchlings are tan colored. Adults have 19 upper teeth on each side; a snout that is 1⅓ to 1½ as long as broad at the base; a rough head but without any ridges; mandibular symphysis extending to the level of the fourth or fifth tooth; pre-maxillo-maxillary suture, on the palate, transverse, nearly straight, or curved forwards; and nasal bones separating the pnemaxillaries above. Four large nuchals form a square, with a smaller one on each side; two pairs of smaller nuchals on a transverse series behind the occiput. Dorsal shield well separated from the nuchal, the scutes usually in 4, rarely in 6, longitudinal series, those of the two median usually considerably broader than long; 16 or 17 transverse series. Scales on limbs keeled. Fingers webbed at the base; outer toes extensively webbed. A serrated fringe on the outer edge of the leg. Adult blackish olive above: young pale olive, dotted and spotted with black.[citation needed]

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).[2] The average size of adult mugger crocodiles in Manghopir Lake was estimated at 2.89 m (9 ft 6 in), with a weight of around 100 kg (220 lb).[9] One male mugger caught in Pakistan of about 3 m (9 ft 10 in) weighed 195 kg (430 lb).[10] The largest zoological specimen in the British Museum of Natural History measures 3.7 m (12 ft 2 in).[11]

Distribution and habitat

Muggers in Chabahar County, Iran
Mugger basking in Chitwan National Park, Nepal

The mugger crocodile occurs in southern Iran, Pakistan, Nepal, India and Sri Lanka, but is probably extinct in Bangladesh.[1] 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.[4]

In Iran, the mugger occurs along rivers in Sistan and Baluchestan Provinces along the Iran–Pakistan border.[1] On the Iranian Makran coast near Chabahar, there is a population of around 200 mugger corocodiles. Due to human activity and a long drought in the late 1990s and early 2000s, the mugger 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.[12]

In Pakistan's 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.[13][14][15]

In Nepal’s Terai, it occurs in wetlands of Shuklaphanta, Bardia and Chitwan National Parks, and in Koshi Tappu Wildlife Reserve.[16][17][18]

In India, it occurs along the Chambal, Ken and Son Rivers, in the Neyyar, Katarniaghat and Kishanpur Wildlife Sanctuaries.[19][20][21][22] In the 1980s, the largest mugger population in Tamil Nadu lived in the Amaravathi Reservoir, and in the Chinnar, Thennar and Pambar rivers that drain into it.[citation needed]

Behaviour and ecology

Muggers basking on sand banks

The mugger crocodile is a powerful swimmer that uses its tail and hind feet to move forward, change direction and submerge. It belly-walks on 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, and during this time is tolerant of conspecifics. Territorial behaviour increases during the mating season.[2]

Like all crocodilians, the mugger crocodile has an optimal body temperature of 30 to 35 °C (86 to 95 °F) and risks dying when exposed to temperatures below 5 °C (41 °F) or above 38 °C (100 °F). It digs burrows as retreats from such extreme temperatures and harsh climatic conditions.[23] 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 so that the mugger can turn around.[2] Temperature inside remains constant at 19.2 to 29 °C (66.6 to 84.2 °F), depending on region.[24]

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.[3] Hatchlings feed mainly on insects such as beetles, but also on crabs and shrimp and on vertebrates later on.[6][7] Subadult and adult muggers favour fish, and prey on small to medium-sized ungulates up to the size of chital.[25] When hunting large mammals such as deer they will sometimes leave it to rot while wedged under water before pulling it apart.[17] They seize and drag potential prey approaching watersides into the water, when the opportunity arises. Adult muggers also feed on turtles and tortoises.[26][27] Muggers have also been observed while preying and feeding on a python.[28]

Tool use

Mugger crocodiles have been documented using lures to hunt birds.[29] 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.[30]

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). The reproduction cycle starts earliest in November and extends to September in Sri Lanka. Courtship and mating starts at the onset of the cold season. Between February and June, females dig 35 to 56 cm (1.15 to 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. 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 between April and June in South India, and in Sri Lanka between August and September. Eggs weigh 128 g (4.5 oz) on average. When they hatch two months later, 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.[2][3]

Healthy hatchlings develop at a temperature range of 28 to 33 °C (82 to 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 to 31 °C (82 to 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). 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.[5] Hatchlings are 25 to 30.5 cm (9.8 to 12.0 in) long and grow about 4.25 cm (1.67 in) per month during the first two years.[2]

Sympatric crocodilians

The mugger crocodile is sympatric with the gharial in the Ganges, Chambal, Son, Ramganga, Girwa and eastern Mahanadi river systems, the Rapti and Narayani Rivers.[31][19][18]

In a few coastal areas, it overlaps in distribution with the saltwater crocodile but normally is able to avoid direct conflict by favoring different habitats. Mugger barely enters the brackish and saltwater habitat and prefers shallower waterways. It forages on more diverse prey.[4][32][33]

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.[34] In the 1990s, several fatal attacks of muggers on humans have been reported in Gujarat, India.[35]

Since large muggers occassionally 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.[7][36]

Threats

The mugger crocodile is threatened by habitat destruction because of conversion of natural habitats for agricultural and industrial use. As humans encroach into natural habitat, incidents of conflict increase. Muggers are entangled in fishing equipment and drown, and are killed in areas where fishermen perceive them as competition.[1]

Conservation

The mugger crocodile is listed in CITES Appendix I, hence export of wild-caught specimen is banned.[1]

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.[1]

The Amaravati Sagar Crocodile Farm was established in 1975 in Tamil Nadu, and is the largest crocodile nursery in India. Eggs were collected from wild nests along the Amaravathi Reservoir, and hatched and reared at the farm. Up to 430 captive animals were maintained at one time. Young crocodiles were reintroduced into the wild.[37]

Etymology

The Hindi word मगर magar means crocodile.[38] This is in turn derived from makara, a Sanskrit name for a mythical water monster that is sometimes depicted as a crocodile.[39]

See also

References

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  2. ^ a b c d e f g Whitaker, R. and Whitaker, Z. (1984). "Reproductive biology of the Mugger (Crocodylus palustris)". Journal of the Bombay Natural History Society 81 (2): 297−317.
  3. ^ a b c Whitaker, R. and Whitaker, Z. (1989). "Ecology of the mugger crocodile". Crocodiles, their ecology, management, and conservation (PDF). Gland: IUCN Crocodile Specialist Group. pp. 276−296.
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