Crocodylus palustris

Geographic Range

The range of the mugger crocodile ( Crocodylus palustris ) encompasses most of India except for a small part of northern India. It stretches east to Burma (specifically, the city of Tinsukia) and west to Iran (town of Iranshahr). This crocodile is found as far north as Kibar, India. The crocodile’s range continues southward to the island of Sri Lanka.

• Biogeographic Regions
• oriental oriental
  • native native

Habitat

The mugger crocodile ( Crocodylus palustris ) is most commonly found in freshwater environments such as rivers, lakes, hill streams, and village ponds. It can live in fresh water and coastal saltwater lagoons. It also can live in human-made reservoirs. Typical depths for this species is 5m. This crocodile does not migrate seasonally, inhabiting the same locale in wet seasons or dry seasons. This species makes burrows on land in a wide variety of habitats.

• Habitat Regions
• terrestrial terrestrial
• saltwater or marine saltwater or marine
• freshwater freshwater

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh marsh
• swamp swamp

• Other Habitat Features
• riparian riparian

Physical Description

The maximum length for this crocodile is 4-5 meters, and maximum weight is 700 kg. It has rough thick scales covering the whole body with a muddy brown coloring. It has the widest snout among all crocodile species. The length of an adult crocodile’s tail is about 1.8 meters long. There seems to be no visible difference between the sexes, except that the female is smaller.

A hatchling would measure 0.27 meters and weigh less than 0.3 kg. It is considered a juvenile when it reaches 1.4 meters long and weighs 3-30 kg.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Development

Crocodile hatchlings are in clutches of 25-30 eggs. They require a specific temperature and humidity for them to develop successfully. Grigg and Kirshner (2015) reported the temperature needed for successful growth and survival has been recorded at an average 37.0C and a humidity of an average of 75.3%. However, for sex determination, Lang et al. (1998) report that all females develop at temperatures between 28-31C. At temperatures of 32.5C and above, all males develop. However, Lang et al. report "Both sexes are produced in varying proportions at 31.5, 32.0, and 33.0C." This temperature discrepancy may be related to recording errors in the wild as compared to the constant temperatures that can be maintained in captivity.

The hatchlings lay under little shelves underneath the entrance, in the nest where they are able to hide from other species. They are unable to defend themselves until they yearlings. The female mugger crocodile is sexually mature when it is 1.8-2 meters long. Females takes about 8-10 years to reach sexual maturity. It takes males 12-15 years to reach sexual maturity.

• Development - Life Cycle
• temperature sex determination

Reproduction

Not much has been reported for the mating habits of the mugger crocodile. However, in other species in the same genus there are many ways that crocodiles perform rituals before mating. In Nile crocodiles ( Crocodylus niloticus ) the male must swim around the female before it can show its testis. Nile crocodiles slap their heads against each other to compete and earn the privilege to mate with the female. The crocodiles make humming sounds for courtship. Females lift their snout to signal submission when approached by a male. This can also mean submission for courting. The mugger crocodiles make burrows for their nests. Either the female or the male can make the nest, but the female maintains it.

Although reproduction in captivity is difficult the successful cases have been reported. In the wild females reach sexual maturity at lengths of 1.8-2m and ages of 8-10 years. It takes males 12-15 years to reach sexual maturity. Mugger crocodiles lay eggs during the annual dry season. They have been known to lay around 25-30 eggs per clutch. In captivity they are known to lay 2 clutches a year. However, this has not been observed in the wild. The average incubation period for the eggs is 55-75 days. The crocodiles can become independent when they are yearlings and large enough to defend themselves.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

The female mugger crocodile defends and attends to the nest. The female continuously adjusts the temperature of the nest for suitable conditions for hatchlings and herself. It is difficult to observe how the mugger crocodile takes care of the hatchlings due to inaccessibility of the nests. The young stay near the nest until they are yearlings, but it's unclear how much care the female extends towards them. The male does not take care of the young.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Information about the mugger crocodile’s longevity is understudied and any information about it is conjectural. Carey and Judge (2000) report this species living 28.4 years in the wild. Snider and Bowler (1992) have it recorded as it living as long as 31.5 years in captivity.

Behavior

The crocodiles are poikilothermic reptiles and they need to alter their internal temperature by basking. Mugger crocodiles dig burrows to help maintain and protect them from ambient temperature changes. These burrows are important for the crocodile’s survival, protecting the crocodiles when temperature drop below 5 degrees Celsius or exceed 38 degrees Celsius. Individuals of all ages dig burrows to do this. Members of this species are ferocious when threatened or when their nest is being preyed upon.

Although assumed to be rather sedentary, it's been reported that this species takes "long-distance overland treks" in portions of its range. These treks have been reported in India, Sri Lanka, and Iran.

• Key Behaviors
• terricolous
• fossorial fossorial
• natatorial natatorial
• motile motile
• territorial territorial

Home Range

Home range has not been reported for the mugger crocodile. Females are known to defend burrows but an area has not been defined.

Communication and Perception

Mugger crocodiles normally float on the surface of the water with just their nose or eyes protruding from the surface of the water. They rely on their eyes, nose, and ears when they are above the surface of the water. When they are submerged, they rely on their skin, feeling vibrations in the water. Their skin is a unique sensory organ. It is similar to the lateral line network in fish but is unique to the crocodiles. They are so sensitive that they can detect the pH of the water. This sensory network presumably plays a part in the crocodile’s courtship behavior. They stroke and rub each other’s head for mating rituals.

• Communication Channels
• visual visual
• tactile tactile

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations

Food Habits

The mugger crocodiles are opportunistic carnivores. They are capable of eating any animal smaller than them including other crocodiles. They are considered ‘sit and wait’ hunters and can eat birds and bats that try to eat off the surface of the water. They eat even other eggs of species. As hatchlings, mugger crocodiles eat small insects and other small invertebrates, including crustaceans. However, as they grow, so does the average size of their prey items. Crocodiles can eat 10% to 25% of their body weight in a single meal. For a crocodile with a length greater than 2 meters they can eat 3000g of food. However a crocodile smaller than 0.5 meters can only eat 150g of food in one feeding.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore
  • eats eggs
  • insectivore insectivore
  • eats non-insect arthropods

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• eggs
• insects
• terrestrial non-insect arthropods
• aquatic crustaceans

Predation

The mugger crocodile is the top predator in its ecosystem. The only danger of predation is during the hatchling stage. Crows and dingoes ( Canis lupus dingo ) have been reported as nest predators. There has been human ( Homo sapiens ) predation of the eggs of the species, and human fishermen may occasionally kill an adult.

Ecosystem Roles

Mugger crocodiles perform a role in maintaining the structure and function of fresh water ecosystems because they are a top predator and keystone species affecting all of the animals below them in the food chain. The only recorded species of parasites that have inhabited the mugger crocodile are the tongueworms Subtriquetra megacephala and Subtriquetra shipleyi .

• Ecosystem Impact
• keystone species keystone species

Economic Importance for Humans: Positive

Crocodylus palustris is killed for its skin to make leather products. However, it has decreased since the 1930’s because of laws forbidding hunting of endangered species. However people, Homo sapiens , still hunt for other reasons besides just their skin. Their bones and scales are fabled to have medicinal properties that the older generation still uses. Poachers also steal eggs of the species to sell on the black market.

• Positive Impacts
• body parts are source of valuable material
• source of medicine or drug source of medicine or drug

Economic Importance for Humans: Negative

Mugger crocodiles have been an economic liability in areas where fishing is a large part of the economy. As top predators, these crocodiles may decrease fish biodiversity. Crocodiles have been known to attack fishermen.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

Mugger crocodiles are categorized as “Vulnerable” on the IUCN Red List criteria for threatened species. This species is not under the US list because it is not indigenous to the United States. The crocodile is listed under Appendix I of CITES, this includes species threatened with extinction. Hunting and trading of this species is permitted only in “exceptional circumstances.” That has been stated by the Appendix I of CITES. Historically, the primary threats to mugger crocodiles have been habitat destruction, fragmentation, drowning in fishing nets, egg predation by people, and the use of crocodile parts for medicinal purposes. Currently, the main risks to the species are changes to habitat and mortality in fishing nets. Many breeding facilities that are used to increase the population have been shut down and are used to hold the surplus eggs in stock. This is because there have been observations of the crocodile population increasing. There has been an increase in crocodile sightings and attacks which has led to this reasoning. Many laws have been placed by India, Pakistan, Iran, and Sri Lanka to outlaw the hunting and harming of mugger crocodiles. Mugger crocodiles have received the highest legal protection in Pakistan as it is listed in Schedule I of the Pakistan Wildlife (Protection) Act 1972. Those who have been found guilty have been punished by loss or suspension of their hunting license for all animals.

Additional Links

Encyclopedia of Life

Contributors

Gregory Steeves (author), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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