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.
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
- saltwater or marine
- freshwater
- Terrestrial Biomes
- savanna or grassland
- Aquatic Biomes
- lakes and ponds
- rivers and streams
- Other Habitat Features
- 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
- 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
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- 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
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
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
- natatorial
- motile
- 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.
- Perception Channels
- visual
- tactile
- acoustic
- 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
- eats terrestrial vertebrates
- piscivore
- eats eggs
- 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
- tongueworms ( Subtriquetra megacephala )
- tongueworms ( Subtriquetra shipleyi )
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
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
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.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- terrestrial
-
Living on the ground.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- freshwater
-
mainly lives in water that is not salty.
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
- marsh
-
marshes are wetland areas often dominated by grasses and reeds.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- female parental care
-
parental care is carried out by females
- fossorial
-
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
- natatorial
-
specialized for swimming
- motile
-
having the capacity to move from one place to another.
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- vibrations
-
movements of a hard surface that are produced by animals as signals to others
- keystone species
-
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
- drug
-
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
- insectivore
-
An animal that eats mainly insects or spiders.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
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