Crocodylus acutusAmerican crocodile

Geographic Range

American crocodiles live along both the Atlantic and Pacific coasts, from Central America through South America and the Caribbean Islands. They can also be found along the southeastern coast of Florida. Lake Worth and Cape Sable are the most northern limits of the species. They are more commonly found in the lowlands of Florida, and salt-water marshes throughout Central and South America. (Britton, 2009; Ditmars, 1936)

Habitat

The habitat of American crocodiles includes a broad range of aquatic environments. They inhabit freshwater, including rivers, lakes and reservoirs, and can also be found in brackish environments, such as example estuaries and swamps. There is also a population in a unique hyper-saline lake in the Dominican Republic. Another unlikely environment where American crocodiles are found is along brackish canals bordering a Florida power plant. American crocodiles create complex burrow systems to provide them an alternative shelter when they are vulnerable to low water levels. These burrows are used as shelter from cold weather, as hiding places, and as a spot to rest. Crocodiles may make the burrow large enough for movement or they may be as shallow as only two feet below the ground. The entrance to the burrow is built at least partially submerged, if not fully submerged underwater. American crocodiles choose an area based on the reliability of a food source. As long as there is a sustainable amount of food, they do not leave the area, with the exception of mating season. (Britton, 2009; Guggisberg, 1972)

Physical Description

American crocodiles are moderate sized crocodiles, although some individuals can grow longer than 4 long. There are unconfirmed reports of individuals 7 m long. Males tend to be larger than females. Adults have an olive-brown coloration, whereas younger crocodiles are lighter tan color. They have a narrow head and a long snout (which distinguishes them from alligators). Their sharp, jagged teeth interlock with each other. They have 28 to 32 teeth in their lower jaw and 30 to 40 in the upper jaw. They also have a protective eyelid that allows them to see underwater and the design of their iris gives them good night vision. American crocodiles are distinctive from other crocodile species in their reduced amount of scaly armor. Their tail is extremely long and powerful, and is used for swimming. ("American Crocodile", 2009; Britton, 2009; Ditmars, 1936)

  • Sexual Dimorphism
  • male larger
  • Range mass
    907.2 (high) kg
    1998.24 (high) lb
  • Average mass
    220-450 kg
    lb
  • Range length
    7 (high) m
    22.97 (high) ft
  • Average length
    3.5 m
    11.48 ft

Development

Female American crocodiles incubate their eggs to keep them warm. The sex of the offspring is determined by the temperature at which the eggs are incubated. High temperatures of 88 to 91 degrees Fahrenheit produce male offspring, while anything lower than 88 degrees results in females. However, the temperature must remain above 82 degrees in order for the eggs to hatch. After the young hatch, they rely on the yolk of the egg for nourishment for as long as two weeks. As they age the number of potential predators decreases, but newly hatched and young American crocodiles are particularly vulnerable and therefore must hide. The food supply of the yolk keeps them nourished until they are more competent and secure. As they mature and grow, young American crocodiles start to hunt insects on land, much like the foraging style of other lizards. ("Pet And Wildlife", 2008; Guggisberg, 1972; "The Everglades", 1997; "Pet And Wildlife", 2008)

  • Development - Life Cycle
  • temperature sex determination

Reproduction

Courtship takes place in January and February, when males attract females to mate. Courting can last as long as two months. During mating season American crocodiles display territoriality by males engaging each other in competition for access to females. Males roar loudly, raising their heads and opening their mouths, displaying their impressive teeth as part of the mechanism to attract mates. Females respond to male roars with roars of their own. ("National Environmeny and Planning Agency", 2009; Guggisberg, 1972; "Pet And Wildlife", 2008)

American crocodiles breed seasonally between April and May. Female American crocodiles lay 30 to 60 eggs in a hole or a mount that take approximately 9 to 10 weeks to hatch. Eggs are kept warm through the generation of heat from rotting vegetation placed on the eggs. Females guard nests throughout that period. Sexual maturity in American crocodiles occurs at a length of 1.8 to 2.4 meters, or between 8 and 10 years old. ("Animals", 2009; "Animals", 2009; "Animals", 2009; "Defenders of Wildlife", 2009; Sweeters, 2007)

  • Breeding interval
    American crocodiles breed once yearly.
  • Breeding season
    Egg-laying occurs during April or May.
  • Range number of offspring
    30 to 60
  • Range gestation period
    2 to 3 months
  • Range time to independence
    2 to 14 days
  • Range age at sexual or reproductive maturity (female)
    8 to 10 years
  • Range age at sexual or reproductive maturity (male)
    8 to 10 years

Females build a nest prior to mating. The nest is constructed in an open area, usually above the high water mark. Females dig nests up to 1.5 m deep and up to 1.8 m in diameter. Once the eggs are laid, usually between 30 and 60, the nest is covered with dirt to incubate and they are not uncovered until they hatch. Although the eggs are placed close together, they are separated from each other to prevent them from breaking. When hatching approaches, the female increases the frequency of her visits to the nest site. While the eggs are hatching, the mother displays her protective nature through aggression. The female will rest her head above the nest, listening for noise from the young that cue her to uncover the nest in preparation for their hatching. Once uncovered, the mother aids the hatchlings in climbing out of the eggs, and later escorts the young to the water when they are ready. Once the young are taken from the hatching site they disperse quickly and are subsequently on their own. ("National Environmeny and Planning Agency", 2009; Guggisberg, 1972; "Florida Fish and Wildlife Conservation Commission", 2009)

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

Lifespan/Longevity

American crocodiles have the potential to live as long as 100 years, however their average life expectancy ranges from 60 to 70 years. There is a high mortality rate of offspring. Only 1 in 4 reach the age of 4. This is due to their vulnerability at their hatching size. Young American crocodiles have not yet developed the size and strength necessary to protect themselves from predators. Their vulnerable status along with the lack of parental care puts the young at risk. Also, if nests are built below the water line, flooding can result in mass death of the eggs. In addition, the eggs themselves are at risk to thieves such as raccoons. ("The Everglades", 1997; "Pet And Wildlife", 2008)

  • Range lifespan
    Status: wild
    100 (high) years
  • Average lifespan
    Status: wild
    60-70 years
  • Average lifespan
    Status: captivity
    45 years

Behavior

Most of the time American crocodiles are solitary creatures. In their wild habitat, they prefer to be alone, retreating from most disturbances. However, if they feel threatened, individuals may become quite aggressive. When social interactions do occur, they often take place around dawn before their body temperatures have warmed. During the dry season they become lethargic, burying themselves in the mud and neglecting to eat. Like alligators, American crocodiles bask in the sun, open-mouthed, a behavior called "gaping." This regulates their body temperature. This behavior occurs only on sunny days and acts as a cooling method to help maintain their comfortable 77 degree Fahrenheit body temperature. Also, this basking behavior aids in increasing their metabolic rate; in cold temperature, their digestion tends to be slower, costing extra energy, basking in the sun makes digestion more efficient. Most of their behavior and activity occurs at night, they are inactive during the daytime hours. During the evening, they spend a lot of time submerged in water since the water cools slowly, maintaining the heat for a prolonged period of time. ("National Environmeny and Planning Agency", 2009; Guggisberg, 1972; "The Everglades", 1997)

Home Range

American crocodiles have home ranges that are split between land and water. Sizes are not reported. ("National Environmeny and Planning Agency", 2009)

Communication and Perception

American crocodiles communicate through vocalizations. Roaring acts to defend territory and attract mates. Territorial communication is also displayed through slapping the water with the head and tail. Infrasonic sound is also used which creates ripples on the water's surface. This infrasonic rumbling is used during the mating season to court potential mates. Young American crocodiles communicate to the mother when hatching time approaches. Newly hatched young emit distress calls eliciting protective measures from the mother. The position of the body is also used to indicate dominance or submission. Dominant males swim along the surface of the water, exposing their entire body, while females and submissive males only expose their head or snout while swimming. Tail-thrashing is also used in aggressive behaviors and interactions as a visual cue. Finally, chemosensory cues are used in communication, but have been poorly documented. ("American Crocodile", 2009; "Animals", 2009; Guggisberg, 1972)

Food Habits

American crocodiles are carnivorous, feeding mostly on fish, frogs, turtles and the occasional bird or small mammal. Juvenile individuals eat more aquatic invertebrates and small fish, while recent hatchlings hunt insects on land. A full digestive cycle from swallowing to excretion takes approximately 72 hours. During hunting, prey is grabbed with their powerful jaws, swallowing it whole. American crocodiles also ingest small stones to aid in grinding up their food. ("Animals", 2009; Guggisberg, 1972; "The Everglades", 1997; Sweeters, 2007)

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

Predation

American crocodiles are only vulnerable as prey to other predators when they are young. Until they mature to a larger size, the young are vulnerable to raccoons, certain larger fish and wild cats. In order to protect themselves, they attempt to hide and conceal themselves with their surroundings. Later in life their crypsis is useful to prevent detection by prey. (Britton, 2009; Guggisberg, 1972)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

American crocodiles are top predators in aquatic ecosystems they inhabit. Their waste products and uneaten prey also contribute to other animals in the ecosystem. ("The Everglades", 1997)

Economic Importance for Humans: Positive

American crocodiles have no direct economic importance for humans, however, similar species such as Alligator mississippiensis attract tourists to areas such as the Florida Everglades. In some areas they may be hunted for food or leather.

  • Positive Impacts
  • food
  • body parts are source of valuable material
  • ecotourism

Economic Importance for Humans: Negative

American crocodiles have been known on the rare occasion to attack and kill or injure humans and domestic animals. (Guggisberg, 1972)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

American crocodiles are listed as endangered under the United States Endangered Species Act. In addition, American crocodiles are protected under the Convention on International Trade in Endangered Species internationally, which prohibits commercial trade of these animals. In the past, American crocodiles were subject to poaching for their hides, but now the main threat to their existence is loss of habitat due to the invasion of human development and illegal killing. (Britton, 2009)

Contributors

Jake Fishman (author), James Madison University, Kristin MacKinnon (author), James Madison University, Suzanne Baker (editor, instructor), James Madison University, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

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.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

scavenger

an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

2009. "American Crocodile" (On-line). Accessed April 08, 2009 at http://www.american-crocodile.com/.

2009. "Animals" (On-line). American Crocodile. Accessed April 08, 2009 at http://www.seaworld.org/Animal-info/animal-bytes/animalia/eumetazoa/coelomates/deuterostomes/chordata/craniata/reptilia/crocodylia/american-crocodile.htm.

Defenders of Wildlife. 2009. "Defenders of Wildlife" (On-line). American Crocodile. Accessed March 20, 2009 at http://www.defenders.org/wildlife_and_habitat/wildlife/crocodile.php.

State of Florida. 2009. "Florida Fish and Wildlife Conservation Commission" (On-line). American Crocodiles. Accessed March 20, 2009 at http://myfwc.com/WildlifeHabitats/Crocodile_index.htm.

2009. "National Environmeny and Planning Agency" (On-line). American Crocodile. Accessed April 08, 2009 at http://www.nrca.org/yourenv/biodiversity/Species/crocodile.htm.

National Geographic Society. 2009. "National Geographic Society" (On-line). American Crocodile. Accessed March 20, 2009 at http://animals.nationalgeographic.com/animals/reptiles/american-crocodile.html.

PetandWildlife.com. 2008. "Pet And Wildlife" (On-line). American Crocodile. Accessed March 20, 2009 at http://www.petandwildlife.com/crocodiles/american-crocodile-crocodylus-acutus.html.

Museum of Science, Inc. 1997. "The Everglades" (On-line). American Crocodile. Accessed March 20, 2009 at http://www.miamisci.org/ecolinks/everglades/crocinfo.html.

Britton, A. 2009. "University of Florida" (On-line). Crocodylus acutus. Accessed April 08, 2009 at http://www.flmnh.ufl.edu/cnhc/csp_cacu.htm.

Ditmars, R. 1936. The Reptiles of North America. New York: Doubleday, Doran & Company, Inc.

Guggisberg, C. 1972. Crocodiles. Harrisburg, PA: Stackpole Books.

Sweeters, M. 2007. "Conservation Science Institute" (On-line). American Crocodile. Accessed March 20, 2009 at http://www.conservationinstitute.org/pcn/pcnamericancorcodile.htm.