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Mecistops cataphractusAfrican slender-snouted crocodile

By Joel Lavinder and Joshua Pennington

Geographic Range

Slender-snouted crocodiles are native to central Africa, from as far west as Senegal, to Tanzania in the east, as far north as Chad, Mali, and Mauritania, and as far south as Zambia and Angola. The Saint Paul, Mafa, and Saint John Rivers are all Liberian rivers in which this species occurs. Slender-snouted crocodiles have also been reported in areas of Cameroon and Gabon. (Abercrombie, 1976; Groombridge, 1982; Kofron, 1992; Pauwels, et al., 2003; Radley and Sherlock, 2001)

Habitat

Slender-snouted crocodiles are primarily found in tropical rainforests along the shores of shallow rivers and larger bodies of water, but also in lightly covered savanna woodlands. They are most frequently found in freshwater environments and occasionally in brackish waters of coastal lagoons. When these crocodiles leave the water they tend to stay in sheltered or protected areas to avoid predation. In the water they usually swim just below the surface. (Groombridge, 1982; Kofron, 1992; Radley and Sherlock, 2001)

Physical Description

Slender-snouted crocodiles are small to medium-sized crocodilians, with a maximum recorded length of approximately 4 meters. Sexual dimorphism is present (as in all crocodilian species), with males being larger than females of the same age class. As the common name suggests, this species has a long, slender snout. Protective scales cover the skin, some of which are reinforced by bony plates to provide extra support. The head is equipped with nostrils that sit high on the tip of the snout and eyes that are arranged facing forward at the top of the head. (Grigg and Gans, 1993; Kelly, 2006; Radley and Sherlock, 2001; Waitkuwait, 1989)

Slender-snouted crocodiles can be distinguished from other crocodile species by their extremely slender snout, which lacks any bony ridges, as well as their dark, olive-colored back and bright yellow-colored ventral surface, which also shows several dark patches. (Steel, 1989)

  • Sexual Dimorphism
  • male larger
  • Range length
    3 to 4 m
    9.84 to 13.12 ft

Development

All crocodilian species lay eggs, with the temperature of nesting conditions determining the sex of hatchlings. Young crocodilian hatchlings resemble mature adults, except smaller. They are fully capable of feeding and swimming from the moment that they hatch. Slender-snouted crocodiles are considered to be sexually mature when they reach 2.0 to 2.5 meters in length. (Kelly, 2006; Waitkuwait, 1989)

Reproduction

Little is known about the specific courtship and mating systems of slender-snouted crocodiles. In general, crocodilians engage in mating rituals that include sex-specific interactions. Females approach males in the water and begin the courtship ritual. During this courtship, crocodilians perform several activities involving swimming around each other and bodily contact, and the female may even briefly swim away to encourage the male to chase her, before continuing to circle. Following these ritualistic behaviors, the male places his tail under the female's body for stability in shallow waters and the pair then begins copulation. Crocodilians have been observed copulating on their sides, either with the male on top of the female, or with the female on top of the male. (Grigg and Gans, 1993; King and Dobbs, 2007; Waitkuwait, 1989)

Slender-snouted crocodiles typically reach sexual maturity at 10 to 15 years. Reproduction generally takes place at the start of the rainy season. The entire process begins in January or February and lasts until July. Oogenesis in females and spermatogenesis in males begins in January and February. Copulation generally occurs soon after. After copulation, the embryo and its surrounding eggshell begin to develop. Two to three months later (around April), egg-laying occurs. (Waitkuwait, 1985; Waitkuwait, 1989)

Nests are made by the female, primarily using her hind legs to construct the nest of dead vegetation and mud. They are typically 50 to 80 cm high, 130 to 220 cm long, and 120 to 200 cm wide. Nests house incubating eggs for 90 to 100 days. Little information is available on the average number of eggs in a clutch, although one study found clutch sizes of 8, 17, and 22 eggs. On average, eggs measure approximately 8 cm long and 5 cm wide. Among species in the genus Crocodylus, slender-snouted crocodiles produce the lowest average number of eggs per clutch, but also exhibit the largest average egg size. (Thorbjarnarson, 1996; Waitkuwait, 1985; Waitkuwait, 1989)

During incubation, mothers try to keep egg temperatures between 27.4ºC and 34ºC by keeping the eggs in the nest. The nest is kept moist by rainfall and humidity, helping to insulate the nest and keeping internal temperatures far more stable than temperatures outside the nest. Newly emerged hatchlings measure 28 to 35 cm long. The time for hatchlings to reach independence is unknown, but they have been found near the nest for as long as two weeks after hatching. (Waitkuwait, 1985; Waitkuwait, 1989)

  • Breeding interval
    Slender-snouted crocodiles reproduce once yearly in the rainy season
  • Breeding season
    January-July
  • Range number of offspring
    8 to 22
  • Range gestation period
    60 to 90 days
  • Range age at sexual or reproductive maturity (female)
    10 to 15 years
  • Range age at sexual or reproductive maturity (male)
    10 to 15 years

After a nest has been made and a clutch has been laid, crocodilian mothers guard their nests regularly throughout the incubation period. Soon after the offspring hatch they begin to make squeaking noises, triggering the female to uncover the nest. If some of the hatchlings show no sign of emerging, the mothers will carefully place these eggs in their mouth and crack them. The mother then scoops the hatchlings into her jaws and carries them to the water. Newborns are defended and cared for by both parents for some time after this relocation occurs. (Grigg and Gans, 1993; Thorbjarnarson, 1996; Waitkuwait, 1985; Waitkuwait, 1989)

Lifespan/Longevity

No reliable information is available regarding the average life span of wild slender-snouted crocodiles. Captive individuals have been documented to live for at least 38 years. (King and Dobbs, 2007)

  • Range lifespan
    Status: captivity
    32 to 38 years

Behavior

Although they move somewhat awkwardly outside of the water, due to their limbs being short relative to the size of the rest of their body, slender-snouted crocodiles have several different locomotory modes on land. Mainly, they belly crawl through mud or on the banks of a river. However, they can also high walk by standing straight up on all four legs to move around on rougher, rockier terrain. While swimming, they move in a very graceful serpentine motion through the water. Power for forward propulsion is provided by the tail, with the limbs providing very little, if any, aid in swimming. (Grigg and Gans, 1993; Kelly, 2006; Waitkuwait, 1989)

The head of crocodilians is well-suited for their sit-and-wait predatory life style, with nostrils that sit high on the tip of the snout and eyes that face forward at the top of their head. This allows them to be able to stalk their prey while the rest of their body is submerged under water. When hunting animals that are taking a drink of water from the banks of the river, they will quietly wait for an opportunity to lunge from the water and strike. (Grigg and Gans, 1993; Kelly, 2006; Waitkuwait, 1989)

Male crocodilians do not tolerate other males and will only live near females during mating seasons, passing from female to female within their territory. Female crocodilians of various species have shown evidence that the nests of some species may be shared between multiple females. It’s believed that these species share nests to allow better deterrence of predators. (Waitkuwait, 1989)

Home Range

Although reliable information regarding specific sizes of home ranges and territories is sparse for crocodilians, all species, including slender-snouted crocodiles, display dominance hierarchies between males. Male crocodilians are very territorial and dominant males will not tolerate intruders in their territory, which often leads to a battle between the dominant crocodile and the intruder. Dominant males will breed with all of the females within their territory. (Grigg and Gans, 1993; Kelly, 2006; Waitkuwait, 1989)

Communication and Perception

Little research has been conducted on communication in slender-snouted crocodiles. However, most crocodile species show common communication methods. Hearing is very well-developed in crocodilians and is more sensitive than in other reptiles, with newly hatched young communicating with their mother through high-pitched squeaks. Crocodilians also vocalize during aggressive interactions and while attempting to attract mates. (Grigg and Gans, 1993; Kelly, 2006; Waitkuwait, 1989)

Vision plays an integral role in crocodilian communication, with males showing their dominance to intruders using different rituals, including raising their bodies out of the water to try to appear larger to intimidate their intruders. During mating season, crocodilian species perform visual displays to attract potential mates. (Grigg and Gans, 1993; Kelly, 2006; Waitkuwait, 1989)

When above the surface of the water, vision is an important pathway for perception of a crocodilian's environment. It's assumed that crocodilians can see in color because their eyes have both rods and cones. Their eyes also contain a tapetum lucidum, a layer of guanine-rich retinal cells that amplify incoming light and greatly improve night vision. However, when hunting underwater, a semi-transparent third eyelid closes over the eye, likely limiting vision to light/dark differentiation. Touch receptors and the ears are likely to be the primary sense organs used while crocodilians are underwater. (Grigg and Gans, 1993)

Food Habits

Slender-snouted crocodiles have a predatory diet which, when young, consists mainly of fish and small crustaceans. At larger sizes they feed on mammals that drink from the rivers and lakes where the crocodiles live, such as water chevrotains (Hyemoschus aquaticus). The placement of the eyes and nostrils atop the head and snout, respectively, allows slender-snouted crocodiles (and all other crocodilians) to lie in wait at the edge of the water while almost completely submerged, striking when the prey animal dips its head to drink. Crocodilians have an extremely powerful bite force and their mouths are equipped with many sharp teeth that are designed for grabbing and hanging on to their prey. They also continuously grow new teeth to replace any that are lost through fighting or feeding. (Pauwels, et al., 2003; Waitkuwait, 1989)

Crocodilians do not secrete chitinases, so any chitinous or keratinous substances such as hair or mollusk shells accumulate in the gut and are most likely ejected through the mouth (which has been observed many times in captive individuals). The stomachs of slender-snouted crocodiles and other crocodilian species often contain gastroliths (rocks held in the digestive tract) of various sizes. Although the purpose of these stones has yet to be confirmed, it appears likely that they serve to grind and break down food in the digestive tract, as is the case in other groups (herbivorous birds, seals, sea lions) where they have been found. (Grigg and Gans, 1993; Pauwels, et al., 2003; Platt, et al., 2002)

  • Animal Foods
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • aquatic crustaceans

Predation

Predation on crocodilians occurs mainly at the egg or hatchling stage. Various animals feed on the eggs of slender-snouted crocodiles, including otters (Hydrictis maculicollis), leopards (Panthera pardus), and various bird and rodent species. Recent hatchlings face many of the same predators, as well as potential cannibalism by larger conspecifics. The large size and heavy scales of adults likely protects them from predation by other species, with the exception of humans, who hunt slender-snouted crocodiles for their skin and meat. (Pauwels, et al., 2003; Waitkuwait, 1989)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Slender-snouted crocodiles are predators of many aquatic species (particularly fishes), as well as some terrestrial mammals. Young individuals and eggs serve as prey to fish, birds, mammals, and larger crocodiles. (Grigg and Gans, 1993; Junker and Boomker, 2006; Pauwels, et al., 2003)

Commensal/Parasitic Species
  • Alofia parva (Family Sebekidae, Subclass Pentastomida)
  • Agema silvaepalustris (Family Sebekidae, Subclass Pentastomida)
  • Leiperia cincinnalis (Family Sebekidae, Subclass Pentastomida)
  • Sebekia okavangoensis (Family Sebekidae, Subclass Pentastomida)

Economic Importance for Humans: Positive

Slender-snouted crocodiles provide two major economic benefits. Their skin is very valuable due to its durability and coloring and is often used to make various clothing items and accessories. The meat of slender-snouted crocodiles also provides a means of sustenance in many areas. (Abercrombie, 1976; Pauwels, et al., 2003; Waitkuwait, 1989)

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

Economic Importance for Humans: Negative

As with all crocodilian species, adult slender-snouted crocodiles are capable of severely injuring or killing humans.

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Populations of slender-snouted crocodiles appear to be in a slow decline, mainly due to habitat loss caused by humans. However, there is not enough information on the species to know whether to place it within the endangered, vulnerable or rare category of the IUCN redlist. Some research in the early 1990’s suggested that slender-snouted crocodiles were severely depleted in West Africa, while a separate study in 2003 indicated that they are quite abundant in some parts of Gabon. (Kofron, 1992; Pauwels, et al., 2003)

Other Comments

A recent molecular phylogenetic analysis suggested that slender-snouted crocodiles constitute a distinct genus, for which the authors proposed to use the previously published name Mecistops. This change has not yet been adopted by the International Code for Zoological Nomenclature (ICZN), and most authors continue to use the genus name Crocodylus when referring to this species. (McAliley, et al., 2006)

Contributors

Joel Lavinder (author), Radford University, Joshua Pennington (author), Radford University, Christine Small (editor), Radford University, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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

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.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ectothermic

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

female parental care

parental care is carried out by females

food

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

freshwater

mainly lives in water that is not salty.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

male parental care

parental care is carried out by males

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.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

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

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

terrestrial

Living on the ground.

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

tropical

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

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Abercrombie, C. 1976. Notes on west African crocodilians (Reptilia, Crocodilia). Journal of Herpetology, 12: 260-262.

Conant, R., R. Hudson. 1949. Longevity records for reptiles and amphibians in the Philadelphia Zoological Garden. Herpetologica, 5: 1-8.

Grigg, G., C. Gans. 1993. Morphology and physiology of the Crocodylia. Pp. 326-336 in C Glasby, G Ross, P Beesley, eds. Fauna of Australia, Vol. 2A, Amphibia and Reptilia. Canberra, Australia: Australian Government Publishing Service.

Groombridge, B. 1982. The IUCN Amphibia-Reptilia Red Data Book. Woking, Surrey, U.K.: Unwin Brothers Limited.

Junker, K., J. Boomker. 2006. A check-list of the pentastomid parasites of crocodilians and freshwater chelonians. Onderstepoort Journal of Veterinary Research, 73: 27-36.

Kelly, L. 2006. Crocodile: Evolution's Greatest Survivor. Crows Nest, N.S.W: Allen & Unwin.

King, F., J. Dobbs. 2007. Crocodilian propagation in American zoos and aquaria. International Zoo Yearbook, 15/1: 272-277.

Kofron, C. 1992. Status and habitats of the three African crocodiles in Liberia. Journal of Tropical Ecology, 8/3: 265-273.

Martin, S. 2008. Global diversity of crocodiles (Crocodilia, Reptilia) in freshwater. Developments in Hydrobiology, 198/595: 587-591.

McAliley, L., R. Willis, D. Ray, P. White, C. Brochu, L. Densmore III. 2006. Are crocodiles really monophyletic? - Evidence for subdivisions from sequence and morphological data. Molecular Phylogenetics and Evolution, 39: 16-32.

Pauwels, O., V. Mamonekene, P. Dumont, W. Branch, M. Burger, S. Lavoué. 2003. Diet records for Crocodylus cataphractus (Reptilia: Crocodylidae) at Lake Divangui Ogooué-Maritime province, southwestern Gabon. Hamadryad, 27/2: 200-204.

Platt, S., T. Rainwater, S. McMurry. 2002. Diet, gastrolith acquisition and initiation of feeding among hatchling Morelet's crocodiles in Belize. Herpetological Journal, 12: 81-84.

Pope, J. 2000. Crocodile: Habitats, Life Cycles, Food Chains, Threats. Austin, TX: Raintree Steck-Vaughn.

Radley, G., J. Sherlock. 2001. Waterways. Minneapolis, MN: Lerner Publishing Group.

Riley, J., F. Huchzermeyer. 1999. African Dwarf Crocodiles in the Likouala Swamp Forests of the Congo Basin: Habitat, Density, and Nesting. Copeia, 1999/2: 313-320.

Steel, R. 1989. Crocodiles. Kent, U.K.: Christopher Helm Ltd..

Thorbjarnarson, J. 1996. Reproductive characteristics of the Order Crocodylia. Herpetologica, 52/1: 1/18.

Waitkuwait, W. 1989. Crocodiles: Their Ecology, Management, and Conservation. Gland, Switzerland: International Union for Conservation of Nature and Natural Resources.

Waitkuwait, W. 1985. Investigations of the breeding biology of the west African slender-snouted crocodile (Crocodylus cataphractus) Cuvier, 1824. Amphibia-Reptilia, 6/4: 387-399.

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