Melanosuchus nigerBlack caiman

Ge­o­graphic Range

Black caimans are found through­out much of the Ama­zon Basin; their range in­cludes much of north­ern and cen­tral South Amer­ica. Al­though these an­i­mals are far less com­mon now than a few decades ago. (Brit­ton, Sep­tem­ber 15, 1999; Thor­b­jarnar­son, 1998; Thor­b­jarnar­son, July/Au­gust 1999)

Habi­tat

Melanosuchus niger is often as­so­ci­ated with steep banks along­side slow-mov­ing fresh­wa­ter rivers, lakes, wet­lands, black water swamps, and sea­son­ally flooded areas of the Ama­zon. (Brit­ton 1999, Mag­nus­son 1987).

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Phys­i­cal De­scrip­tion

The largest preda­tor in the Ama­zon, Melanosuchus niger is ca­pa­ble of grow­ing to more than 6 m. It re­sem­bles the Amer­i­can Al­li­ga­tor but is bi­o­log­i­cally more closely re­lated to the other caimans. The Black Caiman re­tains its dis­tinc­tive skin mark­ings into adult­hood: they dis­play grey or brown band­ing on the lower jaw, and dis­play white or yel­low­ish bands on the sides of the body (Brit­ton 1999, Mag­nus­son 1998).

Re­pro­duc­tion

Good in­for­ma­tion con­cern­ing the Black Caiman's breed­ing habits is not plen­ti­ful. In the dry sea­son, which runs from Sep­tem­ber through De­cem­ber, the fe­male builds a nest mound, using the hind feet to dig an egg cham­ber. Clutch size av­er­ages 39.3 eggs, which are el­lip­ti­cal, with rigid shells, and av­er­age 143.6g. The fe­male gen­er­ally re­mains close to the nest site, al­though not all ac­tively de­fend the nest. She will scrape open the nest when the hatch­lings are emerg­ing. The in­cu­ba­tion pe­riod lasts be­tween two to three months, but may vary with nest tem­per­a­ture. Nests may be warmed by sun­light or by the heat of de­com­pos­ing veg­e­ta­tion. Hatch­ing may cor­re­late with the onset of the rainy sea­son.

Hatch­lings tend to con­gre­gate to­gether in groups called pods. Pods may con­tain in­di­vid­u­als from more than one nest, and they are often pro­tected by the adult fe­male's pres­ence. -M. niger- pods were found to occur in areas of deeper water than -C. croc­o­dilus-, im­ply­ing choice of nest­ing sites in lower-ly­ing areas (Brit­ton 1999, Da Sil­veira et al 1997, Her­ron 1990, Thor­b­jarnar­son 1998).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Lifes­pan/Longevity

Be­hav­ior

Few good eco­log­i­cal stud­ies have been made on the habits of M. niger. De­spite hav­ing a range that over­laps with other species of caimans, M. niger ap­pears to have its own eco­log­i­cal niche that en­ables it to co­ex­ist with­out too much com­pe­ti­tion.

May through July marks a pe­riod of flood­ing in the Ama­zon, and dur­ing this time the pop­u­la­tions of Black Caiman are dis­persed amongst a wide ex­panse of its range. The dry sea­son oc­curs from Sep­tem­ber through De­cem­ber, and at this stage water lev­els re­cede, flooded sa­van­nahs dry, and the Black Caimans are more densely con­gre­gated in the per­ma­nent lakes and rivers.

Croc­o­dil­ians in gen­eral are the most vocal of the rep­tiles, and M. niger emits vo­cal­iza­tions that sound like rum­bling thun­der to com­mu­ni­cate with con­specifics. And like most croc­o­dil­ians, M. niger ex­hibits parental care (Pough 1998, Thor­b­jarnar­son 1998, Thor­b­jarnar­son 1999).

Food Habits

Stud­ies on M. niger's diet are lim­ited, but some have been car­ried out and the diet shows many sim­i­lar­i­ties to that of the Com­mon Caiman (Caiman croc­o­dilus). This may be due to sim­i­lar habi­tats.

Diets can vary de­pend­ing on the age, size, habi­tat, and avail­able prey. Mean prey size is usu­ally pos­i­tively cor­re­lated to caiman size.

Fish, such as pi­ra­nhas and cat­fish, ac­count for a large part of the adult Black Caiman's diet, as do mol­luscs. It also preys on aquatic and ter­res­trial ver­te­brates, in­clud­ing some mam­mals such as capy­bara (Hy­drochaeris hy­drochaeris). Young in­di­vid­u­als tend to eat in­sects, crus­taceans, and other in­ver­te­brates, but many of these are usu­ally re­placed in the diet as the caiman ma­tures. Much hunt­ing is done in the water, but the Black Caiman may emerge to hunt on land as well, usu­ally at night (Brit­ton 1999, Da Sil­veira and Mag­nus­son 1999, Mag­nus­son 1987).

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

As the largest preda­tor in the ecosys­tem, the Black Caiman may play the role of a key­stone species and help to main­tain the struc­ture of its ecosys­tem. Im­por­tant ac­tiv­i­ties may in­clude nu­tri­ent cy­cling and the se­lec­tive pre­da­tion of cer­tain fish species. Its dis­ap­pear­ance from the Ama­zon would leave a large eco­log­i­cal gap, with ad­verse ef­fects for its habi­tats.

If pop­u­la­tions re­cover suf­fi­ciently, the Black Caiman could pro­vide eco­nomic ben­e­fits through con­trolled hunt­ing for meat. This would give local peo­ples more in­cen­tive to pro­tect the species (Thor­b­jarnar­son 1998, Thor­b­jarnar­son 1999).

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There have been claims that the caimans con­sume large quan­ti­ties of com­meri­cial fishes, hav­ing a neg­a­tive im­pact on local fish­er­men, but analy­sis of stom­ach con­tents in one study in­di­cated only small vol­umes of such fish are eaten at any one time. This does not sup­port the fish­er­men's claims, and the Black Caimans prob­a­bly do not sig­nif­i­cantly af­fect local fish­ing.

The Black Caiman will on oc­ca­sion prey on do­mes­tic an­i­mals, and there have also been at­tacks on hu­mans. (Brit­ton 1999, Da Sil­veira and Mag­nus­son 1999).

Con­ser­va­tion Sta­tus

While it was once ex­tremely com­mon through­out its range, com­mer­cial hunt­ing has dev­as­tated pop­u­la­tions of M. niger. Killing black caimans for their skins, which pro­duce a shiny black leather, in­creased dra­mat­i­cally dur­ing the 1940s and 1950s as pop­u­la­tions of other, more pop­u­lar, South Amer­i­can croc­o­dil­ians were de­creas­ing. Hunt­ing con­tin­ued through the 1970s, nearly de­stroy­ing many com­mu­ni­ties. It is es­ti­mated that black caiman pop­u­la­tions have been re­duced by 99% dur­ing the 20th cen­tury.

Il­le­gal hunt­ing re­mains a prob­lem today, but it is not the only threat fac­ing black caimans. The de­struc­tion of its habi­tat by de­for­esta­tion and burn­ing of swamp­lands is slow­ing the re­cov­ery of pop­u­la­tions, as is in­creased com­pe­ti­tion for re­sources with Caiman croc­o­dilus.

While still pre­sent in much of its range, pop­u­la­tions are still se­verely de­pleted in 4 of the 7 coun­tries in which it oc­curs. There are some lo­cally strong pop­u­la­tions in Peru, Ecuador, Brazil, and Guyana; these tend to occur in iso­lated, hard to reach areas of swamp­land. Thor­b­jarnar­son and Da Sil­veira (1998) found a sur­pris­ingly ro­bust pop­u­la­tion in the Mami­raua Re­serve in the Ama­zon.

The lack of re­li­able cen­sus in­for­ma­tion makes pop­u­la­tion sur­veys a cru­cial first step for any man­age­ment pro­gram. Eco­log­i­cal stud­ies are also being car­ried out to help re­veal the be­hav­ior of this poorly un­der­stood rep­tile.

Man­age­ment strate­gies are fo­cus­ing mainly on legal pro­tec­tion of wild pop­u­la­tions, but such laws are not al­ways ef­fec­tively en­forced. Bo­livia pi­o­neered a cap­tive breed­ing and rein­tro­duc­tion pro­gram in 1990 by re­leas­ing 25 ranch-raised adult black caimans; some of these were ob­served to re­pro­duce. There is hope that suf­fi­cient pro­tec­tion and pop­u­la­tion re­cov­ery may allow the im­ple­men­ta­tion of a con­tolled, man­aged har­vest that would ben­e­fit the local peo­ples. This would en­cour­age pro­tec­tion of the species as a val­u­ble re­source and ease the pres­sures from un­con­trolled poach­ing. (Brit­ton, Sep­tem­ber 15, 1999; Thor­b­jarnar­son, 1998; Thor­b­jarnar­son, July/Au­gust 1999)

Con­trib­u­tors

Rose Syd­lowski (au­thor), Michi­gan State Uni­ver­sity, James Hard­ing (ed­i­tor), Michi­gan State Uni­ver­sity.

Glossary

Neotropical

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

World Map

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.

ectothermic

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

freshwater

mainly lives in water that is not salty.

motile

having the capacity to move from one place to another.

native range

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

tropical

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

Ref­er­ences

Brit­ton, A. Sep­tem­ber 15, 1999. "Melanosuchus niger (SPIX, 1825)" (On-line). Ac­cessed No­vem­ber 7, 1999 at http://​www.​flmnh.​ufl.​edu/​natsci/​herpetology/​brittoncrocs/​csp_​mnig.​htm.

Da Sil­veira, R., W. Mag­nus­son. 1999. Diets of Spec­ta­cled and Black Caiman in the Anav­il­hanas Arch­i­pel­ago, Cen­tral Ama­zo­nia, Brazil. Jour­nal of Her­petol­ogy, 33: 181-192.

Da Sil­veira, R., W. Mag­nus­son, Z. Cam­pos. 1997. Mon­i­tor­ing the dis­tri­b­u­tion, abun­dance and breed­ing areas of Caiman croc­o­dilus and Melanosuchus niger in the Anav­il­hanas Arch­i­pel­ago, Cen­tral Ama­zo­nia, Brazil. Jour­nal of Her­petol­ogy, 31: 514-520.

Her­ron, J., L. Em­mons, J. Cadle. 1990. Ob­ser­va­tions on re­pro­duc­tion in the Black Caiman, Melanosuchus niger. Jour­nal of Her­petol­ogy, 24: 314-316.

Mag­nus­son, W. 1998. Croc­o­diles and Al­li­ga­tors. Pp. 224-233 in H Cog­ger, R Zweifel, eds. En­cy­clo­pe­dia of Rep­tiles and Am­phib­ians. San Diego, CA: Aca­d­e­mic Press.

Mag­nus­son, W., E. Viera da Silva, A. Lima. 1987. Diets of Ama­zon­ian Croc­o­dil­ians. Jour­nal of Her­petol­ogy, 21: 85-95.

Pough, H., R. An­drews, J. Cadle, M. Crump, A. Sav­itzky. 1998. Her­petol­ogy. Upper Sad­dle River, NJ: Pren­tice-Hall.

Thor­b­jarnar­son, J. 1998. "Melanosuchus niger" (On-line). Ac­cessed No­vem­ber 12, 1999 at http://​www.​flmnh.​ufl.​edu/​natsci/​herpetology/​act-plan/​mnige.​htm#​TOP.

Thor­b­jarnar­son, J. July/Au­gust 1999. The Hunt for the Black Caiman. In­ter­na­tional Wildlife, 29: 12-19.