Abstract

The Cuban crocodile (Crocodylus rhombifer) is one of the world’s most endangered crocodilians, and wild populations remain in only two small freshwater marsh habitats in Cuba. Loss of habitat, human encroachment, poaching for skin and meat, and ecological competition with two other crocodilian species are threatening the long-term viability of this species. Hybridization with one of those competitors, the American crocodile (Crocodylus acutus), remains the most serious problem threatening the genetic integrity of the species. The Cuban Crocodile Species Survival Plan was formed in 1993 and has focused its efforts on captive management, in-situ education, and select field studies. Recently, a morbidity and mortality review on the ex-situ captive population has been conducted, and at the time of this writing, the first husbandry manual for the species is near completion.

The political relationship between Cuba and the United States has been an obstacle to efficient communication, importation of new animals, and more frequent and comprehensive in-situ activities. In the short and long term, recruitment of additional holding space dedicated for Cuban crocodiles in AZA-accredited zoological parks is vital.

Current Wild Population and Endangered Status

The Cuban crocodile (Crocodylus rhombifer) is classified as endangered (IUCN Red List) and has one of the smallest natural geographic ranges (<500 sq km) for a megavertebrate predator. The species inhabits freshwater marshes and is currently endemic to Cuba. There are currently two remaining wild populations, one limited to central freshwater portions of the Zapata Peninsula and a second reintroduced population tentatively established in the eastern portion of the Lanier Swamp on Isla de la Juventud.

Historically, the species was more widespread throughout Cuba and the Western Caribbean. Natural climate changes (i.e., interglacial period warming leading to rising sea levels) during the Holocene period lead to a progressive decline in the Caribbean freshwater marsh ecosystem.⁵ Human encroachment and poaching for hides and meat have also been responsible for a decline in both the Cuban crocodile range and overall population. Cuban crocodiles were extirpated from Isla de la Juventud before captive-raised animals were reintroduced between 1993–1995. Despite government protection, poaching continues to be a significant pressure on both of the current populations due to inadequate protection and enforcement (Roberto Soberón, pers. comm.).

In addition, Cuban crocodiles currently share their habitat with two other crocodilian species that historically were not present. In the 1950s, spectacled caiman (Caiman crocodilus) were introduced on Isla de la Juventud. By the early 1990s, Cuban biologists estimated a well-established population of over 40,000 animals in the region (Roberto Soberón, pers. comm.). The presence of this adaptable and invasive species has placed added pressure on the Cuban crocodile due to resource competition. More significantly, both remaining Cuban crocodile populations share their habitat with the American crocodile (Crocodylus acutus), another highly adaptable and successful generalist. Historically, the American crocodile occupied brackish or marine regions along Cuba’s coast, allowing Cuban crocodiles to act as the keystone species within interior freshwater swamps. However, manmade canals were constructed in the 1800s beginning from the coastline into the interior of the Zapata Peninsula. These canals were utilized for deforestation and to facilitate industrial and agricultural developments,⁵ and served as an immigration route for the American crocodile to penetrate the interior of the freshwater swamp. Today, American crocodiles cohabitate with Cuban crocodiles in Zapata, as well as on Isla de la Juventud, and unlike with spectacled caiman, these Crocodylus species will hybridize and produce fertile offspring. These hybrid crocodiles, identified phenotypically, range in abundance depending on the locality sampled. Hybridization with the American crocodile remains the most deleterious factor threatening the genetic integrity and existence of the Cuban crocodile.

The Species Survival Plan: Past and Present

The Cuban Crocodile Species Survival Plan (SSP) was formed in 1993 with the goals of helping to ensure the long-term survival of the species in nature as well as to establish a self-sustaining ex-situ captive population. The current SSP-managed captive population consists of only 32 individuals (6.23.3) housed at 10 institutions, ranging in age from 4–50+ years. The 2008 Regional Collection Plan calls for a target population size of 75 animals. Since inception of the SSP, 17 Cuban crocodiles have hatched at two institutions.

The following represents a timeline of significant SSP activities:

1993—The Cuban Crocodile SSP was formed.

1996—The first SSP master planning meeting was held in Toledo, Ohio. In-situ fieldwork was conducted, monitoring the reintroduced population of Cuban crocodiles within Lanier Swamp on Isla de la Juventud. This field study was the first contact between an AZA-accredited zoo and Cuba in regard to Cuban crocodile conservation. An education liaison joined the SSP.

1997—Further in-situ field studies were conducted monitoring the Lanier Swamp population of Cuban crocodiles. At the same time, an attempt was made to raise public awareness about the reintroduction of Cuban crocodiles to Lanier Swamp and foster development of a conservation ethic toward this endemic species. A community festival was planned to promote the Cuban crocodile as a strong patriotic symbol unique to Cuba’s natural heritage.

1999—Further in-situ field studies were conducted in Lanier Swamp. An SSP master planning meeting was held in Louisville, Kentucky. The SSP hosted Roberto Soberón, Cuba’s national coordinator of crocodile programs, at the meeting.

2000—Further in-situ field studies were conducted in Lanier Swamp. The Cuban crocodile festival that was planned in 1997 was implemented and held in Mellá, a small community that borders Lanier Swamp on Isla de la Juventud. In addition, a Populations and Habitat Viability Assessment (PHVA) workshop was held in Varadero, Cuba, in conjunction with the World Conservation Union’s (IUCN) crocodile specialist group meeting. This workshop provided tools to evaluate and integrate the interaction of biological, physical, and social factors on the Cuban crocodile population.

2001—The SSP hosted Damarys Lopez, a Cuban biologist that conducts studies on all three crocodilian species on Isla de la Juventud, at the Louisville Zoo.

2002–2003—The SSP collaborated with the Wildlife Conservation Society/Bronx Zoo and the Havana Zoo in Cuba in offering a series of workshops that offered environmental education materials and training to local educators focusing on wetlands and the Cuban crocodile.

2003—Veterinary advisors joined the SSP. The SSP hosted Dr. Elsie Pérez, then director of the Havana Zoo and head of the Cuban Association of Zoos and Aquariums, at the Louisville Zoo.

2003–2005—A survey was conducted collecting medical records and pathology data from all zoos and related facilities that house, or have housed, Cuban crocodiles. Data collected, including morbidity and mortality information, were compiled.

2004—An SSP master planning meeting was held in Louisville, Kentucky.

2007—An SSP master planning meeting was conducted via electronic mail.

Coming soon—The first comprehensive husbandry manual for the Cuban crocodile.

Veterinary Issues

With proper husbandry, the Cuban crocodile is extremely hardy and long-lived in captivity, and few disease problems have been reported. Most health problems appear to be due to conspecific trauma or husbandry issues (i.e., nutritional diseases, access to coin foreign bodies, exposure to suboptimal temperatures).

Nutritional diseases have been observed. Rickets in the form of general osteopenia, scoliosis, long bone bowing, lameness, and pathologic fractures can occur in young hatchlings that are not fed a diet that meets calcium, phosphorus, and vitamin D₃ needs. Feeding hatchlings whole vertebrate prey or a balanced commercial carnivore diet as early as possible, as opposed to unfortified insects, is desirable. Hypovitaminosis E leading to steatitis has been documented in young Cuban crocodiles fed exclusively fish.⁴ Animals fed unsupplemented, thawed frozen fish are particularly susceptible to hypovitaminosis E. If fish comprise a significant component of the diet, supplementation with vitamin E and thiamin is advised.

Zinc toxicosis secondary to coin ingestion has been seen in at least two captive Cuban crocodiles at two different institutions. Signs included anorexia, weight loss, and depression, and gastric biopsies from one of the animals revealed gastritis and mucosal necrosis. Both cases were treated with coin removal and chelation therapy. Due to the potential for zinc toxicosis from coin ingestion, Cuban crocodiles should be housed in a manner that eliminates, or at least minimizes this risk (i.e., glass or mesh separating the crocodiles from the public). High blood lead levels have also been documented in at least two Cuban crocodiles, although it appears that crocodilians have a tolerance for high lead burdens. In one of those cases, the elevated blood lead level was secondary to feeding urban feral pigeons.¹

Dental issues have also been reported. Malocclusion has been observed in some captive Cuban crocodiles where the teeth from one arcade appear to cause gingival trauma and secondary infection to the opposing arcade. It is unclear if high temperature incubation, chronic lack of ultraviolet light exposure, and/or lack of physiologic jaw loading (i.e., eating soft or small food items) during the more rapid growing years play any role in this observation. A captive adult female Cuban crocodile was euthanatized due to severe, chronic, maxillary and mandibular osteomyelitis. This crocodile had a history of chronic gingivitis and periodontitis suggesting that the bone infection may have been an extension of dental disease.

A review of medical records suggests that endoparasitism does not appear to be a significant problem in captive Cuban crocodiles. Due to this apparent low incidence, routine deworming is likely unnecessary. The Cuban Crocodile SSP does not recommend the use of avermectin anthelminthics (i.e., ivermectin and its relatives) in this species due to reports of toxicity in crocodilians.^2,3

A pathology review was conducted and trauma due to conspecific aggression is the leading cause of morbidity and mortality in this species. Unlike Nile crocodiles (Crocodylus niloticus) or American alligators (Alligator mississippiensis), Cuban crocodiles are less tolerant of conspecifics. Puncture wounds, lacerations, lameness, cloacal trauma, facial/jaw fractures, and secondary infections/abscesses have all been reported by holding institutions. Animals under constant social stress can also suffer from secondary hypoglycemia. Individual housing is recommended for this species except in very young hatchlings or in bonded pairs.

Additional postmortem diagnoses revealed through the pathology survey included bacterial sepsis, pneumonia, visceral and articular gout, coelomitis, myopathy, dystocia, hepatitis, myocarditis, nephritis, and disseminated sarcoma.

The Future

The political relationship between Cuba and the United States has been an obstacle to efficient communication, importation of new animals, and more frequent and comprehensive in-situ activities. It is hoped that in the future, perhaps this relationship will change, allowing for a freer exchange of information, educational materials, animals, and biomaterials. In time, the Cuban Crocodile SSP is interested in the importation of additional founder stock from Cuba, continued monitoring of the two wild populations, significant expansion of in-situ education elements, molecular investigation of the hybridization problem, and a comprehensive health assessment of the free-ranging population.

Although the Cuban crocodile faces an extremely challenging reality in nature, this species may be an ideal animal to manage long term in captivity. The species is relatively easy to propagate, is hardy and long-lived, and individuals remain reproductively viable for decades after reaching sexual maturity. Long generation times are ideal for the long-term maintenance of gene diversity. Additionally, population growth can be managed by selective incubation of eggs, and gender of offspring can be potentially selected for via careful manipulation and monitoring of incubation temperatures. From an exhibition standpoint, Cuban crocodiles are vividly colored, medium sized, living “dinosaurs,” and can facilitate the communication of a compelling conservation story to the public. They are intelligent, food motivated, impressive jumpers, and very trainable; a combination of qualities that offers great potential for utilizing them in public demonstrations. The Cuban Crocodile SSP is very interested in recruiting additional AZA-accredited partners to help grow the captive population. Please contact the SSP Coordinator, Bill McMahan, if interested (502-238-5351, bill.mcmahan@louisvillezoo.gov).

Literature Cited

1.  Cook, R.A., J. Behler, P. Brazaitis. 1989. Elevated heavy metal concentrations in captive crocodilians—2 cases. Proc. Am. Assoc. Zoo Vet. Annu. Meet. Pp. 151.

2.  Dumonceaux, G.A., J. St. Leger. 2004. Ivermectin toxicity in a group of Nile crocodiles (Crocodylus niloticus). Proc. Assoc. Reptilian Amphibian Vet., 155–157.

3.  Huchzermeyer, F.W. 2003. Crocodiles: Biology, Husbandry, and Diseases. Onderstepoort Veterinary Institute, South Africa, CABI Publishing, Wallingford, Oxon, United Kingdom, 337 pgs.

4.  Moliner, J.L., R. Ramos, O. Bello, S. Elizalde. 2000. Consideraciones clinicas y anatomopathologias observadas en la deficiencia de vitamina E (Esteatitis) en el cocodrilo Cubano (Crocodylus rhombifer) del zoocriadero de la Cienaga de Zapata, Mantanzas, Cuba. Proc. Crocodile Specialist Group, IUCN, Varadero, Cuba, 118–123.

5.  Neil, W.T. 1971. The Last of the Ruling Reptiles: Alligators, Crocodiles, and their Kin. Columbia University Press, New York, New York, 486 pp.