Abstract

To provide better medical care and improve husbandry techniques, a brief review of curassow ecology,¹ husbandry,² and screening of curassow medical and necropsy records from the Houston Zoological Gardens (HZG) was conducted. The Houston Zoo has housed over 230 curassows of 10 various species since 1973 from which the records were reviewed.

Curassows are in the family Cracidae, a primitive bird group in the order Galliformes. It is a long-lived (20+ yr), arboreal gallinaceous bird group found in the Central and South American tropics and subtropics. The family Cracidae contains approximately 13 curassow species (Table 1), Chachalacas, and Guans. Curassows are fowl-like with strong legs and feet, ample tail and wings, and a well-developed hind toe used to grasp branches. They are primarily vegetarians with a muscular gizzard which can grind hard seeds and nuts as well as fruit, greens, insects, and invertebrates. Due to the muscularity of the ventriculus, curassows tend to swallow large amounts of small pebbles or gravel. Curassows are the only group of the Cracidae family that have a developed crop. Male birds are usually larger than the females and both sexes are vocal with a well-developed syrinx. Certain species of male curassows: Nothocrax urumutum, Crax globulosa, C. pauxi, and C. mitu have an elongated trachea, used in vocalization for increased loudness or low pitch sounds. The trachea extends under the skin, and in some species overlays the abdomen, then curves back around and enters the thoracic inlet. Some curassow species have a feathered crest on the top of the head. Curassows’ natural enemies include predatory birds, mammals, and man.

Table 1. Curassow taxonomy (genus and species vary slightly with different authorities)³

Table 2. Representative hematology and plasma biochemistry values of the curassow (Crax globulosa) from International Species Information System (ISIS)³ and the Houston Zoological Gardens (HZG) in-house analysis

Curassows are generally monogamous and occur in pairs, although trios (cock and two hens) or family groups can be found. Males have an intromittent organ, which can be used to sex young birds. Adult birds are sexually dimorphic, with the males being larger in size than females and in many species the males have a large knob or wattle on the cere. The female lays and broods two eggs, incubation lasts approximately 29–32 days. Females can produce four clutches per year if the eggs are pulled for artificial incubation or domestic chicken brooding after the clutch is laid. Chicks are precocial, grasping and perching as soon as they are hatched, thus smaller perching should be provided. They are fed by both parents by offering foods in the beak, curassow parents do not regurgitate for their young.

Certain normal mannerisms of the curassow, if one is not aware of them, can lead to misdiagnosis of neurologic disease. Curassows have a tendency to flick their heads and present with a head tilt when anxious or nervous. They also will flick their tails up and down as well as pass the head over the shoulders and back.

Curassow pens should be fairly large and contain several perches for roosting due to the birds’ body size and their arboreal nature. It is thought that curassows spend approximately one-half of their time perching above the ground. An enclosed section for protection from the cold and frostbite should be included. Males are territorial and two or more housed together tend to fight. The birds can be excessively aggressive during the breeding season and may even attack zoo visitors. Curassows may also be aggressive towards and can kill smaller birds and generally do not make a good species for free-flight pens.

In general, curassows are hardy birds and are not prone to disease. Because they are classified in the order Galliformes, it is felt that curassows are susceptible to most of the diseases affecting poultry such as reticuloendothelial virus, Salmonella spp., Mycoplasma spp., and Chlamydia. Very few infectious diseases have been diagnosed in live curassows at the HZG. Bacterial pododermatitis has affected some birds. Low numbers of endoparasites have been found and included ascarids, Capillaria, strongyles, Strongyloides, Dispharynx, Heterakis, and coccidia. Feather lice and mites have also been found on several birds.

Non-infectious diseases predominated in curassows presented for medical attention at the HZG. The birds often are found to have general clinical signs such as debilitation, emaciation, weight loss, abnormal behavior, lethargy, lameness, and occasionally moribund. Trauma was the medical problem most commonly diagnosed for the following reasons: cagemate aggression, parental trauma to young, self-mutilation (rubbing), restraint, and incompatible neighboring species. Fractures, of toes, legs, and wings, and integument lacerations and tears were common. Other integument problems consisted of overgrown beak, toenail trauma, and uropygial impaction. Curassows are susceptible to frostbite when temperatures approach the low 40s (Fahrenheit) or lower. Curassows also have a tendency to pick objects off the ground, thus there have been several cases of zinc toxicosis in captive zoo birds but only rare instances of intestinal obstruction. Reproduction problems were also commonly found in curassow hens due to their large egg size and included eggshell retention, egg binding, and cloacal prolapse. Intromittent organ prolapse and infection was seen in one adult male. Curassow chicks greater than 1 day of age generally have few problems at HZG, but rotational leg deformities were found in chicks that did not have good perching material supplied after hatching. Many chicks had problems with poor or abnormal hatching.

Diagnoses of necropsies performed at the HZG reflected the clinical signs and diagnoses found in live birds. Forty-two complete necropsy reports of approximately 60 available were reviewed and diagnoses recorded. Necropsy results not included were those that were incomplete or the diagnoses were not confirmed by histologic review. Diseases affecting multiple organs were peritonitis, primarily due to egg yolk contamination, and septicemia. Digestive tract diagnoses included enteritis, colitis, and hepatitis. Respiratory lesions found were pneumonia and aspiration (especially in newly hatched or pre-hatched chicks), bronchitis, and aspergillosis. Reproductive diseases of hens were similar to those in the live birds such as egg binding, salpingitis, metritis; one ovarian granuloma was found. Histologic lesions often were not found in chicks, many appeared to die during hatching, sometimes associated with abnormal positioning. Histologically, omphalitis and yolk sacculitis predominated. The HZG has seen necropsy lesions in several curassows that are typically found in birds infected with reticuloendothelial virus (REV) such as lymphoid leukosis, lymphoma, and lymphoreticular disease. Reticuloendothelial virus infection was not confirmed in any of these cases, as most were diagnosed histologically before REV PCR testing was available. Other neoplasias found were intestinal carcinoma and adenocarcinoma. Non-infectious, gross necropsy lesions from birds that were euthanatized due to poor prognosis or had died included hypothermia, frostbite, trauma, and musculoskeletal deformities and malformations (rotational deformities, fractures, scoliosis, slipped tendons, bumblefoot, myopathy).

In conclusion, curassows are large, unusual tropical gallinaceous birds that are not hard to keep and maintain in a zoological setting. The species is susceptible to many diseases, but with good quarantine, disease screening protocols and husbandry procedures, most diseases found can be prevented or treated.

Literature Cited

1.  Delacour, J. and D. Amadon, 1973. Curassows and Related Birds. Chanticleer Press, Inc., New York, New York.

2.  Todd, W.T., R. Plasse, and C. Eckert, 1992. Curassow Husbandry Manual. 2nd ed. Houston Zoological Gardens, Houston, Texas, USA.

3.  Med. A.R.K.S., International Species Information System, 12101 Johnny Cake Road, Apple Valley, Minnesota 55124 USA.