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Raptor medicine (Proceedings)

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Nov 01, 2010

Probably because of their size and likelihood of being found injured, raptors continue to be one of the most commonly received groups of birds in wildlife rehabilitation facilities. Although they are susceptible to most of the same diseases as other birds, raptors possess some unique anatomical and life history traits that translate to clinical syndromes unique to this group. In addition, their size and visibility, their long-term associated with humans (ie: through falconry), their position in the trophic chain, and their role as indicators of their environment, make birds of prey important wildlife patients.

Taxonomy

The word raptor is derived from the latin rapere (to grip or grasp).

Birds of prey all have: hooked beaks, talons, are either predators or scavengers. Raptors belong to 2 major groups: the owls and the diurnal birds of prey. The Order Strigiformes (owls) has two families: Fa. Tytonidae (barn and grass owls) and Fa. Strigidae (all other owls). The Order Falconiformes (diurnal raptors) contains: Fa. Cathartidae (New World vultures), Fa. Pandionidae (osprey), Fa. Accipitridae (kites, hawks, Old World vultures), Fa. Sagittaridae (secretary bird), and Fa. Falconidae (falcons and caracaras).

Anatomy and Physiology

Gastrointestinal system: Vultures have well developed crops, whereas red tailed hawks have poorly developed crops and owls do not have crops. Their stomach is simple and muscular. The ceca is vestigial in falcons and hawks, but present in vultures and great horned owls. Owls perform egestion (casting) or the formation of pellets. This is a combination of activity of the stomach and esophageal peristalsis. Pellets are formed of bones, feathers and fur from digested prey. Owl pellets usually contain bones, whereas hawk pellets do not. Owls produce one pellet per meal but hawks eat more than one meal before producing a cast, and cast production is more associated with circadian rhythmn.

Respiratory system: Raptors are fine-tuned athletes. They have extremely efficient respiratory systems for hunting during flight. Successful rehabilitation efforts depend on returning raptors to their full athletic ability.

Cardiovascular system: As with other animals, the heart rates increase with metabolic rates, such that smaller raptors have higher heart rates. Several publications illustrate normal ECG's and echocardiography of the raptor.

Skeletal system: Their feet are covered in thick scales to protect them from injury (ie: bites from squirrels). They have extremely strong toes, ending in triangular talons. The first digit is opposable toe for grasping prey. The digital flexor tendons and their sheath have unidirectional, interlocking ratcheting mechanisms that resist digital extension when the toes are flexed to enhance prey prehension.

Husbandry

Captivity requirements

Raptors require flight cages that allow for proper flight mechanics to occur in the process of rehabilitation. Supplemental heat is important for southern and migratory species and those that are debilitated or have high metabolic rates. At the very least, protection from wind and inclement weather is needed. Hospital cages are ok for short-term care, but must have visual barriers and be padded heavily, as well as contain appropriate sized perches that allow the foot to be held in an anatomical position and the tail to remain off the floor surface. Access to UV light is paramount for synthesis of Vit D3 if maintained in captivity longterm.

Diet/H20 requirements: Raptors are carnivorous birds, and nutritional requires vary with species. Captive diets should mimic free-ranging diets; however, most can be maintained on readily available rodents at least for short term periods of time. It is important to feed whole prey. Pre-prepared diets are commonly used in zoos. Small raptors eat 30% of their body wt daily, whereas larger raptors should be fed 8-10% of body wt daily. Diets composed of heart, muscle, liver or kidney are deficient in calcium and can lead to nutritional secondary hyperparathyroidism. High fat diets are also low in calcium and may prevent absorption of Vit D3. Raptors normally receive their water requirements from ingested prey; nonetheless, fresh water should be offered, both for drinking and bathing. Their estimated daily requirement is 50 ml/kg/24 hrs.

Reproduction

The female raptor is usually much bigger in size. The larger species become sexually mature later in life than smaller sp. Most raptors exhibit strong imprinting, thus care should be taken when orphans are reared.