If an orphaned bird or mammal is found, further information should be sought before attempting wildlife rehabilitation. Specialized books about hand-rearing wild and domestic mammals and birds and the National Wildlife Rehabilitators Association Web site (www.nwrawildlife.org) are valuable resources. The following is a general overview, and all species require more information for a full course of captive care. Correct species and age identification is crucial for determination of behavioral considerations, weaning diets, and adult fate. It is illegal to keep most species of North American wild animals as pets. Permits are required, even by veterinarians, to care for most wild species beyond initial medical care. The USA Fish and Wildlife Service and state natural resource agencies should be contacted for applicable rules. Injured limbs of wild animals should never be amputated without consultation with regulatory agencies, because permanent captive placement for disabled wildlife may be difficult to find. Euthanasia should be considered when injury resolution will result in a disabled, unreleasable animal. When hand-rearing for wild release, infants should be raised with conspecifics to avoid human imprinting, using techniques that avoid habituation. Wild infants must be isolated from domestic animals.
The first step is to determine whether young are truly orphaned. If chicks are returned to nests or mammals are left alone and monitored from afar, the parent may return and resume care. Human handling does not preclude most parents accepting returned offspring. Neonatal wildlife, especially unidentified species, have the best chance of survival if kept warm and taken to local wildlife rehabilitation centers. Skunks, raccoons, foxes, and bats should only be rehabilitated by professionals because of potential zoonotic diseases. Marine mammals and seabirds require specialized care facilities (see Management of Marine Mammals).
All neonates require physical examination and assessment of hydration, body temperature, and weight. Warmth, hydration, and energy are critical. Because most orphans initially cannot maintain or regulate their body temperature, supplemental heat should be provided with heating pads, hot water bottles, incandescent light bulbs, or brooders. A heat gradient for ambulatory young allows orphans to select their own comfort zone. Thermal support of altricial species must be closely regulated. Most placental mammals and birds have normal body temperatures warmer than that of people, and should feel warm to the human hand. Maintaining humidity of 50%–70% in housing reduces dehydration, and insulating orphans from direct heat prevents burns. Hypothermic orphans should be warmed until body temperature is near normal and administered warm fluids to maintain hydration or correct deficits. Once the infant is warmed and well hydrated, species-appropriate diets can be fed to provide energy. Initial feedings should be conservatively sized and dilute until it has been determined that the infant’s excretory systems are functioning. Infants of most species have a stomach or crop capacity of ~50 mL/kg. Overfeeding may result in aspiration pneumonia or diarrhea. Once infants are stabilized, the advice of a permitted rehabilitator should be obtained.
Hair, feathers, skin, and eyes should be kept free of spilled food or excreta, and foods maintained hygienically. Nests/housing should be cleaned regularly and secured against vermin. Treatment for ecto- and endoparasites or fly strike may be necessary. Products deemed safe for infants of domestic species should be used, and an exotic animal formulary consulted for dosing information.
Metabolic bone disease may develop quickly in wild orphans fed inadequate diets. Corvids, other passerines, herons, egrets, shorebirds, raptors, opossums, and canids are especially susceptible, including when transitioned off formulas onto inadequately supplemented animal protein diets before skeletal maturity. Ground meat or poultry must be supplemented with calcium carbonate at 5 g/ 0.5 kg of meat. Growing chicks require a dietary ratio of elemental calcium:phosphorus of ~2:1 by weight.
Nest replacements should be constructed so as to provide nonambulatory chicks with a comfortable upright posture with the head elevated and legs underneath the body. Housing chicks on flat surfaces may result in splayed legs. Fractured bones are considered life-threatening injuries because of the requirement of functionality for release. Trauma to soft tissues can be minimized by stabilizing fractures promptly. Elbow, carpus, spine, stifle, and hock fractures or luxations carry a poor prognosis for release. Mid-shaft long-bone fractures often heal well. Humerus and femur fractures heal best with a simple intramedullary pin, and pinning may be successful even in extremely young or small-bodied chicks. Minimally restrictive splints and wraps for other fractures result in fastest recovery and release. Chicks should be allowed to use stabilized, fractured limbs as normally as possible during recovery. Stable callus formation occurs in 5–7 days in nestling passerines and in 10–21 days in larger-bodied species, well before radiographic changes occur. Some species form joint contractures easily and require physical therapy after the fracture and then continuing intermittently for return to function. Chicks may heal rapidly from seemingly severe soft-tissue injuries. Lacerations should have primary closure to minimize time in captivity and reduce adverse effects on growing plumage. Antibiotic therapy against gram-negative bacteria is advisable for predator-injured chicks; it should be continued until wounds have completely healed. Meloxicam and butorphanol are commonly used for pain. Chicks with head injuries may recover well; changes in neurologic signs can be used as prognostic indicators while giving supportive care. Beak or jaw injuries must resolve with beak tips well aligned to ensure ability to forage normally after release.
Nearly all North American bird species feed vertebrate or invertebrate prey to their chicks. Milk and bread, hamburger, condensed milk, or uncooked rice should not be fed. Soaked dog kibble and monkey biscuits are inadequate for most species. All species require 8–12 hr uninterrupted sleep. Self-feeding requires daylight-level lighting in diurnal species. All growing chicks should gain weight every day, so weight should be monitored closely.
Chicks should be warmed to normal body temperature, hydrated until droppings are produced, and then fed. Tiny, unfeathered chicks require environments as warm as 100°F (37.8°C); larger-feathered chicks do well initially in temperatures of 90°–95°F (32.2°–35°C). Overheated chicks may hold perpetual open-mouthed postures, droop heads over nest edges, and cease producing droppings if dehydrated. Not all species gape/beg (swifts, nightjars). Some species stop begging when full (corvids); some do not and may dangerously overeat (finches, goldfinches). Crops should empty between feeds; not all species have crops (insectivores, owls). Hatchlings require more water than older chicks. Common problems that cause lack of gaping include too cold, hot, weak, or dehydrated; untreated illness or injury; and misidentified species. Overfeeding may cause droppings that appear as undigested diet.
Higher protein/fat, lower carbohydrate diets are desirable for most species. Puréed, high-quality kitten or ferret kibble is an acceptable temporary food for most altricial chicks, supplemented with elemental calcium at 150 mg/kg/day, PO, until on a balanced diet. Puréed, skinned prey animals (quail or adult mice, including bones and organs, minus feet and heads) form an adequate diet for many species. Bone fragments must be completely pulverized to avoid GI trauma. A diet of thawed-frozen prey requires vitamin supplementation. Vitamin E and thiamine supplementation is necessary for species ingesting frozen-thawed fish. Feeding prey frozen >6 mo should be avoided. Vitamin A may be inadequate in insect prey, and deficiency may occur if prey are fed with viscera removed. Pinky mice, insects, and small-bodied fish often contain inadequate calcium for growing birds; hence, supplementation is necessary.
A simple hand-feeding diet consists of 1 cup (116 g) Purina Pro-Plan® kitten kibble, 1.25–1.5 cup (300–360 mL) water, 2 tbsp (14 g) powdered egg white, 750 mg calcium from CaCO3, and ½ tsp (1.4 g) Avi-Era® powdered avian vitamins. Do not delete or substitute ingredients haphazardly, soak kibble and blend until smooth, and feed with appropriately sized syringe. For hatchlings/nestlings, feed 50 mL/kg every 20–45 min (by age) 12–14 hr/day (16 hr/day for insectivores). For fledglings, hand-feed 50 mL/kg every 1–2 hr, 12 hr/day, offering appropriate self-feeding diet.
Commercial diets for hatchlings are RoudybushTM Squab Diet and Lafeber's® Emeraid® Carnivore; for nestlings/fledglings, Kaytee® Exact® Hand Feeding Formula. Crop capacity is 100–120 mL/kg. Birds should be fed when crop empties, 12–14 hr/day, every 1–2 hr until eyes open and then every 3 hr until ambulating and ingesting seed. Palpating the crop before each feeding will assess self-feeding and prevent overfilling.
Hatchlings can be fed small pieces of warm, water-dipped meat every 2 hr, 12 hr/day, with blunt-tipped forceps; tiny bone pieces can be included by day 3 after hatch, and casting material (skin/hair) by day 5. The crop should empty between meals. Most species will pick up chopped prey from a dish by day 14. Feeding with a puppet parent can be done once the eyes open.
Once warm and secure, many species drink and eat independently. Solitude stresses chicks; a mirror, small stuffed animals, clean feather duster, or chicks of closely related species can be companions. Uncommon species and debilitated hatchlings require professional rehabilitative care for a positive outcome. Placing pebbles in water dishes may prevent quail/ducklings from drowning. Hatchling quail/killdeer require habitat brooders kept at 95°–100°F (35°–37.8°C).
Natural duckweed or watercress, small invertebrates, crushed hard-boiled egg, small minnows, and waterfowl starter (Mazuri®) should be offered. Access to shallow water should be controlled; chicks must be able to easily exit water to warm under a heat source. Chicks may lose waterproofing and become chilled if plumage becomes contaminated with food or droppings.
Hypothermia and dehydration must be corrected before feeding neonate mammals. Hairless neonates require ambient temperatures of 85°–90°F (29.4°–32.2°C), while haired infants may be housed at cooler temperatures depending on maturity and body condition. Once warm and hydrated, milk replacer should be introduced using this regimen: 100% oral electrolyte solution, gradually increasing the strength of milk replacer in one to several feedings to ¼ strength, then ½, then ¾, and finally to full strength. During this process, if the neonate develops digestive upset (vomiting, diarrhea, bloating), feeding should return to the last well-tolerated ratio. Overfeeding or sudden diet changes may cause bloating or diarrhea. Neonates need to be stimulated to eliminate by gently stroking the perineal area with warm moist gauze or tissue. Dorsal side up is normal nursing posture; infants should not be put on their backs to feed. The environment should be quiet.
Fawns should be raised in groups with minimal human contact and kept away from dogs. Newborn to 2-day-old fawns should be fed colostrum, such as Colostrx®, for the first 24–48 hr. After reconstitution, one 454-g package can be administered via bottle or stomach tube over 8–10 hr (5 meals/day, 30–40 mL/kg). Acceptable milk replacers include Fox Valley® Milk Replacer, lamb’s milk replacer, or goat’s milk. Fawns 2–7 days old should be fed four times daily, gradually increasing volume to 50 mL/kg. From 8 to 14 days of age, up to 300 mL should be fed, reaching a goal of 300 mL, tid. From 2 to 4 wk, the amount should be increased to 460 mL, tid, adding solid food (eg, goat chow, calf manna, and alfalfa hay). Indigenous natural browse should always be available. By 7 wk, fawns should be eating solid food and fed one 480 mL bottle daily. By 8–10 wk, fawns should eat solid food exclusively.
For squirrels, syringe-feeding is preferred; Catac® nipples work well. Eastern gray and fox squirrel neonates should be fed every 2 hr until 2 wk old. From 2 to 3 wk, feeding should be every 3 hr, eight times/day. At 4 wk, the late-night feed is eliminated. At 5–6 wk, feedings are reduced to five and then to four times/day, at 7–8 wk to three times/day, and at 10 wk to once a day. Weight should be monitored daily, and the squirrel fed 50 mL/kg initially, gradually increasing to 70 mL/kg by 3 wk. Acceptable milk replacers (ratios by volume) include 2:3 Fox Valley® 32/40:water, or 1:½:2 Esbilac® , MultiMilk® , and water. When eyes are open and squirrels are ambulatory, natural foods and rodent block can be offered; fruit should be strictly limited. Ground squirrels wean at 6 wk old, and Western gray squirrels at 12 wk.
Neonatal rabbit stomachs hold 100–125 mL/kg. Healthy neonates should be fed twice a day, although feedings up to four times a day may be needed. Use of a slip-tip syringe is preferred. If suckling response is poor, meals should be tube fed, with the volume reduced by 30% and an extra feeding to ensure adequate intake. Acceptable milk replacers (ratios by volume) include 2:1 parts KMR® powder:water (with pinch of acidophilus) or 1:1 parts Esbilac® powder:water. When the eyes open, a variety of chopped leafy greens and grass (orchard, timothy, or oat) hay should be provided. Because hares are precocial (born furred with eyes open), forage should be offered immediately in addition to milk replacer. Fruits and high-sugar vegetables (eg, carrots) should be avoided.
Infant opossums weighing <20 g have a poor prognosis. Infants weighing 20–35 g should be fed 50 mL/kg, six times a day; those weighing 40–100 g, 50–60 mL/kg, five times a day. An acceptable milk replacer (ratio by volume) is 1:½:2 parts Esbilac® , MultiMilk® , and water. Tube-feeding is preferred, and a size 3.5 French red rubber catheter measured to the caudal rib may be used. If syringe feeding, a cut smoothed tomcat catheter can be attached to the syringe and the infant fed drop-wise. When eyes open (~45 g), infants can be taught to lap formula from a shallow dish. When infants weigh ~60 g and are walking, kitten kibble soaked in Esbilac® can be offered. Once the infant is eating soaked kibble (~80–100 g), 10% other natural food items (crickets, worms, chopped mice, local fruits, high-calcium vegetables) can be introduced. Most opossums self-feed by the time they weigh 100–120 g. Adequate calcium intake must be ensured to prevent metabolic bone disease.
Gloves should always be worn when handling raccoons. Raccoons are the definitive hosts for Baylisascaris procyonis, a roundworm parasite that may be transmitted to people or other animals, primarily via feces, and result in sometimes fatal infection. Raccoons also may carry rabies.
Newborns weigh 60–75 g with eyes and ears sealed. Incubators are necessary until weight is >500 g. The preferred milk replacer is KMR® or Zoologic® 42/25 (1:2.25 parts powder:water). Infants should be fed via 8 French gavage tube, or drop by drop into the mouth (using a cut smoothed tomcat catheter attached to a syringe) until they are stronger and/or eyes are open. Over-feeding should be avoided. The stomach should be plump but not taut. Four PawsTM large squirrel nipple on a 6-mL syringe may be used. Infants should be stimulated to urinate/defecate after each feed until they eliminate without stimulation. Infants should be weighed daily, and fed 50 mL/kg, six times a day, until they weigh 200 g. They can then be fed using a preemie nipple on a bottle or from a dish at the rate of 42.5 mL/kg, five times/day, until they weigh 500 g. At a weight of 400 g, if infants are strong enough and their eyes are open, in addition to the milk replacer, “mush” made of soaked puppy chow, high-protein baby cereal, and KMR® powder (with water added to create oatmeal consistency) can be offered. At 500 g, one of four feeds should be mush in a dish. At 850 g, small bits of cut fruit and soaked puppy chow should be added, decreasing milk replacer to three times a day. As the infants mature, hard puppy chow, prey items (mice, fish), egg, and 10% fruits and vegetables can be offered and formula feeds reduced.