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Home   Rehabilitation   Wildlife Care   Release


In Focus

The rehabilitated animal has endured much to return to its natural environment, and it (as well as the rehabilitator who has invested countless hours in its care and feeding) merits the time and effort required to ensure a successful release.

 


Hawk Release, Toronto Wildlife Centre


 

 Discussion

Release of their patients is the goal towards which all rehabilitators work. However, an animal that is not ready for release, or an animal that has not been prepared for release and conditioned, does not have a good chance of survival.

Before it is released, the animal must be in excellent physical condition and must demonstrate that it has the necessary skills to survive in the wild.

 Birds

Health:

  • The bird should be free of disease and/or parasites.
  • Its weight should be the same as the average for wild conspecifics of similar age.
  • If the bird had an injury, it should be fully healed. If the bird has a permanent handicap (e.g. poor sight in one eye, poor grip in one foot), it must demonstrate that it can compensate. It is crucial to know the bird's method of foraging. A bird of prey must have the ability to grasp and kill prey with its feet. A bird of prey or an aerial insectivore must have 100% normal flight if it is to catch adequate food. A bird must have a strong, normal bill.
  • A bird must be able to perch. A bird with a splayed leg cannot keep the limb warm in inclement weather and may encounter problems with frostbite. A water bird that needs a long 'runway' for take off (e.g. loon) must have two healthy legs (and feet).
  • It is necessary that the feathers of water birds be waterproof. Do not release a bird with missing feathers or feathers that are hunger striped or demonstrate 'white feather syndrome'. These feathers will fray and break, leaving the bird grounded and unable to shelter, feed or avoid predators. Birds with damaged feathers or missing feathers should be held until their feathering is normal.
  • The bird must sustain flight without tiring, panting, trembling, etc. If the bird is an aerial insectivore, it must demonstrate the ability to catch prey in flight. If the bird is a leaf-gleaning insectivore or a hawking insectivore (flies from a branch to catch prey), it must demonstrate the ability to catch insects.

Conditioning and Acclimation:

  • The bird must be completely self-feeding for a period of at least two weeks and able to recognize, find (and 'capture', in the case of faunivores) all the components of its natural diet. Food recognition is especially important when the bird has been raised in captivity. The bird should be eating the diet that is being eaten by conspecifics in the season of release so that it has the digestive enzymes necessary to cope with the foods that are seasonally available. For example, a robin that is released in early spring must be able to digest the insects that are abundant in spring. A chickadee that is being released in fall must be able to digest insects and the seeds and nuts that are abundant in fall and winter.
  • The bird must be acclimated to the outdoors for a period of at least two weeks prior to release so that it is prepared to cope with outdoor temperatures, rain, wind, etc. It must demonstrate the ability to shelter from cold, rain, etc. It must be able to thermoregulate. A bird that has suffered a head trauma may show an inability to thermoregulate when it is being acclimated, and is not a good candidate for release. The bird must be exposed to day and night skies and to the sights and sounds it will encounter in the wild.
  • The bird should demonstrate independence of humans: it should not gape, plead, land upon or seek attention from the caregiver. A bird that is still pleading should not be released. Birds in rehabilitation may not mature at the same rate as wild conspecifics, thus do not release simply because wild counterparts are independent at that age. Wild birds have the support and protection of parents until they are ready for independence, and human-raised birds may require some extra time. A bird that is still gaping, pleading or approaching for food past a reasonable time may have an underlying problem that needs to be addressed (e.g. pathogen, digestive abnormality). Some species stay with and rely upon their parents for a considerable period of time before they are completely independent (e.g. albatross, raven). It is crucial that the rehabilitator be familiar with the bird's natural history and development to determine its progress and readiness for release.
  • The bird must be properly wary of domestic animals and wild predators.
  • The bird should be socialized to its species, exposed to the songs and calls of adults and respond to distress calls.
  • If it is at all possible, release the young bird with an adult of the same species, or release youngsters of the same species in groups. Consult with other rehabilitators in your area to find conspecifics for the bird if necessary.
  • Social species (e.g. crows, pigeons, swallows, swifts, martins) should be released to conspecific flocks. Many birds (crows, bluebirds, and robins are commonly encountered examples) maintain family units for months or longer. If at all possible, birds should be released to the home territory of their own family.
  • Solitary species (e.g. hummingbirds, woodpeckers) are better released in suitable habitat without an overabundance of conspecifics, although conspecifics should be present.
  • Do not release a migratory bird when its conspecifics have migrated from the area or before they return.
 Mammals

Health:

  • The animal should be free of disease and/or parasites.
  • Its weight should be the same as the average for wild conspecifics of similar age.
  • If the animal had an injury, it should be completely healed. If it has a permanent handicap (e.g. poor sight in one eye, poor use of a limb), it must demonstrate that it can compensate. Its teeth must be in good condition and aligned properly, so that it can eat its natural foods. Consider the animal's natural movements and behaviours (e.g. some animals, like the opossum, cannot live normally without a tail).
  • The animal should be able to move, climb, run, burrow (and in the case of bats, fly; in the case of flying squirrels, soar) as is normal to its species.
  • Fur must be clean and normal in appearance. Do not release an animal that has bald patches or thin, poor fur. The fur may not grow in again, leaving the animal vulnerable to cold and insects.
  • The animal must sustain normal levels of activity without tiring, panting, trembling, etc. If the animal is a faunivore, it must demonstrate the ability to find and catch prey.
  • Rabies vector species should be vaccinated, and depending on species, the animal may also require other shots.


Conditioning and Acclimation:

  • Most mammals must be completely self-feeding for a period of at least two weeks and able to recognize, find (and 'capture', in the case of faunivores) all the components of its natural diet. Different species may require more or less time. Food recognition is especially important when the animal has been raised in captivity. It should be eating the diet that is being eaten by conspecifics in the season of release so that it has the digestive enzymes necessary to cope with the foods that are seasonally available.
  • The animal must be acclimated to the outdoors for a period of at least two weeks prior to release so that it is prepared to cope with outdoor temperatures, rain, wind, etc. It must demonstrate the ability to shelter from cold, rain, etc. It must be exposed to day and night skies and to the sights sounds, and smells it will encounter in the wild.
  • The animal should demonstrate independence of humans: it should not come for food, climb upon or seek attention from the caregiver. Young mammals in rehabilitation may not mature at the same rate as wild conspecifics, thus do not release them simply because wild counterparts are independent at that age. Many wild mammals have the support and protection of parents until they are ready for independence, and human-raised animals may require some extra time. It is crucial to be familiar with the animal's natural history and development to determine its progress and readiness for release.
  • The animal must be properly wary of domestic animals and should be socialized to its species. It has a better chance of survival if it responds to distress calls.
  • When possible, release youngsters in small groups. Some species fare better if released with an adult of the same species.
 Reptiles and Amphibians

Health:

  • The animal should be free of disease and/or parasites.
  • Its weight should be the same as the average for wild conspecifics of similar age.
  • If the animal had an injury, it should be completely healed. If it has a permanent handicap, it must demonstrate that it can compensate.
  • The animal should be able to move, climb, run, burrow or swim as is normal to its species.
  • Skin or carapace must be healthy and normal in appearance.
  • The animal must sustain normal levels of activity without weakening or tiring. If the animal is a faunivore, it must demonstrate the ability to find and catch prey.

Conditioning and Acclimation:

  • The animal must be able to recognize, find (and 'capture', in the case of faunivores) all the components of its natural diet.
  • The animal must be acclimated to the outdoors and an environment as natural to it as possible prior to release.
 Soft Release


Soft release describes a gradual return to the wild whereby an animal receives support, shelter and food until it is entirely able to fend for itself. Often, a soft release takes place from a release cage or aviary on-site. The animal has spent time in the outdoor enclosure and is familiar with the sights, sounds, smells, etc. of the area and is aware of the activity of other wildlife in the area. It can return to the enclosure for food or shelter when necessary, and food and water is left outside the enclosure as well. Soft release also describes transport of the enclosure to a specific habitat and subsequent release off-site. Again, this allows the animal opportunity to become familiar with its new home. Off-site soft release in often used when introducing larger mammals to new territory, and research shows that soft-released animals have a better survival rate:

"Further trial and error studies indicated that wolves released into a new area fared much better and remained near the release site longer when allowed to remain in an acclimation pen for an extended amount of time, thus becoming acclimated to the new surroundings. This type of a release is considered to be a "soft" release. It has repeatedly been incorporated into the repatriation of the red wolf back into the wild, and has subsequently been used in the return of wolves in Yellowstone National Park and the Mexican gray wolf in the southwestern United States."
http://wildlifesciencecenter.org/ Conservation.html

 Hard Release


Hard release describes a release directly to the wild without further support or feeding. Hard release is often employed when an animal that came into care as an independent adult is returned to its home territory. Hard release is sometimes necessary when a captive-raised young animal requires a particular habitat or, in the case of birds, introduction to a flock of conspecifics. It is especially important that the animal is completely able to function independently if it is to be hard-released.

When you are satisfied that the animal (or group of animals) is ready for release, plan the event beforehand.

  • Evaluate the release site. Is it a suitable habitat for this species? Are the animal's natural foods, preferred areas for shelter or nesting, and water for bathing and drinking available, accessible and plentiful? Is the area overpopulated with this species or other animals that prey on or compete with this species? Will resident animals chase away this animal? Is there a threat from domestic animals or feral cats and dogs? If you are not familiar with the area, contact a local government agency and/or a wildlife biologist or naturalists/birders group for their suggestions.
  • Check the long-range weather forecast: conditions should be favourable for at least five days, with no extreme temperatures or conditions.
  • Check hunting dates and regulations for the area.
  • Consider time of day. For most animals, an early morning release in preferable. This gives the animal an entire day in which to explore its surroundings, locate food, water and shelter and reunite with conspecifics. If it is a marine animal, consider high tide and low tide. If it is a nocturnal animal, an early evening release, when the animal is more alert, may be preferable.

Unless the animal is a marine or fresh water species, release away from water and towards trees or shelter. To make the experience as stress-free as possible, back away and allow the animal to leave the release cage or animal carrier on its own.

 Conservation, Biodiversity and Law


In many areas, government agencies apply conditions to the release of wildlife in order to protect populations and preserve biodiversity. An animal that is translocated may bring with it parasites and diseases that have negative impact upon local populations, or the animal may impact upon a sensitive ecosystem.

Laws and regulations may require you to release an animal only to the place it was found, or within a particular area. Contact your local government agency (e.g. Department of Natural Resources) to learn about laws, conditions, release criteria, or areas that can sustain the rehabilitated wildlife. Confer with wildlife biologists, birders or naturalists prior to releasing the animal, to ensure that the habitat, foods, shelter, etc. are suitable. There are particular concerns about releasing reptiles (and possibly amphibians) that have been in captivity at all, because of population-decimating diseases that they may then carry; consult a knowledgeable wildlife biologist before you release such an animal.

Regardless of whether or not laws, regulations and criteria apply in your area, it is best to release the animal back to its home territory when possible. It will be familiar with the area, find its territory, and reunite with its mate or group.

However, if the animal came into care as a result of unsafe conditions in its home (e.g. poisoning, forest fire, loss of habitat due to flood, forestry or development, an ongoing disease outbreak, etc.), it may be necessary to find a more suitable and safer environment. Again, consult with local government agencies or local wildlife biologists.

If releasing the animal into an unknown area, bear in mind that it may be run off if the area is the territory of another animal, or if there are not enough resources to support it. Respect and consider those that already occupy the niche. Do not take the chance of releasing an animal into an area where it cannot survive, where it has a negative impact on native populations, or where it may experience conflict with humans. Do not, for example, release a carnivore into a sensitive nesting area for migratory birds, or near a chicken farm. Do not release bears into recreational areas. Do not release waterfowl into man-made lakes or urban areas, etc.

 Information and Training

General information on the release of rehabilitated wildlife is not readily found. The principles and criteria of release are taught by:

IWRC Skills 1AB Seminar

Wildlife Center of Virginia

IWRC's Journal of Wildlife Rehabilitation publishes articles on the rehabilitation and release of many species (e.g. Canada Goose (Branta canadensis) Ecology And Rehabilitation; Journal of Wildlife Rehabilitation Volume 23, Number 1). Tables of contents and abstracts (and in some cases, complete articles) can be found at:
http://iwrc-online.org/journal/journal.html

NWRA's Quarterly Journal publishes a variety of articles, including information on rehabilitation and release.
http://www.nwrawildlife.org

 Research and Data

Rehabilitators can offer invaluable data to the scientific community. Research indicates that rehabilitated wildlife, if properly conditioned and released, can survive, achieve normal life spans, breed and raise young.

Much of this data comes from animals that have been tagged, collared or banded.

Wildlife Radio Telemetry information on can be found at:

British Columbia Ministry of Environment, Lands and Parks
Standards Manual for Wildlife Radio Telemetry

Forum on Wildlife Telemetry
USGS Northern Prairie Wildlife Research Center

LGL Radio-Telemetry
This website explains why radio-telemetry is used, and its applications.

Bird Banding
In many countries, a permit or license (and training) is required to band birds. For information on bird banding, go to:

Bird Banding Laboratory
Bird banding is a universal and indispensable technique for studying the movement, survival and behavior of birds. The North American Bird Banding Program is jointly administered by the United States Department of the Interior and the Canadian Wildlife Service.

Environment Canada
Canadian Bird Banding office

The Global Bird Ringing and Banding Website
Links to information for Africa, Asia (including the Middle East), Australia and New Zealand, South and Central America, North America.

The North American Banding Council (NABC)

USGS Bird Banding Manual