TECHNIQUE

Release of Hand-reared Brown Bears  (Disease Investigation & Management - Treatment and Care)

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Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords Release of hand-reared Ursus arctos - Brown bears
Description Once hand-reared cubs have reached an age at which they can survive in the wild, they may be released.
Release Assessment/Criteria
  • Released mammals:

    • Must have recovered from any injury or illness.
    • Must be able to recognise, catch, manipulate, consume and digest their natural diet.
    • Must be capable of normal locomotion (movement) and have sufficient fitness for sustained activity.
    • Must have adequate sensory ability (sight, smell, hearing).
    • Must be of an appropriate weight for the age, sex, and time of year. 
    • Must have a satisfactory hair coat.
    • Must show appropriate wariness of humans and domestic animals.
    (B468.10.w10c, P19.1.w10, P24.233.w11, J35.147.w1, D27)
  • Appropriate health checks should be carried out prior to release. A careful assessment (risk analysis) must be made as to the risks of released animals introducing novel pathogens (disease agents) into the wild population/environment.
    • These pathogens may have been acquired from domestic animals, other wildlife casualties or humans whilst the animal was in captivity.
    • The health checks should be designed to minimise the risk that pathogens posing a threat to wild populations of this or other species will be introduced into the environment when the animal is released.
    (P28.2000.w1, J15.20.w3, V.w5, V.w6)
  • Bears should be examined physically prior to release to check that they are in good general body and coat condition, without any external parasites or injuries which could be problems for the bear post-release. (D270.IX.w9)
    • Good coat condition is particularly important for bears being released in late fall (autumn) or during the winter.
    • The bear's fat reserves should be adequate for the time of year, and body condition should be at least a "3" on the scale described for polar bears. See: Physical Examination of Mammals (Techniques Overview) - Weight & Body Condition
    • A faecal sample should be taken and checked for internal parasites before the release date.
  • Bears should be assessed behaviourally prior to release, although it is not always possible to assess from behaviour in captivity whether the bear will adapt to the wild or will become a nuisance bear after release. (D270.IX.w9)
Selecting a Release Site

Choice of a suitable release site is extremely important.

  • The presence of adequate, high-quality habitat is one of the key features in success of release. (B468.10.w10b, D252.w29)
  • In general, bear cubs become wary of humans within about 10-14 days after release; release should occur in places, and at times of the year, where they are unlikely to encounter humans during this initial period. (D270.VIII.w8)
  • Is is important that the appropriate permissions are obtained prior to release. (D270.VIII.w8)
  • The release site should be within the historic range for the species, and should provide good habitat, large enough to support a bear population. (D270.VIII.w8)
  • Minimum requirements include: (D270.VIII.w8)
    • the presence of adequate food and water resources during the bears' active season;
    • den sites;
    • relatively low human densities;
    • sufficiently large area to support a bear population.
  • Other considerations are:
    • distance to the nearest human settlement;
    • whether there are hunting seasons for bears/other animals, and if so, the timing of these;
    • poaching risks;
    • whether and what livestock are present;
    • the predominant land use in the area (e.g. agriculture, forestry, wilderness area);
    • attitudes of the local population towards bears;
    • potential conflicts associated with livestock or apiaries (particularly when natural food resources are scarce);
    • status of the resident bear population;
    • presence of potential predators and competitors;
      • release into stable, protected populations with large numbers of adults may increase the risk of released cubs being predated by adult males.
      • bears shot by hunters after release have been in good body condition, suggesting no detrimental effect on the released bears form direct competition for food resources.
    • topography of the site;
      • released bears are likely to disperse from the release site; topography may affect the direction of such dispersal (e.g. travelling down drainages) and therefore the likelihood of encountering people
    • other factors which might limit the bear population.

    (D270.VIII.w8)

  • For brown bears, release into large wild area away from people is essential. (V.w101)

Identification and Post-release Monitoring
  • Before release, cubs should be marked with permanent and/or semi-permanent marks to allow post-release monitoring. (D270.IX.w9)
  • Ear tags, tattoos and transponders are inexpensive but allow only sporadic data collection, generally when bears are captured as nuisance animals, shot by hunters or under depredation kill permits and reported, or killed in accidents and found. (D270.IX.w9)
  • Radio collars (or radio implants) are much more expensive but provide better information. D270.IX.w9)
    • VHF collars are relatively inexpensive but cost more in human effort for monitoring, and may not provide useful signals in some terrains.
    • GPS collars are more expensive to purchase but may be less costly to monitor.

    (D270.IX.w9)

  • Further general information on identification methods is provided in: Mammal Identification (Mammal Husbandry and Management)
  • Further general information on post-release monitoring is provided in: Post-Release Monitoring of Oiled Wildlife (Techniques Overview)
Timing and Type of Release
Summer Release
  • This may be most appropriate if high-quality foods are available in the release area. (D270.IX.w9)
  • This can allow the minimum length of time for cubs to be kept before release. (D270.IX.w9)
  • Hand-reared cubs raised in an appropriate manner can be released successfully at 6 - 7 months old. (B432.w6)
    • When cubs are first let out of the house-den at three months of age, the caretaker should open the door and move away about 30 m remaining not visible to the cubs, then stay still so as not to attract their attention; this encourages the cubs to orientate to one another, not imprint on the human as mother. This is most important on the first occasions, but precautions should be taken certainly until the cubs are five months old. (B432.w6)
    • From 14 weeks, give access to the natural environment, leaving the door of the house-den open all the time. Cubs will gradually acquire knowledge of the local area, moving 200 - 400 m from the house-den by 4 - 5 months, increasing to 5 - 7 km by 5 - 7 months of age; from six months they can use the sun to orientate and take a short cut back to the house-den. (B432.w6)
    • Once food is no longer provided, cubs leave the area and become independent. (B432.w6)
    • At 10 - 11 months, released cubs construct an appropriate den and can overwinter successfully. (B432.w6)
  • Leaving the exit from the enclosure open for most of the time for cubs older than three months allows the cubs to explore the surrounding area, forage for food and find safety from predators. (W159.Apr06.w1)
    • Food can be provided when the cubs are absent, so it is not associated with humans. (W159.Apr06.w1)
    • Cubs of seven to eight months of age, "if they are fat enough and able to survive on their own" can be released "into protected areas where brown bears are scarce or no longer present". (W159.Apr06.w1)
    • Or cubs may be kept over winter and released the following spring or summer at 16 - 17 months old. (W159.Apr06.w1)
    • Cubs are fitted with ear tags and radio-transmitters before release to allow post-release monitoring. (W159.Apr06.w1)
    • Post-release data indicates that the released bears behave like normal wild bears. (W159.Apr06.w1)
  • Cubs are fitted with ear tags and radio-transmitters before release to allow post-release monitoring. (W159.Apr06.w1)
  • Post-release data indicates that the released bears behave like normal wild bears. (W159.Apr06.w1)
Winter Release
  • Cubs can be placed into a natural or artificial den, to continue hibernating through the winter. (D270.IX.w9)
  • These are unlikely to come into contact with humans during the winter or immediately after emergence from the den after hibernation in early spring, during a time when human use of the bear habitat is low. (D270.IX.w9)
  • Occasionally cubs will move from the den into which they have been released, and build another den. (D270.IX.w9)
    • This is less likely if there is more than 30 cm/12 inches of snow on the ground. (D270.IX.w9)
Early Spring Release
  • Hand-reared cubs which have received prolonged human contact (e.g. contact with multiple persons for more than seven days and continuing in cubs older than three months of age), require additional measures to ensure that human avoidance behaviour is developed. This involves special precautions against human contact. If this does not appear to be successful during the cub's first year, then it is kept and overwintered in a den at or near the rearing site (either constructing their own den in the forest, or provided with a hut and plenty of hay) then allowed to start independent life on awakening. (B432.w6)
    • The threshold for defensive behaviour appears to be reduced after hibernation, and it has been found that the bears do not return to human habitation when they waken. (B432.w6)
  • Spring release may be preferred as being similar to the time at which bear families would normally break up. (D270.IX.w9)
  • Hand-reared bears released as yearlings rather than as cubs are larger and may be less likely to be predated. (D270.IX.w9)
Appropriate Use (?) Options available for orphaned wild-born bear cubs include:
  • Leaving cubs in the wild. 
  • Placing cubs into permanent captive facilities. 
  • Hand-rearing for release.
  • Euthanasia.

(D252.w29, D270.I.w1)

Note: Hand-reared brown bear cubs, once released, quickly adapt to their natural habitat. (P71.1995.w16) 

Key elements for successful reintroduction of hand-reared cubs to the wild include:

During rearing:
  • The opportunity to socialise with other bear cubs during early development; (D252.w29)
  • Minimising the amount of contact with humans and the number of caretakers during rearing, particularly after weaning. (B432.w6, D270.X.w10)
    • Cubs with minimum human contact are more likely to be successfully released. (B432.w6)
    • Frequent contact between cub and caretaker is required in young cubs being bottle-fed, and bottle-fed cubs may continue to show dependence on their caretaker for a period after weaning. However, over time they become more independent and, particularly if other cubs are present to interact with, show less interest in their caretakers. Independence increases as cubs reach the age of normal family break-up in the wild. (D270.VII.w7)
    • Fear reactions to new sounds, odours and moving objects can be seen at three months, and are strongly developed by five months, It is important to restrict human contact to interaction with just a single person from about two months onwards so that the cub reacts to odours of other humans with an appropriate fear response. (B432.w6)

Release site & timing

  • Releasing hand-reared brown bears is more likely to result in the creation of problem bears than is the case with other bear species. Hand-reared bears should be released only if this can be carried out in a vast area without people. (V.w101)
  • Release into adequate, high-quality habitat. (D252.w29, D270.X.w10)
  • Releasing with sufficient fat reserves to cover the bears over the initial adjustment to their new surroundings. (D270.X.w10)
  • Releasing when natural foods are abundantly available. (D270.X.w10)
    • Survival of cubs post-release may be dependent on food availability. (P62.4.w2)
  • Timing and choice of release site to minimise the chance that the bears will encounter people in the immediate post-release period. (B432.w6, D270.X.w10)
    • Minimum contact with humans in the first 14 days after release. (D270.VIII.w8)
  • Releasing bears at an age similar to the normal time of family break up. (D270.X.w10)
  • The individual personalities of the bears. (D252.w29, D270.IV.w4)
    • Bear cubs are individuals and have individual personalities; suitability for release may have to be assessed at the time for release. (D270.I.w1)
Notes
  • Bear cubs are individuals and have individual personalities; suitability for release may have to be assessed at the time for release. (D270.I.w1)
  • For North American brown bears, which generally remain with their mothers until about 2.5 years of age, it has been suggested that survival might be increased by not releasing hand-reared cubs until they are 2.0 - 2.5 years of age, rather than earlier as has been carried out successfully in Europe. (D270.IX.w9)
  • Brown bear cubs may be able to survive by themselves in the wild from as young as five to six months old, and and orphans released at six to seven months of age have survived, adapting successfully to life in the wild. (B432.w6)

Individual examples

  • A grizzly bear (Ursus arctos - Brown bear) cub hand-reared for about 15 weeks then released in November into an artificial den survived the winter and into the following spring. (P62.4.w2, P72.4.w2)
  • In one study in Croatia, two cubs hand-reared from 33 days, two from 40 days and one from 89 days were released at about 186 days. All had been held "in house conditions" to about 107 days old, then in a 30 m x 30 m enclosure in natural conditions. They had been weaned while in the outdoor pen, natural food provided, and "contact with people was attempted to be kept at a minimum during that period." Of the five cubs:
    • One hand-reared from 89 days survived for 69 days after release until hit by a vehicle 42 km from the release site. (P85.1.w9)
    • Two cubs hand-reared from about 33 days and one from 40 days, had to be recaptured after repeated interactions with humans. Their weights indicated that they were finding sufficient food, but it was thought that they socially preferred to be near humans. (P85.1.w9)
    • One cub hand-reared from 40 days was seen with the other cubs, following backpackers, in the first days after release, but was not seen thereafter. It did not have a radiocollar and it is not known whether it survived. It did not turn up in the village where the other three cubs appeared. (P85.1.w9)
  • A cub of 186 days old, which had wandered into a village in Croatia in mid-July and been kept on a chain and fed, and was skinny and aggressive, was released just two days after it had been found. It survived at least 451 days (time for which it was radio-tracked), denning properly and having no contact with people. It was thought (circumstantial evidence) that its mother had probably been killed by poachers about a month before (mid-June) it was found, and that its short time in captivity had provided negative conditioning towards humans. (P85.1.w9)
Complications/ Limitations / Risk
  • Some authorities suggest that hand-reared bears or those raised in captivity can not be released, because they have not been mother-trained to find food and dens and to avoid other bears, and are likely either to starve or to become problem bears eating human-related food sources; (P71.1995.w10, B432.w3)
  • Hand-reared cubs may not avoid humans, may become "nuisance" or "problem bears after release, and may then have to be taken into permanent care. (P85.1.w9)
  • Releasing hand-reared brown bears is more likely to result in the creation of problem bears than is the case with other bear species. Hand-reared bears should be released only if this can be carried out in a vast area without people. (V.w101)
  • Cubs which have a history of considerable human contact are less likely to be releasable. (B432.w.w5)
  • A common factor with failed releases appears to be the exposure of cubs to many people during rearing. (D270.VII.w7)
  • Late summer release involves release of cubs when they are not much older than the minimum age at which wild cubs are known to be able to survive when orphaned; cubs released at this age may have a lower survival rate than those released during the winter or as yearlings in spring. (D270.IX.w9)
  • Disavantages of winter release are:
    • Logistics; (D270.IX.w9)
    • The need to tranquillise cubs to move them to the release den, and again on arrival to place them in the den. (D270.IX.w9)
  • Spring release of yearlings involves:
    • increased costs of keeping cubs for longer;
    • contact with humans after emerging from hibernation;
    • possible lack of enclosure space at the time when new orphaned cubs may be arriving for rehabilitation.

    (D270.IX.w9)

Equipment / Chemicals required and Suppliers
  • Sedatives and associated equipment (pole syringe, blowpipe, darts etc.)

  • Transport crates.

  • Straw bales, tarpaulin etc. for constructing artificial dens.

  • Vehicles (e.g. trucks, helicopters) to reach the release site.

Expertise level / Ease of Use
  • Expertise is required to chose appropriate release sites, to determine the timing of release in accordance with local conditions (e.g. temperature and snow cover for winter release, food availability for spring or summer release), and to determine when, and whether, an individual cub is ready for release.
Cost/ Availability
  • Costs include those of pre-release examination, sedation, transportation to the release site, construction of a den (for winter releases into an artificial den) and post-release monitoring.
Legal and Ethical Considerations
  • The potential risks to the individual being released and to the wild population into which it is being released (also to domestic animals) must be considered before release is undertaken.
  • The potential risk to humans and pets from habituated/tame individuals must be considered.
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee --
References B432.w6, B468.10.w10b, B468.10.w10c, D252.w29, D270.I.w1, D270.VII.w7, D270.VIII.w8, D270.IX.w9, P71.1995.w16, P85.1.w9, W159.Apr06.w1, V.w101
General mammal information: J15.20.w3, J35.147.w1, D27, P19.1.w10, P24.233.w11, P28.2000.w1, V.w5, V.w6

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