TECHNIQUE

Release of Hand-reared American Black 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  
Description

Many hand-reared black bear cubs are given sufficient nutrition to grow large enough to survive hibernation. These cubs can be encouraged to hibernate and then released into a hibernation den. For immature cubs, either they are sufficiently grown for a similar release in late-winter (February) or they have to be kept until late spring when wild food resources are plentiful.

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.
    (V.w5, V.w6, P28.2000.w1, J15.20.w3)
  • 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 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. (D252.w29, B468.10.w10b)
  • 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, 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 adult 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 from 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)

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, J417.20.w1)
  • 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
Winter (hibernation) release
Winter release into a den usually takes place in December, but can be carried out as late as February. (B338.23.w23)

Preparation for release:

  • Gradually reduce the food starting in November, and minimise activities around the bears; as the weather gets colder and the bears get sluggish, reduce the food further, then stop feeding entirely. Continue to have water available. (D252.w19)
  • Suggested six week preparation
    • At least six weeks before the intended release date, start reducing food intake; reduce over a period of three weeks. Food intake should be reduced to zero by at least three weeks before the intended release date. (B338.23.w23, J417.20.w1)
    • Provide a suitable den box, with straw for bedding, in the indoor area. (J417.20.w1)
    • Keep the area around the enclosure quiet and undisturbed. (J417.20.w1)
    • From 20 days before release (the cub should by now be spending most of its time in the indoor area), shut it into the indoor part of the enclosure with a water bucket secured to the door and no food. Minimise disturbance: no noise, no light even when checking the water level. Top up the water every second day if required using a hose, quietly inserted through the door. Stop cleaning the cage (should no longer be required since the bear is not eating. Make sure all is kept quiet around the enclosure. (B338.23.w23, J417.20.w1)
    • The bear needs to have been dormant for at least three weeks before it is transported to the release den. (B338.23.w23)
  • Release dens
    • a) a man-made den, built earlier in the year using straw bales. This will have been constructed in an area of suitable habitat (water, forested, natural foods available) away from people and with no or minimal hunting. (B338.23.w23)
      • A U-shaped den can be made from nine straw bales, covered with plastic tarpaulins, boughs and snow; ensure proper ventilation. Line the floor with straw from the den at the rehabilitation centre (familiar in smell). Place the cub with its head and nose near the entrance. Mostly-cover the doorway with straw bales, pine boughs and snow. (J417.20.w1)
      • Watch the cub until it is recovering from the immobilization and becoming more alert, then close the den and leave. (J417.20.w1)
      • Note: Each cub should be placed into a separate den. (J417.20.w1)
    • or b) a den containing a hibernating female with cubs of a similar size, if available (requires knowledgeable local biologist and arrangement with the relevant state or federal wildlife department). (B338.23.w23)
    • or c)  a natural den previously identified at the intended release site and checked to make sure it is not occupied by a wild bear. (D252.w20)

Transportation and release:

  • Method 1)
    • Chemically immobilize the cub with an appropriate anaesthetic agent or combination, delivered by a pole syringe (or a dart gun if necessary). (J417.20.w1):
    • 4.4 mg/kg ketamine plus 2.2 mg/kg xylazine. This combination is inexpensive, rapid acting and has a high safety margin. (D270.IX.w9)
    • 4 mg/kg Tiletamine-Zolazepam. (J417.20.w1) 4.4 - 6.6 mg/kg; this produces a longer anaesthetic time and slower recovery than with ketamine plus zylazine. (D270.IX.w9)
    • Physically examine, take and check a blood sample, place the cub into an appropriate wooden or aluminium transport cart for transport to the release site. (J417.20.w1)
    • Place the cub with its head and nose near the entrance. Mostly-cover the doorway with straw bales, pine boughs and snow. (J417.20.w1)
    • Watch the cub until it is recovering from the immobilization and becoming more alert, then close the den and leave. (J417.20.w1)
  • Method 2)
    • If possible, get cubs to move from the den to a transport crate without sedation; sedate if necessary. (D252.w20)
    • Transport to the release site in crates. 
    • At the release site, sedate the cub(s), examine and measure, fit ear tags and (sometimes) radio collars, then place in the den.
    • Up to three cubs may be placed in one den.
    • Cover the den entrance with pine boughs and snow.
    • Wait until the bears will have recovered from sedation.

    (D252.w20, D252.w22)

Late spring release
  • Cubs may be released in spring (e.g. May) if they have not put on sufficient weight by winter to be hibernated. (D252.w24)
    • Bears are sedated, examined and radio-collars placed before being put into transport crates.
    • At the release site, crates are opened and the bears allowed to emerge.

    (D252.w23, D252.w24)

  • A female was released in June of the year after she was found, close to where she had been found. (P62.9.w1)
    • The bear bolted to a tree and climbed 3.5 - 4 m up it, climbed down a few minutes later and slowly walked away. (P62.9.w1)
  • A male released in mid-July into a pen constructed at the release site (intended as a soft-release) rapidly found a weak spot in the fence and escaped within minutes of release. (P62.9.w1)
    • For several weeks after release the bear remained in the general area of release, in an area about 3.2 - 4.8 km2, always avoiding people. (P62.9.w1)
    • The bear, showing normal wild bear behaviour, was shot by a hunter (who had failed to see the radio-collar) in early September. (P62.9.w1)
  • Note: Behaviour may change considerably from before to after the first hibernation. Two cubs which had been hand-reared after being found with their road-killed mother in April were kept in a 60 x 30 m enclosure June to mid-August, then a larger enclosure from mid-August onwards. After hibernating successfully within the enclosure, they showed wariness and avoidance of their keeper, staying in, or climbing into, a tree while a human was providing food and water. Following release at a site remote from humans, they appeared to behave normally, foraging successfully, appeared to have established home ranges and did not become nuisance bears. (B432.w7, N20.12.w1)

Post-release Monitoring

  • Released bears should be monitored, e.g. using radio transmitters. (B432.w7)
  • Post-release monitoring of 11 hand-reared cubs released by the Appalachian Bear Center at 11-18 months old, most received for rehabilitation in the fall and released in January or March, showed a high survival rate at least in the short term. No definite mortalities of released bears were recorded. Several were lost to follow-up due to dropping their collars or loss of signal, but at least 10 bears survived to more than 45 days after release and at least seven to 122 days post release. One cub was later (after the end of the study) reported killed by a hunter. There were no confirmed nuisance encounter reports of released bears, although there was a single report of a small radiocollared bear approaching a campsite. (J345.13.w5)
  • Post-release monitoring of cubs released into dens (natural or artificial) in Idaho in January found that some cubs abandoned the release den and constructed their own den. (J345.13.w5)
  • Post-release monitoring of two orphaned female cubs in Idaho, radiocollared for five years as adults, found that each produced multiple litters. (J345.13.w5)
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)

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.w13, D270.X.w10)
    • The degree of handling varies during the cub's physical and behavioural development. (B432.w13)
    • 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)

Release site & timing

  • 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)
    • A study carried out by the Appalachian Bear Center found high survival for bears released January to March, when foods are not abundant. These bears were thought to have sufficient fat stores to survive until foods became readily available in early summer. (J345.13.w5)
  • Timing the release to minimise the chance that the bears will encounter people in the immediate post-release period. (D270.X.w10)
    • Minimum contact with humans in the first 7-10 (D252.w29) first 14 days (D270.VIII.w8) after release. 
    • Bear cubs released following hand-rearing should be released into remote areas if they have become tame, to reduce the risk that they will become nuisance bears. (P62.4.w2)
  • Release 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
  • Evidence suggests that while cubs do learn from their mothers, they possess innately all the skills required for survival and do not need to be taught these. (D270.VIII.w8)
  • There appears to be a change in behaviour from before to after the first hibernation; yearlings are more independent and wary after their first hibernation. (B432.w7)
Complications/ Limitations / Risk
  • Avoid releasing during a bear hunting season or during hunting seasons for other large mammals. (D270.VIII.w8)
    • Consider whether hunting or poaching exist in the area when choosing a release site. (D270.VIII.w8)
  • Bears may be shot following release. This usually occurs in the first year of release. (D270.VIII.w8)
    • Released bears might be more vulnerable to hunters because they are travelling widely, or it may be associated with their having been rehabilitated. (D270.VIII.w8)
  • Bears may become "nuisance" bears after release, but this is not a common problem. (D252.w25)
    • This may be related to the individual personality of the bears (D252.w25, D270.IV.w4)
  • A common factor with failed releases appears to be the exposure of cubs to many people during rearing. (D270.VII.w7)
  • 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;
      • However, yearlings seem to be more independent and wary after their first hibernation.(B432.w7)
    • 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.w7, B468.10.w10b, B468.10.w10c, B338.23.w23, D252.w20, D252.w22, D252.w23, D252.w24, D252.w25, D252.w29 [D252 full text included], D270.I.w1, D270.IV.w4, D270.VIII.w8, D270.IX.w9, J417.20.w1

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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