MORBIDITY AND MORTALITY OF FREE-RANGING AMERICAN BLACK BEARS (URSUS AMERICANUS) UNDERGOING REHABILITATION IN EASTERN TENNESSEE, USA, 1996-2021 ...
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DOI: 10.7589/JWD-D-21-00191 Journal of Wildlife Diseases, 58(3), 2022, pp. 000–000
Ó Wildlife Disease Association 2022
MORBIDITY AND MORTALITY OF FREE-RANGING AMERICAN BLACK
BEARS (URSUS AMERICANUS) UNDERGOING REHABILITATION IN
EASTERN TENNESSEE, USA, 1996–2021
Julie D. Sheldon,1,5 Camille Cordero-Aponte,2 Victoria Reibel,3 Coy D. Blair,3 Xiaojuan Zhu,4
Richard Gerhold,3 Andrew Cushing,1 Edward C. Ramsay,1 Dana Dodd,3 and Michelle Dennis2
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1
Department of Small Animal Clinical Sciences, University of Tennessee College of Veterinary Medicine, 2407 River
Drive, Knoxville, Tennessee 37996, USA
2
Department of Biomedical and Diagnostic Sciences, University of Tennessee College of Veterinary Medicine, 2407
River Drive, Knoxville, Tennessee 37996, USA
3
Appalachian Bear Rescue, 121 Painted Trillium Way, Townsend, Tennessee 37882, USA
4
Office of Information and Technology, University of Tennessee, 1015 Volunteer Blvd., Knoxville, Tennessee 37996,
USA
5
Corresponding author (email:jsheldo3@tennessee.edu)
ABSTRACT: Free-ranging American black bears (Ursus americanus) often share habitat with humans
and domestic animals, predisposing them to anthropogenic conflicts. Rehabilitation under professional
care is a management option for orphaned, injured, and/or ill bears. Across several southeastern states,
rescued bears are assessed and treated at the University of Tennessee and rehabilitated at Appalachian
Bear Rescue (ABR). Records from 1996–2021 showed 337 bears (170 males, 166 females, 1 unknown)
from nine states were admitted to ABR. Three bears were admitted twice, resulting in 340 admissions
(42 neonates ,3 mo old, 206 cubs 3–12 mo, 87 yearlings 1–2 yr, and 5 adults .2 yr). Bears presented as
orphans (58%), malnourished (24%), injured or ill (12%), or confiscated/other (6%). Individuals were
returned to the wild (85%); died or were euthanized (12%); or were placed into professional care (3%).
Of released bears, 195 had complete medical records available for evaluation; 31% were healthy upon
intake while the remaining were treated successfully for malnutrition and internal parasites (49%),
orthopedic (9%) and soft tissue injuries (5%), or other diseases (5%). Causes of death determined
during necropsies performed (n¼30) were classified as trauma (50%), developmental (13%),
undetermined (13%), malnutrition (13%), infectious or inflammatory (7%), and toxicosis (3%). Despite
the lack of maternal care and high prevalence of malnutrition and trauma, most bears recovered to
release with appropriate husbandry and medical care. This study provides a foundation for research to
further improve care of rehabilitating black bears.
Key words: American black bear, malnutrition, rehabilitation, release, trauma, Ursus americanus.
INTRODUCTION 0.78 bears per square km, but is less in
surrounding forests (0.12 bears per square
American black bears (Ursus americanus)
km; Clark 2019; Blair et al. 2020).
are an important native species once wide-
Balancing bear conservation with urban
spread across North America but currently in
development ultimately leads to bears sharing
fragmented populations across the country
habitat with humans and domestic animals,
(Scheick and McCown 2014). Due to over-
hunting for meat, fat, and hides, black bear predisposing them to anthropogenic conflicts
populations were eliminated from most coun- (Blair et al. 2020). Free-ranging young bears
ties in Tennessee, US, by the 1970s (Clark et can be orphaned due to abandonment,
al. 2021). Agencies then reduced poaching vehicular trauma, conflict bear management,
and restricted hunting seasons and locations, poaching, falling from trees, or natural disas-
which has allowed bear populations to re- ters (e.g., fire, drought, flooding), which can
bound over the last several decades. Black all be intensified by habitat modification
bear populations in southern Appalachia have (Beecham et al. 2016). Rehabilitation under
continued to grow over the last 30 yr; professional care is a safe and effective
population density in the Great Smoky management option for orphaned, injured,
Mountain National Park (GSMNP), US, is or ill bears (Beecham et al. 2015; Myers and
12 JOURNAL OF WILDLIFE DISEASES, VOL. 58, NO. 3, JULY 2022
Young 2018). However, this requires cohesive from the ground or bowls. Natural outdoor
work between wildlife agencies, appropriate enclosures are 0.2 ha in area; lined by electrified
facilities, and policies to minimize mortality, 3-m–tall chain link fencing, covered with heavy,
dark material as a visual barrier; and resemble
potential bear conflict activity, and disease natural forested settings with natural ground
transmission (Beecham et al. 2016). Rehabil- cover and tree species available for bears to
itation can help recover declining bear climb. Enclosures contain plastic pools (2.5 m
populations, help maintain genetic diversity, diameter) for wading and tubs for drinking and
house up to 10 bears at a time. Food is thrown
and satisfy public demands of action for
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over the fence every 1–2 d from behind blinds to
injured and orphaned wildlife (Lindsey and encourage foraging behaviors and to prevent
Adams 2006; Beecham et al. 2016). Previous human-food association. Diet consists of commer-
studies have shown that bears released after cially available pellets (Mazuri Bear Diet, Purina
rehabilitation do not have increased mortality, Mills, Gray Summit, Missouri, USA) and season-
ally available natural foods such as blueberries
risk of conflict behavior, or homing tendencies
(Vaccinium spp.), blackberries (Rubus spp.),
toward the facility and report survival rates of acorns (Quercus spp.) and muscadines (Vitis
up to 90% (Cant 2013; Beecham et al. 2015; rotundifolia). Once bears are healthy and mature
Hashem 2019; Blair et al. 2020). enough to probably survive in the wild, they are
Across several US southeastern states, released into their habitat of origin in the regions
where they were rescued. Cubs or yearlings are
rescued young black bears are assessed and deemed releasable once they have gained suffi-
treated at the University of Tennessee Veter- cient weight (are at least 18 kg) and appear to
inary Medical Center (UTVMC) and rehabil- have adequate adipose tissue stores. Known
itated at Appalachian Bear Rescue (ABR, a siblings are released together.
501(c)(3) nonprofit organization). This study Postmortem examinations included complete
gross examination (n¼30), with histopathology
describes morbidity and mortality of bears where indicated by history and gross findings
housed at ABR from its inception in 1996 (n¼24). Representative tissues, including brain,
through 2021, to ultimately guide health care heart, lung, kidney, liver, gastrointestinal tract,
and future research. reproductive tract, pancreas, spleen, skin, bone,
and skeletal muscle, were fixed in 10% neutral
buffered formalin, routinely processed, paraffin-
MATERIALS AND METHODS embedded, sectioned at 5 lm thick, and stained
with H&E for examination by light microscopy.
Sick, injured, or orphaned bears are reported to Available medical and husbandry records from
the Tennessee Wildlife Resources Agency, Great UTVMC and ABR were evaluated to categorize
Smoky Mountain National Park Services, or other demographics (date, sex, age, weight, and loca-
wildlife agency in surrounding states by the public tion), reason for intake, outcome, problems for
or wildlife officials. Beginning in 2013, all bears which released bears were successfully treated,
were brought to the UTVMC Zoological Medicine gross and microscopic lesions, results of diagnos-
Service as soon as possible for full veterinary tic tests, and/or cause of death. It was also noted if
examination, diagnostics, and treatments, as the bear experienced injury or illness at ABR
needed. Before 2013, only obviously injured bears separate from any health issues present upon
were presented to the UTVMC. Bears requiring intake. Age was classified as follows: neonates
intensive care were hospitalized in the UTVMC were ,3 mo old, cubs were older than 3 mo but
intensive care unit (ICU), as needed. Bears that ,12 mo, yearlings were 12–24 mo old, and adults
died or were euthanized were submitted for full were .24 mo old. Bears were standardized as
postmortem examination at the UTVMC begin- born on January 17th of each year; any bear
ning in 2006. Individuals that were stable or presenting before April 15th the year it was born
healthy were discharged to ABR for rehabilitation was considered a neonate (Bridges et al. 2011).
until healthy enough for release. Descriptive statistics were performed to evalu-
Curators employed by ABR care for the bears ate state of origin, month, and season of
24 h per day, with continuous video record presentation, age and weight upon intake, weight
monitoring throughout the facility. Neonates are upon release, and number of days in care from
housed in secured, clean cages in climate- intake to outcome. A Shapiro-Wilk test was used
controlled buildings until mature and healthy to determine normality of data sets. Because the
enough to be released into larger acclimation pens Shapiro-Wilk test rejected the normality of the
or naturalistic enclosures. Neonates are bottle-fed continuous variables (P,0.001), the non-normally
as necessary until old enough to feed on their own distributed data is described as median (range)SHELDON ET AL.—AMERICAN BLACK BEAR REHABILITATION MORBIDITY AND MORTALITY 3
TABLE 1. Number of American black bears (Ursus TABLE 2. Number of American black bears (Ursus
americanus) admitted to Appalachian Bear Rescue, americanus) admitted to Appalachian Bear Rescue,
Tennessee, USA, during 1996–2021, grouped by US Tennessee, USA, during 1996–2021, grouped by
state of origin. month of intake.
State of origin No. bears (% of total) Month of intake No. bears (% of total)
Tennessee 221 (65.6) January 23 (6.8)
GSMNPa 49 (14.5) February 24 (7.1)
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Louisiana 18 (5.3) March 36 (10.6)
Arkansas 15 (4.5) April 35 (10.3)
Kentucky 11 (3.3) May 41 (12.1)
South Carolina 11 (3.3) June 42 (12.4)
Virginia 4 (1.2) July 25 (7.4)
North Carolina 3 (0.9) August 30 (8.8)
Georgia 3 (0.9) September 15 (4.4)
Alabama 2 (0.6) October 20 (5.9)
Total 337 November 34 (10.0)
a
December 12 (3.5)
Great Smoky Mountain National Park, in Tennessee and North
Carolina, USA.
Missing date 3 (0.9)
Total 340
while normally distributed data is described as
mean 6 SD. A chi-square analysis or the Fisher
ber (4.4%). Bears were more likely to present
exact test was used to identify if there was an
association between the reason for intake and in spring (32.9%) and summer (28.5%)
outcome. For this statistical analysis, the intake compared with fall (20.3%) and winter
groups were condensed to four categories: or- (17.4%). Three bears were admitted twice,
phaned neonate or cub; malnourished yearling; resulting in 340 admissions (12.4% neonates;
injured or ill; or other (conflict behavior, confis-
60.6% cubs; 25.6% yearlings; and 1.5% adults;
cated, or accidentally trapped). The outcome
groups were also condensed to four categories: Table 3). Upon intake, bears had a median age
returned to the wild (released, fostered, escaped, of 244 d (range 7–956 d) and a median weight
or reunited with mother); placed (transferred to a of 6.8 kg (0.23–79.5 kg). Upon outcome, bears
zoo); euthanized; or died. Odds ratios were had a median weight of 32.7 kg (0.23–132 kg).
calculated via logistic regression. Statistical soft-
Ten case records were missing body weight
ware SAS, version 9.4, release TS1M7 (SAS
Programming, Marlow, UK), was used for all upon outcome. Bears were under care for a
analyses; P,0.05 was considered significant. median of 116 (0–688) d between intake and
outcome. Data for number of care days were
missing for three cases.
RESULTS
Demographics Reasons for intake
From 1996–2021, 337 bears (170 males, Most bears presented as orphaned neonates
166 females, 1 unknown) from nine US states or cubs, or malnourished yearlings, with fewer
were admitted to ABR. The majority of bears bears injured or ill, confiscated, or other
were from Tennessee (65.6%), with bears also (Table 3). Orphaned bears were apparently
originating from eight other US states and the healthy but admitted due to being without a
GSMNP (Table 1). Over the period 2011– mother for 24–48 h or as determined by the
2020, a mean6SD (range) of 20610.3 (5–35) responding jurisdictional wildlife authority.
bears were admitted yearly. Bears were most Potential causes of separation of a mother
likely to be presented in June (12.4%) and and cub include death of the mother due to
May (12.1%; Table 2). Bears were least likely trauma or poaching; euthanasia of the mother
to present in December (3.5%) and Septem- in human-bear conflict scenarios; and possibly4 JOURNAL OF WILDLIFE DISEASES, VOL. 58, NO. 3, JULY 2022
TABLE 3. Number of American black bears (Ursus TABLE 4. Outcome of American black bears (Ursus
americanus) admitted to Appalachian Bear Rescue, americanus) admitted to Appalachian Bear Rescue,
Tennessee, USA, during 1996–2021, grouped by sex, Tennessee, USA, during 1996–2021.
age group, and reason for intake.
Outcome No. bears (% of total)
Group No. bears (% of total)
Released 266 (78.9)
Male 170 (50.4) Died 21 (6.2)
Female 166 (49.3) Euthanized 19 (5.6)
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Unknown sex 1 (0.3) Fostered with new mother 13 (3.9)
Neonates (,3 mo) 42 (12.4) Placed in professional care 10 (3.0)
Cubs (3–12 mo) 206 (60.6) Escaped 5 (1.5)
Yearlings (1–2 yr) 87 (25.6) Reunited with biologic mother 3 (0.9)
Adults (.2 yr) 5 (1.5) Total 337
Orphaned neonate or cub 198 (58.2)
Malnourished yearling 80 (23.5)
Injured or ill 42 (12.4) compared with orphans and malnourished
Confiscated 14 (4.1) yearlings (P,0.001). Injured or ill bears were
Othera 6 (1.8)
more likely to be euthanized than were
Total 340
orphans (odds ratio ¼ 40, P,0.001; Fig. 1).
a
Other ¼ conflict behavior, accidentally trapped, or malnourished There was no significant association between
adult.
reason for intake and death as an outcome
(P¼0.9535). ‘‘Other’’ bears were more likely to
abandonment. Malnourished bears were ad- be placed or transferred than were orphaned
mitted due to being found thin and in poor neonates or cubs (odds ratio ¼ 25.7,
condition without any other physical abnor- P,0.0001).
malities. Injured or ill bears were admitted Four injured or ill bears were admitted to
due to being found wounded or not walking or the ICU at UTVMC. Two of those bears
behaving normally, while confiscated bears survived to release and two were euthanized.
were admitted if found with an illegal
caretaker. Bears in the ‘‘other’’ category were Health problems treated successfully
admitted due to a conflict situation (n¼4),
Routine diagnostic tests on all bears exam-
being accidentally captured (n¼1), or a
ined at UTVMC include a physical examina-
malnourished adult (n¼1).
Outcomes
Individuals were returned to the wild
(85%), died (6.2%), were euthanized (5.6%),
or were placed into professional care (3.0%).
Of those returned to the wild, 92.7% were
released, 4.5% were fostered to wild surrogate
mothers, 1.5% escaped from ABR, and 0.9%
were reunited with their biologic mother
(Table 4).
There was no association between sex and
reason for intake (P¼0.980) or outcome
(P¼0.623). Orphaned neonates and cubs were
statistically just as likely to return to the wild FIGURE 1. Outcomes for American black bears
(Ursus americanus) bears admitted to Appalachian
as were malnourished yearlings (P¼0.431). Bear Rescue, Tennessee, USA, 1996–2021, from each
Injured or ill and ‘‘other’’ bears were signif- intake group (orphaned neonate or cub; malnourished
icantly less likely to return to the wild yearling; injured or ill; and other).SHELDON ET AL.—AMERICAN BLACK BEAR REHABILITATION MORBIDITY AND MORTALITY 5
tion, complete blood count, and plasma anorexia and weight loss, rectal prolapse, an
biochemistry panel. Additional diagnostic tests abdominal wall hernia, vomiting and diarrhea,
include radiographs, computerized tomogra- tooth root abscess, ileus, lameness, septic
phy, ultrasound, urinalysis, tick-borne disease carpal arthritis, and facial soft tissue swelling.
testing, skin scraping, and fecal flotation as
needed based on abnormal physical examina- Pathology
tion findings. Routine treatments for admitted Bears died more often in spring (n¼10) and
bears included subcutaneous or intravenous
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summer (n¼10) months compared with winter
fluids, as warranted, and oral fenbendazole
(n¼4) and spring (n¼6). Causes of death or
(50 mg/kg orally every 24 h for 3 d) and
euthanasia determined by postmortem exam-
praziquantel (8–12 mg/kg orally once) upon
ination (n¼30) were classified as trauma (50%,
intake for reduction of intestinal parasites.
n¼15), developmental (13%, n¼4), undeter-
Other treatments included analgesics, antibi-
mined (13%, n¼4), malnutrition (13%, n¼4),
otics, vitamin B, iron dextran, ivermectin, and
infectious or inflammatory (7%, n¼2), and
in one case a blood transfusion. Surgery was
toxicosis (3%, n¼1). Causes of fatal trauma
performed on 13 bears; 10 of these survived to
included vehicular collision (n¼4), fall from
release.
tree (n¼4), undetermined (n¼5), gunshot
Of released bears, 195 had complete
(n¼1), or electrocution (n¼1). Developmental
medical records available for evaluation. At
causes of death included hydrocephalus (n¼3)
intake, 31.3% (n¼61) were healthy; the
remaining bears were treated successfully for and glenoid shoulder dysplasia (n¼1). The
malnutrition and internal parasites (49.2%, latter was associated with articular cartilage
n¼96), orthopedic (9.2%, n¼18) and soft tissue erosion of the humeral head, which was
injuries (5.1%, n¼10), or other diseases (5.1%, presumptively attributed to osteochondrosis
n¼10). Parasites identified included Baylisas- based on gross examination. Fatal infectious
caris transfuga via fecal flotation and micro- and inflammatory processes included aspira-
scopic identification as well as Ursicoptes and tion pneumonia associated with pyloric mus-
Demodex spp. mites identified on superficial cularis hypertrophy and an acute small
and deep skin scrapes. Orthopedic abnormal- intestinal intussusception (n¼1) and interstitial
ities included fractures of the femur (n¼8), pneumonia with moderate encephalitis of
ribs (n¼2), skull (n¼2), humerus (n¼1), radius- unknown etiology accompanied by subclinical
ulna (n¼1), mandible (n¼1), and carpal septic mild hydrocephalus (n¼1). Ethylene glycol
arthritis with elbow fragmentation (n¼1). Soft toxicosis (n¼1) was the only toxic cause of
tissue injuries included skin wounds of death identified and was diagnosed based on
unknown etiology (n¼6), dart lacerations the presence of severe subacute renal tubular
(n¼2), plant foreign body penetration (n¼1), necrosis and degeneration with intratubular
bite wounds (n¼1), and an abdominal wall calcium oxalate crystals.
hernia (n¼1). Other abnormalities included Bears for which cause of death was
anemia of unknown etiology (n¼4), head undetermined (n¼4) included two with severe
trauma (n¼2), neurologic signs of unknown postmortem decomposition or scavenging.
etiology (n¼2), lymphadenopathy (n¼1), pneu- One case was euthanized after being hospi-
monia (n¼1), and sepsis (n¼1). talized in the ICU twice, 1 mo apart, with
Seventeen bears became injured or ill severe anemia, hyperbilirubinemia, splenic,
during rehabilitation at ABR. Ten were hepatic, and lymphatic extramedullary hema-
ultimately released, four died, and three were topoeisis, pneumonia, and pericardial effu-
euthanized. All four deaths and one euthana- sion. Despite extensive diagnostic testing pre-
sia were due to falling from trees. The two and postmortem testing for infectious diseas-
other euthanized bears were due to severe es, an etiology was not identified. The other
wound infections. Diagnoses of animals treat- bear died under anesthesia during a Cutere-
ed and later released included ripped ear tags, bra sp. removal, and death was hypothesized6 JOURNAL OF WILDLIFE DISEASES, VOL. 58, NO. 3, JULY 2022
TABLE 5. Postmortem lesions, stratified by cause of death, affecting American black bears (Ursus americanus)
admitted to Appalachian Bear Rescue, Tennessee, USA, 1996–2021, with complete postmortem examination at
the University of Tennessee.
Cause of death
Inf or
Lesion Trauma Infla Developmental Undetermined Malnutrition Toxicosis Total
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Number 13 5 4 4 3 1 30
Fractures 7 1 1 9 (30)
Skin or muscle hemorrhages 7 1 8 (27)
Pneumonia 2 2 1 1 1 7 (23)
Gastritis, enteritis, colitis 1 1 1 1 1 1 6 (20)
Emaciation 1 2 1 2 6 (20)
Exfoliative dermatitis or 3 1 1 5 (17)
hyperkeratosis
Visceral organ fracture or tear 5 5 (17)
Hemoabdomen 2 1 1 4 (13)
Hydrocephalus 1 3 4 (13)
Osteomyelitis 2 2 4 (13)
CNSb hemorrhage 3 1 4 (13)
Pyloric muscular hypertrophy 2 1 3 (10)
Hepatic hemosiderosis 2 1 3 (10)
a
Inf or Infl ¼ infectious or inflammatory.
b
CNS ¼ central nervous system.
to be anesthetic-related or due to anaphylaxis DISCUSSION
from a Cuterebra sp.
Over 2.5 decades, ABR in conjunction with
Several other lesions documented on post-
UTVMC and state and federal wildlife agen-
mortem examination were of varying signifi-
cies has rescued, rehabilitated, and released
cance (Table 5). For example, one case of
more than 280 American black bears (85%
malnutrition had fractures associated with
success rate). Most bears presented for being
osteoporosis that was considered pathologic.
orphaned or malnourished, while a minority
Two additional instances of pyloric muscularis
was injured, ill, or confiscated. Despite the
hypertrophy were observed in bears that died
lack of maternal care and high prevalence of
with malnutrition. One case of trauma also malnutrition and trauma, most bears recov-
had a heartworm (Dirofilaria spp.) infection. ered to release with appropriate husbandry
Gastrointestinal parasites observed included and medical care.
gastric Physaloptera (n¼1), gastric acantho- Most bears admitted to ABR originated
cephalan (n¼2), and small intestinal ascarids from the eastern Tennessee and Great Smoky
(presumptive Baylisascaris transfuga; n¼4). Mountain National Park area, which is con-
Five bears had skin lesions. One case was an sistent with this area having the highest
eosinophilic dermatitis associated with Ursi- concentration of bears in the southeastern
coptes americanus. The remaining cases were US. Bears were occasionally admitted to ABR
an alopecia and hyperkeratotic dermatoses from other surrounding states. Most cases
which had similar microscopic features but presented in the spring and summer months.
variable distribution including tail base, ab- Bears are born between December and mid-
domen, and axillary region. Microscopically, February; emerge from dens with mothers in
these had epidermal, follicular, and adnexal their first spring (March–April); spend the
atrophy plus orthokeratotic hyperkeratosis. summer with mothers growing and learningSHELDON ET AL.—AMERICAN BLACK BEAR REHABILITATION MORBIDITY AND MORTALITY 7
about foraging, dangers, and communication; Minnesota (Garshelis et al. 2021), supporting
re-enter dens with mothers the following the inception of wildlife passageways to
autumn; and usually separate after they mitigate population impacts from roadways
emerge in spring as yearlings (Clark et al. (Gilhooly et al. 2019). In contrast to other wild
2021). It is not surprising that in spring and carnivores, trauma due to inter- or intraspe-
summer, when cubs and yearlings are either cific conflict was not observed, similar to
adjusting to life outside the den or trying to observations of free-ranging bears in Minne-
continue life after separating from the mother, sota (Garshelis et al. 2021). No bears died of a
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young bears are more likely to encounter primary contagious infectious disease, which
trauma, difficulty foraging, and conflicts with is also consistent with the previous study
humans. (Garshelis et al. 2021), although whether or
Despite an overall high survival rate for not comprehensive postmortem examinations
admitted bears, injured or ill bears were were performed in that study is unclear. The
significantly more likely to be euthanized low incidence of infectious disease in black
compared with orphaned or malnourished bears is thought to reflect their solitary
bears. Traumatic injuries, undetermined caus- behavior and relatively low population densi-
es of illness, and developmental abnormalities ties (Clark et al. 2021).
all decreased the likelihood of survival. Severe The few bears that were diagnosed with
trauma, wounds, and illnesses often require acariasis all had either easily treated, mild
intensive care, repeated immobilizations, and infections identified on skin scrape or para-
hospitalization. These procedures were only sites found incidentally at postmortem. No
performed on animals with a good prognosis bears were diagnosed with Sarcoptes scabiei.
for return to function without being habituat- An epidemic of severe sarcoptic mange
ed to humans. Veterinarians, rehabilitators, caused by S. scabiei in free-ranging Pennsyl-
and state wildlife officials discussed prognosis, vanian black bears caused severe clinical signs
requirements for recovery, and likelihood of and mortality (Peltier 2016). Recent studies
survival before treatment or euthanasia deci- have developed and utilized a serologic test to
sions were made. determine exposure to Sarcoptes scabei and
At ABR, bears are housed in groups and optimization of treatment protocols (Nie-
outdoor habitats that replicate natural envi- dringhaus et al. 2020; Van Wick et al. 2020).
ronments including trees and pools; thus, In hunter-harvested, free-ranging North Car-
traumatic incidents such as falling from trees olina black bears (n¼45) screened for anti-
and infections from bite wounds or injuries bodies, 18% were seropositive, but none
can be difficult to prevent. As the most sampled were clinically affected (Houck et
arboreal of bear species, ABR recognizes the al. 2021). Black bears in the southeastern US
need to have trees for American black bears to should continue to be screened for S. scabiei
climb within the enclosures. The center has, infection to detect an emergence of mortality-
however, added components to the enclosures causing disease. A hyperkeratotic dermatosis
to mitigate bear escapes as well as to reduce of unknown pathogenesis with epidermal and
the likelihood of tree-falls while still allowing adnexal atrophy not attributable to ectopara-
bears to adequately develop climbing and sites was incidentally documented postmor-
defensive skills. For example, trees within 4.5 tem in four bears. Pathogenesis is uncertain
m of the enclosure fencing are wrapped with and may be diverse, but lesion distributions
slick plastic or metal bands to prevent were not like denning alopecia reported in
climbing close to the top of the fence. black bears in New Mexico (Costello et al.
The most common cause of death of bears 2006).
submitted for postmortem examination was Developmental abnormalities were the
traumatic injury, usually due to vehicular third most common cause of death and were
collision or falling from a tree. This is comprised mostly of three hydrocephalus
consistent with data on free-ranging bears in cases (previously published) that presented8 JOURNAL OF WILDLIFE DISEASES, VOL. 58, NO. 3, JULY 2022
as orphaned with cortical blindness and ataxia success (release rate vs. postrelease monitor-
(Ferguson et al. 2016). The cub with glenoid ing), species, circumstance of presentation
shoulder dysplasia and presumptive osteo- (injured animals have a lower rate of success),
chondrosis of the humeral head presented and demographics such as life stage (Kelly and
with non–weight-bearing lameness and luxa- delBarco-Trillo 2020). Our study and a similar
tion of the left shoulder and was euthanized study of black bear rehabilitation in Virginia
due to poor prognosis. It is unknown if this both report success rates of 85%, which are
lesion reflected an intrinsic abnormality of the much greater than many other reports of
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ossification centers of the scapula or was a rehabilitation success across a variety of
consequence of early trauma. terrestrial species, which range well below
Nonlethal developmental anomalies were 50% (Grogan and Kelly 2013; Hashem 2019;
identified in this study, including an additional Kelly and delBarco-Trillo 2020; Kwok et al.
case of subclinical hydrocephalus and a case 2021). While seven bears died due to condi-
of mild renal dysplasia incidentally identified tions that occurred while in rehabilitation, the
on histopathology. To the authors’ knowledge, causes of mortality included falling from trees
the latter has not been previously described in or infected wounds, which are not conditions
Ursidae. There were also three cases of unique to the rehabilitation setting and also
pyloric muscularis hypertrophy, a component occur in free-ranging bears. We speculate that
lesion of pyloric stenosis in some domestic the reason for high success in black bears in
animals which may be congenital and accom- particular may be a combination of inherent
pany recurrent vomiting, gastric distention, species characteristics of high tolerance of
and poor growth (Weisbroth and Scher 1975; temporary captive environments; hardiness
Gelberg 2017); its significance and the normal against disease and stress; and the number
variation in muscularis thickness in bears are of high-quality black bear rehabilitation facil-
unknown, but the association with emaciation ities with proven methods and monitoring
and aspiration pneumonia in bears of this techniques.
study suggests it may be clinically relevant. Despite black bear resilience, human pop-
Record keeping has improved since 1996, ulation growth and encroachment will contin-
but a limitation of this study is that more- ue to threaten bear habitat and their ability to
detailed information in earlier cases may have thrive and safely distance from people.
been missing, such as less clinically relevant Human-bear conflict is increasing over time
exam findings or treatments. ABR did not and can threaten not only human and bear
bring every bear into UTVMC until 2013. health due to attacks on people and reactive
Earlier medical records were not digital or as bear euthanasia, but the increase in contact
easily accessible, and some bears were occa- between humans, domestic animals, and bears
sionally seen by different local veterinarians. may increase stress, compromise immune
Monitoring wildlife post rehabilitation is vital function, and provide increased opportunity
to evaluating efficacy of the process. In 2015– for transmission of infectious agents. Thus,
2016, 42 bears released from ABR were surveying the current health and pathogens of
collared and tracked to assess survival and a healthy bear population establishes a
postrelease conflict situations for 1 yr. Results baseline and allows us to identify changes in
showed similar or higher survival rates and health and potential zoonotic agents. Future
similar conflict rates as those of nonrehabili- goals of research and care at ABR include
tated free-ranging black bears in this region, environmental and animal parasite load mon-
supporting the overall efficacy of ABR prac- itoring and management, overall convalescent
tices (Blair et al. 2020). Another limitation is health assessments from intake to release that
that this group of necropsied bears does not include hematologic and biochemical param-
include all black bears killed in the region. eters, serologic surveys, anesthetic protocol
Success rates of wildlife rehabilitation optimization, and screening for presence of
programs vary and depend on definition of infectious pathogens.SHELDON ET AL.—AMERICAN BLACK BEAR REHABILITATION MORBIDITY AND MORTALITY 9
ACKNOWLEDGMENTS center of its range. In: Bears of the world: Ecology,
conservation and management, Penteriani V, Melletii
The authors would like to thank the curators M, editors. Cambridge University Press, Cambridge,
and staff at Appalachian Bear Rescue, wildlife UK, pp. 53–62.
officers that have assisted with bear rescues and Gelberg HB. 2017. Alimentary system and the peritone-
releases, members of the public who have um, omentum, mesentery, and peritoneal cavity. In:
reported injured and ill bears, technicians, Pathologic basis of veterinary disease, 6th Ed.,
interns, residents, and veterinary students for Zachary JF, editor. Elsevier, St. Louis, Missouri, pp.
help examining and treating these bears, and the 324–411.
following pathologists for performing the post-
Downloaded from http://meridian.allenpress.com/jwd/article-pdf/doi/10.7589/JWD-D-21-00191/3054120/10.7589_jwd-d-21-00191.pdf by guest on 14 June 2022
Gilhooly PS, Nielsen SE, Whittington J, St. Clair CC.
mortem examinations: Linden Craig, Robert 2019. Wildlife mortality on roads and railways
Donnell, Nathan Hoggard, Denae LoBato, Mal- following highway mitigation. Ecosphere 10:e02597.
com D. McCracken, Debra Miller, Kim Newkirk, Grogan A, Kelly A. 2013. A review of RSPCA research
Shelley Newman, Daniel Reel, and Mee Ja Sula. into wildlife rehabilitation. Vet Rec 172:211.
Hashem BJ. 2019. Evaluating the success of an orphaned
LITERATURE CITED American black bear (Ursus americanus) rehabilita-
Beecham JJ, de Gabriel Hernando M, Karamanlidis AA, tion program in Virginia. J Wildl Rehabil 39(2):7–12.
Beausoleil RA, Burgess K, Jeong DH, Binks M, Houck E, Olfenbuttel C, Stoskopf M, Kennedy-Stoskopf
Bereczky L, Ashraf NVK, Skripova K, et al. 2015. S. 2021. Seroprevalence of Sarcoptes scabiei in free-
Management implications for releasing orphaned, ranging black bears (Ursus americanus) in eastern
captive-reared bears back to the wild. J Wildl Manage North Carolina. J Wildl Dis 57:628–631.
79:1327–1336. Kelly G, delBarco-Trillo J. 2020. Importance of taxonomic
Beecham JJ, Loeffler IK, Beausoleil RA. 2016. Strategies group, life stage and circumstance of rescue upon
for captive rearing and reintroduction of orphaned wildlife rehabilitation in Ontario, Canada. J Nat
bears. J Wildl Rehab 36(1):7–16. Conserv 57:125897.
Blair CD, Muller LI, Clark JD, Stiver WH. 2020. Survival Kwok ABC, Haering R, Travers SK, Stathis P. 2021.
and conflict behavior of American black bears after Trends in wildlife rehabilitation rescues and animal
rehabilitation. J Wildl Manage 84:75–84. fate across a six-year period in New South Wales,
Bridges AS, Vaughan MR, Fox JA. 2011. Reproductive Australia. PLoS ONE 16:e0257209.
ecology of American black bears in the Alleghany Lindsey KJ, Adams CE. 2006. Public demand for
Mountains of Virginia, USA. J Wildl Manage 75: information and assistance at the human-wildlife
1137–1144. interface. Hum Dimens Wildl 11:267–283.
Cant M. 2013. The rehabilitation of black bears (Ursus Myers PJ, Young JK. 2018. Post-release activity and
americanus) in North America: A survey of current habitat selection of rehabilitated black bears. Hum-
practices. MS Thesis, Animal Science, University of Wildl Interact 12:322–337.
British Columbia, Canada, 107 pp. Niedringhaus KD, Brown JD, Ternent M, Peltier SK, Van
Clark JD. 2019. Comparing clustered sampling designs for Wick P, Yabsley MJ. 2020. Serology as a tool to
spatially explicit estimation of population density. investigate sarcoptic mange in American black bears
Popul Ecol 61:93–101. (Ursus americanus). J Wildl Dis 56:350–358.
Clark JD, Beckmann JP, Boyce MS, Leopold BD, Loosen Peltier SK. 2016. Sarcoptic mange in black bears (Ursus
AE, Pelton MR. 2021. American black bear (Ursus americanus) in Pennsylvania. MS Thesis, Science,
americanus). In: Bears of the world: Ecology, University of Georgia, Athens, Georgia, 90 pp.
conservation and management, Penteriani V, Melletti Scheick BK, McCown W. 2014. Geographic distribution
M, editors. Cambridge University Press, Cambridge, of American black bears in North America. Ursus 25:
UK, pp. 122–138. 24–33.
Costello CM, Quigley KS, Jones DE, Inman RM, Inman Van Wick P, Papich MG, Hashem B, Dominguez-Villegas
KH. 2006. Observations of a denning-related derma- E. 2020. Pharmacokinetics of a single dose of
titis in American black bears. Ursus 17:186–190. fluralaner administered orally to American black
Ferguson SH, Novak J, Hecht S, Craig LE. 2016. bears (Ursus americanus). J Zoo Wildl Med 51:691–
Hydrocephalus in three juvenile North American 695.
black bears (Ursus americanus). J Zoo Wildl Med 47: Weisbroth SH, Scher S. 1975. Naturally occurring
632–635. hypertrophic pyloric stenosis in the domestic rabbit.
Garshelis DL, Noyce KV, Ditmer MA, Coy PL, Tri AN, Lab Anim Sci 25:355–360.
Laske TG, Iaizzo PA. 2021. Remarkable adaptations
of the American black bear help explain why it is the Submitted for publication 29 November 2021.
most common bear: A long-term study from the Accepted 11 February 2022.You can also read
