Abstract
Five radio-collared female bear were monitored from April-December 1992 in
Garrett County, MD. Two females
were intensively monitored for during two five week periods; (July 8 - August 9,
1991) and (July 6 - August 7, 1992).
For 1991, the home range for the barren female was 14.9 sq km; twice that
of the sow with cubs (7.0 sq km). (This
contradicts most established results. See
Discussion below.)
For 1992, mean annual home range was 40.5 sq km.
Mean spring-summer was 28.4 sq km, and mean fall was 31.0 sq km.
Mean home ranges for the barren versus the sow with cubs was virtually
identical (22.1 vs 21.3 respectively).
The
barren sow spent more time in open than the sow with cubs, but both chose the
deciduous woods over open lands (approximating 68% to 77% of the annual range),
and both avoided roads.
In general, research has shown that mean home range is inversely related
to the quality of the habitat (specifically, food abundance).
Home range also varies by season as the food source availability changes.
Other factors include maternal, breeding, social and various ecological
factors.
Approximately 150 - 170 black bear reside in Garrett County in 1992 (thus,
pretty much, all of Maryland). This
total went from 150 bear in 1937 to only 12 bear in 1956.
It was placed on the state’s endangered species list in 1972, only to
be removed in 1980 to the status "nongame species of special concern” (due to
increased black bear sightings and bear damage complaints). In 1985, the status was again changed to forest game species
to enable a hunting season (if the population increased beyond public
tolerance). (Editor’s note; as of the 2001 season, no hunting has been
permitted.)
Numbers of bear in MD increased in the 70's due to increased maturity/
improved habitat quality of the forests, and dispersal of PA’s stocking
program into MD.
The long-term goals of the Maryland Department of Natural Resources’
Wildlife Division in the Black Bear Management Plan are two-fold: 1) to manage
the black bear as a native wildlife species in western Maryland where suitable
habitat exists and is compatible with other land uses, and 2) to manage the
black bear resource to provide recreational opportunities for citizens of
Maryland.
Discussion
Home range size is an important index of food resource availability for
black bear. Black bear must meet
their annual nutritional requirements in a 5 to 8 month period. Their feeding habits are characterized by the use of
herbaceous vegetation in the spring, berry-producing shrubs in the summer and
hard mast in the fall. In this
study, common forage included skunk cabbage in the spring, colonial
hymenopterans (ants and bees), squawroot, and tree-born soft mast (Prunus
species). Based on these seasonally
available food sources, home range varies by season on a predictable manner.
Home ranges of 40 sq km found in this study compare with annual home
ranges of 28 and 33 sq km for PA, 38 sq km for VA, and 27 sq km for WVA.
Home range is also influenced by reproductive status, with sows and cubs
generally covering a larger range than barren sow, or sows with yearlings.
Although this study did not reveal this result (limited sample size),
study results from Maine and PA show sows with cubs have a larger annual home
range than solitary females (PA had 45 sq km for females with cubs vs 20 sq km
for solitary females). Many studies do point out that for up to the first four
months after leaving the den, sows with cubs do, in fact, limit their range. By
fall, sows with cubs have their greatest home range, while solitary females have
their largest home range in summer. Such
large ranges of solitary females coincides with the peak breeding season.
Similarly, males maximize their movements during this same breeding
season. Fall movement often
directly correlates with the availability of hard mast.
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Abstract
The study is based on radio tracking of five female bear; three from
shortly after den emergence to den entrance in 1993 and 1994, and two bear
monitored for one year each during the same period.
Mean annual, spring-summer, summer, and fall home range estimates were 35
sq km, 28.5 sq km, 19.3 sq km, and 13.1 sq km respectively. Solitary females had larger annual and spring-summer home
ranges but smaller fall home ranges than females with cubs (summer ranges were
about the same). Summer home ranges
for all bears were larger than fall home ranges.
Mixed forest and wetland habitats were the most preferred on an annual
basis. Bears preferred habitat with
relatively high stream densities.
Corn crop depredation by bear was found to be more related to available
adjacent cover than quality of adjacent habitat (refuting the hypothesis that
corn depredation was greater adjacent to lower quality habitat).
Introduction
and Background
An estimated 500,000 black bears exist in North America. In 1987, research was initiated and determined the estimated
population in Maryland to be 150 - 170. Age
at maturity was three years of age, and mean litter size was 3.1 (Garner and
Mathews, 1992).
Home
Range
The home range of males are generally larger than that of females, with
the polygamous male range overlapping those of several females, as well as other
males. Mean home range in the
Smokies was 42 sq km for males and 15 sq km for females. Arizona figures were
543 and 98 sq km for males vs females, and in New Jersey, the comparison was 178
for males and 16 for females. Solitary
females have larger annual home ranges than females with cubs. However, this author
recognizes this applies especially in spring, when young cubs limit movement.
Further, is is recognized that movement of solitary females decline in
fall, as ranges are maximizing among females with cubs.
Yearlings are separated from their mothers in May and June, either through
maternal hostilities, or possible voluntary dispersal by the young males.
Yearling females will often establish home ranges within or near home
ranges of their mothers, with the mother shifting her home range to accommodate
the young females. Yearling males rarely settle within the home ranges of their
mothers, often moving from 60 km to more than 96 km from their birth places.
Females maximize their range during the breeding season; lasting from May
to September (peaking from mid-June through mid-July in PA).
Habitat
Use
Black bears are associated with wetlands and riparian habitats.
Some research shows that escape cover can be more important than food
availability in determining habitat use by black bears, with clear cuts being
avoided despite abundant soft mast.
This
author presents studies of bear movement being attracted to restricted access
roads. Trails and logging roads
were also noted by two authors to be preferred by black bear. Such conflicting
results may reflect hunting pressures, and/or experience of bear with people
(adults avoided roads more than subadults in the Smokies).
Between 1890 and 1920, most of MD’s forest was clear-cut and burned.
Now, most of the forests are between 70 and 90 years of age, principally
restricted to the mountains and more rugged slopes not suited for agriculture.
Mixed forest was preferred over deciduous forest, and evergreen forest was
equally preferred to mixed forest annually.
Cover is an important habitat requirement, along with food resources.
Former rhododendron thickets were prime bear habitat, now replaced by
pole-sized evergreen stands. Large
evergreen trees (white pine) were preferred climbing trees for escape.