brown bear (ursos arctus l.) in slovenia, 2002 ppt

8/8/2019 Brown Bear (ursos arctus L.) in Slovenia, 2002 ppt

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Spatial Expansion of the Brown Bear (Ursus arctos L.) in Slovenia:

Speed of Expansion and Saturation Dependent Dispersion.

Klemen Jerina, Miha AdamicUniversity of Ljubljana, B.F. Department of Forestry

Vecna pot 83, 1000 Ljubljana, Slovenia,E-mail: [email protected]


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Characteristics of the brown bear

population in Slovenia:

Population size is increasing rapidly:

in 1957: 160 bears

in 2000: 400 - 450 bears


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Population size is increasing rapidly

Spatial expansion out of the core

management area:

Core management areacomprised:

in 1957: 95 % of population

in 2000: 75 % of population


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Population size is increasing fast

Spatial expansion out of the core

management area

Recolonization

BUT!

Conflicts:

Increased depredation

Fear among people


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Purpose of the research:To estimate the speed of the spatial expansion of the brown bear

out of the core protective area,

To study the sexual structure (and its variation in time and space) of the

bear population out of the core area,

To study the factors influencing the dispersion of the bear.

Methods:Data: recorded locations (x,y) of the brown bear out of the core protective

area in the period between 1945 - 1995.


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Data: recorded locations

Observations (footprints, visual contact, other signs),

Harvested bears,Reported damages.


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Methods:Data: recorded locations (x,y) of the brown bear, out of the core

protective area in the period between 1945 - 1995.

All recorded locations contain information about:

gender of the bear (if possible; harvested bears, females with cubs),

the year of the observation,

the distance from the edge of the core protective area.


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Methods:Data:

recorded locations of the brown bear,

other data, collected or estimated in our previous studies:


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Optimal habitatPotential (max.) habitat

Spatial habitat modell of the brown bear in Slovenia


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0

50

100

150

200

250

300

350

400

450

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

0

20

40

60

80

100

120

Entire population

External part

Modell estimated size of the brown bear population in Slovenia


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Methods:Data:

recorded locations of the brown bear,

other data, collected or estimated in our previous studies:

spatial habitat modell, population size modell.

Analyses:The speed of the spatialexpansion of the brown bear.


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Analyses:

The speed of the spatialexpansion of the brown bear

Basic idea: recorded locationspopulation densities, accordingto the time and the distance from the core protective area

multiple regression modells speed of the population expansion

The locations of the observed bears were reclassified according

to the time of the bear observation into four classes:

year 1945-1966, 1967-1976, 1977-1986, 1987-1995

In each class the frequency of the bear observations was established.

The frequencies were recalculated into the average annual population

size by the use of the modell estimated population size.

In each time interval, population size was reclassified according to thedistance from the core area into 8 classes.

Thus elaborated 32 (=8 x 4) population size estimates transformed into the

relative population densities (in each distance class, population size was

divided by bear-available area, estimated from the spatial habitat modell).

Whole procedure was performed once with all locations, and once only with

female observations.


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56728291

5 15 25 35 45 55 65 78.15

0102030405060708090

100

90-100

80-90

70-80

60-70

50-60

40-50

30-40

20-30

10-20

0-10

56

728291

5 15 2535 45 55 65 78.15

0369

12151821242730

27-30

24-27

21-24

18-21

15-18

12-15

9-12

6-9

3-6

0-3

All locations

Females only

Relative population densities with regard to the time and the distance

from the core protective area


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Regression analyses of the determined population densieties (All locations):

Use of multivariate regression modells; function type: dens=f(-Adist+Btime);

(dens=0 dist/time = B/A = speed

Used modells:

Linear function (dens = C - A dist + B time),

Exponent function (dens = C + exp(D - A dist + B time)),

Modified Bertalanffy function (dens = C(1-{1- exp(D - A dist + B time)}E),

Results: the speed of the population expansion is between 2.0 - 3.5 km / year


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A = 0.004325; B =0.1382 speed = B/A = 3.2 km/year

R = 0.98***

The population density with regard to the time and the distance from the core

protective area function, calculated by the use of non-linear multiple regression


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Analyses:

The speed of the spatial expansion of the brown bear

The analyse of the factors influencingthe dispersalof the brown bear

Basic idea: when the number of dispersals is big, the most distant bears will be

observed further away from the core protective area analyse of the outmost

locations will give us insight into the dinamics of the bear dispersal!

For each year, the outmost border of bear colonization was estimated


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Distance


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Analyses:

The speed of the spatial expansion of the brown bear

The analyse of the factors, influencingthe dispersalof the brown bear

Basic idea: when the number of dispersals is big, the most distance bears will be

observed furter away from the core protective area analyse of the outmost

locations will give us insight into the dinamics of the bear dispersal!

For each year, the outmost border of bear colonization was estimated

Time-variating distance of the outmost border of the colonization was used as

dependent variable in multivariate linear regression modell. Annual relative

and absolute number of harvested bears in and out of the core protective area

and the brown bear population size in and out of the core protective area were

as used as independent variables.

Results: outmost border of the bear colonisation is:

positively dependent on the size of the external bear population

(expected result!)

and negatively dependent on the relative number of harvested bears in

the core protective area.


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Dist = 44891 + 828pop.size_ext - 116963hunt_rel_core

Method stepwise; E of both variables


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Discussion and conclususions:

The bear population expands its range of activity by two different ways:

1) by the postnatal dispersion, which is biased toward the males,

2) and by the establishment and the expansion of the individulal areas of

activity near the ranges of the parents.

The popualtion cliff was expanding away from the core protective

area by an average speed 2 - 3.5 (median: 3) kilometers per year.

Within the research period the bear population increased annualy for

2.3% on average.

The portion of females is increasing in time and decreasing with

distance from the core protective area (our previous study)

So the stability of the newly formed population nuclei, located far

away from the core protective area depends on the constant flux ofdispersals from the reproductive - female habitats.


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Discussion and conclususions:

The distance of the outmost border of the bear colonized areas

correlates positively with the population size (population is spatialy

expanding as a balloon when the population size is increasing)It also corelates negatively with the relative number of the harvested

bears in the core protective area. This negative correlation indicates that

the dispersals from the core protective area (source population)

influenced the colonization of the external area.When the relative

harvested quota in the core protrective area was big, potential dispersalsprobably established their ranges of activity in the core protective area.

They were not forced to emigrate out of the core protective area.

So the dispersion depends also on the saturation of the population and not

only on its absolute density.When the relative number of extracted bears

was big, the populations saturation decreased and vice versa.

brown bear (ursos arctus l.) in slovenia, 2002 ppt

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