Transcript LIFE HISTORY AND HARVESTING - University of Illinois at Chicago

LIFE HISTORY AND HARVESTING
READINGS:
FREEMAN, 2005
Chapter 52
Pages 1206-1213
Chapter 54
Pages 1277-1283
ENDANGERED AND
THREATENED SPECIES
• Endangered means a species that is in danger or
extinction throughout all or a significant portion of
its range.
• Threatened means a species that is likely to
become endangered within the foreseeable future
throughout all or a significant portion of its range.
• The Endangered Species Act (EAS) was passed
in 1973 to protect listed species for the “esthetic,
ecological, educational, recreational, and scientific
value to our Nation and its people”.
WILDLIFE PROTECTION IN
NATIONAL PARKS
WILDLIFE REFUGES AND
WILDERNESS AREAS
• In addition to the National
Parks, Federal public lands
include National Wildlife and
Wilderness Areas that act to
provide habitat for
threatened and endangered
species.
• Of the 700 million acres
(about 1/3 of the US), that
are in the public domain
about 170 million are
devoted to this preservation
effort.
Larger Preserves Provide
Greater Protection Against
Extinction
Newmark, 1987
• A study has followed
mammal extinctions in
National Parks in the US and
Canada.
• Species loss in 14 western
North American National
Parks is consistent with the
species area relationships
seen earlier.
• Number of extinctions was
greatest in smallest parks.
CHANGING SURVIVORSHIP
AS A MANAGEMENT TOOL
• Age specific mortality and natality data
can be used to make management
decisions in harvesting or conserving
wildlife populations.
• Assume that a population of interest is
growing at too high a rate, what are the
consequences of harvesting old versus
young individuals on changing the rate
of population growth?
MANAGING A GRAY
SQUIRREL POPULATION
• This squirrel
population living in
an Ohio woodlot has
a type II survivorship
curve.
• Typical of a
population with
accidental death.
MANAGING A GRAY
SQUIRREL POPULATION
• Squirrel populations
begin reproduction
at the end of the first
year and continues
throughout life.
• The average
number of offspring
produced decreases
with age.
A GRAY SQUIRREL
POPULATION
X
0-1
1-2
2-3
3-4
4-5
5-6
lx
1.00
0.796
0.344
0.151
0.054
0.011
mx
lx mx
0
1.55
1.35
1.25
1.20
1.15
0
1.23
0.46
0.19
0.06
0.01
A GRAY SQUIRREL
POPULATION
X
0-1
1-2
2-3
3-4
4-5
5-6
lx
1.00
0.796
0.344
0.151
0.054
0.011
mx
0
1.55
1.35
1.25
1.20
1.15
lx mx
0
1.23
0.46
0.19
0.06
0.01
Ro = 1.95
What will happen if all
squirrels 2 years and older are
harvested?
X
0-1
1-2
2-3
3-4
4-5
5-6
lx
1.00
0.796
0.344
0.151
0.054
0.011
mx
lx mx
0
1.55
1.35
1.25
1.20
1.15
0
1.23
0.46
0.19
0.06
0.01
What will happen if all
squirrels 2 years and older
are harvested?
X
0-1
1-2
lx
1.00
0.796
mx
lx mx
0
1.55
0
1.23
What will happen if all
squirrels 2 years and older
are harvested?
X
0-1
1-2
lx
1.00
0.796
mx
lx mx
0
1.55
0
1.23
Ro= 1.23
All the squirrels you can eat and more!!!!
How to establish a squirrel preserve?
X
0-1
1-2
2-3
3-4
4-5
5-6
lx
1.00
0.410
0.172
0.076
0.027
0.006
mx
lx mx
0
1.55
1.35
1.25
1.20
1.15
0
0.63
0.23
0.10
0.03
0.01
Reduce survivorship of 1 year old squirrels to about 1/2 the
original value and establish a new age distribution.
How to establish a squirrel preserve?
X
0-1
1-2
2-3
3-4
4-5
5-6
lx
1.00
0.410
0.172
0.076
0.027
0.006
mx
lx mx
0
1.55
1.35
1.25
1.20
1.15
0
0.63
0.23
0.10
0.03
0.01
Ro= 1.00
Reduce survivorship of 1 year old squirrels to about 1/2 the
original value and establish a new age distribution.
Managing Populations Within
Reserves: A Case Study
• The Nature Conservancy in
Scotland purchased an
overgrazed isle with the goal of
restoring the vegetation. The
sheep were removed and the
red deer population was hunted
to remove 1/6 of adults after
each spring census.
• Is the level of Hunting:
1) high enough to prevent
overgrazing by deer?
or
2) too high so as to result in
extinction of red deer?
Managing A Red Deer Population
• Recall that we found out that knowing
something about the demography of a
population would allow one to predict if the
population was growing, declining or more or
less stationary.
• Records of survivorship and reproduction
should allow us to answer these questions.
• Survivorship of a cohort of female red deer
and age specific births for the herd gave the
following results:
Demography of the Red Deer Population
X
0
1
2
3
4
5
6
7
8
lx
1.00
1.00
0.94
0.75
0.50
0.31
0.19
0.14
0.03
mx
0
0
0.3
0.3
0.3
0.3
0.4
0.3
0.7
lx mx
0
0
0.282
0.225
0.150
0.093
0.076
0.042
0.021
X
0
1
2
3
4
5
6
7
8
lx
1.00
1.00
0.94
0.75
0.50
0.31
0.19
0.14
0.03
mx
0
0
0.3
0.3
0.3
0.3
0.4
0.3
0.7
lx mx
0
0
0.282
0.225
0.150
0.093
0.076
0.042
0.021
Ro = 0.889
Demography of the Red Deer Population
• With Ro = 0.889, harvesting deer at this
rate will result in a slow decline of the
population. If allowed for a long period of time
the vegetation will do fine, but eventually the
red deer population would go locally extinct.
• Thus hunting will have to be decreased
slightly. One way would be to restrict hunting
to those females over 3 years old and harvest
1/6 of the population over that age.
Managing Populations Without
Over Harvesting Is A Challenge
• Humans still harvest ocean populations of
fish. Many of these fish stocks have been
over fishes.
• By applying sound principles of ecological
management it should be possible to fish
for many generations.
• Remember harvesting is OK if Ro > 1.00.
How Not To Over Harvest Is The
Question? But What Is The Answer?
X
0
1
2
3
4
5
6
7
8
lx
1.00
0.40
0.20
0.20
0.20
0.20
0.20
0.20
0.15
mx
0
0
0
1
1
1
3
2
1
lx mx
0
0
0
0.20
0.20
0.20
0.60
0.40
0.15
Harvest The Oldest 3 Age Classes?
X
0
1
2
3
4
5
6
7
8
lx
1.00
0.40
0.20
0.20
0.20
0.20
mx
0
0
0
1
1
1
Ro = 0.60 Population declines
lx mx
0
0
0
0.20
0.20
0.20
Harvest 1/2 Of The 3 Oldest Age Classes?
X
lx
mx
lx mx
0
1
2
3
4
5
6
7
8
1.00
0.40
0.20
0.20
0.20
0.20
0.10
0.05
0.02
0
0
0
1
1
1
3
2
1
0
0
0
0.20
0.20
0.20
0.30
0.10
0.02
Ro = 1.02 Population stationary; harvest for all time.
Sound Management Practices
For Natural Populations
• In managing natural populations it is
important to understand basic principles
of demography, control potential
competitors or predators or pathogens
and monitor population dynamics.
• Also, recognize that small populations
are particularly vulnerable to
environmental changes.
Population Viability Analysis
• This is a model that estimates the
likelihood that a population will avoid
extinction for a given period of time.
• Freeman (2005, page 1210) describes
how it was used to manage an
endangered marsupial population in
Australia.
Population Viability Analysis
For An Elephant Population
A population viability
analysis was
conducted to
answer the
question:
How Large Should
An Elephant
Reserve Be?
How Large Should An
Elephant Reserve Be?
Assumptions:
1) Survivorship in normal years is known
and can be estimated for 3 drought
regimes.
2) 2) Age to first reproduction and calving
interval is density dependent.
3) 3) Extinction occurs when N = 0 or N
is all the same sex.
Female Survivorship in
Normal Years
Results: Lifespan is
around 60
years.Substantial
“infant” mortality until
large enough to avoid
most predators
(approximately 5 years).
Type II survivorship up
to about age 45 then
rate increases.
Projected Population Growth
in Normal Years
Results: Starting off
with 11 males and
11 females with an r
= 0.03 and living in
an area of 4,000
square miles, the
population leveled
off at around 12,500
individuals in about
625 years.
Probability of Extinction
Results:
1) If the reserve is 20 square mile the
probability of extinction is 1 after only 250
years.
2) If the reserve is 200 square miles the
probability of extinction is 0.1 after only 700
years.
3) If the reserve is 1,000 square miles the
probably of extinction is 0.005 after 1,000
years.
How Large Should An
Elephant Reserve Be?
Conclusion: At a maximum population
growth rate of 3% per year and a
density of 3.1 elephants per square
mile, a minimum reserve size of 1,000
square miles is necessary for a 99%
probability of persistence for 1,000
years.
ILLINOIS IS THE PRAIRIE STATE
• At the time of
settlement, Illinois was
dominated by grassland
(prairie) communities.
• With the invention of the
mold-board plow by
John Deer, a resident of
Illinois, prairie was
rapidly converted to
farm field.
• Today, less than 1/10 of
1% remains today.
Nature Preserves In Northern
Illinois
• The Chicago Region has a rich heritage of
nature preserves.
• The so called “Chicago Wilderness” occupies
about 225,000 acres.
• It includes around 106 nature preserves.
• One can find out more about them by visiting:
http://dnr.state.il.us/INPC/area2.htm
• Two of particular interest are Woodworth
Prairie and Wolf Road Prairie.
COOK COUNTY FOREST
PRESERVE
The Cook County Forest
Preserve District consists of
67,000 acres (11% of
county) acquired “for the
purpose of protecting and
preserving the flora, fauna
and scenic beauties within
such district, and to restore,
restock, protect and preserve
the natural forests and such
lands together with their flora
and fauna, as nearly as may
be, in their natural state and
condition.”
WOLF ROAD NATURE
PRESERVE
• This 80 acre preserve is
combination of three
native community types:
prairie, savanna, and
wetlands.
• It was too wet to plow or
graze extensively and
has survived as the
largest black-soil prairie
east of the Mississippi.
Plant Species at Wolf Road
Prairie
• These are less than 1%
of the native plant
species reported to live
at Wolf Road Prairie
(327 species).
• An online tour of WRP
is available by visiting:
http://www.savetheprairi
esociety.org/
LIFE HISTORY AND HARVESTING
READINGS:
FREEMAN, 2005
Chapter 52
Pages 1206-1213
Chapter 54
Pages 1277-1283