LIFE HISTORY AND HARVESTING

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LIFE HISTORY AND HARVESTING

• READINGSFREEMAN, 2005
• Chapter 52Pages 1206-1213
• Chapter 54Pages 1277-1283

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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.

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WILDLIFE PROTECTION IN NATIONAL PARKS
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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.

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Larger Preserves Provide Greater Protection
Against Extinction

• 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.

Newmark, 1987
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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?

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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.

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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.

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A GRAY SQUIRREL POPULATION
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A GRAY SQUIRREL POPULATION
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What will happen if all squirrels 2 years and
older are harvested?
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What will happen if all squirrels 2 years and
older are harvested?
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What will happen if all squirrels 2 years and
older are harvested?
All the squirrels you can eat and more!!!!
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How to establish a squirrel preserve?
Reduce survivorship of 1 year old squirrels to
about 1/2 the original value and establish a new
age distribution.
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How to establish a squirrel preserve?
Reduce survivorship of 1 year old squirrels to
about 1/2 the original value and establish a new
age distribution.
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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?

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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

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Demography of the Red Deer Population
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Ro 0.889
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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.

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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.

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How Not To Over Harvest Is The Question? But What
Is The Answer?
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Harvest The Oldest 3 Age Classes?
Ro 0.60 Population declines
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Harvest 1/2 Of The 3 Oldest Age Classes?
Ro 1.02 Population stationary harvest for
all time.
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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.

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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.

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Population Viability Analysis For An Elephant
Population

• A population viability analysis was conducted to
  answer the question
• How Large Should An Elephant Reserve Be?

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How Large Should An Elephant Reserve Be?

• Assumptions
• Survivorship in normal years is known and can be
  estimated for 3 drought regimes.
• 2) Age to first reproduction and calving interval
  is density dependent.
• 3) Extinction occurs when N 0 or N is all the
  same sex.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.savetheprairiesociety.org/

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LIFE HISTORY AND HARVESTING

• READINGSFREEMAN, 2005
• Chapter 52Pages 1206-1213
• Chapter 54Pages 1277-1283