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Imperiled Populations II. 10 Sept 2009. Pacific Walrus - under review for ESA listing -. Pacific Walrus - under review for ESA listing -. What would you do?. Pinchot. Muir. Leopold. Demographic Stochasticity.

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Imperiled Populations II

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Imperiled Populations II

10 Sept 2009


Pacific Walrus- under review for ESA listing -


Pacific Walrus- under review for ESA listing -

What would you do?

Pinchot

Muir

Leopold


Demographic Stochasticity

Random fluctuations in demographic parameters (birth & death rate, immigration & emigration rate, sex ratios, or age structure).

Allee effects become increasingly problematic at small population sizes:

probability of encountering mates

communal mating activity

cooperative/group defense & hunting success

communal insulation & nesting


Environmental Stochasticity

Fluctuations in reproduction and survival due to:

Habitat alterations

Increased interspecific pressure

Competition

Predation

Parasitism

Disease

Natural disasters


Black stilts lay eggs in river bed gravels. Increasing frequency of flooding, due to rapid glacial melt, causes high egg mortality.


Environmental Stochasticity

Fluctuations in reproduction and survival due to:

Habitat alterations

Increased interspecific pressure

Competition

Predation

Disease

Natural disasters


Competitive interactions between trout are influenced by water temperature.

Come and get it!

!#@?


Environmental Stochasticity

Fluctuations in reproduction and survival due to:

Habitat alterations

Increased interspecific pressure

Competition

Predation

Disease

Natural disasters


Tropical frogs are highly vulnerable to chytridiomycosis. Chytrid fungus thrives within cloud forests. Climate change drives cloud formation at higher elevations.


Environmental Stochasticity

Fluctuations in reproduction and survival due to:

Habitat alterations

Increased interspecific pressure

Competition

Predation

Disease

Natural disasters


How do you plan for these demographic and environmental uncertainties?


Population Viability Analysis (PVA)

  • A mathematical modeling procedure used to determine whether a population is likely to become extinct within a given time frame.


Population Growth Equation

Nt+1 = Nt + B - D + I - E

Where:

B = birth rate

D = death rate

I = immigration rate

E = emigration rate

t = current time interval (e.g. this year)

t+1 = next time interval (e.g. next year)


Population Viability Analysis

Deterministic Models

Variables

Model Output

Initial N = 500

Nt+1 = Nt + B - D + I - E

Birth rate = 60 / yr

Death rate = 60 / yr

Probability of extinction within next 100 years:

~0%

Immigration = 20 / yr

Emigration = 20 / yr


Doctors say that Nordberg has a 50 - 50 chance of living. . . though there's only a 10 percent chance of that.


Population Viability Analysis

Stochastic Models

Probability Distribution

Model Output

Variables

Initial N = 500

How often does the population survive:

10 yrs

50 yrs

100 yrs

etc. . .

Birth rate = ?


Probability Distributions

6

Number of possibilities

0

2 3 4 5 6 7 8 9 10 11 12

Combination


Probability Distributions- Deaths by age in the U.S. -

% of deaths

Age


Population Viability Analysis- deterministic vs. stochastic models -

Stochastic Model

Probability Distribution

Model Output

Variables

(many repetitions)

Initial N = 500

How often does the population survive:

10 yrs

50 yrs

100 yrs

etc. . .

Birth rate = ?

Death rate = ?

Fires, etc. = ?


PVA in action- the Northern Spotted Owl -

Video A

Video B


PVA in action- the Northern Spotted Owl -

Population Size

birth rate

death rate

emigration

immigration

barred owls

West Nile V.

logging

fires

nest predation


PVA in action- the Northern Spotted Owl -

Suitable habitat (33 grey hexes) is randomly scattered.


PVA in action- the Northern Spotted Owl -

Suitable habitat (33 grey hexes) is clustered in a single location.


PVA in action- the Northern Spotted Owl -

Suitable habitat clusters surrounded by marginal habitat


www.vortex9.org/vortex.html


Minimum Viable Population (MVP)

The smallest population size that can be predicted to have a very high chance of persisting for the foreseeable future.


PVA in Action- the Northern Spotted Owl -

Suitable habitat (33 grey hexes) is randomly scattered.


PVA in Action- the Northern Spotted Owl -

Suitable habitat clusters surrounded by marginal habitat


PVA & MVP can suggest how large populations should be.What if existing populations are too small?


Introductions / Reintroductions- Northern Rocky Mtn. Wolf -

Flashdance is the greatest movie ever!

(play video)


The Logistics of (Animal) Introductions/Reintroductions

  • Sufficient habitat

  • Sufficient food

  • Genetic diversity

  • Veterinary medicine

  • Social dynamics & learned behaviors

  • Long-term funding & political support


Wolves do kill. . .


. . . and cultural norms run deep


Ex-Situ Conservation- African Black Rhino -

(click)

(click)


Amphibians are dropping like flies

(click)


Ex-Situ Conservation- The Amphibian Ark -

ensuring the global survival of amphibians, focusing on those that cannot currently be safeguarded in nature


Ex-Situ Conservation- The Amphibian Ark -

ensuring the global survival of amphibians, focusing on those that cannot currently be safeguarded in nature

Amphibian Conservation Action Plan

(www.amphibianark.org/pdf/ACAP.pdf)


Reading Assignments

Read text p. 455-462.


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