Predator prey relationships
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Predator-Prey Relationships. What are Predators?. What are predators?. Carnivory Herbivory (plants vs. seeds) Cannibalism Parasitism. Human Attitudes and Predators. Humans perspectives Human persecution. OVERCOMING HISTORY. Fairy Tales: “Little Red Riding Hood”

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Predator-Prey Relationships

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Predator-Prey Relationships

What are Predators?


What are predators?

  • Carnivory

  • Herbivory (plants vs. seeds)

  • Cannibalism

  • Parasitism


Human Attitudes and Predators

  • Humans perspectives

  • Human persecution


OVERCOMING HISTORY

  • Fairy Tales: “Little Red Riding Hood”

  • “ The Three Little Pigs”

  • Wolf attacks on humans


OVERCOMING HISTORY

  • Old attitudes die hard

  • Urban residents and predators


Predation in Natural Communities

  • Almost all animals have significant predators- exceptions are:

  • Herbivores:Top predators:

  • Bison Grizzly

  • Elephant Lions

  • Rhinos Polar bear

  • Hippos Killer Whale


Predation in Natural Communities

  • Do predators regulate prey populations?

  • Ecosystems and predator communities


Major predators of the Arctic NWR

Wolf

Polar Bear

Grizzly

Ermine

Arctic fox

Snowy Owl


Predator-Prey RelationshipsResponse to Prey

1. Functional Response

Tendency of the predator to eat more of a prey species as the prey become more abundant


Predator-Prey RelationshipsFunctional Response


Predator-Prey RelationshipsResponse to Prey

Numerical Response

Number of predators increases with an increase in the density of prey animals


Predator-Prey RelationshipsNumerical Response(Buckner and Turnock 1965)


Annual cycle of a prey population

100

Energy shortages

Energy shortages

Accidents

Disease

Accidents

Predation

Percentage of Population

Disease

Predation

J F M A M J J A S O N D


Population Cycles

Snowshoe hare

Lynx

No. in thousands

Years


Muskrat and Mink

Paul Errington’s Classic study of muskrat populations


Muskrat info

Habitat: wetlands, especially marshes

Food: marsh vegetation

Predators: mink, coyotes, great horned owls

eagles


Muskrat and predation

  • Observations:

    • Predation and population size

    • Predation and individual vulnerability


Muskrat Behavior

  • Population size and social intolerance

  • Population size and social outcasts


Muskrat and Mink interactions:Conclusions

  • Social interactions may be more important than predation in limiting numbers of prey.

  • The total effect of predation cannot be assessed simply by counting the number of animals killed by predators (selectivity)


Isle Royale

  • Size: 45 miles long x 9 miles wide

  • Protection: National Park established in 1940

    Wilderness designation in 1976

    National Biosphere Reserve 1980

  • A location of a long term study of the relationships between the moose and gray wolf


Historically, two large ungulates occupied Isle Royale:

Woodland CaribouMoose


Caribou Population

  • Settlers arrived in late 19th century

  • Hunted caribou

  • Responsible for fire, and forest cutting

    Fires resulted in changing old-growth coniferous forests to younger deciduous forests

    Caribou became extinct on the island


Moose History

  • Fires resulted in changing old-growth forests to younger forests

  • Around 1910, moose came across the ice from Minnesota and became established

  • Moose outcompeted woodland caribou; island was better habitat for the moose after fires (early succession, deciduous trees)


Wolfe Population

  • Winter 1949, gray wolf arrives by crossing ice from mainland


Current Populations on Isle Royale

Winter 2000-2001

Moose850

Wolf 29


Present Wolf Population on Isle Royale

The wolf population is now divided into 2 territories, rather than the 3 that have been present for some time:

West Pack: gone

Middle Pack: 12

East Pack: 10

Roaming animals: 5-7


Food Chain

Wolf

Moose Small rodents Beaver

Grouse berries

Vegetation


Wolf Response to Moose

  • Functional Response: lots of moose,

  • Possible because wolfs are cooperative hunters


Wolf Response to Moose

  • Numerical Response: lots of moose,

  • wolves reproduce well

  • Immigration is unlikely since it depends on Lake Superior freezing.


Moose Response to the Wolf

  • Wary; formidable prey

  • Moose in good condition can withstand an attack by a wolf pack.

  • Can’t turn and run: wolf can sever back leg tendon which renders the moose helpless.


Moose Response to the Wolf

  • most vulnerable moose are the very young and the old (infirm)

  • most killed moose show signs of malnutrition and disease (i.e. they are more vulnerable)

  • Males most vulnerable: go into winter in relatively poor shape because of rut


Wolf Population

Three major factors that control the wolf

population:

1. Moose numbers

2. Linear dominance hierarchy in

wolf population

3. Genetic diversity (inbreeding effects)


For more Information

www.admin.intu.edu/urel/PressRelease/feature/wolves/wolf.

Html

www.timberwolfinformation.org/programs/awp/awpi/Isle.htm

http://midwest.fws.gov/wolf/proposal/nr_71100.htm

Or simply type in key words: “wolf”,

“timber wolf”, or “Isle Royale”


How Does The Prey Fight Back


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