Apples and oranges

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Apples and oranges
Final from here

• How can we take the findings from a domestic
  situation where a cat comes home to a bowl of
  food to
• A predator that has to hunt down its prey
  regardless of what species it is???
• Pumas dont normally kill adult cows, in New
  Mexico IF they do kill cattle it is the calves.

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Why the calves?

• Because ranchers find it more convenient to have
  cows give birth in the mountains!!!
• Again, the root of the problem is not the
  predator but how humans have changed the system!!

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One last word on subsidizing

• What ever happened to Buffer Species????
• Remember them?
• Suppose to take the pressure off of a less
  preferred species!
• Didnt fit our preconceived ideas so we changed
  it to subsidized, base on HOUSE CATS!!!

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What do we make of all this??

• Why then, do we see these effects sometimes but
  not others? Why do we see difference among
  areas.
• Is there something we are missing?
• What is being left out of all these models??
• Lets revisit some of these examples to see if we
  can find out more.

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Forty-mile herd in the Yukon

• 1920s-30s, gold miners/hunters killed tens of
  thousands Overhunting but should come back!
• What else? Second world war, Alaska highway and
  other roads were built. Change of habitat!

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Wildebeest of Kruger

• cropping again overhunting
• but before decline fires in the 1950s and 60s
  reduced woodland density.
• During 1970s Elephants kept woodland low
• 1980s poachers reduced elephants and woodland
  grew back. Habitat change

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Pumas and big horn sheep

• After all is said and done, they mention the
  encroachment of woody vegetation may increase
  hunting success of ambush predators like mountain
  lions.
• Admit that there has been a change in habitat
  characteristics.

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New one wolves/caribou/moose

• British Columbia Wolves feed on caribou, no
  moose historically.
• Moose came in since 1900s as a result of logging
  practices.
• Habitat change

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Birds

• habitat fragmentation for passserine birds
  breeding in deciduous forests of North America is
  thought to be the primary reason for the major
  decline in their populations.
• Predation rates are inversely related to forest
  patch size.
• Change in habitat

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Differences among areas

• Why do we see 20 fold difference across habitats
  that have
• predators?
• - Habitats are different

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The list goes on and on

• Important reoccurring points 1)Human
  disturbance
• The one example where human influence is the
  least (Isle Royale) we see a different system.

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Isle Royale

• 535 km2 50 wolves (93 wolves/1000 km2)
• 800 moose (1,495 moose/1000 km2)
• Other
• 56 wolves
• 1,495 moose
• Lowest
• Moose den
• Is 1,134!

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Compare that with this

• 93 wolves/1000 km2
• 1,495 moose/1000 km2
• Where would that
• point fall??
• Highest wolf/moose
• ratio ever!!
• Other 56 wolves

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What is going on??

• Yet this system has not collapsed!!!
• Actually quite stable (600-2400)
• Remember stable wildebeest population
  900,000-1,300,000!
• Obvious wolves have not devoured all their prey!
• This garden seems to be doing fine even with
  the weeds

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• What is different??
• Human influence minimal National Park
• What are we missing???
• What is being left out of the equations??
• What is the one thing we identify as being the
• most important in wildlife management??
• Habitat!!!

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Second commonality

• Not just human interference per se What are
  they disturbing/changing??
• In all cases either changed the habitat somehow
  or in the case of the caribou comparison, was
  comparing different habitats that had different
  densities.

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Have they totally left it out?

• Might be too harsh on reductionists
• K was meant to reflect what the habitat could
  support natural limit of a population set by
  resources in a particular environment.
• The Rosenzweig and MacArthur model tries to
  incorporate it somewhat. But just a varying K

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Population ecologists view of habitat
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Population ecologists view

• In this scheme, the important aspect of the
  environment or habitat is its sum or average, not
  its makeup or variance
• So, more ignored that climate is the actual
  playing field where predator-prey interactions
  are carried out!!
• Add that to this.

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Ecologists view of predation

• One ball killing another, the end!

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No wonder we have problems!

• By stripping off the behavior of animals and the
  variability of habitat, we may be able to get to
  the roots of scientific principles but they
  will be devoid of any realism.
• Thus producing the conflicting results we see and
  the extreme level of confusion

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What do we need to do?
here

• To try and make sense of all this we need to
  evaluate what role habitat plays in the predator
  prey relationship.
• We then have to see if this helps us explain more
  than what we can now.
• Hopefully this will give us a better
  understanding of the role of predator-prey
  relationships in ecosystems AND how to manage
  them!!.

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How does habitat make a difference

• Habitat is probably THE most important aspect of
  wildlife ecology and management but yet we often
  give it lip service only.
• So lets start with the basics.
• What is habitat?
• Suite of resources (food, shelter) and
  environmental conditions (abiotic and biotic)
  that determine the presence, survival, and
  reproduction of a population.

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Base problem

• One of the basic problems is in the definition
• Suite of resources..
• Talks about sum and total, not its makeup, often
  assume uniformity.
• Habitat in an area is not uniform so we need to
  look at the makeup of the habitat and the
  juxtaposition of its elements.

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Landscape view

• Need to look at habitat on a landscape level.
• Landscape ecology does this and is where the
  composition of habitat elements become important.
• No time for landscape course but will look at
  elements that are important regarding
  predator-prey.

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First off, prey

• Had said that patch characteristics, quality,
  size, shape, location were important in adaptive
  foraging strategies.
• Here we are equating patch to landscape element.
• Also mentioned that predation risk was considered
  relative to patch use.
• Would only consider it IF it differed among
  patches

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So basics

• Landscape elements or patches vary across home
  range of an animal.
• Vary in forage quality, predation risk, and use
  for missed opportunity activities.

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So habitat looks not like this but more like
this
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• Each patch has its own characteristics
• AND the composition of these patches CHANGES from
  home range to home range and on a larger scale!

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Result?

• Result of this is that indeed each animal faces
  different possibilities and limitations on how it
  can use its home range.
• On a larger scale, whole populations face
  different combinations.
• Obviously affects foraging strategies but can
  also affect population dynamics.

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Simplest

• Size and number of food resource patches gives us
  those different values of K that give us so much
  trouble.
• But they also affect the predator-prey
  relationships
• No wonder we get different results.
• Like doing parallel experiments under totally
  different conditions one green house in the sun
  and other in the shade!

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Habitat differences make a difference!!

• To understand how habitat makes a difference in
  predator prey relations, we need to first
• Look at the predators landscape.

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A predator and its landscape

• Predator also has to look for food found in
  resource patches
• However, unlike herbivores, food moves AND does
  not like to be eaten!
• So, as we saw earlier, need to incorporate not
  just abundance or availability of prey but their
  catchability.
• This varies across habitat types!!

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Need to talk about lethality

• So unlike prey where how much you eat depends on
  how fast you can bite and chew or how rich the
  food patch is, a predator has to be able to catch
  its food.
• Predator lethality basically how efficient it is
  in catching a prey. If your good, your lethal,
  if not.
• What is predator efficiency?

Here
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Predator efficiency

• Definition successful captures/total attempts
• Difficult to quantify in the wild
• Rarely ranges over 30
• Average probably around 20
• Is quite variable

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Reasons for variability?

• Health of prey
• Young, sick, and old more vulnerable so hunting
  efficiency would be higher for these groups
• Mid-aged healthy prey can defend themselves
• But their ability to do so varies with habitat

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Habitat and predator efficiency

• Each predator has strengths/weaknesses
• Wolves Adapted to run prey down, attack from
  behind.

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A moose in trouble!

• Go to video

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Cougars and deer

• Cougars stalk their prey.
• Need to get within 20-25 meters to have a chance.
• Need cover

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Cougars and deer

• Cougars are predators of the forest and edge!
• More than 70 of the time
• in one or the other.

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• And they are successful!

75
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Patch quality for predator

• So high quality patches for predators are ones
  where they have a good chance of making a kill.
• How important is this to the predator?
• Presentation on edge effects

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The landscape of opportunity

• So through the eyes of the predator, the
  landscape is one of a mixture of successful and
  less successful patches.

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Return to our habitat patches

• Now each has a success value to it for predator.
  Based on
• lethality of
• predator.

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How about the prey?

• It is within this framework of predator lethality
  that the prey must make their foraging decisions!
• So. Becomes not as simple as selecting the patch
  with the highest food resources.
• Need to balance food resources and predation
  risk.

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Which is more important?

• In the past, placed most (if not all) emphasis on
  resource levels (remember K again).
• How long does it take to starve?
• How long does it take to get killed by a
  predator?
• Food is important but not if your dead!

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Predation risk
here

• So the risk of being killed (predation risk)
  becomes overlying factor in how a prey will use
  the habitat.
• What are its options?
• 1) use dangerous areas less/safe ones more
• 2) If you have to go, spend little time/use
  vigilance to offset dangers/reduces feeding
  efficiency

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Two principle lines of investigation

1. Changes in habitat
2. Changes in the amount of vigilance.

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Where risk is low - Use all parts of habitat
Where risk is high - Use the most secure
areas
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2. Changes in Behavior. -Time foraging vs
surveying.
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Where risk is low - eat more and survey less.
Where the risk is high - survey more and eat
less.
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Since the 1980s lots of studies
Mech, L.D. 1977. Wolf-pack buffer zones as prey
reservoirs. Science 198320-321.
Edwards, J. 1983. Diet shifts in moose due to
predator avoidance. Oecologia 60185-189.
Stephens, P.W. and R.O. Peterson. 1984.
Wolf-avoidence strategies of moose. Holarctic
Ecology 7239-244.
Scrimegeour G.J. and J.M. Culp. 1994. Foraging
and evading predators the effect of
predator species on a behavioural trade-off by a
lotic mayfly. Oikos 6971-79.
Hunter, L.T.B. and J.D. Skinner. 1998.
Vigilance behaviour in African ungulates the
role of predation pressure. Behaviour.
135195-211.
And more.
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All indicate that the prey are adjusting their
behavior because of the risk of predation.
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So what do we have?

• Predator that has varying lethality
• Prey that responds to this by avoiding high
  risk/lethal areas

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All this made us think of what might be the
basic force to explain these reactions of prey
to their predators.
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Fear of predation changes how they use the
landscape
as they move about the landscape to reduce
predation risk.
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Thus a landscape of physical features
Or
is seen through their eyes as a landscape of
differing levels of risk or fear
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A Landscape of Fear
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We chose the concept of fear because. We
know it is an emotion that exists on the intra
specific level (complement agression!).
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If a subordinate animal can show fear of its
superior.
Imagine what its emotion would be when faced with
a predator that is going to kill it!
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Flip side of landscape of Opportunity

• So predators look at landscape relative to
  opportunities
• Prey look at it relative to fear!
• Evidence that prey respond to this use safe
  areas more than risky one.
• Lets return to the predator

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What should a predator do?

• Conventional wisdom predator should hunt where
  there is the most prey.
• Landscape of fear/opportunity why should
  predator hunt were it is the most difficult to
  catch its prey?
• Maybe conventional wisdom is not so wise??

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Add the two together

• How should predator and prey concurrently use
  habitat?

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Space use race

• Andy Sih in the 1980s proposed the concept of a
  behavioral response race.
• Prey should avoid predators and if can, will be
  more prevalent where there are low predator .
• Landscape of fear model predicts the same.

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Predator?

• Behavioral space race predicts predator should
  actually hunt where there are less prey!
• Landscape of fear/opportunity predicts the same.

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So what do we have?

• Two player game prey trying not to be eaten
• Predator trying to eat!
• We should see a separation of the two over the
  landscape, prey using safer areas more, predators
  using areas of less prey but where they are more
  lethal.
• Evidence for this?
• presentation

here
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Summary
here

• Habitat MAKES a difference!
• Non-lethal effects may be more important to
  wildlife management than lethal ones.
• May be able to manage impact of predation via
  habitat.
• Landscape of fear/opportunity may be the most
  valuable management tool in management AND
  conservation.
• Example?? Go to sheep presentation