#10 Habitat Selection IV

What are 2 types of models used in ecology, especially in habitat selection studies?

• RSPF = Resource Selection Probability Function

• RSF = Resource Selection Function

RSPFs

estimates the actual probability of selecting a resource or habitat type

• Generate an idea of the probability a certain area will be used in a certain time-frame

What does RSPFs do?

• Randomly/systematically sample points across a habitat of interest

• Record presence/absence (or whatever qualifies as ‘use’ in your study)

What do RSPFs usually require

random sampling of available points and design-based sampling assumptions

What is the main thing about RSPFs?

wants to offer a specific number that this resource has a certain likelihood of use

When would you use a RSPFs?

• You have data on used vs. available habitat

• You want to model relative selection

• You don't have strong sampling control

Which function is this?

RSPF

RSF

a model that estimates the relative probability that an animal will use a certain habitat or resource based on its characteristics

What function do you use when asked this question: Given what's available, which resources or habitat features does the animal prefer to use more often?

RSFs

What is the first step in a RSF?

Collect known use points (usually through prior survey), then randomly or systematically sample all available habitat

• Sites of known use/occupancy

What is the second step in a RSF?

• background availability

  • availability across the whole landscape

• Compare use vs availability

• Creates an index of relative selection

  • What appears preferable/avoidable

What is the main thing about RSFs?

• Want to say

  • These animals appear to select for these habitats and avoid these ones

• Relative signals and selection preferences

When do you use an RSF?

• You have a rigorous sampling design

• You want to estimate actual probabilities

• You're doing management or conservation planning that needs real use probabilities

Which of the two functions is a more common approach?

RSFs

Which model does this represent the most?

RSF

Why is behavioral considerations important?

In addition to “state”, behavioral decision making plays a role in habitat selection

• Habitat selection is not always just a question of finding the fundamentally ‘best’ habitat and going there

  • More useful to look at behavioral side of things and not habitat

  • Best might not always be the one to select

What 3 ways can behavioral habitat preferences arise in?

• “Innate”; genetic, heritable

• Imprinted

• Learned

Heritable/innate preferences (hard-coded genetically)

Solid consistent preferences regardless of preferences and other factors

• Natural selection will favor a more reliable cue => more advantageous to always go for the cue

• selection regardless of experiences

• Often strongly related to proximate cues

Imprinted preferences

Preference becomes set, often at a critical period

• Juvenile stage when they learn certain habitat preferences and then they become hardcoded afterwards

• Less flexible to change preference

Learned preferences (flexible)

Learn habitat preferences from conspecifics

• Often parents to offspring

• More common in species with high offspring investment

  • Bigger brain = more flexible in preference

What can Learned preferences (flexible) also be from?

• self or non-relatives

  • Other individuals will watch others to see if that action is preferable

• High parental care

  • More learned preferences

    • Share habitat preferences

How can Conspecifics of social groups be good?

• Use to look for good social opportunities

• Mating opportunities

• Potential resources

• Many eyes/dilution effects

• Information sharing

How can Conspecifics of social groups be bad?

• Intraspecies competition 

  • for food/ mates

• Territoriality 

  • Monopoly on the territory 

• Disease 

• Attract predators

• Cannibalism

• Near-complete niche overlap

What is a general rule for how Conspecifics of social groups can be bad?

the more vulnerable you are (ex: prey species), the more likely you are to be attracted to conspecifics!

• Predators might not benefit from conspecifics 

  • Avoid factor

What are the 2 types of distribution to assess quality?

• IFD→ Ideal Free Distribution

• IDD→ Ideal despotic distribution

Ideal Free Distribution

How animal density relates to the quality of the habitat

• Occupy the best habitat until it becomes so crowded that the next best habitat is better

What happens when a habitat becomes overcrowded?

Animals will “ideally” distribute themselves proportionately across habitats of different quality so that individual fitness is equal

What is the idea about habitat selection that Fretwell and Lucas came up with?

• when you switch habitat it relates to the relative quality and relationship between density and individual benefit

  • When the individual benefit equalizes with the benefit of the second habitat, they will switch, and so on

What happens when the distribution between two habitats is equal?

both habitats equal out with the amount of benefit per individual→ amount of individuals in their habitat will balance out

• Animals will distribute themselves proportionally to the quality of habitat

What are the rules about Ideal Free Distribution?

• Some variation in habitat quality

• Animals always act to maximize fitness (“optimality”)

What are some Assumptions about Ideal Free Distribution?

• Scramble/exploitation competition only 

• Animals have complete knowledge of all available habitats (ideal)

• All habitats equally accessible, free dispersal

• Increasing density is negatively related with fitness

What is the assumption about Scramble/exploitation competition only?

• Assuming no animals are being territorial 

• They are equaly capable they can all scrabble for the resources

What are some Predictions about Ideal Free Distribution?

• When habitats are full, fitness of individuals is equal in all habitats

  • Regardless of quality

• Habitats with the highest densities have highest fundamental/inherent habitat quality

  • Hold the most animals

Is every competitor equal?

No

• Monopolize limited resources

• Exclude competitors

• “Ideal Despotic” distribution

“Ideal Despotic” distribution

Actively exclude competitors from coming in and destroying your good habitat

What are the rules for Ideal despotic distribution?

• Some variation in habitat quality

• Animals always act to maximize fitness

What are the assumptions for Ideal despotic distribution?

• Animals have complete knowledge of all habitats (ideal)

• Behaviorally dominant individuals secure resources via interference competition (despots)

• Increasing conspecific density is negatively correlated with fitness

• Subordinates pay disproportionate costs for competing with despots

What does the Ideal despotic distribution do instead of Scramble/exploitation competition?

Behaviorally dominant individuals will push out other competitors

• instead of scramble

What are the predictions for Ideal despotic distribution?

• Fitness of individuals is unequal in all habitats

• Density not always correlated with habitat quality/fitness

  • Strongest occurs in the best quality habitat only

  • monopolize the habitat

Why does Ideal despotic distribution have the assumption that fitness of individuals is unequal in all habitats?

dominant individuals who settle in habitats with the highest fundamental quality→ obtain highest fitness

How can we use IFD/IDD to assess quality?

• IFD: Best habitats have the highest densities of individuals

• IDD: Best habitats have the most dominant individuals

What is one way to test how IFD and IDD assess quality?

• Removal experiments

  • Remove some individuals (or alter patch profitability) and observe response in distribution

  • Test where individuals are removed to study redistribution

What are some factors that affect IFD/IDD?

• Scale

• heterospecifics

• Juvenile dispersal

• Sex-biased dispersal

What is the order in which habitats are colonized by newly-arriving individuals?

• True novel colonization

• Returning migrants

• Dispersers

True novel colonizers

first to occupy a new area

Returning migrants

come back to previous breeding sites

Dispersers

move from natal or previous territories to new areas

Intraguild Predation

Predation between competing species that use similar resources

What example shows animals avoiding areas due to intraguild predation?

Eurasian Pygmy Owls avoid nesting near Boreal Owls—a larger, competing species

• showing how intraguild predation affects distribution

How can scale influence habitat selection patterns?

distribution mechanisms differ across spatial scales

• larger scales (e.g., home range), animals may follow IFD patterns.

• At smaller scales (e.g., microhabitats within home ranges), competition may create despotic patterns (IDD)

Can heterospecifics (different species) influence habitat selection?

Yes

• Some species are more likely to co-occur even after controlling for habitat characteristics

• This suggests positive attraction (e.g., for safety, resource cues, etc.).

Juvenile dispersal

Disperse from natal site to avoid being outcompeted by older, more-established conspecifics

• Also avoids inbreeding and competition with close relatives

What is Sex-biased dispersal?

occurs when one sex disperses more frequently than the other

• varies depending on whether mate competition or resource competition most limits fitness

What are some other factors that affect IFD/IDD?

• Risk (predation)

• Disease/parasitism

• Sampling and cognitive ability

• Reliability and stability of habitat cues

• Habitat selection is COMPLEX!