use of space - habitat selection behaviour

Important features in habitat Selection

• Food, water

• Breeding sites

• Hunting spots, shelter, refuges

• Terrain (elevation, bathymetry)

• structure (eg. vegetation, rocks)

• Previous experience

• Other animal- repel or attract

what are the two ways an association with a particular habitat can arise?

1. Through random dispersal and differential mobility (individuals that happen to end up in favourable habitats establish and reproduce, and those that don't, end up
   dying)

2. Through behavioural preference for places that are likely to enhance reproductive success and /or survival

what is a habitat?

Any part of the biosphere where a particular species can live, either temporarily or permanently

what is Habitat availability?

Accessibility and procorability of physical and biological components of a habitat by animals

What is habitat use

• the manner in which an animal uses the physical and biological resources in a habitat

• may be used for foraging, cover, mating, nesting, denning, or other life history traits

Habitat selection

Hierarchical process involving a series of innate and learned behavioural decisions made by an animal about what habitat it would use at different scales of the environment.

Active behavioural process by an animal as it searches for features within an environment to use.

habitat preference

• Consequence of habitat selection, choice resulting in the (disproportional) use of some resources over others.

when are habitat preferences most obvious?

Preferences are most strikingly observed when animals spend a high proportion of time in habitats that are not very abundant on the landscape.

Mechanisms of Active habitat preference

1. Individuals that use the habitats in which the most progeny can be raised successfully are favoured by natural selection (marginal habitats may not allow for more offspring)

2. Natural selection may act on a particular behaviour that chooses a habitat or it may act on the capacity to learn which habitat is appropriate for a given situation. (over time, selection will favour the behaviour that selects the successful habitat.)

does habitat preference have heritable genetic basis?

Choice experiments showed that both wild-caught and captive-bred birds actively prefer their native habitat when given a choice

• link between habitat behaviour and adaptive skills

• habitat preference shaped by learning and experience

What is Habitat suitability?

Suitability – an index of habitat quality (preferred, intermediate, poor)

suitability is equal to fitness

what is HSI?

Habitat Suitability Index represents the combined interactions of all species-habitat relationships. The output is a numerical index that scores the capacity of a habitat to support the selected species.

challenges in identifying a “suitable habitat”

We look at distribution of animals among habitats and try to infer what habitats are most important to our species of interest.

This allows us to compare use of habitat to availability of habitat (which is often defined as selection), but does not allow us to say ANYTHING about preference of habitat

Habitat use ≠ Habitat preference (or quality!)

• Habitat use may be passive

• Predators may have non-consumptive effects (ecology of fear)

• Movement characteristics influence availability

• Internal state can constrain accessibility

• Selection decisions can be maladaptive

• Competitive exclusion may force animals to settle in suboptimal habitat

using detailed behavioural study to understand habitat selection

• Understand the mechanism & functional adaptations that produce distributional patterns

• If all else is equal, is a certain habitat selected over another?

• Usually takes an integrated experimental approach – field, lab (choice experiments), simulation & statistical modelling

how does suitability change as a function of exploitation by other individuals?

• High-quality habitats are certain to be exploited first.

• This depletes resources or renders them inaccessible, but it may also increase the level of interface experienced by competing individuals.

• So what starts out as the best place to be may soon become no better than a site of previously lower quality.

• this is ideal free distribution

(1) Ideal Free Distribution models can be used for:

1. Predict how individuals should first settle into habitats

2. Predict the equilibrium frequency of individuals in different patches (8 in ‘good’, 5 in ‘poor’

Ideal free distribution assumptions:

• all individuals know the value of alternative patches.

• all individuals are free to move between patches.

• all individuals are equal competitors.

ideal free distribution outcomes

• a distribution in which all individuals have access to the same amount of resources, such that no individual would gain from switching location.

• at capacity (high density), the fitness for individuals settling in poor habitat should be equal to that of individuals in good habitat.

2) Ideal Free Distribution – Unequal Competitors (needs)

• Ideal free distributions of competitive abilities, rather than individuals.

• Number of competitive units, rather than number of individuals, is equalized across patches.

• payoff is still the same since matched to their requirements

(3) Ideal Despotic Distribution

Distribution is affected by some individuals which are competitively superior and can excludeother individuals from an area.

• Territorial / aggressive behaviours of already-established animals

• Behaviours force others to marginal habitats before the realized suitability of preferred habitat drops below the threshold level

• Density not necessarily lower in marginal habitats

• Predicts that fitness will be lower in the marginal habitats

Implications for Habitat Suitability Modelling

• If populations follow IFD (ideal free distribution), models may underestimate the importance of “poor habitats”

• If populations follow IDD (ideal despotic distribution), models may underestimate the importance of habitats with few individuals