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I.C. Behavioral Ecology. Definition: How an individual animal’s behavior interacts with its environment to affect its survival and reproduction. Foraging ecology (also falls under physiological ecology, e.g., energy acquisition) Territoriality Mating systems.

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I.C. Behavioral Ecology

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I c behavioral ecology l.jpg

I.C. Behavioral Ecology

  • Definition: How an individual animal’s behavior interacts with its environment to affect its survival and reproduction.

  • Foraging ecology (also falls under physiological ecology, e.g., energy acquisition)

  • Territoriality

  • Mating systems


More behavioral ecology use of space l.jpg

More behavioral ecology: use of space

  • Home range: everywhere an animal goes during some time period to meet all of its needs (food, water, shelter, mates, nest sites, etc.)

  • Time period can be whatever is of interest to the ecologist: daily, seasonally, yearly


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Home Range northern water snake

Nerodia sipedon


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Home range size v. body size (more)

Smaller animals can travel over more of their home range in one day compared to larger animals.

Linear measure of distance


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Home range size in primates

Something to do with scaling and energy requirements


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Home range size, by trophic level

Predicted

Observed:

Terrestrial herbivores (mammals)

Terrestrial carnivores (mammals)

Terrestrial carnivores (birds)

Higher trophic level needs more space, why?

Haskell et al. 2002


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Home range size v body size

  • Haskell et al. 2002 study:

  • Home range size scaling depends on:

    • not only body size ~ energetic demand scaling (not sufficient to predict scaling exponents

    • but also fragmentation of resources at larger spatial scales

  • Larger animals and higher trophic levels more susceptible to human habitat fragmentation


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Home range & territories -- sand wasp

Microbembex

cubana

Feeding on nectar

Nests, defense of nest sites by both males and females


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Home range vs Territory

  • Territory: that part of an animal’s home range that is defended;

  • Defense: costly to the territory holder (energy to chase, risk of injury, risk of attracting predators).

  • Why defend if there is a cost?

  • BENEFIT: the territory contains something valuable that is defensible.


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Territoriality

  • Behavioral ecology of territories is related to foraging, because most territories are defended for the food that they contain.

  • Benefits that are most often defended:

  • Food or other resources (nest sites)

  • Mates (attracted to food or other resources


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Benefits of territories (fish example)

Foraging

Mating

Offspring survival

Territory holder survival

Escaping predators


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Benefits of territories (fish example)

Benefits of territories compared to no territories

  • Foraging

Biomass, productivity higher; Feeding rate higher

  • Mating

More reproduction and more successful reproduction

  • Offspring survival

More offspring survived in territories, with guarding parent

  • Territory holder survival

  • Escaping predators

Shelter holes limited, survival increased in territories


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Costs of territoriality (fish example)

Time

Energy

Injury

Opportunity

(other costs than time)


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Costs of territoriality (fish example)

Costs of territories compared to no territories

  • Time

More time spent fighting

  • Energy

Lower liver glycogen; fighting activities use more energy than non-fighting activities

  • Injury

More injuries to fins and scales in territory holders

  • Opportunity (other costs than time)

Territory holders lost weight during defense


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Cost of territoriality --salamander example


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Evidence of territories

  • Defense: you can observe defensive behaviors: fighting, chasing, marking, displaying

  • Spacing: when animals defend territories they create space around themselves.

When animals are defending and competing for space, they become evenly dispersed in the environment.


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Goldeneye Bucephala cangula territories


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Gannet Territories

Gannet, seabirds nest on rocky cliffs on sea coasts

See gannet colony movie on the EVE 101 web site


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Spatial dispersion patterns Fig. 9.10 p. 217

Spaced =

Regular

Clumped

Random

Clumped resources or benefit to togetherness

No interactions among individuals

Competition?


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Redwinged Blackbirds

A male Red-winged Blackbird displaying on his breeding territory in a marsh

Red-winged blackbird territorial song


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Benefits of defense: exclusive access to resources or mates

Female red-winged blackbird

Nest of red-winged blackbird

Good nest sites that attract females to the territory


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Predicting territories

  • Ecology is a science, so behavioral ecologists seek to form hypotheses and make predictions, that they then test with data.

  • The “no free lunch” principle more formally stated states that a behavioral trait will evolve if the benefits outweigh the costs--and there are always costs.


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Optimal territory size

  • A simple model says that:

  • Benefits increase with the size of a territory;

  • Cost of defense also increases with the size of a territory;

  • Animals should defend exactly that size of territory where the NET benefits are maximum.


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Benefit (can’t use it all)

T2

Cost or Benefit

T*

T1

cost

Territory Size

Optimal territory size

Prediction: this “optimal” size is the predicted size of territories in the real world, given these costs and benefits.

Costs exceed benefits here

Net benefits are maximum here

= optimal territory size

A simple economic model


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Optimal territory size -- Predictions

Rich

Poor

Costs or benefits

  • PREDICTION: Richer territories should be smaller

Size at which costs exceed benefits

Territory size


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Test of optimal territory size:Sceloporus lizards

Territory size (m2)

When food is added to a territory experimentally, the territory holder adjusts the size of the area defended. Why?

Males have bigger territories than females for a given prey abundance: Why?

Prey abundance


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Test of optimal territory size:Coral reef fish

Territory size (cm2) =

Distance an intruder is chased

Food abundance


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Territories can contain mates


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Mating systems

  • Definition: The study of the behavior, physiology and morphology related to how mates are chosen;

  • The study of how such mating “systems” could evolve;

  • Principle = those characteristics enhancing an individual’s fitness will be more common in the next generation

  • Mating systems depend more on the ecological setting than on the organism’s evolutionary history


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Sexual reproduction

  • Sexual reproduction evolved with the first eukaryotes;

  • “Anisogamy” = gametes (n, haploid) are different from each other;

  • Microgamete: small--many = MALE

  • Macrogamete: large--few = FEMALE

  • Dichotomy of strategies in parental investment, especially per offspring.


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Mating systemsdepend on parental investment

Investment in offspring after the gamete stage is related to the mating system

Tradeoff: mates v care of young

Number of mates for each sex:

Parental investment


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Two examples illustrating how ecological conditions determine the mating system

Resource defense polygyny:

Males defend resources to attract as many mates as possible

Lek polygyny:

Resources are not defensible so males compete for the opportunity to mate


Red winged blackbird agelaius phoeniceus resource defense polygyny facultative l.jpg

Red-winged blackbird Agelaius phoeniceus:Resource defense polygyny: facultative

Male red-winged blackbird displaying with the flash of the wings and a song. This display is intended to advertise his territorial boundaries to other males. This type of display lowers the cost of defense. Why?


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Males arrive before females in the spring and set up territories, vying for the “best” places.

The birds accommodate human altered habitats easily, using irrigation ditches as territories, and displaying from fences and telephone wires.


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A few weeks later, the female arrive to check out the males and their turf

They choose a place they like to settle down. What conditions are they looking for?


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Nest sites are over water in semi-aquatic vegetation or over land in thorny vegetation


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Both the male and the female bring food to the young

See movie of parents feeding offspring on the EVE 101 web site


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Chicks “fledge” (leave the nest) 9 days after they hatch! Why???

Parents continue to feed the fledgling for several weeks until it is “weaned”.

Nestling stuffing itself with dragonfly abdomens brought by the parent.


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Why is this male red-winged blackbird chasing this heron???

Is this play? Couldn’t the male get seriously hurt? Why bother with a heron?


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Value of the red-winged blackbird territory

  • Primary factor: Predation

  • Nests are in “flimsy” vegetation over water so predators cannot climb easily into the nests.

  • Herons can wade over and love a meal of nestling.

  • Nests are also in thorny vegetation over land

  • Fledglings grow incredibly rapidly and fledge in only 9 days--being in the nest makes them easier for predators to find

  • Best nest sites are in areas “safe” from predators and near a good food supply (caterpillars or dragonflies)


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Polygyny-threshold model

1 f/terr.2 ff/terr.3 ff/terr.

RS

Males with variable territories

A B C D

Territory Quality


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  • Polygyny threshold model

    • territories vary greatly in quality

    • multiple females on best territories

    • Red-winged Blackbird

  • More polygyny in more productive habitats

  • Most males are monogamous in most habitats

  • Only a few males have more than 1 mate (skewed mating distribution)


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Sexual size dimorphism: primate examples


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Grouse examples

Extreme polygyny: Leks

Monogamy

Capercaille (grouse) UK

Males 200% size of females by weight

Gray Partridge (Europe)

Males and females the same size


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Lek mating systemTerritoriality defending opportunity to mate (no resources)Resources or females are too dispersed to be defensible

  • Manakins (tropical rainforest)

  • Red-capped Manakin Pipra mentalis Panama

  • Dr. Kimberly Bostwick, Curator of Birds & Mammals, Cornell University Museum of Vertebrates

See manakin movies on EVE 101 web site


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Lek mating systemTerritoriality defending opportunity to mate (no resources)Resources are too scarce to be defensible; female home range very large

  • Sage Grouse (arid land steppes) Centrocercus urophasianus

  • Eastern Sierra California, eastern Oregon, Wyoming, Utah, Colorado, etc.

  • Dr. Gail Patricelli, Evolution & Ecology UCD

See grouse movie on EVE 101 website


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