Learning to describe and quantify animal behavior

Learning to describe and quantify animal behavior

• Objectives– 1) Be able to describe the scientific

method for making observations and testing hypothesis about animal behavior

– 2) Be able to compare and contrast the multiple met

It all begins with an observation…

Squid Inking

Scientific Method

• Observations• Form a hypothesis–Null hypothesis – Alternate hypothesis

Scientific Method

• Make Specific Predictions– Determine your independent and

dependent variables• (Independent variable) causes a change in

(Dependent Variable) and it isn't possible that (Dependent Variable) could cause a change in (Independent Variable).• Determine what specific behavioral

response are you measuring – Are you measuring the state of an animal or an

action/event that is occurring?

Scientific Method

• Test Predictions– Identify or develop sampling or

experimental techniques to test hypothesis

– Select analytical tools to determine if your data supports you null or alternate hypothesis

Behavior Experiments: Testing your hypothesis

• The method you use often depends on your question– 1) What is the effect of factor X on

variable Y? Manipulative Experiments -• Pros: allows you to isolate variables• Cons: experiments can be difficult and time

consuming; behaviors hard to observe in some manipulations

Behavior Experiments: Testing your hypothesis

• The method you use often depends on your question– 1) “Are there spatial or temporal

differences in Variable Y?”• Requires survey data to sample behaviors or

another variable at two different sites or times

• Pros: sampling is often easier than manipulation

• Cons: Correlation is not causation! – Many times survey data is just a first step

Behavior Experiments: Testing your hypothesis

• For instance: • Do fish avoid shallow water to avoid

foraging birds?–Hypothesis: fish numbers should be

lower in shallow habitats with high numbers of foraging birds

Behavior Experiments: Testing your hypothesis

• Other variables might explain this pattern– Seagrass

density?–Nutrients?– Abundance of

fish prey?–Human

disturbance?

Fish abundance in shallow habitats

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Behavior Experiments: Testing your hypothesis

• The method you use often depends on your question- But what if your question is about the

difference in strategies or adaptations within or amongst species?- You can perform comparisons between

individuals of the same species- Do fish in schools avoid predators better than

solitary fish?» Often complicated by confounding variables-

solitary animals behave differently than schooling animals

The comparative method

• A comparison of groups of related species to determine how their differences in behavior reflect their differences in ecology

Testing your hypothesis

• Method depends on your question– 1) Manipulative Experiments – 2)Comparisons between individuals of

the same species• Often complicated by confounding variables

– 3) Comparisons among species• Differentiate different adaptations, or

environmental selection on entire species– Why does Species A use X Strategy and Species

B use Y strategy?

Black Back vs. Kittiwake gulls

• Black back gulls nest on the ground – Observed behaviors

• Adults fly over approaching predators and send out alarm calls for attacks

• Adults don’t defecate near nests• Remove empty egg shells (white

interiors)• Chicks are camouflaged and hide in

vegetation

– Hypothesis: These are adaptations to avoid predation, because gulls nests are vulnerable to attack on the ground

Black Back vs. Kittiwake gulls

• Kittiwake gulls nest on cliffs, and are therefore harder to attack and less vulnerable to predation pressure

Problems with the Comparative Method

• Alternative hypothesis– Could the difference between these two

gulls be due to other traits? Competition? Proximity to feeding grounds?

Problems with the Comparative Method

• Alternative hypothesis• Doesn’t quantify ecological

variables– Do eggshells make chicks more

vulnerable to predators

Problems with the Comparative Method

• Alternative hypothesis• Doesn’t quantify ecological

variables• Alternative adaptive peaks or non-

adaptive differences–Not all differences between species

must be adaptive

Problems with the Comparative Method

• Alternative hypothesis• Doesn’t quantify ecological

variables• Alternative adaptive peaks or non-

adaptive differences• No Statistical Analysis– Common in many early ecological

studies

Phylogenetically Independent Contrasts

• Species are not independent– Species can share traits because they

share a common ancestor

A B C D E F

Phylogenetically Independent Contrasts

• But what if you found out Animals A,B,C all descended from a common ancestor?

• Hyptohesize Larger rodents have larger range sizes (due to metabolic needs)– Compile species values, and then

regress body mass against home range sizeHome range

(Dependent)

Body Mass(Independent)

Phylogenetically Independent Contrasts

• However, a species body size or home range size is not independent of its relatives– Therefore species are not necessarily

independent data poits

Phylogenetically Independent Contrasts

Phylogenetically Independent Contrasts

• Species are not independent– Species can share traits because they

share a common ancestor• Confounds independence

• Must take evolutionary relationships/phylogeny into account and remove phylogenetic independence

Phylogenetically Independent Contrasts

• Felsenstein (1985)– A set of traits– A fully resolved

phylogeny– A model of evolution• (time of species

evolution, time of divergence etc)

Comparative studies

• Most useful to examine broad trends in evolution, social organization, and ecology

• Proper use requires– Controlling for social organization– Avoiding or addressing confounding variables

using experimental manipulation– Using phylogenetically independent contrast

to account for evolutionary constraints– Account for alternative hypothesis and address

them when necessary

Returning to comparing gull species

• Comparative studies can yield specific hypothesis to test with experiments

• What happens if egg shells aren't removed?

But behavior is not always adaptive

• Some behaviors are just a different way to accomplish the same goal

• Unfortunately, determining if a behavior isnt adaptive is an exclusionary case

Class Exercise

Designing Behavioral Experiments

Sea Turtles and Light Pollution