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What is behavior?

Any sort of reaction to stimuli


Scientific approaches to animal behavior

– Inside the skin: physiologists study the machinery of behavior. Nervous system, endocrine system, skeleto-muscular system.
– Outside the skin approach: comparative psychologists – lab oriented; use a few species to formulate general rules. Ethologists– study behavior in the wild. Behavioral ecologist – study behavioral interactions among animals and interactions between animals and their environment


Why study animal behavior?

– Wildlife management/conservation
– Improves understanding/care for domesticated/companion animals/ourselves
– Improves understanding of biological principles such as natural selection, community ecology, etc.


Konrad Lorenz

Discovered principle of imprinting


Niko Tinbergen

With Lorenz, founded ethology, the scientific study of animal behavior in nature


Carl von Frisch

Animal communication (honeybees)


Jacob von Uexkull

– Animals experience umvelten (perceptual worlds) Different from us and from each other. For example, insects/birds see ultraviolet wavelengths. Elephants here infra sound


Charles Darwin

– Theory of natural selection: no two individuals alike, some of this variation has heritable basis from alternative alleles.
– – Offspring are overproduce, strongest survive through competition, predation, climate, disease – all are selective pressures
– Some offspring have heritable traits that confers survival and reproductive advantages.
– – These traits become more prevalent in populations over time and individuals carrying less advantageous traits are removed
– Natural selection produces adaptations: traits that enhance an individuals ability to survive and reproduce in its environment



Lifetime reproductive success. Ability to contribute genes to next generation. Measured by: lifetime production of viable offspring. Unit of selection: the individual


First observational experiment in ethology

– The Bee wolf
- Timbergen used subtle environmental manipulation to figure out how bee wolfs find their burrow in the burrow field


Tinbergens 4 questions

Defined research process to determine what animals are doing and why.

1. Causation - (Proximate question – anything relating to it is a proximate explanation) (ex-Physiological explanation) Example for bee wolves, proximate explanation would be that bee wolves use landmarks to find burrows
2. Development (ontogeny). (Proximate question) Physical process. Behaviors can develop and particular ways in a species/individual. Example: when do be wolves begin doing it? Does it involve a particular hormone during a certain stage of development? Isn't learned or innate?
3. Function (Ultimate question/explanation) Does it advance reproductive sexcess? Play a role in feeding, defense, mate attraction?
4. Evolution (phylogeny) ( Ultimate question) Deeper questions – through what evolution process did this behavior arise? Did behavior originally arise under natural selection and then co-opted for other purpose other than the original one?


How do you get at an animals behavior at all levels guided by Tinbergens 4 questions

Ex - prairie voles are monogamous why?

In the central palladium of the male vile, there is a high concentration of receptors for hormone that helps them to feel "warm and fuzzy" after mating, to feel attachment to mate. "Reward center"
--why is this? Prairie voles have gene erosion of avpr1a that up-regulates these receptors (transcribes more of these receptors - makes them respond more even when very little of the hormone is present, makes them more sensitive to it)
--can make predictions based on this
---ex: if extra copies of this gene are introduced to central palladium and different parts of the brain and measured how often voles spend time with own mate vs. a strange female. Voles with extra copy in central palladium (with up-regulation) showed difference, ones in different part had no effect.
----resulted in exaggerated version of behavior vs. control gene in same area or same gene in diff area
----did same thing for a diff non-monogamous species and got same results
----this is a proximate explanation to determine what the gene does and how it produces the reinforcement for the males to stay with their mates - proximate stimulus.
- Deeper evolutionary question: infanticide occurs often in rodents as well. But not in Prairie voles. Could it be a result of this behavior/reduce infanticide and increase odds of your own offspring surviving?


Fixed action patterns

Innate, stereotyped (Done the same way by everyone in population/species) Behaviors carried through to completion once triggered without any prior experience (Lorenz and Tinbergen)
---Today called modal action patterns
---Stimulated by simple key stimuli


Proximate causation: stimuli. First ethologists studied instinctive behavior

– Example: geese egg rolling eggs back into nests. Do geese know that's their egg/what they're doing?
– Example: red breasts in male European Robin triggers aggression and other male robins. What's the stimulus that's most important to the Robin? Is it just the red, or do they know they're responding to another male?


Sign stimuli (SS)

– External stimuli that triggers FAP's. Also called "releasers".
– Example: reflexive pecking behavior in black backed gull chicks, who pack at red dot on parents beaks to trigger regurgitation.


Rove beetle

Ants use tactile cues to communicate with other ants; can tap on other aunts mouthparts to get food from other ants. Rove beetles use the signal to get ants to regurgitate food for them in the same manner – controlled the stimuli to get response.


Supernormal stimuli

Exaggerated sign or stimuli or releasers. When presented with exaggerated stimulus, animals will preferentially respond to it. Built in bias from nervous system. Can explain brood parasitism in birds/flashiness and males


Effects of sign stimuli on behavior

- elicit (triggers behavior)
- maintain
- orient
- inhibit


Innate releasing mechanism (IRM)

- Internal decision-maker located somewhere in nervous system
- Sign stimuli –> innate release mechanism –> fixed action pattern

– – However, animals don't always respond to sign stimuli in their environments. Example: stickleback fish. Redbelly ask as releasor only during mating season. Will responds to read because during mating season when males are defending territories, they develop a bright red stomach. Only reacts to redbelly during mating season, not outside of it when not defending territory


What explains animals changing motivations

– FAP's may also occur in absence of SS or vice versa
– – Lorenz's theory: Action specific energy (ASE). Builds up as time you lapses since last performance of behavior. Lowers animals threshold of response to releasers. Example: if go a long time without eating, will devour food.

- now we know it has to do with homeostatic model


Homeostatic model

– Negative feedback: Corrects deviation from homeostatic setpoints
-- stimulus -> receptor -> integrator (brain control centers such as the hypothalamus) (comparison with "set point") -> appetitive (ex-water seeking), consummatory behaviors (ex- drinking that returns body to set point) -> back to beginning (stimulus, etc)
– It is a negative feedback because no matter which way things deviate, body must correct back to set point


Internal stimuli

– Also trigger behavior. Internal sensory receptors, hormonal activity.
– Both are activated by: deviations from homeostasis, seasonal/reproductive cycles, maturation

– Internal stimuli modulates the IRM
- SS -> IRM -> FAP


Reaction to stimulus requires

Sensory perceptions/sensation, command for action, and motor response


What is the detection/response system required to respond to a stimulus

– Nervous system (endocrine system can chime in too, but more slowly - can change responsiveness of nervous system on short-term basis)


What is the basic nervous system cell

- Dendrites: receive signals, one neuron can have many dendrites
– Cell body: contains the nucleus;controls basic cell functions
– Axon: conduct signals away, only one axon per neuron. Can branch but there is only one


What is a nervous signal

– Action potential: electrical, all or none signal
– – At rest, neuron membranes are negatively charged on inside; positively charged on outside
– – Neurons are essentially only batteries; separation of charges allows for the ability to do electrical work
– – Charges are attracted to each other; generally are separated, but work can be generated when they are brought together


What is the difference in charge (membrane potential) between neuron membranes based on

– Buildup of an NA+ on outside, K+ on inside
– – Set up by the sodium/potassium pump
– –– Continuously running. Pump sodium out, potassium in, which sets initial conditions
– – Potassium keeps leaking out down its concentration gradients. Occurs through "leak channels". Large negative proteins build up along inside of membrane and try to follow the potassium ions, but can't escape

– Sodium on outside attracted to inside by negative proteins and by concentration gradient
– – But sodium ions can't leak as easily as potassium, build up along outside of membrane

When neuron is stimulated, special gates will open to allow in sodium


Resting membrane potential

-70mV (Equilibrium point between all forces)


Three types of potential charges

– Depolarization: inside becomes more positive. Sodium rushes in when gated channels open, which is caused by stimulus
– Repolarization: Inside returns to resting potential after depolarization. Potassium rushes out through gated channels to restore negative charges around narrow zone inside of membrane
– Hyperpolarization: membrane potential drops below resting. Excess potassium rushes outs: inside of membrane becomes briefly more negative.

All these happen every time there is an action potential


Action potentials (APs)

– All or nothing waves of the polarization that travel from trigger zone to axon tip. Returns to normal after wave has passed as it travels down next time. Initiation must occur in trigger zone – sodium gates open, cause positive feedback where more sodium gates then open, creating the wave of depolarization. Potassium gates immediately open and slam shut afterwords to allow membrane state to return to normal.

Threshold potential, refractory zone