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8th January 2014 Bio 335 - Animal behavior - Week 1 - Lecture 1 1

WEEK 1 – Jan 8th and 9th 2014Studying animal behavior – questions and

methodsPart 1 - Tinbergen's four questions

Raghav RajanBio 335 – Animal Behavior

Jan 8th 2014


Brief history of animal behavior

● Ethology – derived from the Greek word 'ethos' – study of character

● Modern discipline attributed to the studies of Karl von Frisch, Konrad Lorenz, Nikolaas Tinbergen

● Nobel Prize in Physiology and Medicine in 1973● Discoveries concerning the organization and

elicitation of individual and social behavior patterns in animals


Ethology – the study of animal behavior

During the first decades of this century research concerning animal behaviour was on its way to be stuck in a blind alley. The vitalists believed in the instincts as mystical, wise and inexplicable forces inherent in the organism, governing the behaviour of the individual. On the other hand reflexologists interpreted behaviour in an one-side mechanical way, and behaviourists were preoccupied with learning as an explanation of all behavioural variations. The way out of this dilemma was indicated by investigators who focused on the survival value of various behaviour patterns in their studies of species differences. Behaviour patterns become explicable when interpreted as the result of natural selection, analogous with anatomical and physiological characteristics. This year's prize winners hold a unique position in this field. They are the most eminent founders of a new science, called "the comparative study of behaviour" or "ethology" (from ethos = habit, manner). Their first discoveries were made on insects, fishes and birds, but the basal principles have proved to be applicable also on mammals, including man.

http://www.nobelprize.org/nobel_prizes/medicine/laureates/1973/press.html


Tinbergen's four questions related to any behavior

● Ultimate mechanisms – First HALF of the course● Function – Why does the animal perform this particular behavior

– Effect on survival

– Effect on reproductive success● Evolution of the behavior – how has it changed over evolutionary

time

● Proximate mechanisms – Immediate causes – Second HALF of the course - NEUROETHOLOGY

● Causation – What internal/external factors cause that behavior to be produced at that particular time

● Development – How does the behavior change over development and what internal/external factors affect it


BEHAVIOR

Always a case of cause-effect

Proximatemechanisms

Ultimatemechanisms

What causes the behavior?

What are the effects on survival, reproductive success?


Case study – cockroach escape response

● Cockroaches reliably escape from predators● One such predator is the toad and cockroaches

escape from the toad's tongue


How does the cockroach escape the toad? Proximate question

● Careful analysis of videos of toad striking at a cockroach (64 frames/s)

● Initially roach pivots away and then runs

● Similar to response to gusts of wind

http://faculty.bennington.edu/~sherman/neuro/escape%20cockroach%20toad.pdf


Does a toad strike have a gust of wind associated with it?

● Anesthetized cockroach dragged about 1cm away from anemometer

● Takes about 16 frames (250ms) for toad to touch cockroach after strike starts (tongue begins to move)



Toad strike is associated with appreciable wind speeds throughout

● What time do successful cockroaches start running?




● e – Time when toad touches cockroach

● d – time when successful cockroaches start escaping

● c – 58 ms prior to d which is the ~latency of the escape response of the cockroach

● Mean wind speed at c = 0.02m/s






● c – 58 ms prior to d which is the ~latency of the escape response of the cockroach

● Mean wind speed at c = 0.02m/s

● Roaches can detect wind speeds of 0.003 m/s – occurs at b

● a – first detectable movement by toad



Other cues ruled out - important

● Beyond antennae, so tactile stimulation not used● Would crawl over non-striking toads – olfactory

cues not used● no response to taps (auditory stimuli)● Finally, little or no response to toads striking from

behind a plastic screen – visual cues also not used



Approx. 18ms from time when cockroach escapes to toad touching cockroach



● Very little margin for error

● Importantly initial movement is the pivot away and then run



Can go back to videos and calculate safety margin (in terms of frames)

● Frame when cockroach started moving

● to frame when tongue would have touched the head



Very little margin for error – finely tuned behavior

● Caveats● Tongue could travel a

little more in the inter-frame time

● Not clear if tongue could touch legs

● Not clear if tongue touching always implies being eaten

● Still present estimate is conservative



Mediated by cerci on the abdomen

● Wax covers cerci● Wax covers abdomen -

control



More proximate mechanisms

● Giant interneuron that mediates response

● Cerci have about 220 hairs

● Each hair is hinged such that it can move in one of two directions (180 deg. apart)

● Different hairs move in different directions

http://nelson.beckman.illinois.edu/courses/physl416/ventralNerve.html

http://nelson.beckman.illinois.edu/courses/physl416/ventralNerve.html


Alternative strategies – why the present strategy is optimal

● Initial pivot is important before running away (although may seem counter-intuitive)

● While pivot could be in other direction – most often other direction pivot resulted in being caught (3/4)



Function – survival value – Obvious!

● In fact detailed analysis of behavior says cockroach can run away earlier

● Why not?● Possibly because if the

cockroach waits till the toad is committed, then better chance of escaping

● Overlap between questions



Evolution – how did this evolve?

● Survival advantage – faster cockroach may have more offspring

● If there is a genetic basis, then faster offspring● Predator, prey co-evolve● Among living relatives, lots of insects have cerci,

giant interneurons, escape response

– Some fly away, some jump – flexibility● Possibly inherited it from a common ancestor


Development – does the newly hatched roach do this?

● Yes!● Without any prior experience● With just 4 sensory hairs as compared to 440 in the

adult●

● Still, this “innate” behavior can be modified if adult loses one of its cerci

● If it survives, by 30 days, nervous system learns to perform correctly with just one cercus!


BEHAVIOR

Always a case of cause-effect

Proximatemechanisms

Ultimatemechanisms

What causes the behavior? How does it change over development?Can be answered but in the lab (not natural settings

What are the effects on survival, reproductive success?Can be answered in various ways – sometimes practically difficultHow did it evolve?Difficult to answer, but we can compare across livingspecies and guess

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WEEK 1 – Jan 8th and 9th 2014 Studying animal behavior ...raghav/pdfs/animalbehavior/Lecture1_Tinberge... · Studying animal behavior – questions and methods Part 1 ... With just