ethology: development of animal behavior

ETHOLOGY

Prof. S. D. RathodB N Bandodkar College of Science

Thane, Maharashtra, India

Ethology: Definition

Study of animal behavior in their natural environment.

Ethology is biological study of animal behavior.

Development of Animal Behavior Animals exhibit different behavior at their

different ages more or less in orderly sequence.

When and how the animals start exhibiting different kinds of behavior in their life time?

Therefore study of onset (development) of behavior is of utmost concern.

Firstly we consider ontogency i.e. study of development of learning and memory in embryonic condition.

Ontogency: Ontogeny of Behavior Ontogency is studied at

embryonic stage of animals. Study is divided in to three

stages viz. 1) Neonatal roots of behavior; 2) Maturation and behavioral

changes and 3) Phenomenon of equifinality

Neonatal roots of behavior

Behavior can be observed at embryonic stages such as twitching and jerking movements of appendages.

Flexes the hind leg Pecks beak inside

egg

Types of embryos Precocial: when newly born resemble

adult and can feed, move and defend themselves e.g. Lamb of sheep.

Altricial: when are helpless without parent can’t survive e.g. Joey of kangaroo.

Precocial Altricial

Concepts of Behavioral development 1. Preformation 2. Epigenesis: Proposed by Needleem

in 1959; many supported it, Davis, Kutsch, HamburgerBrown (1975) explained epigenesis

P1+G1+E1 = P2P2+G2+E2 = P3P3+G3+E3 = P4

3. Reflexogenous concept: Neuromuscular pathways are predetermined but movements are not exhibited until pathways develop.

4. Systemogenous behavior: Movements or behavior develop before birth and pattern of behavior depends up on the environmental factors available at that time. The behavior also vary from species to species.

Probabilistic viewpoint: a/c this the early behavioral development is not predetermined rather it is probabilistic dependent on the stimulating factors.

Maturation and behavioral changes

Frog jumps to blue background

Tadpole jumps to green background

As animal grows, it Practices for survival: involves increasing completion, organization or reinforcement of neural pathways

Practice also improves behavior

Phenomenon of equifinality It is a phenomenon by which a

structure or behavior pattern may develop by different pathways. There are vast number of process to finalize the personality of a fully mature grown up adult.

Conclusions:

Simple "nature/nurture" or "instinctive/learned" dichotomies have now been abandoned

Nowadays ethologists and psychologists are less divided by the nature - nurture debate. Both groups are interested in how genetic and environmental factors interact to control the development and expression of behaviour.

All behaviour depends on both genes and environment

Impact of environment on behaviour

Effect of Environment Enriched environment enhance the problem

solving ability in rats whereas the deprived environment has been found to affect the performance of them at later stage.

Enriched environment during development led to heavier and thicker brain cortex tissue, larger neurons and more dendrites of rat and also the increase in acetylcholine esterase activity as compared to rats living in deprived environment.

Environmental impact on behavior occur during sensitive period or critical period only.

Sensitive Period In CatsDavid Hubel and Torsten Wiesel’s experiments

Kitten is deprived of normal visual experience during a critical period

One eyelid was sutured shut. When it reached adulthood (around 6 months), its eyelid was opened again. Showed an abnormally low number of neurons and loss of binocular vision as compared to other eye. Visual deprivation took place during the first three months of the cat’s life. 

Eye of an adult cat was sutured for a year had no effect on its visual ability.

Sensitive Period In PrimatesPhenomenon also occurs

in primates, Critical period is longer (up to age 6 months). 

Austin Riesen reared monkeys in darkness for the first 3 to 6 months of their lives. When these animals were then introduced into a normal environment, they had great difficulties in distinguishing even the simplest shapes.

Sensitive Period During Development Various behaviors are acquired by individuals during

sensitive or critical period of their life e.g. imprinting or song in singing birds.

Filial imprinting: young animals form an impression of their parent soon after hatching or birth and follows them. If any object is produced during birth as the young one accepts it as parent and follows it.

Chick follows even the object which is available at hatching and understands it as parent.

This diagram shows the similarities in the sonograms of two geographically dispersed subspecies of white crowned sparrow: (Zonotrichia leucophyrs) Californian Sierra

Nevada mountains

The central Californian coast

Swamp sparrow 

(Melospiza georgiana) different species

Development of white crowned sparrow song under normal conditions From 10 to 50 days of age, the young male's

template accepts this adult male white crowned sparrow song as a model:  

and rejects this swamp swallow song as a model: 

The improved template now specifies the dialect he has to learn. The young bird does not sing, but the model is remembered for two months or more

The maturing male begins singing its sub song at about 150 days of age. During this period vocal output is gradually matched to the dialect specified by the improved template

Primary song –white crowned sparrow

At about 200 days of age full song begins, it is a copy of the model he learned in his youth:

Juvenile Behaviour

Juvenile Behaviour

Frog jumps to blue background

Tadpole jumps to green background

Juvenile behaviuor

Juvenile behave different than the adults…….

While Goose is ready to fight enemy, goslings hide in the grass

Innate Behaviour

Innate Behaviour

Behavior may occur as a result ofan external stimulus (e.g., sight of a predator)

internal stimulus (e.g., hunger) Stereotypic in response to a stimulus or, more often, a mixture of the two

(e.g., mating behavior)

Stimulus IRM FAPe.g.:- three spined stickleback fish

Innate Behaviour

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