ETHOLOGY Prof. S. D. Rathod B 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 AnimalBehavior 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 ofBehavior 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 Behavioraldevelopment 1. Preformation 2. Epigenesis: Proposed by Needleem in 1959; many supported it, Davis, Kutsch, Hamburger Brown (1975) explained epigenesis P1+G1+E1 = P2 P2+G2+E2 = P3 P3+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 behavioralchanges 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
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 occursin primates,Critical period is longer(up to age 6 months).Austin Riesen rearedmonkeys in darkness forthe first 3 to 6 months oftheir lives. When theseanimals were thenintroduced into a normalenvironment, they hadgreat difficulties indistinguishing even thesimplest shapes.
Sensitive Period DuringDevelopment 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 theobject which isavailable at hatchingand understands it asparent.
This diagram shows the similarities in the sonogramsof two geographically dispersed subspecies of whitecrowned sparrow: (Zonotrichia leucophyrs) Californian Sierra Nevada mountains The central Californian coast Swamp sparrow(Melospiza georgiana) different species
Development of white crowned sparrow songunder normal conditions From 10 to 50 days of age, the young males 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 crownedsparrow At about 200 days of age full song begins, it is a copy of the model he learned in his youth:
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