Honours / Discipline Specific Elective (DSE)
ANIMAL BEHAVIOUR & CHRONOBIOLOGY
►Unit 1: Patterns of Behaviour
Stereotyped Behaviours (Orientation, Reflex); Individual Behavioural patterns; Instinct vs. Learned Behaviour; FAP, Associative learning, classical and operant conditioning, Habituation, Imprinting.
Q. What is imprinting?
Imprinting is a form of learning in which an animal gains its sense of species identification. Birds do not automatically know what they are when they hatch – they visually imprint on their parents during a critical period of development.
After imprinting, they will identify with that species for life. Imprinting occurs when an animal learns to make a particular response to only one type of animal or object. There are two kinds of imprinting: filial imprinting and sexual imprinting. The study of imprinting is an interesting story with recent research that extends our conceptualization of this process to include the notion of ontogenetic niche.
Q. What do you mean by operant conditioning? Give example.
I(i)Also known as goal-directed learning, occurs when the response that is made by an animal is reinforced (increased) by the presentation of a reward or the termination of an aversive stimulus, or when the response is suppressed (decreased) by the presentation of aversive stimulus or the termination of a reward.
(ii)In instrumental learning, the animal must undertake some action or response in order for the conditioning process to produce learning.
The classic example of operant conditioning is a rat pressing some sort of lever (that is, taking an action) to get food to drop into its cage. Rats associate pressing on the lever (response) with some probability of getting food (outcome) and learn this task.
►Unit 2: Social and Sexual Behaviour
Social organisation in termites; Communication (dance & pheromones in Bees) Social behaviour: Altruism (Hamilton’s rule and concept of haplodiploidy), Cooperation and Selfishness Sexual Behaviour: Sexual dimorphism, Mate choice in peacock, Intra-sexual selection (male rivalry in red deer) Kinship theory: Relatedness & inclusive fitness; parental care in fishes (Nest Building & cost benefit), conflict within families: parent offspring conflict and sibling rivalry
Q. What is sibling rivalry? Give two examples.
Animals, including siblings, compete for resources such as food, territory, and potential mating partners. In animal sibling rivalry, individuals compete for parental care or limited resources, which can sometimes result in siblicide (Siblicide is a consequence of sibling rivalry, and its occurrence may be due to a variety of factors, such as food shortages and limited parental care. Killing a sibling could be advantageous for an animal because it monopolizes more resources through the elimination of a competitor). Sibling rivalry occurs in many different forms. Siblings may compete for resources in a prenatal and/or post-birth environment. The degree of rivalry varies, ranging from a low level of violence in non-aggressive to the killing of kin in siblicide.
i)Blue-footed booby (Sula nebouxii) siblings often exhibit aggression towards each other, with older chicks pecking at younger chicks. This behaviour increases when there are food shortages, indicating more intense competition.
ii)American robin (Turdus migratorius) chicks compete for food provided by their parents through louder and more prominent cheeps or other vocalizations, with the most food given to chicks exhibiting the most intense begging behaviour.
Q. Comment on function of ‘queen pheromone’ in honeybee colony.
(i)Bees use chemical cues to interact with each other and to manage colony organization. In honey bees the targets of pheromonal messages are usually members of the same colony.
(ii)The honey bee queen represents the main regulating factor of the colony functions. This regulation is largely achieved by means of pheromones, which are produced by different glands and emitted as a complex chemical blend, known as the “queen signal.”
(iii)The queen signal acts principally as a primer pheromone, inducing several physiological and behavioural modifications in the worker bees of the colony that result in maintenance of colony homeostasis through establishment of social hierarchy and preservation of the queen’s reproductive supremacy.
(iv)The effects of the queen signal are maintenance of worker cohesion, suppression of queen rearing, inhibition of worker reproduction, and stimulation of worker activities: cleaning, building, guarding, foraging, and brood feeding .
(v)It is known that when the queen is old or sick (low pheromonal signal) or it dies (no pheromonal signal), workers are driven to rear new queens from young brood within 12–24 hours. The removal of the queen in absence of young brood soon leads to the decline of the colony: the workers stop performing their activities and start to lay unfertilized eggs that develop into male adults (drones); the colony becomes disorganized, unfit, dirty, susceptible to diseases and prey of predators; it rapidly depopulates and goes toward a certain death.
►Unit 3: Chronobiology & Biological Rhythm
Types and characteristics of biological rhythms: Short- and Long- term rhythms; Circadian rhythms; Tidal rhythms and Lunar rhythms, Circannual rhythms; Photic and non-photic zeitgebers; Role of melatonin. Biological clock and its adaptive significance. Circannual rhythm in bird migration.
Q. Discuss with suitable diagram the role of Supra Chiasmatic Nucleus in maintenance of circadian rhythm.
(i)Hypothalamus controls many basic activities in mammals and hence seems to be a logical place to look for the site of biological clock.
(ii)A specific region of hypothalamus, known as Suprachiasmatic nucleus (SCN), is considered to perform as circadian clock.
(iii)SCN is a cluster of cells, which receive direct and indirect inputs from nerve fibers originating in retina. Because SCN receives information about day and night length, which can be used to control the clock, it is a logical candidate to regulate clock mechanism.
(iv) The neural pathways from retina to SCN serve the purpose for entrainment.
(v)Experimental proof: Surgical destruction of SCN in hamsters and Norway rats results in a subsequent loss in circadian rhythms in locomotory cycle, feeding behaviour, hormone secretion pattern etc.
(vi)Chemical messengers from SCN activate secretary cells of pineal gland to secrete a hormone the melatonin. SCN suppresses melatonin synthesis during daytime; as a result, more melatonin is secreted in those 24- hour days, which are shorter in day length. Hence melatonin is popularly known as "chemical expression of darkness". (vii)Thus variations in secretion serve as an indicator of seasonal changes in the day length.
Disturbances in melatonin secretion seem to be associated with Jet-lag, when the people suffer from a drastic deprivation from the registered sleep/ wake cycle due to air travel. Again, anti-gonadal role of melatonin has been demonstrated in a number of mammals. Then pineal gland may have a key function in controlling annual cycle of reproduction. Probably, seasonal changes in the photoperiod registered by SCN are translated into physiological changes via pineal and it’s other endocrine associates. (For further information follow our contact section)