[su_heading size=”20″]Introduction to Animal Behaviour[/su_heading]
Behaviour is a fundamental characteristic of animals, who survive and adapt to their surroundings only by the dint of it through their interactive expressions for their basic requirements and competetions. As blessed with locomotive power, the animals use their behavioural power for various purposes of their life, like – procuring food, selecting mates and mating with them for their descendants. So, behavioural changes in animals has been a way of their life since their origin and adaptive radiation. It is obvious, some of those changes are common to all for their survival and adaptation, but there are many which are very specific and vary animal to aninal. The study of animal behaviour has been so important to us at present that we can not think of an animal without studying its behaviour. Even the human race itself is not out of it, from the cave-man to the modern one, whom we can study properly through their behaviour. It becomes clear from the vivid Cave-arts engraved 4000 years ago that, humans alway wanted to convey some message to their descendents in any of their behavioural patterns. The term Ethology (ethos=character, habit, custom; logia=the study) has recently been coined, that pertains to a modern science dealing with animal behaviour. It was first coined by St. Hilaire in the last part of 18th century, ment as a science of habits and characteristics of animals, either instinct or acquired and their lerning capabilities or behavioural patterns; which vary time to time at different situations. So, Ethology has been defined as the study of behaviour within a zoological context and includes, Ecology, Genetics, Physiology and Psychology as well. We are indebted to Karl von Frish, Konrad Lorenz and Niko Tinbergen for developing such a section of Zoology in the very recent times, for which they were awarded the Nobel Prize in 1973 in the field of Physiology and Medicine.
[su_spoiler title=”Definition of Ethology” style=”default” icon=”chevron”]
- The biological study of behaviour, a formation that mentions both observable phenomenon and methods of study.
- A scientific and objective study of animal behaviour, especially under natural conditions.[/su_spoiler]
[su_spoiler title=”What is Behaviour” style=”default” icon=”chevron”]
By the term Behaviour, we mean the expressions of animal life for different aspects, like how it responds to its external (overt) and internal (covert) stimuli, how it learns to respond to those, how it procures its food, how it builds its house or nest, how it ensures its security, how it responds to its sexual attitude and convinces others to respond to it, and after all, how it defends its competents for food, shelter and sexuality.
Definition of Behaviour
- Behaviour may be defined as the outwards expressed course of action produced in organism in response to stimuli from a situation.
- Behaviour is the movements, that animals make – Niko Tinbergen
- According to Aubrey Manning (1979), Behaviour includes all those processes by which an animal senses the external world and the internal state of its body, and responses to changes which it perceives.
In a word, all the activities done (seen or unseen) by an animal is its behavour which can be physical or psychological or psycho-physical and is either exposing or learning. [/su_spoiler]
[su_spoiler title=”The Nature of Behaviour” style=”default” icon=”chevron”]
The Macaque monkeys of the Pacific Islands of Koshima of Japan, alike humans, washes the sweet potato with water before eating. This habit was not found in them earlier, but once a mother monkey learnt it from a human child while doing it. Gradually, the total population acquired this behaviour which they still exhibit. The Rainbow Lorikeet females comb the eye-plumages of males with their beautiful beaks, the Starlings (Mynas) clean their nest with neat skills, the Mongooses capture and dominate over their preys (Snakes) with much speed and clevery, and the Cheetahs approach their prey with extreem cover, care and silence – all those are their behavioural skills, according to scientiests, of which some are innate and others learnt; and the science dealing with those is Ethology.
But, behaviour is not only upto this; like – the running of a prey for saving own life, running of a predator to capture a prey for own survival, wounderful archetechture of birds in building their nests and in spiders configuring their web, building under water entrance in a Beaver’s nest, incubating eggs and post-natal parental care, inter-continental migration of large and small birds in the same route and to a particular recurrent destination, non-stop day and night journey of migratory animals to a particular direction and location, etc. hundreds and thousands of activities are jointly known as animal behaviour.
To adapt to the ever changing environment and at the same time to respond to different stimuli, an animal has to bring considerable change in its behaviour. This simulation continues for years, ultimately making the animal conditioned to it and which can even be genetically transmitted over generations. The external environment stimulates the nervous, endocrinal or muscular system of the animal, and as a reflex, the animal exhibits some other behaviour to respond to those, like – oral sound, physiclal movement, colour change (camouflage), emission of gas or smell, aggresive or frightened attetude etc. [/su_spoiler]
[su_spoiler title=”What is stimulus” style=”default” icon=”chevron”]
A Stimulus is a signal, which can be identified and represents a sense. It can be both external and internal. For instance, when our cell phone rings, we can understand both by its tone and vibration, hence is a case of external stimulus. Likewise, when we get hungry, there is a different sensation that indulges us to take some food, so it is an internal stimulus. Obviously, the response to a cell phone is to respond to the call, while the response to a hunger is to take some food.
The external stimuli involves – light, temperature, smell or aroma, a sound or a noise etc., while the internal ones are – love, hatrad, thirst, hunger, feelings etc. It is noteworthy, all animals do not necessarily have the same type of feelings and of a same level – rather it varies species to species. Human beings have – vision, audition, taste, smell and touch, these five types of stimuli which are always active, but it is never the case with other animals. Similarly, the gravitational and other magnetic forces have a great impact on birds and some other migratory animals, while those have no impact on us.
Behavioural Changes due to Stimulus
All our mental or behavioural conditions are stimulus based, which brings about responses. In this case stimulus-response law are applicable; the modernized form of which is stimulus-orgnism-response law. Further, these three elements combine to represent an Emotion. To behaviourists, emotion is never a mental contion but a physical change. Its a physiological, external or behavioural change. According to them, a change in environment can bring about emotional changes which changes the behaviour. So, the environment is the factor of behaviour and not the heredity – they believe.
A Stimulus in an animal body creates emotion and different stimuli can create different emotions. The basic emotions in humans are – Happiness (Pleasure), Surprise (Quarry), Sadness (Sorrow), Anger (Temper), Disgustion (Hatrad), Fear (Shudder) etc. (Matsumoto & Ekman, 1989)
- Hapiness – This emotion happens in a person due to some expected pleasant stimulus, resulting in a happy expression in the animal. In this case, the face gets brighter, with a tendency to laugh and the animal rejoices.
- Surprise – This emotion happens in people, due to a very strong unexpected stimulus. In this case, a retardness in mental condition happens and the animals turn motionless.
- Sadness – This emotion happens in a person due to some unexpected or sorrowful stimulus. It affects the autonomous nervous system of the person, resulting in responses, like – shedding of tears, mumbling etc..
- Anger – It is a basic emotion of animals. In this case, as a relult of a stimulus, the autonomous sympathetic organ of the animal get very much active, resulting in the expression of anger, which brings about physical changes.
- Disgustion – This emotion happens in a person due to the presence of a special stimulus. In this case his disgustion changes into dislikings leading to Anger in its extreme condition.
- Fear – This emotion happens in a person due to some harmful or scary stimulus. This results in a flying tendency, abnormal restlessness and change in the heart-beat.
[su_spoiler title=”Physiological changes due to Emotion” style=”default” icon=”chevron”]
The following physiological changes takes place, due to any of the above emotions –
- Secretion of Pituitary Gland (CSH secretion).
- Secretion of Adrenal Gland (Adrenalin secretion).
- Change in Galvano skin response (electricity on the skin).
- Change in the Glucose level of the body (Insulin activity).
- Change in body temperature.
- Change in heart-beat (palpitition).
- Change in the rate of respiration (breathing rate).
- Change in blood-pressure level.
- Change in digestive function.
- Secretion of certain exocrine glands, like – Salivary gland, Sweat gland, Lacrymal(tear) gland etc. [/su_spoiler]
[su_spoiler title=”Behaviour and Heredity” style=”default” icon=”chevron”]
Behaviour is deeply related to heredity. The process through which paternal or maternal characteristics are transmitted to their offsprings, is known a heredity, due to which the latter resemble their parents. But, sometimes in some species variations are also seen and to understand all those resemblence and variance a branch of biological science, Genetics is underway for its knowledge and research.
In other words, Genetics is the science of Gene and its functions and Genes are hereditary units, present in Chromosomal DNA and is responsible for carrying and transmitting single characters from parents to offsprings and in this way generation to generation. It is the peternal or metarnal genes which controls – the height and structure, complextion, colour of hair and iris etc. and even the mental conditon of a child, who receive it through pairs of genes, one from father and the other from mother.
In case of animal behaviour, natural selection and genetics are involved; in fact, the role of genetics is important in case of animal behaviour. Particular genes for behaviour are selected naturally and become dominant in offsprings; that’s why the behaviourists use genetics in analysing the behavioural variations and accept genetical ideas in the following cases –
- They use the laws of Mendel in understanding the distribution of the phenotypes of behaviours.
- They take help from genetics in understanding the influence of sex linked (limited) characteristics.
- To understand a behaviour, they involve genetics to determine the inherited and natural influence on it.
So, determining the inherited pathway of behaviour is tough to identify, as so many genes interact among themselves as well as with environment, and along with that, genetics and environment influence each other. But, we are indebted to Gregor Johan Mendel, who has postulated two laws of genetics, the first law or the law of Seggregation and the second law or the law of Independant assortment.
According to Mendel’s first law, a pair of genes (paternal and metarnal) having contrusting characteristics, is responsible for a given characteristic in an offspring, which never lose their integrity and seggegate out into two different gametes during its gametogenesis. Fig. 12.2 shows an example in this favour.
The honey bees are attacked by a bacterial disease, American foulbrood (Bacillus larvae) resulting in the death of a number of bee larvae. So, the bees expell the infested larvae to reduce the probable attack and intensity of infestation. W. C. Rothenbuhler observed and identified two types of behaviour in them.
There are one type of bees, called Hygenic, which can –
- Uncap the cell-lids in a honey comb to expell the infested larvae.
- Expells all the infested larvae from the honey comb.
- Have two separate recessive genes to show above functions.
Now, if a recessive gene ‘u’ is functional for uncapping the lids; and another recessive gene ‘r’ is functional for clearing the infested larvae; and, if a cross is made between a Hygenic bee (u/u, r/r) and a non-hygenic bee (U/O, R/O), then all the honey bees in the first filial generation will be non-hygenic. Only the worker bees (homozygous dominent) show normal behaviour.
This is an example of genetical base of a given behaviour. Besides, the science of genetics is now used to show the influence of heredity upon behaviours related to – variations, environment and inherited characters:
[su_spoiler title=”Types of Animal Behaviour” style=”default” icon=”chevron”]
Animal behaviour can be divided into two categories, like – a. Innate Behaviour and b. Learned Behaviour.
The instinctive behaviour is sometimes called Innate, as it is inborn and need no learning. But there is no shart demarkation in between the two and in developed animals most of their behaviours is an overlaping of both. As for instance, we can consider the speech of a human. One can think its innate as all of us talk; but in fact, everybody can not speak. A born deaf, through tedious endeavour, can be taught how to speak; otherwise as a deaf is usually a dumb. In general we learn to talk listenning to others. That’s why our children talk in Bengali and a French child speach French. In fact, the power of speech in human is inherited, but what we speak, is learned. [/su_spoiler]
[su_spoiler title=”Modes of Behavioural Patterns” style=”default” icon=”chevron”]
The behavioural patterns in animals are the following –
- Spatial Orientation (Kinesis and Taxes)
- Natural wit or Instinct
- Motivations [/su_spoiler]
[su_spoiler title=”Taxis (pl. taxes)” style=”default” icon=”chevron”]
A taxis or tactic movement is a type of movement of a freely motile organism, or a freely motile part of an organism, in response to a directional stimulus. Taxis is observed in plants and animals as well, and depends upon the nature of the stimulus. If the stimulus is such that the response draws the animal or plant closer to the source of stimulus, it is termed as Positive Taxis, and while it pushes plant or animal away from the source, it is termed as Negative Taxis. Taxis can vary from animal to animal and from plant to plant, and even from one part of the plant or animal body to the other. The best example of taxis is the growth of plant root and stem. We know, the former shows negative phototaxis, while the latter show positive phototaxis.
Salient features of Taxis
- It is a particular reaction, moreover a stereotyped pattern.
- It is concerned wtih special orientation.
- The total body’s orientation takes place here.
- The direction of movement is controled by an external stimulus.
- The orientation is directly proportional with power of the directional stimulus.
Kinds of Taxis
Based upon the type of stimulus, taxis can be divided into the following categories –
- Phototaxis – The orientation created through the reaction with light is termed as Phototaxis. For instance, Euglena swims towards light; same is the case with fruit fly and a growing stem (shoot), which moves towards a light source. Those are examples of Positive Phototaxis (Trapotaxis). On the other hand, House fly larva or maggot searches a dark place for the development of its pupa; newly growing radicle of a seed move away from light, which are examples of Negative Phototaxis (Pharotaxis). Likewiese, Earthworms, Woodlice and Cockroach show negative phototaxis.
- Geotaxis – The orientation created due to gravitational force, universal to all animals, is termed as Geotaxis. Many animals including vertebrates, carry gravity sensing organs, like – Statocyst, Circular canals etc. In insects there are sensory cells which can detect the direction of gravitational force. Most of the animals can critically detect the upward and downward directions and show Positive Geotaxis (downward movement) and Negative Geotaxis (upward movement). For instance, some Planula larvae of Cnidarians (Coelenterates) swim towards the bottom of the sea (+ve geotaxis) and some Ephyra larvae swim away from the bottom (-ve geotaxis).
- Phonotaxis – The orientation produced due to a sound or noise source is called Phonotaxis. Alike Phototaxis (Trapotaxis and Pharotaxis), Phonotaxis is also precise. For instance, during its movement in the darkness, Bats produce sounds; echos of which are received through Traggus, special orgnans in their ears, which help them detect an obstacle in their navigation route. Likewise, certain Moths can detect those sounds produced by some inectivorous bats, through two Phono-receptors present on their thorax, which help avoid their potential predators. Crickets and Grasshoppers produce sounds by organs present on their forelegs, which help the female approach the sound sourse for mating. Birds and Mammals can detect a sound sourse and orient themselves accordingly by comparing the sound received by two years and search movements by moving their head right and left or up and down. In all those functions, i.e., acoustic localization, the extended and movable Pinna of Cats, Dogs and Horses are more functional than that of us.
- Chemotaxis – It is the orientation produced due to diffused gas or chemicals exposed in air or water. It is also a common taxis but not precise like Phototaxis or Phonotaxis. For instance, many insects and animals like Cevets liberate gas on air containing a pungent smell that attacts the female to detect its source for mating, is an example of Positive Chemotaxis. The avoiding of insect repellent (sprays) by the mosquitos, is an example of Negative Chemotaxis. Paramecium and many protozoans exhibit back and turn movement in a medium with noxious chemicals; this type of negative chemotaxis is known as Phobotaxis (Jenning, 1900).
- Klinotaxis – It is the orientation produced through the gradual change in the intensity of the tactical source. It is observed in animals with the presence of asymmetrical individually working receptors; in this case, they can not balance between the two and act on individual reception. In case of negative phototaxis, Blow fly exhibits Klinotaxis, i.e., the more it gets away from the source the less is its speed. The swinging of head of a larva, right and left to detect a rear light source, is another example of Klinotaxis; if the left source is stronger, it turns right and vice versa, showing that it detects the source by its two receptors separately instead of a balance between them.
- Tropotaxis – It is also an orientation produced due to gradual change in intensity of the tactical source. It is observed in animals with the presence of asymmetrical combinely working receptors; in this case, they can balance between the two and act on combined reception. For example in Planaria larva, the negative phototaxis depends on a balanced decision. Another example is Pill woodlouse (Armadillidium bulgare), which shows positive phototaxis and can directly move towards the light source; but, if one eye is covered, it moves in a circuar order, showing that it needed two eyes to balance to find the right track. So, Klinotaxis differs from Tropotaxis in the way that the former don’t need two receptors (eyes) to find the right track, while the latter does, it balances between them and can get the right track.
- Telotaxis – It is also an orientation produced due to gradual change in intensity of the tactical source. It is observed in animals with the presence of symmetrical jointly or individually working receptors; in this case, they can balance between the two and act on combined reception as well as they can do so, if in case one is not working. It is found in Honey bee and if somehow (due to pollans) one eye is covered, it has not impact on detecting its source or moving in a particular direction with a single eye. In the same way, Hermit Crab exhibit Telotaxis and if there are two tactical sources, they always move towards one and never in a median direction.
- Pharotaxis – It is a complex phototactic orientation, which can be compared to leading a ship based upon a distant light-house. Most of these cases are misled, producing destructive results. For instance, some Moths plunge into fire or are eaten by predators, as they move towards a light source.
- Menotaxis / Compass Orientation (Griffin,1955) – It is a kind of Pharotaxis in which the animal maintains an angle to the light source during its movement. The best example is, using light compass in homing ants, which are partially influenced by solar positioning. If the positions are changed artificially by mirrors, the ants show changes in their direction of movement.
- Nemotaxis (Kuhn,1919) / Piloting (Griffin,1955) – It is a kind of complex orientation by which an animal can identify the path to its destination through welknown landmarks. For instance, Digger Wasp (Philanthus triangulum) exhibit this type of taxis in finding its digging places. [/su_spoiler]
[su_spoiler title=”Reflex action” style=”default” icon=”chevron”]
The term Reflex was first coined by Sherrinton and can be defined as a simple act of behaviour in which an external or internal stimulus produces a specific, short-lived response. Reflex means the instant response produced due to a particular stimulus. It is controled by the Spinal cord and not by the Brain. So, the sequence in a reflex action is –
Receptor (Epithelium) – Sensory neuron (Cell body) – Dorsal root (Spinal cord) – Synapse – Grey matter (Spinal cord) – Synapse – Motor neuron (Cell body) – Ventral root (Spinal cord) – Effector (Muscle).
In this way, it is an instant response of a living body to an external or internal stimulus, induced through our epithelial tissue (touch or pressure) and responded by our muscular movements. For instance, any minute object falls in our eye, closes it or any small food particle stuck in our trachea or oesophagus induces choking. The parthway of a Reflex action (given above) is known as the Reflex Arc and one have no control over this action, as it is autonomous.
Usually the Reflex actions are divided into two categories –
- Inborn or unconditioned Reflex – It is an innate reflex, present from the birth and not dependant on an experience or habit. Like the constriction of eye-pupil in a flood-light, or jerking of knee, ankle or biseps muscle etc.
- Aquired or conditioned Reflex – This type of reflex is based upon experience and aquired through practice. For example – training a pet animal for a particular sport (playing with ball etc.)
Innate Reflex actions can be divided into two categories based on the position of receptors –
- Superficial Reflex – When the receptor works on the superficial area of a living body, like – constriction of pupil in a flood-light (pupilary reflex), movement of finger in front of one’s eye closes it (conjunctival reflex), tickling on the sole constricts toes (plantar reflex) etc. are examples of superficial reflex.
- Deep Reflex – When the receptor is deep inside a living body in the muscle or tendon, like – Knee jert, Ankle jerk, biceps jert, Triceps jerk, Jaw jerk etc. are examples of deep reflex.
The Salient features of Reflex behaviour are –
- They are the simplest unit of complex behaviours.
- They are the results of a neural mechanism and so, they are innate (inborn) which exist since post-natal condition.
- They do not need a stimulus to guide them all the time.
- They are automatic, involuntary and sterotyped (i.e., can happen multiple times without any variation).
- Unlike Taxis, Reflex is the movement of a living body due to a stimulus, while the former is involved with movement to a particular direction (either positive, means towards the point of stimulus; or negative, means away from that).
- They are directly proportional to the stimulus strength; the stronger the stimulus, the shorter the latent period, likewise, the weaker the stimulus, the longer the latent period. (The latent period is the time lag between a stimulus and a response). [/su_spoiler]
[su_spoiler title=”Instincts” icon=”chevron”]
Instincts are innate natural behabiour that an organism exhibits in response to adapt to a change in the environment. “They are complex, inborn, stereotyped behavioural patterns of immediate adaptive survival value to the organism and are produced in response to sudden change in the environment”. They are unique for a given Species, differ from Species to Species and vary in their complexity from simple reflex to more complex one. Nobel loreate Conrad Lorenz explains instincts as – unlearned specific motor patterns of a given Species due to its biological rhythms, territorial behaviour, courtship and mating, social hierarchies including altruism. In some the behaviour is hereditary, like – in migratory birds, who become impatient for flying during the time of migration, even in captive condition; and when left alone, can find out its regular route of migration and a particular recurrent destination.[/su_spoiler]
[su_spoiler title=”Appraisal / Test / Examples of Innate Behaviour” style=”default” icon=”chevron”]
Adaptation is the capability or changes of an organism to synchronize with its ever changing environment. All Flora and Fauna exhibit the quality to adapt to their surroundings; and in animals their innate and learnt behaviours help them to do it. [/su_spoiler]
[su_spoiler title=”Winter Migration of Birds” style=”default” icon=”chevron”]
Migration (Lat. migratus=wonder) is the movement of organisms temporarily or permanently from one place to other due to certain environmental causes. Migration in different birds is their instinct behaviour performed over years from generation to generation in quest of food, reproduction or cosy atmosphere which is more tolerant to them over a given period of a year. Migration can be local or continental, depending upon the need and situation as well as the body weight of the bird.
Many of the bird from the northern hemishpere migrate throusands of miles to go to their esteemed destination of better food, shelter and spawnning ground in the southern hemisphere in the same route they perform it every year and at the same location they had come the previous years. Sometimes the latter is changed in quest of a better survival and spawnning but this is an uncommon phenomenon. Usually the tropical locations in the southern hemisphere is more feasible than that in the much colder northern one, their original habitat. So, migration can also be termed as a temporary change in habitat and habits. But, the southern hemisphere birds are found to be locally migrants and never a continental one to the northern. Birds which undergo migration are known a Migratory birds, who get back to their original habitat after the tough time has been over.
Migration is an innate behaviour in certain birds and a common example is the winter bird migration to our country. Birds like – Bar-headed Goose (Anser indicus), Pintail (Anas acuta), Baikal teal (Anas formosa), Ruddy Shelduck (Tadorna ferruginea), Shrikes (Lanius sp.), Wagtails (Motacilla sp.), Leaf Warblers (Phylloscopus sp.), Finches (Pyrrhula sp.), Skylarks (Aluda sp.), Swallows (Hirundo sp.) etc. are examples of winter migrants in our country. Besides, Lesser and Greater Whistling teals (Dendrocygna sp.), Eagles (Haliaetus sp.), Pariah Kites (Milvus sp.), White backed Vulture (Gyps sp.), Hawks (Aviceda sp.), Malcoha (Rhopodytes sp.), few Owls (Strix sp.) etc. are locally migrants. The esturine and inland waters as well as the islands and marshy areas are traversed by – Gulls (Larus sp.), Terns (Sterna sp.), Spoonbill (Platalea sp.), Ibises (Plegadis sp.), Openbill (Anastomus sp.) and Adjutant (Leptopilos sp.) Storks, Sarus Crane (Grus antigone) etc. which are large locally migrant birds.
So, this innate migratory behaviour of birds have been observes, tracked and experimented since a long time and today through satelite. It has been found that their navigation is either controlled by solar position by the day or star positions by the night or they have some other GPS positioning system within their brane still unknown to us. Anyway, the behaviour is peculiar and found to be trasmitted generation to generation. Same is observed in Green and other marine turtles who traverse a long way underwater for laying eggs in the same place they do every year during a particular period. So, the Stimuli or factors are directly involved with it are –
- Environmental Stimuli – A major change in everything in the North Hemishpere takes place at the advent of winter. Gradually the temperature fall, there is scarcity of food, situation goes bad or worse for breeding. So, birds have to move out to another destination where all those facilities can be found. In the same way in some other part of the year some birds from the south hemishpere migrate to the north for certain causes, but these instances are very rare.
- Maturity of Gonads – This sort of behaviour in some birds is a simulated affect of their hormone secretion and change in reproductive characteristics in a particular part of the year. So the maturity of gonads works as a stimulus in favour of their migration.
- Ultimate Causation – The ultimate cause of this sort of behaviour has been described as an environmental factor and as a long enduring result of organic evolution during a longer period of time.
- Metabolic Activities – As a result of metabolic functions in the body a huge amount of fat is depositied, which works as an active source of extra energy suppliment during a migration. So, migration might also be done to maintain a balance of the body materials in birds. [/su_spoiler]
[su_spoiler title=”Spider Web” style=”default” icon=”chevron”]
The Spider is a surprising animal and more peculiar is its web. Scientists believe this primitive animal has been existing since the Cretaceous era. The web is actually a secretion of a Spinneret gland present in its abdominal region and the web is prepared through its innate instinct. Biochemical experiments reveals that the web consists of combination of amino acids like – Glycine, Alanine, Serene and Tyrocine. The web is used for various purposes and the most significant and common one is capturing its prey through the web.
Scientists believe that, during its change from the aquatic to terrestrial habitat in Devonian Era, the spider wrapped its body with a protective silky device, the web. Later, with considerable change in its constituents and conplicacy in weaving, the web has been an wounderful device today for both housing and food capture. The fibre used in it, just like in silk moth larva, is a secretion of their abdominal Spinneret gland, secreting 8 types of fibre today, each used for a different purpose. Some of those are used in climbing, others in housing, food capture, wrapping a prey and much more. Spiders are only animals in the world which captures their prey without minimum loss of energy; and that is possible by the dint of the web.
But, it is noteworthy, a lot of time, energy and endeavour is spent by a Spider in building and maintaining its web through proteins out of its body. Moreover, the fibres lose their temper withing a short time when they have to rebuilt it losing more energy. The fibres are durable like Nylon, but more elastic; and at the same time they are stronger than steel fibres of the same diameter. From the weight bearing point of view they are next to fused Quartz fibres.
The web maintains a lot of diagrametic archetechtural designs, that varies from species to species, but same for a given one. They can be sperical or ovoid, octagonal or multigonal, funnel shaped, spiral or tube shaped. But, whatever is its size the arrangement of fibre is very much even and scientific. The web is always attached to more than one substratum with equal strain at all sides. Usually the size depends upon the spider which is seen sitting at the centre or it hides building different structures on the web. Flying insects all over the world and even small birds in Amazon velly (taken by Brazilian large spiders) are confused by the web and never feel conscious about it.
The fibre is liberated from the gland as liquid, made up of amino acids like – Glycine, Alanine, Serene and Tyrocine, which over its exposure to air and strain changes into a sticky fibre with much strain. The spider fixes the fibre at different points and move in a particular direction keeping even spaces among the central and circular weaving attachments in a web. The claws in its eight legs and unsmooth bristles around help them in weaving the net as well as walking at ease on any surface or in jumping. Sometimes it hangs for a long distance to understand the air flow and in quest of a suitable place for its web. Spiders are very intelligent creatures and keen listeners which can receive a vibration upto 1 GHz. Some of them build their web very quickly on the path of a flying insect, listenning to it buzzing and measuring its speed, weight and direction. It understands its success by the vibration produced in the net, when it comes forward and very quickly wrappes its prey with huge fibre. When the prey has almost lost its energy, the spider poisions it and takes time in sucking its body materials gradually. [/su_spoiler]
[su_spoiler title=”Parental Care in Fishes” style=”default” icon=”chevron”]
Parental care in fishes is rare but very distinctive in some. Each of the functions related to offspring like – Egg laying, Preparing a nest and securing it for egg laying, raring of newly spawned fries for a definite period, all fall under parental care. In fishes, the male or female or both take part of share in the practice.
The male Sun fish prepares a cup-like nest for the egg laying purpose of the female. Lung fishes like Protopterus and Lepidosiren make out deep holes where the female lays their eggs. During the spawnning the male guards the nest. Likewise, Amia prepares a circular nest with acquatic plants.
The male Three-spine Stickleback (Gasterosteus aculeatus) selects a place and prepares a nest with plant parts and roots, mixing sticky materials secreted from their kidneys. The nest has a central tunnel where the female lays its eggs and the male fertilizes them later. Then they stand at one side of the tunnel and fan with their Pectoral fins so that a water current is produced through the tunnel increasing the Oxygen content of the water in it. In this way they wail till the eggs are hatched and again they guide the fries for the next 15 days till they become able to move in shoals.
Besides, Tilapia (Tilapia mossabica) is a mouth breeder, i.e., the fertilized eggs are housed in the buccal cavity and released later. The male Sea Horse (Hippocampus sp.) carry fertilized eggs and care them till hatching. [/su_spoiler]
[su_spoiler title=”Parental Care in Toad” style=”default” icon=”chevron”]
The parental care in Amphibians like – Toad or Frog is very rare and not more than 20%. But, they adopt innate techniques, for egg laying, protecting, proper hatching and protecting the young ones. Frogs’ (e.g., Toad-like Frog Alytes) tendency for parental care depends upon their habitats especially the area of water body they spawn in. Usually the intensity and variation of parental care increases with smaller water bodies. As the probability of attack from a predator is higher in a larger water body, the amphibians adopt a number of preventive measures to protect their young ones. Sometimes it is observed that they lay eggs on the shores and regularly keep them moist for a better hatching and then transfer the hatched ones into the water. Parents take part in all those events. All their events can be summerized in the following points –
- Seclection of a safer place for egg-laying – A secured place is the most important necessity for egg laying. Some amphibians lay eggs in protected places next to a water body, some lay eggs on leaves of trees (arboreal frogs) very near to a water body, so that the eggs may drain with rain into the water.
- Preservation of eggs and security of the spawning area – Amphibians with a tail protects an intruder by its tail, some protect their eggs directly. The female animal after laying move them for better ariation and Oxygen supply. The tailless amphibians protects their eggs physically and ensure security of the spawning ground. A few of them lay eggs inside thick jelly but others lay eggs in a muddy place, protected by the males.
- Parental care – Some amphibians are wounderful examples of parental care and rendering sucurity to their young ones. Like, Salamanders lay their eggs in shallow moist places and encircle their eggs like a sanke to protect them. A few species of frogs lay their eggs first on ground and then attach them on their back and carry them till hatiching. Some uses jelly like protective media for egg protection (toad and frog). The marsupial frogs/toads keep their eggs withing the sac they carry on their back and protect them till hatching.
- Delivary of offsprings – A few tailess ovo-viviparous amphibians retain their eggs in the oviduct and later deliver mature offsprings, reducing the probability of their loss due to environmental factors or predators.
In this way, Amphibians exhibit wounderful parental care from their egg laying stage till the growth of larvae into adult stage. [/su_spoiler]
[su_spoiler title=”Parental Care in Bird” style=”default” icon=”chevron”]
The parental care in Aves, i.e., birds is very distinctive feature in them. We observe a kind of helplessness to self-reliance attitude in their life. Many of the altrician birdlings are smaller in size, sight and featherless, devoid of movement, seriously helpless and depended on parental care and nestling. But, on the other hand many precocian birdlings can move, are feathered and collect their own food i.e., are selfdependant. So, the former type needs parental care over a longer period of time while the latter needs it for a very short period. The stages of parental care in birds are as follows –
- Nesting (Nest building) – Nest building is the most archetechtural exposure of a bird and the nests vary Species to Species, for their shape, size, altitude and above all their configuration and structure. A nest is usually not used twice but in big birds, who mend or reconstruct it every time. The nest building materials vary considerably Species to Species, but each Species uses more or less the same materials for their nest. In one hand each nest is water ringing and dry but in other hand each one is secure with well-perculation of air but well-retainer for incubation heat. It is contructed in such a way that never dismantles or dislocates easily even in strong winds and is a safe housing for both parents and the eggs or the birdlings. Sometimes they are deserted as the birds need to change their location (microhabitat). Birds build their nests any where, like – on the roof (House Swift) or ventilator (Sparrow) of an old building, on a suitable triradiate branch junction (Black Drongo), rolling a large leaf (Tailor bird), or on debris (Larks) or holes on river basins (Bank Myna). The bottle-like hanging nest of Baya Weaver birds found hanging from Palm trees are pobably the most important example of nature’s architechtural innate capability transmitted over generations.
- Incubation – Both precocial and atrical types of bird need to incubate their eggs for a given period of time depending upon their body size and weight. Usually in smaller ones the period is less as the egg-size is smaller, while in bigger ones the time is more, as the egg-size is bigger. In smaller ones the period extends from 12-14 days, while in bigger ones it can take even 40-50 days. In Albatros it takes 80 days. The body temperature in birds is around 100oF and the male or female or both exert it on the eggs depending on Species. For instance, the Hen usually incubates the eggs, but in Ostrich the male does it; in cases like Jungle Babbler both male and female does it in turns. The altrical birds need a longer incubation period than the precocial ones.
- Parental care – Hatching of eggs in bird comes under two heads – a. Precocial and b. Altricial. In the former type the birdling is immaturely hatched out but is found more selfdependant that the other. It can see, procure its food, covered with hatching plumes and almost unrest in nature. They can run and even swim, but can not fly. Koels, Chicken, Ducks, Doves etc. fall under this category. But, the other type is maturely hatched out but is found very much dependant upon its parents. Like, Swifts are plumeless and blind as they are hatched. They have to be in the nest throught the following week or more, solely dependant upon their parent’s nestling. The parents ensure their security and food as well as the extra heat needed for their further development. But, afterwards, they pleume and grow very quickly and learn how to fly and become selfsufficient, but it needs much more time than the other type. [/su_spoiler]
[su_spoiler title=”Learning or Learned Behaviour” style=”default” icon=”chevron”]
The behaviour which is acquired and modified in response to experience is called learned behaviour. For instance, a birdling of 3 days learns how to peak at food and Honey bees learn to identify flowers with more necter. The main benificial feature that works inharently in learning behaviour is adaptability, in comparison to innate behaviour. So, it can be changed keeping pace with the surrounding requirements or changes. In one word, a learning behaviour is the achievement of a new behavioural pattern, based upon previous experience.
W. H. Thorpe (1963) has defined learning as – “That processes which manifests itself by adaptive changes in individual behaviour as a result of experience“. Lorenz (1969) defined learning as – “An adaptive change in behaviour that results from experience“. [/su_spoiler]
[su_spoiler title=” Types of Learning” style=”default” icon=”chevron”]
There is no acceptable or unanymous classification of Learning yet. But, it can be categorized as follows –
- 1. Habituation
It is the simplest learning behaviour. In this case due to the continued lack of prize or punishment the animal gradually turns nonresponding to a given stimulus. So, it rather can be termed as a learning not to respond to a given stimulus. The merits of habituation includes responding to a peculiar stimulus with a probability of danger and subsequently not responding to it feeling safe due to the lack of any consequense of it.
Habituation is a common learning behaviour, observed everywhere in the animal world. For instance, when touched even by a leaf, a snail retreats back into its shell. It continues doing this over and over as touched more and more. But, after a few retructions, it avoids the stimulus being habituated not receiving any harm from it; it continues its movement without responding to the stimulus. Another instance is the fledding of Pegions from crop field with a Gunshot bird-scaring device. The birds respond to it in the primary sequences but not later, as they observe it over a period of time that there is no reaction or consequense of those noises. Later instead of the noise, they continue their feeding peacefully in the cropfield without flying away, what they did in the beginning, a few times.
Likewise, we can easily sleep inside a loud but familiar noise, but on the other hand we wake up in a small sound, which is new or peculiar to us.
- Conditioning or Associative Learning
Associative learning includes the involvement of two or more Stimuli at a time. In this process an animal can identify a Stimulus and can understand what is going to happen along with it; as it knows the situation which happened multiple times earlier. In this case the animal involves two Stimuli together. For instance, the going of a Farmar to his cropland by a Tractor is reacted by his Cattles, but doing such on other veheicles are overlooked. Because, the Cattle involves the Tractor and the Farmar with their food. Conditioning is of two types –
A. Classical or Pavlovian Contioning and
B. Operant Conditioning (Trial and Error Learning)
- A. Classical or Pavlovian Conditioning
In 1902 a Russian Physiologist, Ivan P. Pavlov (1849 – 1936) studied the secretion of saliva in Dog due to food reaction. He observed, the vision, smell and the taste of food induces or changes the section of saliva. His experiment (Fig. 12.3) was as follows –
- He let the Dog hear the Ding-dong sound in a Metronomy Machine, when there was no change in the amount of saliva secretion.
- He then presented some powdered meat to the Dog and measured the amount of saliva secreted.
- Then he represented to the Dog powdered meat and Ding-dong sound simultaneously and repeated it 5 or 6 times.
- Then he observed the secretion of saliva in the Dog only with Dong-dong sounds, never seen before in Case-1.
- With the repeatition of Case-4, the amount of saliva secretion falls gradually due to the lack of its involvement with food.
So, in this experiment, the Dog learns the involvement (relationship) of sound with food. This type of learning is termed as Classsical Conditioning. The response of saliva secretion with the ring of bell is a case of Conditioned Reflex. It is obvious that, the presentation of food is necessary within 1:00 minute of the sound production, to trigger the condioned reflex.
Features of Conditioned Reflex
- It is the involvement of two different stimuli presented at a time.
- It is totally a temporary condition.
- The response is totally involuntary.
- It is reinforced by its repeatition.
- Removal of the cerebral cortex totally ceases the response.
- 3. Complex Learning : Imprinting
Imprinting is a kind of simple but specialized learning. In comparison to others the Imprinted behaviour is fixed and not easily adapted. During the early days of their life cycles, Birds and Mammals undergo imprinting specially in their Receptive Stage (Critical period – Lorenz; Sensitive period – Recent). At this period the newly born individuals develop a bond with a comparatively large moving object and develop their permanent relationship on the basis of physical contact or heat reception. For example, a newly hatched goose follows anything moving infront of it. Naturally, mother is their first target of movement they try to follow. But, Australian zoologist and founder of Ethology, Conrad Lorenz, in his renowned book – King Solomon’s Ring describes that, parentless gooselings and ducklings followed him and considered him as their alternative parent. He revealed and described a wounderful practical instance of imprinting in Greyleg Goose (Anser anser) (Fig. 12.4)
In nature there are examples exposing adaptive significance, like – the learning capability through parents; e.g., learning how to fly, capture a prey, fight a foe or run away from a predator. For instance, the `smell’ of the steam in which migratory Salmon were hatched and to which they return to spawn.[/su_spoiler]
[su_spoiler title=”Altruism or Cooperation to each other” icon=”chevron”]
The term Altruism (Fr. altruisme, Ital. altrui) is a philosophical theory, postulated by welknown French Philosopher August Kooth. The term means –
- Unselfish regard for or devotion to the welfare of others.
- Behaviour by an animal that is not beneficial to or harmful to itself but that benefits others of its species.
According to this theory, each and every individual has its own generic characteristics which increases peace and happiness and decreases sorrow or unhappiness in others. One thing has to be found in this context, whether peace or happiness is the real target of life. The answer is, the real peace lies under the happiness of others, i.e., peace is achieved only when someone does some selfless dedication for his mates.
Altruistic Behaviour in Honey Bee Hive
The Honey bee (Apis) is a social insect and maintains a peculier life style. They live a colonial life in a bee hive, containing about 60,000 – 70,000 members, maintaing an organized systematic order of life with a division of labour for each and every individual. There are three castes found in a hive – The Queen, Drones and Workers.
The queen is the only fertile female in the colony, easily identified for its very large size and shape, who lays about 1000 – 1500 eggs per day; eggs can be fertilized and unfertilized. Within a week of its birth, the queen can mate a Drone and starts laying eggs within the next 2-3 days. She survives for 2-3 years and continuously enriching its colony. Form her fertilized eggs are produced the Workers, huge in number and from the unfertilized ones the Drones, few in number.
The Drone is bigger than a worker but smaller than the queen, healthy in structure and doing only a single function – mating the queen and survive a period of 2-12 days. According to some, they die just after the copulation and are taken up by other members (canabalism).
The workers are unfertile females, unable to produce eggs. But, some can give unfertilized eggs in absence of a queen from which small unfertile males generate. These female worker bees are called egg laying workers and can produce at best 28 eggs in their total life. The workers perform almost all the duties in a colony other than fertilizing an egg or mating, like –
- They consturct the bee hive with their body wax and ensure the security of the total colony.
- They forage a long distance in quest of honey and flower and bring information to the colony.
- They lead the total workers’ team to the esteemed target flowers and collect honey as a team-work.
- They scoop up the necter from the nectries of flowers and keep it for a time being in their very large crop where they let the necter to mix with their enzymes and which then converts into honey.
- They then pour the honey in a given pocket of the bee hive and fan it for dehydration.
- They rare the eggs keeping them in special cells in the hive, take care of larvae as they come out of eggs by feeding them Royal Jelly, a paste prepared with honey and their salivary juice; some larvae are fed with bee-bread, a mixture of pollen and honey.
- The royal jelly fed larvae turn into workers and drones, while the bee-bread eaters turn into queens.
- After a few ecdysis (moulting) the larvae convert into adult bees, but the interim guidance is given by workers.
- In case that the colony members have attained their maximum limits, a new queen with a number of drones and a huge number of workers, start for a new destination, built a hive there and lead a next colony.
- Even in that case, the workers bring information and location of the new colony site and build a hive in there.
So, the social life of Honey bees, especially the workers, is the best example of Altruistic behaviour. [/su_spoiler]
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Photo Credit: Capt. Kawsar Mostafa