REPRODUCTIVE BEHAVIOURS IN ANIMALS

WEEK: 6

SUBJECT: BIOLOGY

TOPIC: REPRODUCTIVE BEHAVIOURS IN ANIMALS

CONTENT: 1. Paring

1. Territoriality
2. Display of body colours
3. Seasonal migration

SUB-TOPIC 1: COURTSHIP BEHAVIOURS IN ANIMALS

Courtship is a collection of ritualized behaviours unique to each species that lead up to and enable animals to have successful sex union. Courtship may be simple, involving a small number of chemical, visual or auditory stimuli. It may also be a highly complex series of act by two or more individuals using several modes of communication. It helps strengthen pair bonds that may last through rising of the young. It particularly helps birds to select compatible or best mates and ensure viable offspring.

Types of Courtship Behaviour

Different species of animals show different methods and signs unique to them. Some courtship behaviour of animals is as follows:

• Paring

Many animal species exhibit pairing. These include toads, termites, fishes, human and some mammals. Pairing refers to a behavior that involves a mature male and female choosing each other and leaving their fold. They usually go together in twos (pairs)for a fresh or different place leaving the others behind. For instance, winged termites pair up and eventually start a fresh colony elsewhere. In the new place, the female becomes the king. Initially, the female attracts the male by releasing a scanty hormone (pheromone).They shed off one wing and later the second, first by the male and then followed by the female. These paired termites are usually seen at the start of the rainy season, swarming at night, especially near electric bulbs or lanterns.

• Territoriality

Territoriality is the behavior by which animal lay claim and defends an area against others of its species and sometimes members of other species. The territory defended could be hundreds of square miles in size or only slightly larger than the animal itself. A single animal, a pair, a family or entire herd may occupy the territory. Some animals use the territory as a source food and shelter and thus hold and defend it year round. Other animals establish a territory only at a certain time of the year, when it is needed for attracting a mate, breeding or raising a family.

The male Agama lizard exhibit territoriality. Usually there is only one adult male Agama lizard in a territory which could be an exclusive portion of a lawn, part of a roof or garden. Several female lizards and young males are usually the other members of this territory. The adult male lizard leads others back to its territory where they would stay overnight for protection against danger or predators. To gain dominance, the male becomes aggressive as soon as an intruding or rival adult male lizard enters its territory. It may make loud noise, launch forward to an opponent and even attempt to bite the rival male. It can threaten a rival by bobbing its head and expanding its gular fold. If the rival does not leave, a fight may ensue.

Establishment of territories ensures that there are enough compatible mating partners, no overcrowding or even under-crowding.

Humans also exhibit territoriality as they too defend their home out of jealousy.

• Display of Body Colours
  

Some animals carry out courtship exhibitions called displays. They are designed to show their interest in mating. Such animals include birds (fowls, hens, turkey and peacock) cricket, winged termite, lizard and he-goats. Display takes various forms in humans. They include the use of perfume, voice (intonation), beauty, seductive walking, facial expression, dressing and decoration. They use them to attract members of the opposite sex.

Display may be in the form of spreading beautiful feathers, making noise, wagging of tail, giving a hot chase, singing, dancing, feeding and building nest.

Display is exhibited in the following ways in some animals;

1. Goat: – The he goat chases the she goats hotly and makes a peculiar noise.

1. Lizards:-In their natural habitat, the female curves its back and rises up tail. The male in turn wags its tail, nods its head and shows off its brightly coloured (red) head and body to the female. The female could be attracted by this display.

1. Cricket: – The male cricket attracts the female by making shrill noise with its outer wings.
2. Birds:-Different birds exhibit diverse types of display. These include singing, dancing, feeding, building nests, preening and showing off their beautiful feathers and body.
3. Fireflies: – The male fireflies use flashes of light when flying around to seek mate. Female fireflies will use the same flashes to communicate their readiness for the male if interested. Some species even use different colours and intensities of light to signify their intentions.

• Seasonal Migration

These are seasonal movement of animals in response to unfavorable climatic conditions, food availability or to ensure reproduction. Animals migrate in order to bear their young in places relatively safe from predators and rich in resources. The female green turtles swim from their feeding grounds off the coast of Brazil when the time for laying their eggs draws near. They swim to tiny Ascension Island over 2000km away, haul themselves unto the sandy beach, scrape out shallow nest, and deposit their eggs. Once the eggs are deposited, they swim back to Brazil.

The fresh water eels spend most of their adult lives in the river of North America and Great Britain. However, during the spawning season, the adult migrate more than 5000km to the weedy Sargasso Sea between Bermuda and Puerto Rico to bread and spawn. The young eel take a year or two to reach America shores and they are often three year old before they reach European rivers where they feed and grow.

Types of migration include complete, partial, altitudinal, removal, latitudinal, reproductive, nomadic and irruptive migration.

SUGGESTED PRACTICALS

1. Teachers should show students pictures of colourful birds such as peacock, turkey and big cocks. He should encourage them to observe courtship features of these animals and discuss how the birds display them and for what purpose.
2. Students should be taken to the school farms or lawns. They should be shown how to identify the male lizard basking. Students should be shown how to identify the male lizard and how it claims or defends its territory. They should observe and discuss how it exhibits its courtship behavior.
3. Record and discuss your observation on the following:
   1. The aggressive nature of males to intruders
   2. Territorialism in Lizards
   3. Chasing strategy of cocks
   4. How the he-goat pursues the she-goat around the vicinity.

OBJECTIVE QUESTIONS

1. Reproduction behavior in animals include all of the following except ———- (a) Territoriality

(b) displays (c) Pollination (d) Pairing.

1. Identify the false statement in this list: (a) He-goat often pursues she-goat for mating purpose

(b) Male crickets attract female by making shrill noise (c) Some birds such as cocks and hens display dancing (d) Male toad often carries female toad during breeding.

1. Which of these animals exhibit seasonal migration? (a) Cattle egret (b) Peacock (c) Lizard (d) Turkey
2. When two mature animals go away from the rest in twos, this is referred to as ———– (a) Migration (b) Territoriality (c) Pairing (d) display
3. Courtship behavior in cock or turkey does not include one of the following (a) Feeding (b) Singing (c) dancing (d) Fee migration

EVALUATION

1. (a) State three courtship behavior in named animals
   1. Described any two of them concisely
2. 1. (a) Explain the term pairing
      1. Described the behavior with a relevant example

1. (a) What is the meaning of territoriality in animals?
   1. Described this behavior in a named animal.

WEEKEND ASSIGNMENT

Read about Biology of heredity: Transfer and expression of characters in organism. Modern Biology for SSS by Ramalingam S.T. Pages 540-555

WEEKEND ACTIVITY

1. State the differences between (i) dominant and recessive character (ii) Genotype and phenotype
2. Described the structure of DNA