• N V Joshi

      Articles written in Proceedings – Animal Sciences

    • Observations on the natural history and population ecology of the social waspRopalidia marginata (Lep.) from Peninsular India (Hymenoptera: Vespidae)

      Raghavendra Gadagkar Madhav Gadgil N V Joshi A S Mahabal

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      Ropalidia marginata, the most common Indian social wasp, belongs to a crucial stage of social evolution showing no obvious morphological caste differentiation but a behavioural caste differentiation and a dominance hierarchy that appears to influence division of labour. The nests consist of a single open comb that can sometimes have up to 500 cells and 10 pedicels. Nests are initiated and abandoned all round the year. Initiation is by 1–20 foundresses, 1–4 being the most common number. There is a great deal of variation in brood developmental times both within and between nests. Male progeny disappear from the nest soon after emergence while daughters stay on at the parent nest for a mean period of about a month. Small nests have a single egg layer while large nests have two or more females with well developed ovaries that presumably lay eggs. Most nests are short-lived, small nests being highly susceptible to failure. Large nests are less susceptible to failure but the emergence of multiple egg layers reduces the average relatedness of workers to the brood which presumably is the cause for large scale emigrations from these nests. An interaction of ecological and soical factors therefore appears to determine the growth of a nest.

    • On the communication of well-being

      Madhav Gadgil Malati Hegde N V Joshi Sulochana Gadgil

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      The form that any communicatory exchange takes would depend on the extent to which the interests of the signaller and the recipient are at variance. Where such interests coincide, i.e. in cases of mutualism, the signals may be conspicuous when an immediate response is favoured, but rather subtle and variable otherwise. Over 80 % of the events of tactile communication that we have noted in our study of the social behaviour of free ranging groups of tame elephants appear to belong to this latter category. On Smith’s standard classification, they can only be classified as ‘associative’, related to remaining in the company of another individual. However, such signals are commoner by a factor of 20–100 amongst elephant calves and their mothers and allomothers when compared to exchanges between adult cows. We suggest that the function of these signals is mutual monitoring of the state of well being amongst related individuals. The considerable degree of altruistic behaviour displayed in social groups, such as those of elephants is now believed to subserve the function of enhancing the inclusive fitness of the individuals concerned. We explore a mathematical model of exchange of social aid which suggests that animals in social groups may enhance their inclusive fitness further by adjusting the amount of social aid exchanged in relation to the state of well being of the donor as well as the recipient. Our model further suggests that optimal social aid depends on the state of well being in a complex fashion making it difficult for the recipient to deceive the donor so as to extract more aid. We therefore expect that by and large honest communication of the state of well being would be characteristic of the higher social animals. Such communication would be based on normal physiological changes consequent on a change in well being. Thus animals with a superior degree of well being would take postures conducive to greater activity, would be more receptive to sensory inputs and may also shift the balance of production of various metabolites. This monitoring of the well being has greatly advanced in the human species and may be at the base of the elaborate health care amongst human societies.

    • Growth in the Asian elephant

      R Sukumar N V Joshi V Krishnamurthy

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      Records of captive Asian elephants (Elephas maximus) were used to derive parameters of the von Bertalanffy function for growth in height, body weight and circumference of tusks with age. There was some evidence for a post-pubertal secondary growth spurt in both male and female elephants. Domestic elephants which were born in captivity or captured at a young age also showed a reduced growth in height in both the sexes and in body weight in males compared to wild elephants. Aspects of allometric growth such as height-body weight relationship are examined. The height was twice the circumference of front foot throughout the life span, indicating an isometric relationship.


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