K. Kortmulder

Reproductive biology of six Barbus species indigenous to Sri Lanka

SynopsisSix Barbus species were sampled monthly in two river systems of SW-Sri Lanka, over a 15 month period. Sex ratio, size at maturity, maximum and modal sizes, distribution of egg sizes in mature ovaries and individual fecundities were measured. Seasonal changes in size distributions, sex ratio, frequency of female gonadal stages and the gonado-somatic index (GSI) were analysed on the basis of the monthly samples. Seasonal cycles in reproductive activity were assessed, using mainly the two last-mentioned parameters and the appearance of young in the populations. It was found that three of the species (B. bimaculatus, B. cumingi, B. vittatus) tend to concentrate their reproductive activities in certain months of the year, roughly coinciding with the seasonal peaks of precipitation. The other three (B. nigrofasciatus, B. dorsalis, B. titteya) spread their reproductive efforts more evenly through the year. Sexual dimorphism with females bigger, relatively early maturation of males, high maximum GSI values, a distinct ‘final mode’ of large mature ova in the egg-diameter distribution, and a comparatively steep increase of fecundity with body weight or gonad weight were found to be more or less consistently associated with seasonal reproduction.

Dry-season spawning in a cyprinid fish of southern India

SynopsisA population of the S. Indian cyprinid fishBarbus melanampyx was sampled monthly through 24 months. Seasonal cycles of the gonado-somatic index (GSI), ovarian stages, male breeding tubercles, spawning behaviour and population structure were assessed. These fish breed strictly seasonally during the main dry period: December/January through April. Comparison with other Barbus species of the same general region led to the conclusion that the patterns of reproductive investment ofB. melanampyx are similar to those of perennial species, and different from those of wet-season spawners. The reasons for this rather unexpected result were found in the more constant conditions prevailing during a dry season as compared to the monsoon. It was argued thatB. melanampyx and the species spawning perennially are in effect ‘small-brood’ spawners, rather than partial spawners.

Habitat, associations and competition of eight Barbus (=Puntius) species (Pisces, Cyrinidae) indigenous to Sri Lanka

A detailed description of the typical habitats of 8 Barbus species of Sri Lanka is given. The distribution of their typical habitats over the various waters leads to the grouping of species in associations. Quantitative analysis of catching data corroborates these groupings. Food competition and competition for spawning grounds is discussed following the species associations.

On ethology and human behaviour

SummaryThe paper provides a critical discussion of the role ethology may play in the study of human behaviour. The mechanisms of avoidance of consanguineal mating in some animal species and Man are analysed and compared. Aggression and competition are discussed in relation to agonistic courtship, and play behaviour.

Displacement Behaviour Solving a Silent Contradiction

Displacement acts, once a hot topic in ethology, but wrapped in silence for two decades since, have recently been suggested to indicate and relax social tension (Maestripieri et al., 1992; Wiepkema, 1987). The first of these contentions seems to be in contradiction with some of the classical ethological studies of displacement behaviour, in particular those supporting the disinhibition hypothesis, since the latter would not predict any positive correlation between amount of tension (i.c. intensity of the conflict) and the occurrence of displacement acts.A critical examination of these studies reveals that a positive correlation of the sort has been found, but that proponents of the disinhibition hypothesis tried to explain it in terms of their own model, rather than taking it at its face value. (The reason for this is that they viewed it as pleading for the surplus hypothesis which they rejected). It can be shown that at least some of their explanations are grounded on assumptions which are arbitrary. Also, the disinhibition hypothesis does not account for the occurrence of displacement behaviour in contexts with tension but without conflict.This discussion leads to a new interpretation of displacement behaviour, in which tension is the direct cause, whether generated by conflict or otherwise, and relaxation is brought about by a breaking of the cognitive symmetry between actors. It is indicated how this interpretation may be tested with experiments.

Play-like behaviour: an essay in speculative ethology

It is claimed that certain processes of individual behaviour and of interaction between individuals run parallel. Such parallels are seen along three axes: antagonism-coordination, constriction-expansion and neutral-play-like.Characteristics of ritualized behaviour and play are analysed and the two categories of behaviour are compared in detail. They are shown to differ largely in degree of expansion. They also differ along the antagonism-coordination axis. Both are play-like.A theory comprising both ritualized behaviour and play is attempted. The concept of field interaction is introduced. The physical theory of elect ro-magnetism is used as a conceptual model.Positive and problematic aspects of the theory are discussed: Is the behavioural field polarised or not? The relationship between aggression and play-like behaviour is considered, both as a motivational problem and in phylogenetic perspective. Some limits to the theory are indicated. Relationships of the theory to some other theories are briefly discussed.

A Combined Field Study of Barbus (= Puntius) Nigrofasciatus GÜNther (Pisces, Cyprinidae) and Water Chemistry of Its Habitat in Sri Lanka

This paper is part of a series dealing with the biology and behaviour of Sri Lanka Cyprininae (DE SILVA & KORTMULDER, 1977; DE SILVA, KORTMULDER & WIJEYARATNE, 1977). The present paper investigates the natural environment (both morphologically and chemically) and the behaviour in the field of Barbus nigrofasciatus, a species formerly studied in detail in captivity. Concordance between the behaviour as observed in aquaria and in the field is nearly perfect. Predictions, based on the aquarium studies, as to the shape of the natural environment and of the movements of the fishes in it are tested in the field and found to be largely correct. The species is likely to be endangered if present trends (deforestation, fishing) continue. Further, in this paper, the assessment of pH by means of a colorimetric method is critically evaluated and corrections on the method proposed.

Towards a field theory of behaviour

Classical ethology, with its emphasis on separability of parts, has largely failed to do justice to the wholeness of the individual animal, to the integrity of group behaviour and to the continuity between observable behaviour and consciousness. Field theory has potentialities to do better, as illustrated in this paper with reference to morphogenetic and behavioural fields. A behavioural domain is delineated — playlike behaviour — where field theory is particularly relevant. It is shown that the concept of symmetry can suggest new questions as well as explain some generally known phenomena of group behaviour. New interpretations of displacement activities and of etho-ecological adaptations are offered, both of which involve the whole individual animal.

On some generative orders of behaviour

The sociobiological fashion has for a long time discouraged the development of theories of the immediate causation of behaviour. It is only recently that new approaches are being developed to improve on the classical ethological theory originated by Lorenz and Tinbergen. One new departure is behavioural field theory (BFT) which brings back the concept of energy in behaviour, without being susceptible to the drawbacks of the ‘energy’ or fuel concept of classical theory. In this paper the new theory is explained in some detail and it is shown to be illuminating, predictive and testable in examples of play-like and territorial behaviour.

The congener: a neglected area in the study of behaviour

This paper seeks a deeper understanding of the congener as a factor in animal and human behaviour. It does so, not by concentrating on analyses of stimulus exchanges - largely specific to the species - by which a congener is recognized, but on the more general questions of why a notion of congener exists at all and why it plays such an extraordinary important role in animal and human behaviour.Three separate approaches, by way of anthropomorphic psychology, a paraphysical energy model and the physical theory of the implicate order, lead to the recognition of a certain inseparability of ‘self’ and ‘congener’; and to an interpretation of the content of the notion of congener and of the behaviour in relation to it, in terms of the fundamental concept of energy and the even more fundamental one of order.