Variation In Reproductive Behaviour Research Articles

Behavioural allometry and interdemic variation in sexual behaviour of the sailfin molly, Poecilia latipinna (Pisces: Poeciliidae)

Sailfin mollies, Poecilia latipinna, exhibit remarkable levels of intraspecific variation in reproductive behaviour. Larger males exhibit higher rates of courtship and lowered rates of gonoporal nibbling and gonopodial thrusting (forced copulation attempts). Larger males have relatively longer and higher dorsal fins than smaller males. The dorsal fin is a prominent component of the courtship display. Variation in fin measurements, behaviour patterns, and body size of mature males is continuous, and fin shape and behaviour patterns are allometrically related to body size. The allometric pattern is displayed by individual traits as well as by the morphological or behavioural traits in ensemble. Eight populations of mollies from markedly distinct habitats exhibited similar consistent levels of intrademic variation in the size of mature males. Detailed studies on three populations showed that dorsal fin shape could be described by the same regression relationship in all populations, and indicted that a male's shape was determined by his absolute body size. By contrast, there was some variation among populations in the relation of behaviour patterns to male body size. The pattern of this interdemic variation indicated that a male's behaviour patterns were influenced by his relative size in a population. Successful inseminations following forced copulations were rare. The average size of successful males was smaller than the average size of unsuccessful males in all three populations. These results indicated that successful insemination through forced copulation was, like behaviour patterns generally, more a function of the relative size of the male, than his absolute size.

Metabolic Correlates of Anuran Behavior

Frogs exhibit extensive diversity in their repertoires of social, reproductive, defensive, and predatory behavior, and in the metabolic processes that support these activities. Three aspects of anuran biology (foraging mode, post-metamorphic ontogenetic changes in ecology, and reproductive behavior) are analyzed for their correlations with metabolic capacities. Anurans that forage widely for prey have greater capacities for aerobic ATP production than do sedentary foragers. This relationship appears to extend to intraspecific analyses; significant differences in aerobic capacity among populations of a species of dart-poison frog are associated with differences in feeding ecology. Ontogenetic change in metabolic capacity is directly coupled with ontogeny of behavior. The magnitude of post-metamorphic changes in physiology, behavior, and ecology appears to be related to differences in life history. A relatively short larval stage and small body size at metamorphosis, such as that found in American toads, are associated with extensive post-metamorphic changes in oxygen carrying capacity of the blood, cardiac muscle mass, and aerobic capacity of predispersal juveniles. In contrast, predispersal juveniles of species with long larval periods and large body size at metamorphosis possess adult physiological and behavioral features. Anuran reproductive activities, especially calling to attract mates, are energetically demanding, suggesting that the behavior of male frogs at a breeding pond may be limited by their metabolic capacities. However, the only study that has attempted to relate individual variation in reproductive behavior to individual variation in aerobic capacity found no correlation between those characteristics. The complexity of anuran biology ensures that physiological characteristics of anurans reflect many aspects of ecologyand behavior, some of which act independently, others in concert. Carefully designed experiments that incorporate both field and laboratory data are required to assess these interlocking features.

Annual variation in reproductive behavior, testosterone, and plasma FSH levels in the Rouen duck, Anas platyrhynchos

The annual variation in four types of reproductive activity (social display, sexual behavior, aggressive behavior toward males, and toward females) were studied in five male domestic ducks kept in controlled environmental conditions. The changes were compared with the variation in the plasma levels of testosterone and follicle-stimulating hormone (FSH) as measured by radioimmunoassay. The hormone levels are compared with the data available on the hypophyseal-gonadal cycle. The behavior and physiological variations were analysed statistically. Sexual behavior correlates with testosterone levels while social displays rather surprisingly appear linked to the titre of blood FSH. The possibility of a direct behavioral effect of gonadotropins is discussed.