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The article discusses behavioral studies of Cuban Crocodile Crocodylus rhombifer alongwith information on observations made at the Smithsonian National Zoological Park in Washington, D.C. It reveals that object play is the most common type of play reported in crocodilians. It also mentions play types such as locomotion play, social play and object play and also reveals that C. rhombifer is in serious danger of extinction.

Sexual selection requires both that there is heritable variation in traits related to fitness, and that either some of this variation is linked to traits of the parents, and/or that there are direct benefits of choosing particular individuals as mates. This suggests that if direct benefits are important offspring performance should be predicted by traits of the rearing adults. But if indirect benefits are more significant offspring performance should be predicted by traits of the adults at the nest-of-origin. We conducted cross-fostering experiments in great tits (Parus major) over four years, in two of which we manipulated environmental conditions by providing supplemental food. In a third year, some nestlings were directly supplemented with carotenoids. Nestlings in broods whose rearing adults received supplemental food were heavier and had improved immune responses even when controlling for body mass. Nestling immune function was related to measures of the yellow plumage color of both the rearing male and the putative father. Nestling body mass was influenced by the coloration of both the rearing female and the genetic mother. Our results suggest that features of both their social and putative genetic parents influence nestling health and growth. From this it would appear that females could be gaining both direct and indirect benefits through mate choice of male plumage traits and that it would be possible for males to similarly gain through mate choice of female traits. [ABSTRACT FROM AUTHOR]

It has been suggested that secondary sexual ornamentation signals male ability to resist infections, as only high-quality individuals are able to invest both in high immune defence and elaborate ornament expression. Such ornaments could thus serve as indicators of male quality and could be used by females in choosing mates. Ostriches are sexually dimorphic with regard to coloration of their feathers, bill, neck and legs, and have a promiscuous mating system, with a high degree of reproductive skew, particularly in males. We investigated the relationship between the coloration of the feathers, bill, neck and legs of 15 male ostriches, maintained in a breeding flock, and the cell-mediated (measured using a phytohaemagglutinin (PHA) injection) and humoral components of their immune systems, as well as their heterophil:lymphocyte ratio. We found that male responses to PHA injection and humoral responses to tetanus were predicted by leg coloration, humoral responses to diphtheria were predicted by white feather coloration, and the heterophil:lymphocyte ratio was related to bill coloration. These traits, which relate to male immune capacity, are exposed during male–male interactions and courtship display, so we suggest that these visual cues could provide valuable information on male quality to females (as well as rival males), forming the basis of mate choice in this species. [Copyright &y& Elsevier]

Life history theory predicts that females should modify their investment in a particular breeding attempt according to the likelihood of its success, as the investment of females in reproduction is typically higher than that of males. The ostrich mating system is promiscuous, and is thus a particularly interesting one in which to investigate differential investment by the sexes. To date, there has been no evidence that female ostriches discriminate between males as potential mates, but the degree of dimorphism in this promiscuous species and the variation in chick size within clutches suggest that differential maternal investment is likely. We investigated the relationship between egg mass and coloration of the feathers, bill, neck and legs of 15 male ostriches, maintained in a breeding flock at an ostrich farm in South Africa. Paternity was determined using microsatellite markers. We found that the colour of the neck, white and black body feathers, and the brightness of black feathers, predicted egg mass. These traits are exposed during the male courtship display, so we suggest that these visual cues influence the degree of maternal investment in eggs through their influence on female perception of mate quality. [Copyright &y& Elsevier]

For intersexual selection to occur, it is necessary that females choose between males. It is now well appreciated that constraints exist, which preclude females sampling all the available males in a population. These constraints are likely to have caused the evolution of sampling rules (such as the “best-of- n” rule) by which females sample males. Here we investigate the impact of female subsampling of the male population, not on the evolution of sampling behaviour, but on the population-level correlation between a male trait and currencies such as reproductive success. This study is important as it illustrates when population-level correlations can be safely used to infer the presence and strength of sexual selection in the field. We find that the correlation between a male trait and a mate choice variable rises steeply as the number of males sampled by each female increases, flattening above seven to ten males sampled. This shape is found to be remarkably robust, and little affected by, for example, the mate choice variable used, by noise in assessment, by sampling behaviour depending on female quality, or by population size. The only variable found to have a large impact is male clumping according to their “quality”. If females are sampling about four males, the maximum correlation that can be found at the population level is in the range 0.4–0.6, perhaps as little as 0.1 if males are strongly clumped. A recent review of the literature suggests that four is the average number of males that females sample. Thus, the absence of a strong correlation cannot by itself be used to infer that sexual selection is weak, as it may be due to females sampling few males. [ABSTRACT FROM AUTHOR]

Suggests that the size of pectoral tufts and tail length in male scarlet-tufted malachite sunbirds are influenced by environmental conditions rather than male age. Mediation of male-male competition; Differences in the condition of males; Population tail length; Availability of food.

Presents information on wrens, Troglodytes troglodytes, while focusing on the usefulness of cues in mate choice to females. Evaluation of the information contained in cues used in mate choice; Information on an experiment conducted in 1994; Results of the experiment.

Summary: Models of sexual selection suggest that mate-choice preferences are favored because differences between males in their degree of ornamental exaggeration convey useful information about the direct or indirect benefits they have to offer . Such arguments assume that variation in male ornament size can be attributed to variation in the degree of sexually selected exaggeration. We provide the first test of this assumption by conducting tail-length experiments in male barn swallows. Over the last twenty years, a large amount of work has shown that female barn swallows are influenced by male tail length when choosing a mate . Recent experiments have shown that a combination of natural and sexual selection results in the elongated tail streamer—a tail that is on average across the population about 12 mm (∼10%) longer than the aerodynamic optimum . We show that the aerodynamically optimal tail length varies significantly between males, whereas the extent of streamer elongation beyond the optimum does not. Similarly, the aerodynamically optimal tail length significantly predicts observed tail length and conveys information about flight performance, whereas the extent of sexually selected exaggeration of streamer length does not. Therefore, contrary to handicap models of sexual selection, the sexually selected exaggeration of this trait provides females with little information about any aspect of mate quality. [Copyright &y& Elsevier]

Sexual selection requires both that there is heritable variation in traits related to fitness, and that either some of this variation is linked to traits of the parents, and/or that there are direct benefits of choosing particular individuals as mates. This suggests that if direct benefits are important offspring performance should be predicted by traits of the rearing adults. But if indirect benefits are more significant offspring performance should be predicted by traits of the adults at the nest-of-origin. We conducted cross-fostering experiments in great tits (Parus major) over four years, in two of which we manipulated environmental conditions by providing supplemental food. In a third year, some nestlings were directly supplemented with carotenoids. Nestlings in broods whose rearing adults received supplemental food were heavier and had improved immune responses even when controlling for body mass. Nestling immune function was related to measures of the yellow plumage color of both the rearing male and the putative father. Nestling body mass was influenced by the coloration of both the rearing female and the genetic mother. Our results suggest that features of both their social and putative genetic parents influence nestling health and growth. From this it would appear that females could be gaining both direct and indirect benefits through mate choice of male plumage traits and that it would be possible for males to similarly gain through mate choice of female traits. [ABSTRACT FROM AUTHOR]