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The link between the expression of the signals used by male animals in contests with the traits which determine success in those contests is poorly understood. This is particularly true in holometabolous insects such as horned beetles where signal expression is determined during metamorphosis and is fixed during adulthood, whereas performance is influenced by post-eclosion feeding. We used path analysis to investigate the relationships between larval and adult nutrition, horn and body size and fitness-related traits such as strength and testes mass in the horned beetle Euoniticellus intermedius. In males weight gain post-eclosion had a central role in determining both testes mass and strength. Weight gain was unaffected by adult nutrition but was strongly correlated with by horn length, itself determined by larval resource availability, indicating strong indirect effects of larval nutrition on the adult beetle’s ability to assimilate food and grow tissues. Female strength was predicted by a simple path diagram where strength was determined by eclosion weight, itself determined by larval nutrition: weight gain post-eclosion was not a predictor of strength in this sex. Based on earlier findings we discuss the insulin-like signalling pathway as a possible mechanism by which larval nutrition could affect adult weight gain and thence traits such as strength. [ABSTRACT FROM AUTHOR]

Changes in female reproductive investment can have large effects on offspring quality and thus maternal fitness. An immune activation is often expected to lead to a reduction in reproductive effort in order to release resources necessary for costly resistance to infection. Alternatively, an increase in investment in current reproduction may occur in order to maximize lifetime reproductive success: the so-called “terminal investment” effect. Additionally, females are expected to invest more in their reproductive effort when mating with higher quality males. Here, we investigate how an immune response and male quality affect the reproductive decisions made by female dung beetles, Euoniticellus intermedius. Female dung beetles invest a large amount of energy into each offspring, building large brood balls into which a single egg is laid. Maternal investment is therefore easily estimated from the number and size of the brood balls constructed. We found no affect of the mated male quality on female current reproductive investment. However, immune activation with lipopolysaccharide caused a significant reduction in the number of brood balls produced but did not affect brood ball size. An immune activation therefore caused resources to be diverted away from reproduction, as predicted by the “cost of immunity” hypothesis. Although life-history theory predicts 2 potentially opposing outcomes of an immune activation, a summary of studies investigating the trade-off between immune investment and current reproduction fails to provide any clear trends of what may predict the direction of this trade-off. [ABSTRACT FROM PUBLISHER]

1. Signals used during male combat are expected to be honest indicators of fighting ability. However, recent studies show that dishonesty in male signalling is more prevalent than previously believed. 2. Here we show that regenerated (leptochelous) claws in male Uca mjoebergi fiddler crabs are not only dishonest signals of two types of whole-organism performance capacities that are likely to be useful during fights (claw closing force and pull-resisting force), but they are also less effective as weapons in situations where males are unable to bluff. 3. Original (brachychelous) male claws are statistically significant predictors (independent of body size) of both closing force and the force required to pull a male out of a tunnel. By contrast, leptochelous claw size does not convey information on those performance capacities following control for body size. 4. Furthermore, claw size affects fighting ability such that leptochelous residents are at a significant competitive disadvantage to brachychelous residents, although claw type does not affect the ability of non-resident males to win fights. 5. This study is among the first to show that male armaments can dishonestly signal performance traits that are likely important for winning fights, and is the first to show evidence for dishonest signalling of multiple components of fighting ability. [ABSTRACT FROM AUTHOR]

While mate choice is often assumed to be based on an absolute value that may reflect underlying male quality, many mating systems facilitate the comparative evaluation of males. Females can encounter a number of potential mates, either sequentially or simultaneously, before making a mate choice decision. Consequently, the attractiveness of one male may depend on the attractiveness of other males a female has previously encountered. To examine whether female choice in the fiddler crab Uca mjoebergi is based on the comparative evaluation of males, I altered the social context in which a set of males were encountered. Using a robotic crab system to manipulate claw size and wave rate directly, I determined female preference for two male options in the absence and presence of an asymmetrically dominating decoy option. The decoy male option was designed to change the relative attractiveness of the initial two male options. The presence of the decoy significantly altered the absolute preference, but not the relative preference, for the two male options. While this study clearly demonstrates that female U. mjoebergi are not using strict absolute preferences when ranking each male''s attractiveness, it does not conclusively support comparative evaluation mechanisms. One possibility is that sexually selected traits in a complex signalling system often vary in how reliably they reflect male quality, and females may use a combination of absolute and comparative measures when assessing male quality. [Copyright &y& Elsevier]

Underlying male quality is often reflected in the condition of sexually selected traits. In fiddler crabs, male success in both intra- and interspecific interactions is highly dependent on the size of the major claw. However, males are often forced to autotomize their major claw. Claw regeneration significantly altered the structure of a males'' major claw in Uca mjoebergi. We found, however, that claw regeneration did not affect signal quality. Both males and females were unable to visually distinguish a regenerated claw from an original claw. Although regenerated males were inferior fighters, males were able to compensate for this fighting disadvantage by avoiding fights with other males. Regenerated males were, however, less likely to acquire and defend high-quality territories and consequently suffered a decrease in mating success. [Copyright &y& Elsevier]

Evidence is growing that an individual's propensity to take risks in the presence of a predator is correlated to behaviors that can affect individual fitness. We examined whether risk-taking behavior predicts aggression, surface activity levels, and mating success in male fiddler crabs, Uca mjoebergi. Risk-taking behavior was highly consistent among individuals, remained stable over time, and was unrelated to male size. We found that males that took greater risks in the presence of a potential predator also behaved more aggressively when searching for a new territory. In addition, bold males exhibited higher surface activity levels and spent more time courting females compared with their shy counterparts. Although risk-taking behavior was independent of other sexually selected traits, it accurately predicted male mating success in U. mjoebergi. We suggest nonsexually selected traits, such as risk taking, may represent important behavioral predictors of success in other species. [ABSTRACT FROM PUBLISHER]

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout-vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85 mm SVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17-19 mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significant decrease in testicular activity was in mid-winter (June-August), thus, spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended to eat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance. We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items. [ABSTRACT FROM AUTHOR]

Although many animals use refuges to avoid predators, it is often costly to do so. The longer an individual remains in a refuge, the less time it has available for other essential activities, such as foraging and mate searching. Animals should therefore optimize the time spent in a refuge after an attack by adopting a flexible approach to predator avoidance. I examined refuge use in the fiddler crab, Uca mjoebergi, under variable foraging and mating contexts on a mudflat in Australia. There were no sex or size differences in refuge use, suggesting that there are no morphological or gender biases in predation risk. Risk-taking behaviour in U. mjoebergi was, however, highly flexible and appeared to be strongly dependent on the trade-off between the costs and benefits of hiding. Refuge use varied between optimal foraging and reproductive periods of a semilunar cycle. Loss of foraging time influenced risk-taking behaviour in both males and females since both were quicker to re-emerge when food levels were high. During the reproductive period, crabs took longer to re-emerge because of few foraging opportunities, as well as few mating opportunities since receptive females were rare. However, when mating opportunities for males were experimentally increased by introducing a tethered female, actively courting males engaged in highly risky behaviour and re-emerged after a few seconds, with some males abandoning refuge use completely. Refuge use in U. mjoebergi is therefore highly flexible, with the decision to re-emerge influenced by fitness benefits. [Copyright &y& Elsevier]

We studied tree agama (Acanthocercus a. atricollis) habitat use in the Magaliesberg mountain range in northern South Africa using sightings of marked individuals, and in a few cases, radio-telemetry. Acanthocercus a. atricollis preferentially selected thorn trees (46%; Acacia karroo), followed by common sugarbush (10%; Protea caffra) and dead trees (9%). The type of tree selected was unrelated to lizard age class or sex. Multivariate analysis failed to show any age class or sex effects for specific tree physical characteristics, but did reveal a preference for trees with greater diameter, canopy cover and incidence of parasitic plants. We suggest that more 'complex' trees may enhance crypsis, facilitate escape from predation, or provide a foraging advantage. Acanthocercus a. atricollis selected night-time perches higher than those used during the day, possibly further offsetting predation risk. [ABSTRACT FROM AUTHOR]

Summary: Male fiddler crabs (Uca mjoebergi) produce highly synchronized courtship waves. Is this a cooperative behaviour because females preferentially approach groups that wave synchronously? Or is it a competitive behaviour because of female choice for males that wave first, with the resultant selection on males generating synchrony as an epiphenomenon ? To find an answer we used robotic male crabs to measure female mating preferences. We show that females do not prefer males waving in synchrony, but they strongly prefer males that wave first (‘leaders’). Synchrony therefore appears to be a by-product of competitive interactions between males. [Copyright &y& Elsevier]