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Current climate change is leading to increasingly unpredictable environmental conditions and is imposing new challenges to wildlife. For example, ambient conditions fluctuating during critical developmental periods could potentially impair the development of cognitive systems and may therefore have a long-term influence on an individual's life. We studied the impact of temperature variability on zebra finch cognition, focusing on song learning and song quality (N = 76 males). We used a 2 × 2 factorial experiment with two temperature conditions (stable and variable). Half of the juveniles were cross-fostered at hatching to create a mismatch between pre- and posthatching conditions, the latter matching this species' critical period for song learning. We found that temperature variability did not affect repertoire size, syllable consistency, or the proportion of syllables copied from a tutor. However, birds that experienced variable temperatures in their posthatching environment were more likely to sing during recordings. In addition, birds that experienced variable prenatal conditions had higher learning accuracy than birds in stable prenatal environments. These findings are the first documented evidence that variable ambient temperatures can influence song learning in zebra finches. Moreover, they indicate that temperature variability can act as a form of environmental enrichment with net positive effects on cognition. [ABSTRACT FROM AUTHOR]

Opponent asymmetries often determine the probability of winning a fight in agonistic situations. In many animal systems, the asymmetries that drive the dynamics and outcome of male—male contests are related to resource holding potential (RHP) or territory ownership. However, recent studies have shown that this is not the case among females and suggest that resource valuation may be more important in that context. We studied contests between the female jumping spider, Phidippus clarus, and compared them with male–male contests in this same species. Our observations document several key differences between the sexes: Precontact and contact phases are longer in females, ritualized displays are rare in females but common among males, and female fights are more likely to end in injury or death. In sharp contrast with male contests, female weight and size do not correlate with signaling behavior, and the outcome of fights is predicted by differences in resource valuation rather than RHP. We interpret these differences in light of the different natural history of the sexes and discuss how the economics of fighting may lead to the evolution of ritualized displays in males and a “desperado effect” in females. [ABSTRACT FROM PUBLISHER]