Tufted titmice, Baeolophus bicolor, produce calls in the contexts related to threat and approach of, and capture by, a predator. In titmice, these calls transition from the chick-a-dee call, used in a wide range of social contexts, to ‘distress’ calls that are produced by birds when captured and held by a predator or human observer. A recent study indicated that titmice modify the note composition of their calls in the presence of such threatening stimuli. Here, we tested whether female and male titmice differed in their calling behavior, as relatively few sex differences have been documented in calls shared by female and male songbirds. Individual titmice were captured in walk-in treadle traps, and we gradually increased the level of fear or arousal by approaching and finally capturing the bird in the hand. Male titmice produced more chick-a-dee calls than females as the level of threat increased, up to the point of capturing the bird in the hand. Furthermore, the note composition of calls produced by males differed from that of calls produced by females. A limitation to our study is that our method did not allow us to rule out the possibility that size or dominance differences, rather than sex, were the main reason for the differences in calling we detected. However, increased size generally was not associated with increased calling. We discuss some possible explanations for variation in distress calling behavior in titmice.

Throughout their lives, animals adapt their behaviour to environmental fluctuations and to their own requirements. In social insects, behavioural changes are often particularly conspicuous. For example, in many ant species, reproductive sexuals leave their maternal nests and engage in risky mating and dispersal activities. Female sexuals experience, during a short period of time, dramatic changes in terms of behaviour and environmental conditions. But because sexual activities of ants are not easily observed, few studies have quantified in detail how behaviour alters with maturation and mating. We studied how various behavioural traits of Leptothorax gredleri female sexuals, a species in which female sexuals attract males by ‘female calling’, change before and after mating. We tested the hypothesis that behavioural variation reflects the altered requirements of queens to adapt to a particular situation. To this end, we compared geotactic, phototactic and locomotor behaviour across a wide range of life stages from lightly coloured, unmated female sexuals to old, mated queens. The results showed that female sexuals of L. gredleri change conspicuously their geotactic, phototactic and locomotor behavioural traits over their life stages. Three different behavioural states were evident (1) from light to dark female sexuals, individuals have negative phototaxis and reduced locomotor activity; (2) mature female sexuals during the daily period of sexual activity have strong phototaxis, negative geotaxis and an important locomotor activity; and (3) freshly mated and old mated queens avoid light and decrease their locomotor activity. These sharp differences in behaviour between stages match the transition from the relative safety of the nest chamber to the adversary world outside the nest, and back.

Soft songs have been detected in many songbirds, but in most species, research on soft songs has lagged behind studies of broadcast songs. In this study, we describe the acoustic features of a soft song in the brownish-flanked bush warbler Cettia fortipes. Compared with the broadcast song, the warbler's soft song was characterized by a lower minimum frequency and longer duration, and it had a higher proportion of rapid frequency modulation notes. Using playback experiments, some in combination with mounted specimens, we found different responses to soft and broadcast songs, and we found that soft song can predict aggressive escalation (attack). We conclude that the soft song is an aggressive signal in this species.

Selection favors larger body size in many taxa. In some species, larger individuals are more active and bolder than smaller conspecifics, but the nature of this relationship is unclear: Is body size a predictor or a consequence of behavior? Any effect of behavior on body size may be through its effect on competitive ability, suggesting that the presence of potential competitors could exaggerate or suppress this relationship. In this study, we tested whether an individual's activity rates early in life predict its future body size by measuring same-aged, sibling eastern fence lizards before (8 d) and after (8 wk) they significantly diverged in body size. We tested for an effect of conspecific presence (potential competition) on the relationship between early behavior and future body size by housing some lizards in sibling groups and others individually, using a split-clutch design. Our results reveal that individuals' activity rates do not significantly differ between 8 d and 8 wk of age. At 8 wk (but not 8 d) of age, more active siblings were also larger in both housing treatments; however, early activity rates did not predict body size later in development for either of these groups. Conversely, body size at hatching did predict size at 8 wk. Although variation in activity rates exists prior to divergence in body size, and activity and body size are correlated later in development, our results suggest that higher activity rates are unlikely to be driving body size divergence in this species. Instead, very small differences in body size at hatching appear to be compounded over time and drive much more exaggerated differences in later body size.

In polygamous mating systems, a capability to discriminate against familiar mates may be beneficial to both sexes. Polyandrous females, for instance, may enhance the odds of finding sires with optimal genetic compatibility or high genetic quality by mating with multiple different males; polygynous males, in addition, may more efficiently invest their limited ejaculates across multiple (rather than single) females. The Coolidge effect facilitates this kind of mate discrimination, as sexual motivation declines across consecutive copulations with a familiar partner but resurrects with a novel mate. In simultaneous hermaphrodites, we expect the Coolidge effect to show sex role-dependent patterns and vary with previous sex-specific mating activity. Using the promiscuous hermaphroditic sea slug Chelidonura sandrana, we investigated (1) whether sexual motivation indeed declines when repeatedly exposed to familiar partners, (2) whether the Coolidge effect occurs in a sex-specific manner and (3) whether ejaculation is strategic with respect to partner familiarity. We found neither mating latency, nor penis intromission duration, mating propensity or the frequency of sex role alternations to vary significantly with treatments. Furthermore, slugs did not donate larger ejaculates to novel than to familiar partners. Partner novelty thus elicited no detectable response in sexual motivation or mating effort in C. sandrana. We suggest that the sea slugs' promiscuous mating system in often large mating aggregations makes mate discrimination based on novelty obsolete in comparison with more relevant criteria such as partner body size or mating history.

In many animals, response to predators occurs at greater distances the further an individual is from a refuge, but this has rarely been investigated in birds. Here, we test the hypothesis that the further from refuge (i.e. water) a foraging black swan Cygnus atratus is situated, the longer its flight initiation distance (FID) in response to a pedestrian approach on land. As predicted, swans situated farther from water exhibited longer FIDs compared with those closer to the shore. In addition, there was the possibility of an interesting interaction effect (p < 0.061) of sex and direction of approach on FID. Whilst males tended to not alter their response in relation to the angle of approach relative to the water, females tended to respond at longer distances, when approached from the shore than when approached from the land or parallel to the shore. This is one of the first reports of sex differences in FIDs for birds, with sex differences only manifesting themselves under certain approach types. Group size, the order of repeated approaches, and time of day did not influence responses, although starting distance of approach was positively related to FID.

Consistent individual differences in behaviour of animals, that is, personalities, are both widespread and widely studied, but very few studies also include cognitive traits in this context. Animal personality has recently been integrated into the pace-of-life-syndrome hypothesis, relating individual behavioural traits to life history. Variation in cognitive traits could be explained well by this theoretical framework. A risk-reward trade-off might lead to different cognitive types: Active birds that learn fast, take risks and probably have a fast lifestyle and less active, slow learning birds that are risk averse but thereby perform better in reversal learning as they probably pay more attention to external cues. We investigated the performance of zebra finches (Taeniopygia guttata) in a cognitively challenging reversal learning task and linked this to two personality traits: activity and fearfulness. Male birds were better in reversal learning than females. While no personality-related differences occurred in the initial learning of our task, more active and fearful birds relearned the cue–reward association faster. While birds of different sex might have revealed different risk-taking strategies in the training, our findings do not reveal the expected direction of a risk-reward trade-off in the reversal learning. It seems likely that a more general and personality-related cognitive ability might improve performance across different tasks. The linkage between personality and cognition documented here could hence suggest that cognitive traits are indeed part of an overall pace-of-life syndrome.

Locomotor performance constitutes a major component of whole-animal performance and is involved in several fitness-related behaviors. Locomotor capabilities may also correspond positively or negatively to sexually selected traits (e.g., male ornamentation and/or courtship displays). Negative correlations are predicted if secondary sexual traits take the form of morphological modifications that impose physical or energetic limitations. We tested this cost of secondary sexual traits by comparing locomotor performance in male Schizocosa wolf spiders that exhibit two distinct phenotypes. These phenotypes vary in the presence/absence of a morphological feature assumed to function as sexual ornamentation—foreleg brushes. Given the conspicuously large brushes of hair on the brush-legged phenotype, we expected these males to suffer in locomotor performance. We tested this cost by comparing locomotor performance among male phenotypes (brush-legged and non-ornamented) and females at immature and adult life stages. We did not find strong support for costs of brushes on locomotion. First, brush-legged males showed similar average speeds and endurance as both non-ornamented males and females. Second, while brush-legged males were slower at maximum speeds than non-ornamented males as matures (but not as immatures), they were no slower than mature females. Further, we found no variation in endurance among phenotypes or life stages. Finally, brush size did not correspond to speed. Patterns of morphological variation in traits other than ornamentation may explain these patterns: when morphological variation in leg lengths was accounted for, differences in maximum speed among groups disappeared. We suggest that the faster speeds achieved by non-ornamented males arise as a by-product of selection on morphology and musculature potentially necessary for vigorous courtship.

Activity budgets of animals often show consistent differences between individuals across time, which qualifies them as personality traits. In the case of captive birds, locomotor activity can be divided into two major components – frequency of hopping and flapping flight bouts, which may conceive different information about individual condition. This idea was tested in a 2*2 factorial experiment in wild-caught captive greenfinches (Carduelis chloris), injected with bacterial lipopolysaccharide (LPS) and/or temporarily exposed to an image of a predator. We predicted that LPS injection would reduce both types of activity via induction of sickness syndrome and that predator image treatment would either increase or decrease different components of activity. Both behavioural traits were similarly consistent in time over a 10-d period but the correlations between them depended on measurement context. LPS treatment reduced flapping and hopping frequencies and total locomotor activity. Exposure to the predator image had no effect on flapping frequency, but it decreased hopping frequency and total locomotor activity among the birds that were initially most active. The effects of both treatments on behaviour were relatively long-lasting, that is, detectable at least 87 h after LPS injection and 44 h after exposure to the predator image. Our findings demonstrate the existence of two components of locomotor activity that responded similarly to the physiological but differently to the psychological stressor. The distinction between such components thus increases the information content of activity recordings of caged birds, which is likely to reveal novel aspects of covariation between different aspects of stress responsiveness and other performance parameters.

In this paper, an experimental approach was used to test for the parallel effects of temperature (T) increase on the antipredator behaviour and the cholinergic expression in the juvenile European sea bass (Dicentrarchus labrax L.). The effects of three T treatments (18, 22 and 26°C) were tested on the main behavioural components of the antipredator response towards live aquatic predators and aerial simulated attacks, whereas brain cholinergic expression was evaluated by choline acetyltransferase (ChAT) immunoblotting (Western blot) at the extreme values of the thermal range (18 and 26°C). Antipredator responses towards a live fish were analysed over pre-exposure and exposure phases within a short temporal scale (20 s before and after the stimulus). The results suggest that T modulates several quantitative components of the antipredator behaviour. The mean shoaling index (shoal cohesiveness) was higher at 22°C than at 18 and 26°C during both the pre-stimulus and the exposure phase. Conversely, the mean distances from the predator and the tank bottom were, respectively, lower and higher at 26°C than in the other two treatments. In regard to the antipredator response on the aerial stimulus, comparisons across treatments revealed statistically significant differences between fish performing freezing or latency to recovery, suggesting that the fright reaction has a higher persistence at the coldest T (18°C) than at 22 and 26°C. Western blot analysis revealed a reduction in brain ChAT expression in fish acclimated to 26°C compared to those at 18°C. Results were discussed in the light of the relationships between behavioural traits, metabolism and their consequences on the population level, as a response to climate change in coastal habitats.

Among certain non-human primates, the red-colored genitalia of females are a sexual ornament and attract males. The preference for red clothes among women is at times explained as being a parallel. We used here a within-individual design to investigate the signaling role of the color red with a sample of Slovak participants. As expected, women preferred red clothing both in real-life and would-be situations more than men. The preference for red (but not for other colors) in mating game scenarios was only significant for women, but not for men. A preference for the color red was shown in particular for clothes on the upper parts of the participants' bodies, irrespective of gender. Women who were actually involved in a romantic sexual relationship had a preference for red in would-be situations more than single women, although the menstrual cycle, the total number of lifetime sexual partners, and self-perceived attractiveness were not associated with the preference for the color red. Our results support the sexual signaling hypothesis which suggests that women use the color red to attract potential mates in a similar way as non-human primates.