When aggressiveness could be too risky: linking personality traits and predator response in superb fairy-wrens

Personality syndromes in animals may have adaptive benefits for survival. For example, while engaging in predator deterrence, reactive individuals tend to prioritise their own survival, while proactive individuals engage in riskier behaviours. Studies linking animal personality measured in captivity with individual fitness or behaviours in the wild are sparse, which is a gap in knowledge this study aims to address. We used playback experiments in superb fairy-wrens (Malurus cyaneus), a common Australian songbird with a cooperative breeding system, to assess whether three personality traits measured during short-term captivity correlated with behavioural responses in the wild to a perceived nest and adult predator, the grey currawong (Strepera versicolor). We used three standard measures of personality in birds: struggle responses to human handling (boldness), exploration during a novel environment test, and aggressiveness during a mirror presentation. Superb fairy-wrens showed a significantly stronger response to the predator playback than to the control (willie wagtail, Rhipidura leucophrys) playback, suggesting that they recognised the predator playback as a threat without any accompanying visual stimulus. Birds that attacked their mirror image during the mirror presentation and those that spent a moderate amount of time close to the mirror responded more strongly to predator playback (by approaching the speaker faster and closer, spending more time near the speaker, and being more likely to alarm call) compared to those with low aggressiveness or those that spent very short or long durations close to the mirror. Neither boldness nor exploration in the novel environment test predicted playback response. Our results align with a growing number of studies across species showing the importance of animal personalities as factors for fitness and survival.

The trade-off between color and size in lizards' conspicuous tails

A tail of conspicuous coloration is hypothesized to be an advantageous trait for many species of lizards. Predator attacks would be directed to a non-vital, and autotomizable, body part, increasing the chance of survival. However, as body size increases it also increases the signaling area that could attract predators from greater distances, increasing the overall chance of predation. Here, we test the hypothesis that there is a trade-off between tail color and size, affecting predation probabilities. We used plasticine replicas of lizards to study the predation patterns of small and large lizards with red and blue tails. In a natural environment, we exposed six hundred replicas to the attacks of free-ranging predators. Large red-tailed replicas were more attacked by birds. Mammals and unidentified predators showed no preference for any size or colors. The attacks were not primarily directed to conspicuous tails when compared to the bodies/heads of our replicas. Our study suggests that red color signals in large lizards could enhance their detection by visually oriented predators (i.e., birds). The efficacy of conspicuous tails as a decoy may rely on associated behavioral displays, which are hard to test with static replicas.

Tail autotomy works as a pre-capture defense by deflecting attacks

Caudal autotomy is a dramatic antipredator adaptation where prey shed their tail in order to escape capture by a predator. The mechanism underlying the effectiveness of caudal autotomy as a pre-capture defense has not been thoroughly investigated. We tested two nonexclusive hypotheses, that caudal autotomy works by providing the predator with a "consolation prize" that makes it break off the hunt to consume the shed tail, and the deflection hypothesis, where the autotomy event directs predator attacks to the autotomized tail enabling prey escape. Our experiment utilized domestic dogs Canis familiaris as model predator engaged to chase a snake-like stimulus with a detachable tail. The tail was manipulated to vary in length (long versus short) and conspicuousness (green versus blue), with the prediction that dog attacks on the tail should increase with length under the consolation-prize hypothesis and conspicuous color under the deflection hypothesis. The tail was attacked on 35% of trials, supporting the potential for pre-capture autotomy to offer antipredator benefits. Dogs were attracted to the tail when it was conspicuously colored, but not when it was longer. This supports the idea that deflection of predator attacks through visual effects is the prime antipredator mechanism underlying the effectiveness of caudal autotomy as opposed to provision of a consolation prize meal.

Relative fitness of decoy coloration is mediated by habitat type

Predator-prey interactions can be important drivers of morphological evolution, and antipredator traits in particular. Further, ecological context can be an important factor shaping the evolution of these traits. However, the role of ecological factors such as habitat structure in altering predator-based selection is not well known for antipredator traits such as decoy coloration. We used a combination of a natural history collection survey and a clay model experiment in open- and closed-canopy habitats to study how ecological context alters the fitness benefit of either red or blue decoy coloration in skinks. We found that the development and ecology of red decoy coloration of mole skinks differed substantially from blue tail coloration of other sympatric skink species. Mole skinks do not reach the body size of sympatric species of skinks and retain decoy coloration throughout development. Both patterns of scarring in museum specimens and attacks on plasticine models suggest that red coloration serves as a decoy, attracting attacks to the autotomous tail. While predation rates were similar across habitats, models with red tails were attacked far less frequently in open habitats than models with blue tails, while attack rates were similar in closed habitats. Our results suggest that red decoy coloration in mole skinks could be an adaptation to relatively open-canopy habitats. Our study has important implications for understanding how habitat structure and predator-based selection can alter the evolutionary dynamics of decoy coloration.

Dietary vitamin D in female rock lizards induces condition-transfer effects in their offspring

One way that maternal effects may benefit the offspring is by informing them about the characteristics of the environment. Through gestation, environmentally induced maternal effects might promote in the offspring-specific behavioral responses like dispersal or residence according to their new habitat characteristics. Females of the Carpetan rock lizard (Iberolacerta cyreni) seem to choose their home ranges using the smell of provitamin D3 in scent marks produced by males. Here, we supplemented gravid females of I. cyreni with dietary provitamin D3 or vitamin D3 to examine whether these food resources, also associated with the scent of males, affect the motivation to disperse and the locomotor performance of their offspring. Our results suggest that the supplementary availability of the resource (vitamin D3) to mothers may provoke condition-transfer maternal effects that motivate the residence or the dispersal of the offspring in their postnatal habitat. Thus, hatchlings of supplemented females had a lower dispersal trend in spite of having a greater climbing ability than hatchlings from nonsupplemented females. This suggests that the levels of provitamin D3 and vitamin D3 inside the body of the mother could act as an informative compound of the habitat quality for the offspring.

Maternal diet affects juvenile Carpetan rock lizard performance and personality

Differences in both stable and labile state variables are known to affect the emergence and maintenance of consistent interindividual behavioral variation (animal personality or behavioral syndrome), especially when experienced early in life. Variation in environmental conditions experienced by gestating mothers (viz. nongenetic maternal effects) is known to have significant impact on offspring condition and behavior; yet, their effect on behavioral consistency is not clear. Here, by applying an orthogonal experimental design, we aimed to study whether increased vitamin D3 content in maternal diet during gestation (vitamin-supplemented vs. vitamin control treatments) combined with corticosterone treatment (corticosterone-treated vs. corticosterone control treatments) applied on freshly hatched juveniles had an effect on individual state and behavioral consistency of juvenile Carpetan rock lizards (Iberolacerta cyreni). We tested the effect of our treatments on (a) climbing speed and the following levels of behavioral variation, (b) strength of animal personality (behavioral repeatability), (c) behavioral type (individual mean behavior), and (d) behavioral predictability (within-individual behavioral variation unrelated to environmental change). We found higher locomotor performance of juveniles from the vitamin-supplemented group (42.4% increase), irrespective of corticosterone treatment. While activity personality was present in all treatments, shelter use personality was present only in the vitamin-supplemented × corticosterone-treated treatment and risk-taking personality was present in corticosterone control treatments. Contrary to our expectations, behavioral type was not affected by our treatments, indicating that individual quality can affect behavioral strategies without affecting group-level mean behavior. Behavioral predictability decreased in individuals with low climbing speed, which could be interpreted as a form of antipredator strategy. Our results clearly demonstrate that maternal diet and corticosterone treatment have the potential to induce or hamper between-individual variation in different components of boldness, often in interactions.

Bright birds are cautious: seasonally conspicuous plumage prompts risk avoidance by male superb fairy-wrens

Increased predation risk is considered a cost of having conspicuous colours, affecting the anti-predator behaviour of colourful animals. However, this is difficult to test, as individual factors often covary with colour and behaviour. We used alarm call playback and behavioural observations to assess whether individual birds adjust their response to risk according to their plumage colour. Male superb fairy-wrens (Malurus cyaneus) change from a dull brown to conspicuous blue plumage each year, allowing the behaviour of different coloured birds to be compared while controlling for within-individual effects. Because the timing of colour change varies among males, blue and brown birds can also be compared at the same time of year, controlling for seasonal effects on behaviour. While blue, fairy-wrens fled more often in response to alarm calls, and took longer to emerge from cover. Blue fairy-wrens also spent more time foraging in cover and being vigilant. Group members appeared to benefit from the presence of blue males, as they reduced their response to alarms, and allocated less time to sentinel behaviour when a blue male was close by. We suggest that fairy-wrens perceive themselves to be at a higher risk of predation while in conspicuous plumage and adjust their behaviour accordingly.

Deceived by stripes: conspicuous patterning on vital anterior body parts can redirect predatory strikes to expendable posterior organs

Conspicuous coloration, which presumably makes prey more visible to predators, has intrigued researchers for long. Contrastingly coloured, conspicuous striped patterns are common among lizards and other animals, but their function is not well known. We propose and test a novel hypothesis, the 'redirection hypothesis', wherein longitudinal striped patterns, such as those found on the anterior body parts of most lacertilians, redirect attacks away from themselves during motion towards less vulnerable posterior parts, for example, the autotomous tail. In experiments employing human 'predators' attacking virtual prey on a touchscreen, we show that longitudinal striped patterns on the anterior half of prey decreased attacks to the anterior and increased attacks to the posterior. The position of stripes mattered-they worked best when they were at the anterior. By employing an adaptive psychophysical procedure, we show that prey with striped patterning are perceived to move slower, offering a mechanistic explanation for the redirective effect. In summary, our results suggest that the presence of stripes on the body (i.e. head and trunk) of lizards in combination with caudal autotomy can work as an effective anti-predator strategy during motion.