The artificial selection of traits in wildlife populations through hunting and fishing has been well documented. However, despite their rising popularity, the role that artificial selection may play in non‐extractive wildlife activities, for example, recreational feeding activities, remains unknown. If only a subset of a population takes advantage of human‐wildlife feeding interactions, and if this results in different fitness advantages for these individuals, then artificial selection may be at work. We have tested this hypothesis using a wild fallow deer population living at the edge of a capital city as our model population. In contrast to previous assumptions on the randomness of human‐wildlife feeding interactions, we found that a limited non‐random portion of an entire population is continuously engaging with people. We found that the willingness to beg for food from humans exists on a continuum of inter‐individual repeatable behaviour; which ranges from risk‐taking individuals repeatedly seeking and obtaining food, to shyer individuals avoiding human contact and not receiving food at all, despite all individuals having received equal exposure to human presence from birth and coexisting in the same herds together. Bolder individuals obtain significantly more food directly from humans, resulting in early interception of food offerings and preventing other individuals from obtaining supplemental feeding. Those females that beg consistently also produce significantly heavier fawns (300–500 g heavier), which may provide their offspring with a survival advantage. This indicates that these interactions result in disparity in diet and nutrition across the population, impacting associated physiology and reproduction, and may result in artificial selection of the begging behavioural trait. This is the first time that this consistent variation in behaviour and its potential link to artificial selection has been identified in a wildlife population and reveals new potential effects of human‐wildlife feeding interactions in other species across both terrestrial and aquatic habitats.

Behavioural variation at the individual level has been shown to play an important role in animal ecology and evolution. Whereas most studies have focused on subadult or adult subjects, neonates have been relatively neglected, despite studies showing that neonates can exhibit consistent inter‐individual differences during early developmental stages. Steroid hormones, including glucocorticoids (e.g. cortisol) and androgens (e.g. testosterone), play a crucial role in foetal development and maturation and could therefore drive neonate behaviour, although this relationship is poorly understood in wild animal populations. Our study addresses these knowledge gaps by investigating the association between neonate fallow deer Dama dama fawn inter‐individual variability in behavioural response to human handling and hair cortisol and testosterone levels. We found strong evidence that individual neonates display repeatable differences in the way they cope with a risky situation during their first days of life, and showed how these differences are linked to cortisol and testosterone levels accumulated in utero. We showed that, when both steroids are included in the same model, neonates with high cortisol and low testosterone levels coped in a more proactive way with human handling (higher heart rate during handling and shorter latency to leave when released) compared to those with low cortisol and high testosterone levels (lower heart rate and longer latency to leave). These results provide novel insights into the proximate mechanism leading to neonate inter‐individual variation in a wild population of large mammals. A free Plain Language Summary can be found within the Supporting Information of this article.

Recent debate has focused on whether variation in personality primarily reflects variation in resource allocation or resource acquisition of individuals. These two mechanisms predict different relationships between personality and survival. If personality mainly reflects variation in resource allocation, then bold (i.e. risk-taking) individuals are expected to live shorter lives, whereas the opposite pattern is expected with resource acquisition. Here we studied the relationship between neonate personality and early-life survival in 269 juveniles of a population of fallow deer ( Dama dama ). We found that bolder individuals paid no apparent survival cost. Interestingly, among-individual differences in the physiological response at capture (heart rates, which covary with the behavioural response, i.e. latency to leave) were linked to survival, where individuals with lower heart rates when handled by humans had a higher probability of early-life survival. This suggests that bolder individuals may be of higher state than their shyer counterparts. As the first study linking neonate personality to survival in a free-ranging mammal, we provide novel insights into drivers behind early-life individual variation.

Variation and disparity in resource access between individuals in an animal population within human-dominated landscapes require attention as artificial selection processes may be at work. Independent, recreational human–wildlife feeding interactions constitute an increasingly prevalent, yet understudied, food resource for birds and mammals living in our cities. However, only a limited number of risk-taking individuals may access it. Using urban fallow deer as our model species, we hypothesized that if these interactions result in positive effects for the engaging individual, e.g. increased milk quality and yield, then this would result in the increased growth rates of their offspring. Alternatively, if these individuals were prioritizing investing time in engagement with humans, resulting in decreased maternal care, then this would result in slower growth rates in their offspring. We found that the offspring of those females that regularly interacted with humans displayed significantly faster growth rates than their risk-adverse counterparts. This advantage for fearless mothers in terms of boosted neonatal growth rates could be mirrored in birds accessing garden feeders, seagulls or pigeons utilizing urban resources, or seals approaching city harbours. Here, we add a new piece to the complex puzzle of how humans are impacting wildlife living within human-dominated landscapes.

Individual animals show consistent differences in behavioural responses when coping with environmental challenges. Consistency over time and across context in a behavioural trait is an indication for animal personality. Chronotypes refer to consistent inter-individual differences in diurnal rhythmicity driven by underlying variation in circadian clock processes. Personality traits and chronotype may relate to a single behavioural syndrome, but few studies have investigated such a link explicitly. Here, we explored zebrafish larvae for the presence of consistency in activity levels and timing, and their correlation with and without external cues (Zeitgeber: light–dark cycle versus constant light). We found individual consistency in activity level and timing, and their correlation independent of the presence of Zeitgeber: early-active individuals were less active overall than late-active individuals. Our study suggests a link between personality and chronotype and provides new insights into the early development of individual variation in behavioural tendencies of zebrafish.

Although it is widely acknowledged that animal personality plays a key role in ecology, current debate focuses on the exact role of personality in mediating life-history trade-offs. Crucial for our understanding is the relationship between personality and resource acquisition, which is poorly understood, especially during early stages of development. Here we studied how among-individual differences in behavior develop over the first 6 months of life, and their potential association with resource acquisition in a free-ranging population of fallow deer (Dama dama). We related neonate physiological (heart rate) and behavioral (latency to leave at release) anti-predator responses to human handling to the proportion of time fawns spent scanning during their first summer and autumn of life. We then investigated whether there was a trade-off between scanning time and foraging time in these juveniles, and how it developed over their first 6 months of life. We found that neonates with longer latencies at capture (i.e., risk-takers) spent less time scanning their environment, but that this relationship was only present when fawns were 3–6 months old during autumn, and not when fawns were only 1–2 months old during summer. We also found that time spent scanning was negatively related to time spent foraging and that this relationship became stronger over time, as fawns gradually switch from a nutrition rich (milk) to a nutrition poor (grass) diet. Our results highlight a potential mechanistic pathway in which neonate personality may drive differences in early-life resource acquisition of a large social mammal.

The world has become a noisier place due to the increase in urbanization. Noise is generally considered an impediment, altering an animal’s behavior through masking or distraction. But noise can also provide useful information about the environment. For animals that rely on natural environmental noise as an indicator of favorable foraging conditions, increasing levels of anthropogenic noise might mislead informed decision-making. Bats use rain noise, a natural environmental cue, to delay their emergence from the roost, presumably to avoid sensory and metabolic costs associated with foraging in heavy rain. Here we tested the “misleading cue hypothesis,” asking whether traffic noise is mistaken for rain noise by bats. Given the acoustic similarity between rain noise and traffic noise, we predicted that bats would confuse the two. We conducted a playback experiment using rain, traffic, and ambient noise at natural roosts of common big-eared bats (Micronycteris microtis, Phyllostomidae) and recorded bat emergence behavior. In contrast to their response to rain noise, the bats did not delay roost emergence in response to traffic noise. Thus, we found that bats were able to discriminate between traffic noise and rain noise and were not misled by similarity in acoustic parameters in the two noise types, when emerging from their roost. Emerging bats did show more exploration flights during traffic noise than during rain noise, but not during ambient noise, suggesting that they perceive traffic noise as a novel acoustic cue. Our data provide new insights into perception of traffic noise by bats.

Recent debate has focused on whether variation in personality primarily reflects variation in resource allocation or resource acquisition of individuals. These two mechanisms differ in their expected patterns between personality and survival. If personality mainly reflects variation in resource allocation, then bold (i.e. risk-taking) individuals are expected to live shorter, whereas the opposite pattern is expected with resource acquisition. Here we studied the relationship between neonate personality and early-life survival in 269 juveniles of a population of fallow deer (Dama dama). We found that bolder individuals were more likely to survive, and therefore, paid no apparent survival cost. Interestingly, the physiological but not the behavioural dimension of neonate boldness was directly linked to survival, suggesting that these individuals may be of higher state than their shyer counterparts. As the first study linking neonate personality to survival in a free-ranging mammal, we provide novel insights into drivers behind early-life individual variation.