Does artificial light pollution impair problem-solving success in peafowl?

Embryonic exposure to artificial light at night impairs learning abilities and their covariance with behavioural traits in teleost fish

The natural light cycle has profound effects on animals' cognitive systems. Its alteration owing to human activities, such as artificial light at night (ALAN), affects the biodiversity of mammalian and avian species by impairing their cognitive functions. The impact of ALAN on cognition, however, has not been investigated in aquatic species, in spite of the common occurrence of this pollution along water bodies. We exposed eggs of a teleost fish (the zebrafish Danio rerio) to ALAN and, upon hatching, we measured larvae' cognitive abilities with a habituation learning paradigm. Both control and ALAN-exposed larvae showed habituation learning, but the latter learned significantly slower, suggesting that under ALAN conditions, fish require many more events to acquire ecologically relevant information. We also found that individuals' learning performance significantly covaried with two behavioural traits in the control zebrafish, but ALAN disrupted one of these relationships. Additionally, ALAN resulted in an average increase in larval activity. Our results showed that both fish's cognitive abilities and related individual differences are negatively impacted by light pollution, even after a short exposure in the embryonic stage.

Reward history modulates visual attention in an avian model

Attention can be biased towards previously reward-associated stimuli even when they are task-irrelevant and physically non-salient, although studies of reward-modulated attention have been largely limited to primate (including human and nonhuman) models. Birds have been shown to have the capacity to discriminate reward and spatial cues in a manner similar to primates, but whether reward history involuntarily affects their attention in the same way remains unclear. We adapted a spatial cueing paradigm with differential rewards to investigate how reward modulates the allocation of attention in peafowl (Pavo cristatus). The birds were required to locate and peck a target on a computer screen that was preceded by a high-value or low-value color cue that was uninformative with respect to the location of the upcoming target. All birds exhibited a validity effect (performance enhanced on valid compared to invalid cue), and an interaction effect between value and validity was evident at the group level, being particularly pronounced in the birds with the greatest amount of reward training. The time course of reward learning was conspicuously incremental, phenomenologically slower compared to primates. Our findings suggest a similar influence of reward history on attention across phylogeny despite a significant difference in neuroanatomy.

Urbanization’s Effects on Problem Solving Abilities: A Meta-Analysis

Cognitive abilities are often assumed to be advantageous in urban habitats, but relatively few studies tested this assumption. In a meta-analysis, we tested whether urban animals have better problem-solving abilities compared to their less urbanized conspecifics. After screening 210 papers we collected by keyword search and forward search, we found 12 studies that compared the ability to solve food-extraction or obstacle-removal problems between urban and non-urban populations of the same animal species. These studies were published between 2009 and 2021, and were performed mostly on birds, whereas a quarter of them used mammals as study species. We found a statistically non-significant trend that urban animals are more successful and faster problem-solvers compared to their less urbanized conspecifics. However, both solving success and solving latency effect sizes were highly heterogeneous, therefore hard to generalize. Though the sample was too low to test the factors explaining this high heterogeneity, we suggest that it may be explained by variation in task types, study species, definitions of urbanization, whether the study was performed on captive or free-living animals, geographical location, or publication bias in both directions. Altogether, more studies are needed to either confirm or disprove this trend.

Animal cognition in an urbanised world

Explaining how animals respond to an increasingly urbanised world is a major challenge for evolutionary biologists. Urban environments often present animals with novel problems that differ from those encountered in their evolutionary past. To navigate these rapidly changing habitats successfully, animals may need to adjust their behaviour flexibly over relatively short timescales. These behavioural changes, in turn, may be facilitated by an ability to acquire, store and process information from the environment. The question of how cognitive abilities allow animals to avoid threats and exploit resources (or constrain their ability to do so) is attracting increasing research interest, with a growing number of studies investigating cognitive and behavioural differences between urban-dwelling animals and their non-urban counterparts. In this review we consider why such differences might arise, focusing on the informational challenges faced by animals living in urban environments, and how different cognitive abilities can assist in overcoming these challenges. We focus largely on birds, as avian taxa have been the subject of most research to date, but discuss work in other species where relevant. We also address the potential consequences of cognitive variation at the individual and species level. For instance, do urban environments select for, or influence the development of, particular cognitive abilities? Are individuals or species with particular cognitive phenotypes more likely to become established in urban habitats? How do other factors, such as social behaviour and individual personality, interact with cognition to influence behaviour in urban environments? The aim of this review is to synthesise current knowledge and identify key avenues for future research, in order to improve our understanding of the ecological and evolutionary consequences of urbanisation.

Light, Sleep and Performance in Diurnal Birds

Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light on sleep and subsequent performance in birds. There is accumulating evidence that exposure to natural and artificial sources of light regulates and suppresses sleep in diurnal birds. Sleep also benefits avian cognitive performance, including during early development. Nevertheless, multiple studies suggest that light can prolong wakefulness in birds without impairing performance. Although there is still limited research on this topic, these results raise intriguing questions about the adaptive value of sleep. Further research into the links between light, sleep and performance, including the underlying mechanisms and consequences for fitness, could shed new light on sleep evolution and urban ecology.

Artificial Light at Night Affects Emergence from a Refuge and Space Use in Guppies

Artificial light at night (ALAN) is a major form of anthropogenic pollution. ALAN is well known to affect different behaviours during nighttime, when changes in light conditions often have immediate consequences for the trade-offs individuals experience. How ALAN affects daytime behaviours, however, has received far less attention. Here we studied how ALAN affected daytime personality traits and learning ability. We exposed Trinidadian guppies, Poecilia reticulata, for 10 weeks to different ALAN levels: bright light (24 hrs bright light, ~5,000 lx), dim light (12 hrs bright light; 12 hrs dim light, ~0.5 lx) and control (12 hrs bright light; 12 hrs dark). Afterwards, we tested how the treatments affected diurnal emergence from a refuge, space use, activity, sociability and the ability to memorize the location of companion fish. Individuals exposed to the light treatments (both dim and bright light) emerged quicker from a refuge and fish from the bright light treatment spent relatively more time in the open area of the arena. ALAN did not affect any of the other behaviours, although memory could not be tested since fish did not learn the companions' location. Our results demonstrate that ALAN, next to affecting nocturnal behaviours, can also affect key diurnal behavioural processes, associated with risk-taking.