Animal Coloration in the Anthropocene

Abstract

Natural habitats are increasingly affected by anthropogenically driven environmental changes resulting from habitat destruction, chemical and light pollution, and climate change. Organisms inhabiting such habitats are faced with novel disturbances that can alter their modes of signaling. Coloration is one such sensory modality whose production, perception and function is being affected by human-induced disturbances. Animals that acquire pigment derivatives through diet are adversely impacted by the introduction of chemical pollutants into their environments as well as by general loss of natural habitat due to urbanization or logging leading to declines in pigment sources. Those species that do manage to produce color-based signals and displays may face disruptions to their signaling medium in the form of light pollution and turbidity. Furthermore, forest fragmentation and the resulting breaks in canopy cover can expose animals to predation due to the influx of light into previously dark environments. Global climate warming has been decreasing snow cover in arctic regions, causing birds and mammals that undergo seasonal molts to appear conspicuous against a snowless background. Ectotherms that rely on color for thermoregulation are under pressure to change their appearances. Rapid changes in habitat type through severe fire events or coral bleaching also challenge animals to match their backgrounds. Through this review, we aim to describe the wide-ranging impacts of anthropogenic environmental changes on visual ecology and suggest directions for the use of coloration both as an indicator of ecological change and as a tool for conservation.

Avian colouration in a polluted world: a meta‐analysis

“…This study examined the influence of anthropogenic pollution on an important signalling modality in birds – the expression of colourful signals (Koneru & Caro, 2022). Analysing 421 effect sizes from 59 studies, we found evidence suggesting a negative impact of pollution on the expression of colour traits, consistent with the hypothesis proposed by Hill (1995).…”

“…The influence of anthropogenic pollutants and urbanisation on avian colouration has been addressed previously in several narrative reviews. Koneru & Caro (2022) provided a comprehensive overview of animal colouration in the Anthropocene, including signal transmission and perception in altered habitats and the consequences of climate change for colour trait expression. Lifshitz & St Clair (2016) summarised current knowledge on colour ornaments as potential bioindicators, and Peneaux et al (2021a) considered the effects of pollutants on carotenoid-based colouration and provided guidelines for the use of colour signals as bioindicators.…”

Hoist the colours: silviculture impacts butterfly assemblage colours in the Atlantic Forest

“…However, these interactions vary over time and space since colours can perform their functions and be perceived by animals in different ways, depending on environmental conditions (Endler 1990), resulting in several biotic and abiotic factors competing with each other and acting as selective pressures on colours (Endler 1992;Postema et al 2023). Unfortunately, colour also re ects the impacts of environmental degradation caused by anthropogenic actions (Spaniol et al 2020; Koneru and Caro 2022;López-Idiáquez et al 2022) in abiotic characteristics of environments, affecting the e ciency of their functions (Endler 1978;Burtt 1981), with reported cases ranging from changes in speci c species (Cook 2003) to whole communities in environments such as tropical forests (Spaniol et al 2020) and marine environments (Coker et However, only one study seems to have evaluated quantitative butter y colour (diversity, brightness, hue and saturation) responses to anthropogenic actions (Spaniol et al 2020). Treating colours as functional traits and using them as indicators for deforestation impacts in the Amazon Rainforest, we have shown a loss of colouration diversity with increasing habitat disturbance, in which forest fragmentation and deforestation strongly affect colour traits, with butter ies less colourful in areas of early succession and forest fragments; in the former areas, they also had higher saturation and a red hue but lower brightness, indicating the predominance of camou age as a strategy.…”

“…Animal colouration plays a functional role associated with distinct aspects of organismal natural history, ranging from intra- (Rowland 2018) to interspeci c communication (Caro and Allen 2017), in which there seems to be a direct and positive association between species biodiversity and colour diversity (Koneru and Caro 2022) since environments with different landscapes and species compositions can lead lineages to acquire different strategies involving this trait (Adams et al 2014). Body colours end up mediating communication and interactions between animals and other organisms and with the surrounding environment (Cuthill et al 2017).…”

Habitat change alters the expression and efficiency of a female ornament

“…Stickleback males reduce their investment in their ornament, red nuptial coloration, when visibility deteriorates ( Candolin et al 2016 ), but across species the pattern varies; some species adjust their ornaments to visibility, such as the brown trout Salmo trutta ( Eaton and Sloman 2011 ) and the western rainbowfish Melanotaenia australis ( Kelley et al 2012 ), whereas others do not, such as the pipefish Nerophis ophidion ( Sundin et al 2016 ). These differences in responses are probably related to temporal and spatial variation in visibility and the evolutionary history of the species, which has determined the evolution of reaction norms for plastic responses ( Chevin and Hoffmann 2017 ; Candolin 2019 ; Koneru and Caro 2022 ). The responses may be adaptive or not, depending on how they influence the costs and benefit of ornamentation.…”