Urban Impacts on Oxidative Balance and Animal Signals

Abstract

Though many animal ornaments and signals are sensitive to and encode information about the oxidative balance (OB) of individuals (e.g., antioxidant supplies/activity, reactive oxygen species, cellular oxidative damage/repair), often the environmental and/or physiological sources of such OB are unknown. Urban development is among the most recent, pervasive, and persistent human stressors on the planet and impacts many environmental and physiological parameters of animals. Here we review the mechanistic underpinnings and functional consequences of how human urbanization drives antioxidant/oxidative status in animals and how this affects signal expression and use. Although we find that urbanization has strong negative effects on signal quality (e.g., visual, auditory, chemical) and OB across a range of taxa, few urban ecophysiological studies address signals and oxidative stress in unison, and even fewer in a fitness context. We also highlight particular signal types, taxa, life-histories, and anthropogenic environmental modifications on which future work integrating OB, signals, and urbanization could be centered. Last, we examine the conceptual and empirical framework behind the idea that urban conditions may disentangle signal expression from honesty and affect plasticity and adaptedness of sexually selected traits and preferences in the city.

A review of urban impacts on avian life‐history evolution: Does city living lead to slower pace of life?

“…Although an abundant literature has been published on variation in personality (e.g. Bokony, Kulcsar, & Liker, ; Bokony, Kulcsar, Toth, & Liker, ; Mueller, Partecke, Hatchwell, Gaston, & Evans, ; Niemelä et al., ; Papp, Vincze, Preiszner, Liker, & Bókony, ; Reale et al., ) and acoustic signals (reviewed by Hutton & Mcgraw, ) along the urbanization gradient in birds, we do not include these traits in this review for several reasons. First, recent experimental studies suggest that personality does not integrate well with pace‐of‐life syndrome, suggesting that associations between life‐history and behavioural tendencies are environmentally determined (Debecker, Sanmartin‐Villar, De Guinea‐Luengo, Cordero‐Rivera, & Stoks, ; Niemelä et al., ).…”

The role of the antioxidant system during intense endurance exercise: lessons from migrating birds

“…If foraging for fruits (dietary antioxidants and fat) is costly at sites that are lower in quality (e.g. sites with more non-native than native fruiting shrubs), then birds at stopover sites may upregulate their endogenous antioxidant system in preparation for migration (Hutton and McGraw, 2016;Smith et al, 2013). However, endogenous production of antioxidants requires resources such as amino acids or dietary metal cofactors, thus preventing their use for other physiological processes, such as rebuilding muscle on stopovers.…”

“…The regulation of oxidative damage may act as an underlying driver of aging or longevity (Montgomery et al, 2012;Selman et al, 2012). Other reviews have focused on the regulation of RS production from an evolutionary perspective (Costantini, 2008(Costantini, , 2014Costantini et al, 2010b;Monaghan et al, 2009;Speakman, 2008;Speakman et al, 2015;Williams et al, 2010), or on the role of RS in conservation physiology (Beaulieu and Costantini, 2014;Isaksson, 2010), in signaling (Garratt and Brooks, 2012) and as an important indicator of bird health for field ornithologists (Hutton and McGraw, 2016;, or on the importance of dietary antioxidants for wild animals (e.g. Beaulieu and Schaefer, 2013;Catoni et al, 2008b).…”

Plumage micro-organisms and preen gland size in an urbanizing context

“…Despite their increased investment in antimicrobial defenses, urban birds still carried three times more feather-degrading bacteria than rural birds, and this has potentially large fitness consequences, in terms of reduced thermoregulation, aerodynamics, and plumage coloration. To our knowledge, no studies have ever compared plumage quality (proportion of damaged vs. undamaged barbs, Shawkey et al 2007) between urban and rural birds, but an increased and faster feather degradation caused by feather-degrading bacteria might be an important component explaining the decreased coloration recurrently found in urban birds (Hõrak et al 2000, Isaksson et al 2005, Giraudeau et al 2015, Hutton and McGraw 2016. Most of the plumage colors that have been studied in urban ecological contexts result from the combination of a keratin-based background structure that reflects light and pigments that absorb light (Jacot et al 2010).…”