Crocodiles Alter Skin Color in Response to Environmental Color Conditions

Merchant, Mark; Hale, Amber; Brueggen, J.C.; Harbsmeier, Curt; Adams, Colette

doi:10.1038/s41598-018-24579-6

Cited by 17 publications

(18 citation statements)

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“…Some extinct Crocodyliformes had much more varied diets and included cases of herbivory (Melstrom & Irmis, 2019), raising the possibility that extinct members of the clade could have expressed carotenoids in integumentary structures, although more study into the mechanisms of and constraints on carotenoid expression in nonavian reptiles are needed. It is also possible that the absence of carotenoid‐consistent color expression in skin or keratin in extant crocodilians has been driven by selection for crypsis or other environmental factors (e.g., Merchant et al., 2018; reviewed in Somaweera et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs

Davis

Clarke

2021

Evolution

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Carotenoids are pigments responsible for most bright yellow, red, and orange hues in birds. Their distribution has been investigated in avian plumage, but the evolution of their expression in skin and other integumentary structures has not been approached in detail. Here, we investigate the expression of carotenoid-consistent coloration across tissue types in all extant, nonpasserine species (n = 4022) and archelosaur outgroups in a phylogenetic framework. We collect dietary data for a subset of birds and investigate how dietary carotenoid intake may relate to carotenoid expression in various tissues. We find that carotenoid-consistent expression in skin or nonplumage keratin has a 50% probability of being present in the most recent common ancestor of Archosauria. Skin expression has a similar probability at the base of the avian crown clade, but plumage expression is unambiguously absentin that ancestor and shows hundreds of independent gains within nonpasserine neognaths, consistent with previous studies. Although our data do not support a strict sequence of tissue expression in nonpasserine birds, we find support that expression of carotenoid-consistent color in nonplumage integument structures might evolve in a correlated manner and feathers are rarely the only region of expression. Taxa with diets high in carotenoid content also show expression in more body regions and tissue types. Our results may inform targeted assays for carotenoids in tissues other than feathers, and expectations of these pigments in nonavian dinosaurs. In extinct groups, bare-skin regions and the rhamphotheca, especially in species with diets rich in plants, may express these pigments, which are not expected in feathers or feather homologues.

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Section: Discussionmentioning

confidence: 99%

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs

Davis

Clarke

2021

Evolution

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“…For many other reptiles, body colour can change dynamically to varying degrees (Cooper, Greenberg & Gans, 1992), from lightening and darkening seen in most lizards and even crocodilians (e.g. Boyer & Swierk, 2017; Merchant et al ., 2018) to the rapid multi‐hue changes seen in chameleons and some agamids (Stuart‐Fox & Moussalli, 2009). Thus, physiological colours can play an interesting and possibly adaptive role in the ecology of sleep.…”

Section: Sleep Traitsmentioning

confidence: 99%

The ecology of sleep in non‐avian reptiles

et al. 2021

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Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep, the ecological context of sleep in non‐avian reptiles remains understudied and without systematic direction. In this review, we examine multiple aspects of reptilian sleep, including (i) habitat selection (sleep sites and their spatio‐temporal distribution), (ii) individual‐level traits, such as behaviour (sleep postures), morphology (limb morphometrics and body colour), and physiology (sleep architecture), as well as (iii) inter‐individual interactions (intra‐ and inter‐specific). Throughout, we discuss the evidence of predation, competition, and thermoregulation in influencing sleep traits and the possible evolutionary consequences of these sleep traits for reptile sociality, morphological specialisation, and habitat partitioning. We also review the ways in which sleep ecology interacts with urbanisation, biological invasions, and climate change. Overall, we not only provide a systematic evaluation of the conceptual and taxonomic biases in the existing literature on reptilian sleep, but also use this opportunity to organise the various ecological hypotheses for sleep characteristics. By highlighting the gaps and providing a prospectus of research directions, our review sets the stage for understanding sleep ecology in the natural world.

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“…Vegetation characteristics of the landscape may have also influenced the colouration of crocodylians. On a short‐term physiological basis, members of Crocodylidae can rapidly change colour in response to background, potentially for crypsis to evade predators, an ability quite limited in members of Alligatoridae (Merchant, Hale, Brueggen, Harbsmeier, & Adams, ). Although, from a long‐term natural selection or evolutionary point of view, hatchling crocodylians may have specific colourations that are well‐camouflaged and match background vegetation, thus affording a higher degree of protection from aquatic and aerial predators (Hunt & Watanabe, ).…”

Section: Vegetation Interactions and Outcomesmentioning

confidence: 99%

Direct and indirect interactions with vegetation shape crocodylian ecology at multiple scales

Somaweera

Brien²,

Manolis³

et al. 2018

Freshwater Biology

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As one of the world's largest predators of freshwater environments, crocodylians play an important role in shaping their community. In turn, many aspects of crocodylian life histories are influenced and have been shaped by characteristics of their environment, especially vegetation. However, our understanding of just how vegetation impacts crocodylian life histories remains limited, particularly in regard to indirect interactions. Such interactions can be critical for understanding population dynamics and, therefore, for informing conservation management decisions. We reviewed contemporary understanding of these plant–crocodylian interactions in peer‐reviewed journals and the grey literature, synthesising life history‐shaping dynamics against aspects of their ecology. We then conceptualised how global environmental change, including climate change, species invasions and land use change, may threaten these critical dependencies, and how future conservation plans need to account for these pressures. We identified five primary aspects of crocodylian ecology—habitat selection, nesting ecology, communication, physiology, and feeding ecology—that are probably shaped by vegetation interactions at different spatial scales. These interactions include direct and indirect impacts, with both positive and negative outcomes from a crocodylian perspective. Anthropogenic impacts on environments via global environmental change drivers is causing unprecedented change to vegetation dynamics. What is often overlooked is how these changes impact large aquatic predators such as crocodylians. Our synthesis shows that while many impacts can be identified, their magnitude and mechanism are not well understood, making management driven mitigation challenging. We recommend that future studies prioritise quantifying how vegetation communities shape the suitability of crocodylian nest sites, and how to best detect the fingerprint of impacts caused by invasive alien plants on demographic change in crocodylians over longer durations. An improved understanding of the impact of vegetation impacts on crocodylians is essential for building effective conceptual frameworks and management agendas for the conservation of these iconic reptiles.

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Crocodiles Alter Skin Color in Response to Environmental Color Conditions

Cited by 17 publications

References 50 publications

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs

Estimating the distribution of carotenoid coloration in skin and integumentary structures of birds and extinct dinosaurs

The ecology of sleep in non‐avian reptiles

Direct and indirect interactions with vegetation shape crocodylian ecology at multiple scales

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