Why reptiles are more colorful in open habitats

Reptiles from diverse habitats display a stunning range of colors, from those that match the glow of a sun-drenched desert to those that camouflage in the cool shadows of a dense jungle. But these patterns are more than skin deep – they reflect a long history of environmental change and adaptation.

Recent findings from researchers at Lund University in Sweden reveal that habitat openness, more than any other factor, drives how reptiles evolve their color over millions of years. The results offer a fresh way to understand how species respond to climate shifts, and what may lie ahead as the world warms and dries.

Reptile coloration has fascinated scientists for decades. It’s well known that animals adjust their appearance for camouflage, communication, or thermoregulation. But one big question remained – what explains the global variation in reptile color across time and space?

The new study, which combines advanced modeling with over 10,000 reptile images, brings us a step closer to answering that question.

Reptiles and the color-habitat connection

To investigate, the researchers studied 1,249 species of scaled reptiles from around the world. They focused on dorsal brightness – how light or dark the animal’s back is – since brightness plays a critical role in how animals interact with sunlight.

The team analyzed this trait alongside six key eco-environmental variables: habitat openness, latitude, altitude, body mass, concealment, and activity time.

The researchers found one pattern that held steady across time, space, and species. Reptiles living in open environments, for example deserts, grasslands, and savannas, tended to have brighter, lighter colors. In contrast, reptiles in closed, forested areas were darker.

“Color evolves under the influence of several competing selection forces from different ecological and environmental factors. By identifying the driving forces behind global patterns of color variation, we can gain a deeper understanding of how species can adapt to changing environmental conditions,” explained biology researcher Jonathan Goldenberg.

Why habitat openness matters most

Among the six variables tested, only habitat openness was consistently linked to reptile color brightness. Latitude and altitude had some influence, but only in species with small body sizes. Even activity patterns – whether species are active by day or night – had little effect.

Instead, the clearest signal came from vegetation density. More open landscapes allowed more sunlight to reach the animals, increasing the need for lighter coloration.

The researchers suggest this might help reptiles reflect sunlight and avoid overheating. Bright colors may also play a role in visual communication under open skies, but the link to heat absorption is particularly strong.

Interestingly, subterranean species didn’t follow this trend, which is unsurprising given that light rarely reaches them underground.

“We also discovered that the rate of color brightness evolution probably follows major changes towards a colder and drier climate. This suggests that reptiles have probably adapted their coloration to new habitats in response to changes in the landscape,” said Goldenberg.

Global cooling led to lighter reptile colors

Reptiles have walked the Earth for over 200 million years, and their color patterns tell a story of change. The team found that periods of rapid environmental transformation, especially during global cooling events, coincided with major bursts in the evolution of brightness.

Using δ18O – a chemical marker of past temperatures – the study showed that color brightness increased during the Miocene and Pliocene.

These epochs saw large-scale aridification, which led to more open landscapes. As deserts and grasslands expanded, reptiles likely evolved lighter colors as a means of adapting to these new environments.

The data revealed that almost all families followed this trend. After long periods of evolutionary stasis, sudden bursts of change emerged when the climate became colder and drier.

Exceptions included some early-bright species like those in the families Phrynosomatidae and Varanidae, which may have adapted more rapidly to those conditions.

Adaptation across time and lineage

Not all reptile families reacted the same way. Iguanas and geckos grew brighter over time, while snakes in the Elapidae family and lizards in the Teiidae family became darker. These shifts likely reflect local adaptations and different ecological strategies, such as body size or preferred habitat.

Smaller-bodied reptiles showed more sensitivity to variation in temperature and elevation. These reptiles heat and cool faster and therefore experience greater pressure to adapt their color for thermoregulation. Larger species, in contrast, maintain more stable internal temperatures and show less dramatic color changes.

At the family level, some surprising results emerged. In the Phrynosomatidae, smaller species in open areas were darker than those in forests, reversing the usual trend. But as body mass increased, this pattern flipped.

These complex interactions suggest that color evolution is not only about sunlight exposure but also about how species handle heat exchange.

Brighter colors, new opportunities

The study argues that integumentary color brightness helped reptiles enter new habitats during climate stress. As grasslands and deserts spread, reptiles with lighter skin had an edge. This led to adaptive radiation, where species rapidly diversified to occupy vacant ecological niches.

“Scaled reptiles are the largest extant order of four-limbed animals. The study helps us to understand how climate change and habitat shifts may affect animals’ survival and adaptation in relation to color. This is crucial for predicting the consequences of future climate change,” concluded Goldenberg.

These insights not only enrich our understanding of the past but also serve as a warning. As climate change continues to reshape ecosystems, reptiles may again face pressure to adjust their colors and behaviors. Some will adapt. Others may not.

Reptile colors and conservation efforts

The researchers have created a massive database of reptile brightness across space and time. Future studies could use it to explore how individuals from different genera or regions respond to climate extremes.

With many reptiles already under threat from habitat loss and warming, these findings could prove vital for conservation.

Understanding how reptiles use color to cope with their environments offers a new lens on evolution. It also highlights how one environmental factor – habitat openness – can shape life in a particular lineage for generations.

In a world that is currently growing hotter and more open, the colors of reptiles may once again begin to shift.

The study is published in the journal Nature Communications.

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