philosophy

Beyond Shrinking Bodies: Why One Trait may not be Enough to Predict Climate Responses

/ gtattersall

A new Perspective out today in Nature Reviews Biodiversity, by Matt Symonds, Sara Ryding, and Marcel Klaassen (Deakin University), with Josh Tabh and Andreas Nord (Lund University) and myself, tackles a problem that has been nagging at climate-change biologists for years: why do studies of a single trait, like body size, or metabolic rate, so often give inconsistent answers about how animals are responding to a warming world? Textbook “rules” like Bergmann’s (smaller bodies in warm climates) and Allen’s (bigger appendages in warm climates) might predict tidy, single-trait shifts through time as the planet heats up.

But real animals don’t have the luxury of changing one thing at a time. Morphology, physiology and behaviour are tangled together, and a change in one can mask, amplify, or completely offset a change in another. A bird that isn’t shrinking might instead be shifting its foraging schedule to the cooler part of the day; a bird with no obvious behavioural change might be quietly ramping up its evaporative cooling capacity instead. Look at any one trait in isolation and you risk concluding “no effect” when there’s really just a hidden trade-off.

Our Perspective lays out what’s currently known about how each of these three trait categories from form to function responds to geographic and temporal temperature gradients, then digs into the ways they interact with and constrain each other. Rather than just cataloguing the problem, we sketch out a path forward: comparative multi-species studies, wide-ranging single-species studies across many populations, and controlled mesocosm experiments that track morphology, physiology and behaviour simultaneously in the same individuals, so trade-offs actually become visible instead of disappearing into separate, disconnected data sets. The hope is that this kind of integrative, multi-trait thinking will let us better identify which species are truly vulnerable to climatic warming, rather than mistaking a “silent” trait for a species that isn’t responding at all.

Citation

Symonds, M.R.E., Tabh, J.K.R., Nord, A. Klaassen, M, Tattersall, G.K., and Ryding, S. Moving beyond single traits to predict endotherms’ responses to climatic warming. Nature Reviews Biodiversity (2026). https://doi.org/10.1038/s44358-026-00195-5

For access to the full paper, this is a shareable link: https://rdcu.be/ypK7CBgbw1va

Try Before You Buy: How Experience Shapes What Bearded Dragons Prefer

/ gtattersall

A recent paper from the lab, led by PhD student Melanie Denommé, examines a foundational assumption in reptile husbandry: that animals will inherently prefer naturalistic enclosures over simpler, more utilitarian ones. Using bearded dragons (Pogona vitticeps) as a model species, Melanie conducted preference tests in which lizards were given free choice between naturalistic and standard enclosure styles (Figure 1). Critically however, individuals had been reared under two different housing conditions and tested at multiple time points across their lives, allowing us to shed light on preferences shaped by experience. Contrary to expectations, the dragons did not show an immediate or universal preference for the more naturalistic enclosures. Instead, their choices were strongly influenced by prior housing conditions, age, and timing of the tests, demonstrating that familiarity and developmental context play an important role in how captive reptiles evaluate their environments. 

Figure 1. Graphic abstract from the study, describing the timing of the preference tests and housing conditions lizards were under at the two time points when preferences were tested. The y-axis describes a bias index, describing what proportion of time lizards spent within each enclosure style (values of 0 indicated 100% of time spent in standard, values of 1 indicate 100% of time spent in naturalistic).

Despite the absence of a consistent enclosure-level preference, the behavioural data told a more nuanced and compelling story. When lizards engaged in key species-typical behaviours such as climbing, digging, and hiding, they overwhelmingly used naturalistic resources rather than the simpler substitutes provided in standard enclosures. This finding suggests that while reptiles may not always “choose” a naturalistic enclosure outright, these environments are clearly superior for facilitating motivated behaviours that are closely linked to welfare. As part of Melanie’s broader PhD research program, this work emphasizes the importance of empirically testing husbandry assumptions rather than relying only on tradition or aesthetics alone, and it provides concrete guidance on which enclosure features matter most from the animal’s perspective. More than that, we argue that context and experience are important considerations in these kinds of studies.

Citation

Denommé, M and Tattersall, GJ. 2026. Try before you buy: Preferences for naturalistic-style enclosures are influenced by experience in bearded dragons (Pogona vitticeps). Journal of Applied Animal Behaviour Science, 295:106887. https://doi.org/10.1016/j.applanim.2025.106887