Size-dependent colouration balances conspicuous aposematism and camouflage
Bibliographic record
Abstract
Abstract Colour is an important component of many different defensive strategies, but signal efficacy and detectability will also depend on the size of the coloured structures, and how pattern size interacts with the background. Consequently, size-dependent changes in colouration are common among many different species as juveniles and adults frequently use colour for different purposes in different environmental contexts. A widespread strategy in many species is switching from crypsis to conspicuous aposematic signalling as increasing body size can reduce the efficacy of camouflage, while other antipredator defences may strengthen. Curiously, despite being chemically defended, the gold-striped frog (Lithodytes lineatus, Leptodactylidae) appears to do the opposite, with bright yellow stripes found in smaller individuals, whereas larger frogs exhibit dull brown stripes. Here, we investigated whether size-dependent differences in colour support distinct defensive strategies. We first used visual modelling of potential predators to assess how colour contrast varied among frogs of different sizes. We found that contrast peaked in mid-sized individuals while the largest individuals had the least contrasting patterns. We then used two detection experiments with human participants to evaluate how colour and body size affected overall detectability. These experiments revealed that larger body sizes were easier to detect, but that the colours of smaller frogs were more detectable than those of larger frogs. Taken together our data support the hypothesis that the primary defensive strategy changes from conspicuous aposematism to camouflage with increasing size, implying size-dependent differences in the efficacy of defensive colouration. We discuss our data in relation to theories of size-dependent aposematism and evaluate the evidence for and against a possible size-dependent mimicry complex with sympatric poison frogs (Dendrobatidae). Abstract For chemically defended species, colouration evolves as a balance between the benefits of a salient and recognisable warning signal (aposematism) and the benefits of avoiding unnecessary attention from predators (camouflage). Detectability will depend on many factors, including colour, pattern, and body size. Here, we examined size-dependent colouration in the gold-striped frog (Lithodytes lineatus), where small frogs have bright blue-white stripes, mid-sized frogs have bright yellow stripes, and large frogs have dull-brown stripes. We found that the trade-off between aposematism and camouflage depends on both colour and body size, such that frogs of different sizes employ different defensive strategies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".