# A Comparison of Image Statistics of Peacock Jumping Spider Colour Patterns and Natural Scenes

## TL;DR

Male peacock spiders evolve color patterns that stand out from their environment, while females blend in, suggesting visibility rather than processing ease drives their evolution.

## Contribution

The study reveals that male peacock spider color patterns diverge from natural scene statistics, challenging the sensory drive hypothesis.

## Key findings

- Male peacock spider color patterns have image statistics that differ from natural scenes.
- Female peacock spider color patterns match the image statistics of natural scenes.
- The results suggest that color patterns evolve for visibility, not for ease of processing.

## Abstract

The form of arbitrary sexual signals may be driven by the need to be detectable against the background or, alternatively, by selection for efficient processing by the nervous system. This latter alternative is a prediction of the sensory drive hypothesis extended to include efficient coding as a driver of the form of sexual signals. This hypothesis posits that animal visual systems are adapted to process the visual statistics of natural scenes, and that easily processed stimuli induce a sensation of pleasure in the viewer. In support of this, natural scene statistics have been found to be preferred not only by humans, but by the peacock spider
Maratus spicatus
. Here we test if male peacock spiders of the highly sexually dimorphic Maratus genus generally (a) evolve colour patterns with image statistics that contrast with the natural background or (b) exploit a potential processing bias by evolving colour patterns with visual statistics similar to those of natural scenes. We analyse and compare multispectral images of male and female spiders of 21 Maratus species and of natural scenes similar to the spiders' habitat. We find that the image statistics of male patterns diverge from those of natural scenes, whereas the statistics of female patterns do not. Our results support the idea that colour patterns evolve contrasting image statistics to increase conspicuousness and matching image statistics to be camouflaged. Any processing bias for natural scene image statistics in Maratus thus appears to play little role in the evolution of their sexual signals.

What drives the evolution of colour patterns in peacock spiders: Standing out or processing bias? Hardenbicker et al. found that the image statistics of male colour patterns diverge from those of natural scenes, whereas the statistics of female patterns do not. It seems that when it comes to image statistics in Maratus, it is not about ease of processing but about being seen.