Canal construction disrupts background matching camouflage in two sympatric estuarine crab species

Estuarine ecosystems provide essential habitats for fiddler crabs, whose survival heavily relies on background-matching camouflage. Anthropogenic modifications such as canal construction can alter the visual properties of these habitats, yet direct empirical evidence of their impact on crustacean camouflage remains limited. This study investigated the effects of habitat canalization on the camouflage effectiveness of two sympatric crab species, Parasesarma pictum and Perisesarma bidens. We quantified color matching using the chromatic just noticeable difference (CJND) metric, comparing individuals in engineered canal habitats versus adjacent natural mudflats. Results demonstrated a significant reduction in camouflage efficacy in canalized areas for both species. The CJND values were markedly higher in canal habitats (P. pictum: 10.29 ± 5.475; P. bidens: 12.61 ± 4.832) compared to natural habitats (P. pictum: 7.465 ± 3.855, Z = -7.698, P < 0.001; P. bidens: 9.512 ±..., , # Canal construction disrupts background matching camouflage in two sympatric estuarine crab species

Dataset DOI: [10.5061/dryad.08kprr5h2](https://doi.org/10.5061/dryad.08kprr5h2)

## Description of the data and file structure

The dataset primarily focuses on evaluating differences in camouflage effectiveness between two crab species, *Parasesarma pictum* and *Perisesarma bidens* . The analysis compares their camouflage across two distinct habitats—a human-modified canal habitat and a neighboring natural habitat—using four key indices: CJND, LJND, PED, and GabRat.
### Files and variables

#### File: Raw_data.xlsx

**Description:** **Differences in camouflage effectiveness between** ***Parasesarma pictum*** **and** ***Perisesarma bidens*** **were assessed across canal and adjacent natural habitats.**

##### Variables

* CJND: Chromatic just-noticeable difference
* LJND: Luminance just-noticeable difference
* PED: Pattern Energy Difference
* GabRat: Gabor edge disruption Ratio

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