Aberrant Pigmentation in a Schooling Cownose Ray (Rhinoptera bonasus) in Chesapeake Bay, Virginia, USA

TL;DR

A cownose ray with unusual white patches was observed schooling normally with others, suggesting pigmentation anomalies don't hinder social behavior.

Contribution

First in-situ evidence showing pigmentation anomalies in cownose rays don't disrupt social integration.

Findings

A cownose ray with aberrant pigmentation was observed schooling normally with conspecifics.

Pigmentation anomalies did not disrupt coordinated group behavior or social dynamics.

This case adds to the limited records of pigmentation disorders in Rhinoptera bonasus.

Abstract

While pigmentation disorders such as albinism have been documented in a range of elasmobranch species, including the American cownose ray (
Rhinoptera bonasus
), the implications of these rare conditions for behavior, social dynamics, and fitness remain speculative and unverified. Here, we report a case of aberrant pigmentation in a single cownose ray observed schooling among conspecifics in the nearshore waters of Chesapeake Bay, Virginia, USA. The individual displayed pronounced white coloration against a notably dark dorsal surface of both pectoral fins, contrasting sharply with the otherwise uniform brown tones of the surrounding rays. The ray was fully integrated into the school and exhibited no abnormal behavior, suggesting that this pigmentation anomaly did not disrupt social dynamics. This observation augments the small but growing number of reports of pigmentation disorders in
R. bonasus
, suggesting that important social acceptances required for incorporation into the aggregation were unimpeded by the aberrant pigmentation.

We report a rare case of aberrant pigmentation in a cownose ray (Rhinoptera bonasus) observed schooling naturally within Chesapeake Bay, Virginia. Drone and in‐water imagery revealed a piebald‐like pattern without any disruption to coordinated group behavior, providing the first in situ evidence that pigmentation anomalies in this species do not necessarily impair social integration. This observation contributes to the growing record of phenotypic variation in elasmobranchs and highlights the importance of behavioral context in assessing potential fitness consequences of pigment disorders.

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