Grapsus grapsus
Identification.
Adults are vivid red, orange and blue against black lava rock; juveniles are black or dark brown for camouflage, gaining color with each molt.
Galápagos context.
Recorded directly by Charles Darwin during his visit.
Encounter context.
Extremely agile, able to run in any direction and jump rock to rock, effectively appearing to walk on water in short hops. Its generalist diet (algae, carrion, picking ticks off marine iguanas, scavenging sea lion placenta) provides a real ecosystem cleanup service.
Seasonality.
Present year-round with no defined breeding season.