Sucker fish are hiding in manta rays’ ‘butthole,’ new study reveals

image via New Scientist

May 11, 2026, 8:06 PM

• •Remoras are observed entering manta rays' cloacal openings.
• •This "cloacal diving" could offer remoras hiding, feeding, or hitchhiking benefits.
• •The behavior could potentially disrupt manta ray mating, birth, or defecation.
• •The study was published in the journal Ecology and Evolution.

A recent study documents remoras, fish known for attaching to hosts, entering the cloacal openings of manta rays. This behavior, termed "cloacal diving," is unwelcome by the rays but potentially beneficial for the remoras, offering hiding, feeding, or hitchhiking opportunities. The researchers suggest the remoras may benefit by hiding from predators, feeding on the host's waste, or reducing drag while hitchhiking. This unusual behavior may impact the ray's mating, birthing, or defecation if the remora stays for an extended period.

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