What Are Barnacles on Whales? The Hitchhikers Explained

Q: Are the white patches on whales actually barnacles?

Often, yes — particularly on gray whales and humpback whales, the crusty white or grey patches visible on the skin (especially around the head, jaw, and flippers) are commonly barnacles that have settled and grown on the whale's skin. Not every mark on a whale is a barnacle — some patches are scarring, skin discoloration, or other organisms — but barnacles are a frequent and well-documented part of what gives certain whale species their mottled appearance, to the point that the pattern of barnacle attachment is sometimes used by researchers to help identify individual whales.

Q: How do barnacles end up on a whale in the first place?

Barnacle larvae are free-swimming in their early life stages, drifting in the water as plankton themselves before settling onto a surface and developing into the immobile, shelled adult form most people recognize. A whale's skin is one of the surfaces a settling larva might encounter — and once attached, the barnacle builds its calcareous shell directly onto the whale's skin and remains there, filter-feeding from the water that flows past as the whale swims. This is the same general life cycle as barnacles that settle on rocks, boat hulls, or pilings — a whale is just a (very large, mobile) surface among the possible options.

Q: Does having barnacles hurt the whale?

Generally not in a major way — the relationship is typically described as commensalism, where the barnacle gets a clear benefit (a stable surface plus a passive ride through plankton-rich water, which it filters for food) while the whale experiences little to no meaningful cost. There can be very minor effects — some added drag from a heavy barnacle load, and some localized skin irritation at attachment points — but these are generally not considered serious health issues for the whale. This is quite different from a true parasitic relationship, where one organism actively harms the other for its own benefit; a barnacle isn't taking anything from the whale directly (it's filtering plankton from the water, not feeding on the whale itself).

Q: Are whale lice the same thing as barnacles?

No — whale lice are a completely different organism, despite often being mentioned alongside barnacles and sometimes found in the same areas of a whale's body (particularly around barnacle attachment sites, callosities, and wounds, where their flattened bodies can grip more easily). Whale lice are amphipod crustaceans — small, flattened, many-legged animals — rather than the shelled, sessile barnacles discussed here. Both are crustaceans broadly speaking (barnacles in a genuinely surprising way, covered in our guide to whether barnacles are poisonous), but whale lice and barnacles are different groups with different body plans and different relationships to their whale host — whale lice are generally considered closer to true parasites than barnacles are, though even they're not typically considered seriously harmful.

By Hektor Jorgo Published December 18, 2030 Updated June 15, 2026 4 min read

A whale's skin showing patches of attached barnacles

Quick Facts

What They Are: Barnacles — filter-feeding crustaceans that attach to whale skin (especially gray whales and humpback whales)
Why Whales Specifically: A whale's skin provides a stable surface and moves through plankton-rich water, giving attached barnacles a passive feeding advantage
Relationship Type: Generally considered commensalism — the barnacle benefits, the whale is largely unaffected
Common Locations: Head, jaw, flippers, and tail — areas with relatively slow water flow where larvae can settle
How They Get There: Free-swimming barnacle larvae settle on whale skin and develop into the attached adult form
Do They Hurt The Whale?: Generally not directly — though heavy loads may add minor drag, and the skin irritation they cause is usually minimal
Species-Specific: Some whale species (gray whales, humpbacks) commonly host barnacles; others rarely do, often related to skin texture and swimming speed
Whale Lice Are Different: Often seen alongside barnacles, whale lice are a separate organism (amphipod crustaceans, not barnacles) with their own relationship to the whale

Anyone who's seen a close-up photo of a gray whale or humpback whale has probably noticed the crusty, mottled patches covering parts of its skin — and the explanation is one of the more low-stakes hitchhiker relationships in the ocean.

Short Answer

Those patches are often barnacles — filter-feeding crustaceans whose free-swimming larvae settled on the whale's skin and grew into the attached, shelled adult form. The relationship is generally considered commensal: the barnacle gets a stable surface and a free ride through plankton-rich water (which it filters for food as the whale swims), while the whale experiences little to no meaningful harm. It's a far less dramatic relationship than the word "parasite" might suggest — barnacles aren't feeding on the whale itself.

How Barnacles Get There

Like other barnacles, the ones found on whales start life as free-swimming larvae, drifting in the water column as a form of plankton. When a larva encounters a suitable surface — a rock, a boat hull, or in this case a whale's skin — it settles and begins developing into the immobile adult form, building its calcareous shell directly onto that surface. From the barnacle's perspective, a whale is simply a large, mobile surface that happens to spend a lot of time moving through plankton-rich water — which is a genuinely useful place to be if you're an animal that feeds by filtering plankton.

This "planktonic larva settles onto a surface" pattern shows up across many marine invertebrates, not just barnacles — Nassarius snail eggs in a reef tank follow the same basic life-cycle logic, just on a much smaller scale and without a whale involved.

Why Some Whales and Not Others

Barnacle loads vary considerably by species. Gray whales and humpback whales are particularly well known for carrying visible barnacle populations, often concentrated around the head, jaw, flippers, and tail — areas where water flow is relatively slow and larvae have a better chance of settling and staying attached. Faster-swimming whale species, or those with different skin textures, tend to host fewer barnacles. The pattern of barnacle attachment on individual whales is distinctive enough that researchers sometimes use it (along with other markings) to help identify and track specific individuals over time.

Does It Hurt the Whale?

For the most part, no — at least not in any serious way. The barnacle isn't extracting nutrients from the whale's body; it's filtering plankton from the surrounding water, using the whale purely as a surface to attach to. The effects on the whale are generally minor:

Slightly increased drag from a heavy barnacle load, though whales are large enough that this is a small effect relative to their overall size and power
Localized skin irritation at attachment points, generally not considered a significant health concern

This puts the relationship closer to commensalism (one organism benefits, the other is largely unaffected) than true parasitism (one organism actively harms the other for its benefit).

Whale Lice: A Different Animal Entirely

Barnacles often get mentioned in the same breath as whale lice — but these are a separate organism. Whale lice are amphipod crustaceans: small, flattened, many-legged animals that grip onto a whale's skin, often clustering around barnacle attachment sites, callosities, or wounds where their body shape gives them better purchase. Both barnacles and whale lice are crustaceans in the broad sense (a classification that surprises people for barnacles specifically, covered in our guide to whether barnacles are poisonous), but they're different groups with different body plans — and whale lice are generally considered to have a closer-to-parasitic relationship with their host than barnacles do, though neither is typically considered a serious threat to a healthy whale.

Quick Reference

The mottled white/grey patches on whales (especially gray whales and humpbacks) are often barnacles
Barnacle larvae are free-swimming and settle onto a whale's skin, then develop into the attached adult form
The relationship is generally commensal — the barnacle benefits, the whale is largely unaffected
Minor effects on the whale can include slight drag and localized skin irritation
Barnacle attachment patterns can help researchers identify individual whales
Whale lice are a separate organism (amphipod crustaceans), not barnacles, often found in the same areas

Frequently Asked Questions

Are the white patches on whales actually barnacles?

Often, yes — particularly on gray whales and humpback whales, the crusty white or grey patches visible on the skin (especially around the head, jaw, and flippers) are commonly barnacles that have settled and grown on the whale's skin. Not every mark on a whale is a barnacle — some patches are scarring, skin discoloration, or other organisms — but barnacles are a frequent and well-documented part of what gives certain whale species their mottled appearance, to the point that the pattern of barnacle attachment is sometimes used by researchers to help identify individual whales.

How do barnacles end up on a whale in the first place?

Barnacle larvae are free-swimming in their early life stages, drifting in the water as plankton themselves before settling onto a surface and developing into the immobile, shelled adult form most people recognize. A whale's skin is one of the surfaces a settling larva might encounter — and once attached, the barnacle builds its calcareous shell directly onto the whale's skin and remains there, filter-feeding from the water that flows past as the whale swims. This is the same general life cycle as barnacles that settle on rocks, boat hulls, or pilings — a whale is just a (very large, mobile) surface among the possible options.

Does having barnacles hurt the whale?

Generally not in a major way — the relationship is typically described as commensalism, where the barnacle gets a clear benefit (a stable surface plus a passive ride through plankton-rich water, which it filters for food) while the whale experiences little to no meaningful cost. There can be very minor effects — some added drag from a heavy barnacle load, and some localized skin irritation at attachment points — but these are generally not considered serious health issues for the whale. This is quite different from a true parasitic relationship, where one organism actively harms the other for its own benefit; a barnacle isn't taking anything from the whale directly (it's filtering plankton from the water, not feeding on the whale itself).

Are whale lice the same thing as barnacles?

No — whale lice are a completely different organism, despite often being mentioned alongside barnacles and sometimes found in the same areas of a whale's body (particularly around barnacle attachment sites, callosities, and wounds, where their flattened bodies can grip more easily). Whale lice are amphipod crustaceans — small, flattened, many-legged animals — rather than the shelled, sessile barnacles discussed here. Both are crustaceans broadly speaking (barnacles in a genuinely surprising way, covered in our guide to whether barnacles are poisonous), but whale lice and barnacles are different groups with different body plans and different relationships to their whale host — whale lice are generally considered closer to true parasites than barnacles are, though even they're not typically considered seriously harmful.

Sources & Further Reading

About the Author: Hektor Jorgo

Co-Founder & Marine Biologist

Hektor is a co-founder of Sea Life Planet and has kept reef and freshwater aquariums for over 15 years. He holds a background in marine biology and focuses on species care accuracy, water chemistry, and tank husbandry.