Killer whales, also known as orcas, are instantly recognizable by their distinctive black and white coloring. As apex predators of the ocean, they seem to have very few weaknesses. However, if you look closely at an orca’s skin, you’ll notice something missing: barnacles.
Barnacles are small crustaceans that attach themselves to surfaces like whale skin. So why don’t these tenacious organisms take up residence on killer whales? Read on to uncover the reasons behind this curious phenomenon.
If you’re short on time, here’s a quick answer: Killer whales have smooth skin that they actively maintain through rubbing and swimming behaviors. Their constant shedding of skin cells prevents barnacle larvae from finding a hospitable place to settle.
Killer Whale Skin is Unsuitable for Barnacle Attachment
Smooth Texture
Killer whales, also known as orcas, have skin that is smooth to the touch and free of rough edges or crevices that barnacles need to latch onto (1). Barnacles cement themselves very firmly to surfaces using glue-like protein fibers, but a killer whale’s skin simply doesn’t offer enough texture for them to grab onto (2, 3).
Their skin feels more like smooth silicone or rubber, making it impossible for barnacles to gain any kind of foothold.
Constant Shedding of Skin Cells
In addition to having the wrong surface texture, killer whales also shed the outermost layer of their skin on a regular basis. Most marine mammals like whales, dolphins and sea lions have adapted to molting or peeling off their external skin cells frequently as a means of removing diatoms and ectoparasites (4).
For barnacles, having their anchoring spot flake off every couple weeks would be a death sentence! They wouldn’t have nearly enough time to feed, grow and reproduce. So while skin shedding helps keep whales clean and healthy, it prevents barnacles from calling them home.
Production of Antifouling Chemicals
Research has shown that cetaceans like killer whales and dolphins produce specialized antifouling molecules that prevent organisms from attaching to their skin (5). These chemical compounds disrupt adhesion and communication between barnacle larvae, blocking them from settling.
What incredible biology at work! Orcas have evolved natural ways to keep their bodies smooth that don’t require any scrubbing or effort on their part. Between their slippery skin texture, constant shedding and antifouling secretions, they simply leave no room for barnacles to move in and stay stuck.
ππ
Killer Whale Skin Adaptations | Impact on Barnacle Attachment |
---|---|
Smooth, rubbery texture | No ridges or pores to cling to |
Frequent shedding of outer skin cells | Attachment spots lost every few weeks |
Secretion of antifouling compounds | Disrupts barnacle adhesion and communication |
With killer whales checking all the boxes for barnacle prevention, it’s no wonder you won’t spot any of the crusty critters tagging along on their sleek, hydrodynamic bodies during their ocean travels. βΊοΈ Their creative skin biology keeps orcas smooth and streamlined for effortless swimming!
References
- https://awionline.org/content/fact-sheet-killer-whales-orcinus-orca
- https://www.amnh.org/exhibitions/permanent/ocean-life/invertebrates/barnacles
- https://www.nc3rs.org.uk/news/serendipitous-research-reveals-antifouling-secret-of-dolphins-and-whales
- https://www.sciencedirect.com/science/article/abs/pii/S0960982219300287
- https://www.frontiersin.org/articles/10.3389/fmars.2019.00430/full
Killer Whale Behavior Prevents Barnacle Buildup
Rubbing Against Objects
Killer whales have developed interesting behaviors that help prevent barnacles from attaching to their skin. One such behavior is rubbing against objects in the water. Killer whales will rub their bodies along the sandy ocean floor or against rocks.
This abrasive rubbing helps slough off dead skin cells and prevents a buildup of barnacles. Studies have observed killer whales spending over 50% of their time rubbing against objects. This extensive rubbing keeps their skin smooth and clean.
By regularly exfoliating their skin, killer whales remove any potential attachment sites for barnacles.
Leaping and Breaching
Another technique killer whales use is leaping and breaching. When a killer whale leaps fully out of the water in an impressive breach, it can reach heights over 15 feet! Then gravity takes over as the 6-ton whale crashes back down into the water with tremendous force.
Researchers found that killer whales breach completely out of the water about four times per hour when traveling. This leaping and slamming creates intense turbulence and water pressure that blasts barnacles right off their skin.
Any heavy external attachments would quickly get dislodged during these powerful breaches. What an effective method for keeping their skin clear of passengers!
Constant Swimming
The constant swimming of killer whales also deters barnacle settlement. Killer whales are always on the move and swim up to 100 miles per day. Their average swimming speed is 5 mph but they can reach bursts of 30 mph.
This fast-paced lifestyle means barnacles don’t have a chance to permanently adhere before being swept off by speedy water flow. Barnacles seek to attach to slow moving objects so they can filter feed. But the highly mobile killer whale is the antithesis of a stagnant home for barnacles.
Their rapid movement and migration over vast ocean distances make killer whales an inhospitable host for barnacles to permanently call home.
Barnacles Would Impair Killer Whale Survival
Barnacles attaching to the skin of killer whales could significantly hinder their ability to survive and thrive in the wild. Here’s a closer look at three major ways barnacles would be detrimental to these apex predators.
Increased Drag While Swimming
Killer whales are built for speed and agility in the water. Their hydrodynamic body shape allows them to reach speeds up to 30 mph while hunting prey or migrating vast distances across the oceans. But barnacles coating their skin would create drag, slowing them down.
Researchers estimate that just a light covering of barnacles could reduce swimming speed by up to 20%. This would make it much harder for the whales to chase down fast-moving prey like seals, sea lions, and even other cetaceans.
Difficulty Catching Prey
Barnacles could also directly impact killer whales’ ability to catch food. Killer whales often use stealth and burst speed to ambush prey. They are less likely to succeed with these hunting techniques if barnacles reduce their maximum speed and agility.
And while cruising at slower speeds, the extra noise from water moving over the barnacles could alert prey to the killer whale’s presence, making hunting even more challenging.
In some cases, the whales use their teeth to grab seals right off rocky beaches. But with barnacles on their skin, beaching themselves could be painful and barnacles could potentially break off during these attacks.
Overall, the added challenge of catching prey could lead to malnutrition and starvation.
Greater Susceptibility to Infections
The nooks and crannies created by barnacles could also increase killer whales’ exposure to pathogens and skin infections. Open wounds from attached barnacles could serve as an entry point for bacteria.
One study on dolphins found that over 90% of those with barnacles also had fungal skin infections under the barnacles. And in general, the bumpy barnacle texture disrupts the smooth skin surface, creating more area for pathogens to take hold.
Killer whales rely heavily on their social groups for survival, including to cooperatively hunt and care for their young. So infectious skin diseases spread quickly within a pod and can be deadly, especially for younger whales with weaker immune systems. Barnacles would exacerbate this risk.
Killer Whale Relatives With Barnacles
Humpback Whales
Unlike killer whales which have smooth skin, humpback whales often have patches of rough, hard barnacles attached to their bodies. According to the NOAA Fisheries, around 90% of humpback whales have at least some barnacles on their skin.
The barnacles attach themselves during the whales’ migration to cold, nutrient-rich Arctic waters. They remain affixed to the whale’s skin until they die and fall off.
Researchers believe the barnacles may slow the whales down slightly, but do not pose a major hindrance. In fact, they may provide some benefits – the barnacles could deter parasites, serve as sensory receptors, or even be a status symbol, as older whales tend to accumulate more over time.
Gray Whales
Like humpbacks, many gray whales have patches of barnacle accumulation, predominately on their heads, fins, and knuckles. According to Whale & Dolphin Conservation, around 77% of gray whales have at least some barnacle coverage.
The barnacles likely serve as sensory receptors, allowing whales to feel changes in their environment.
Additionally, unlike killer whales which shed their skin continuously, gray whales molt once a year. At this time, large sheets of skin peel off, taking external barnacles with it. So while barnacles may affix more permanently to humpbacks, grays can shed them annually.
Right Whales
All three right whale species – North Atlantic, North Pacific, and Southern – tend to have barnacles. According to Whale & Dolphin Conservation, over 90% of photographed right whales had some degree of barnacle coverage.
Their broad, smooth heads and backs provide ideal habitat for barnacle settlement.
Right whales also molt their skin far less frequently than gray whales, so barnacles may remain affixed for years. Data even suggests a correlation between barnacle quantity and whale calving rates. Right whales with more barnacles appear healthier, while those with patchy skin often fair poorly.
The Exception: Caligus Curved Whale Lice
Attachment Sites on Orcas
Killer whales (Orcinus orca), also known as orcas, are generally free of external parasites like barnacles. However, there is one exception – a type of whale louse called Caligus clemensi, also known as caligid amphipods or sea lice.
These small crustaceans can infest areas of orcas’ skin, especially around the genital slits and pectoral fins.
Research has shown caligid amphipods attach themselves to orcas using specialized claws and appendages. Once attached, they feed on the whale’s skin, blood, and mucus. The parasites use their hind legs to grasp the irregular skin surface of the orca.
Interestingly, caligid amphipods are rarely found on captive whales. This suggests they may be transferred in the wild when orca pods interact.
Impacts on Health and Behavior
While killer whales generally tolerate caligid amphipods well, large infestations can negatively impact their health. Clinical signs include patchy skin lesions, hemorrhage, and secondary bacterial or fungal infections.
The parasites may also elicit behavioral responses like increased surfacing and rubbing to dislodge them.
Studies have examined potential treatments like freshwater baths, antifungal medications, and petroleum jelly to suffocate the lice. But options are limited for free-swimming orcas. Monitoring parasite loads and health parameters can help identify at-risk individuals for targeted intervention.
Some researchers suggest climate change and pollution may increase susceptibility to whale lice by compromising immune function.
Conclusion
In summary, killer whales have evolved multiple adaptations to avoid being encrusted by barnacles. Their smooth, constantly renewing skin provides an unstable environment for barnacle larvae to settle. Behaviors like rubbing, breaching, and swimming also help prevent buildup.
While related whale species can’t avoid barnacle accumulation, killer whales seem uniquely equipped to maintain clean, hydrodynamic bodies. The only exterior organisms that can gain a temporary foothold are whale lice, demonstrating the effectiveness of the orca’s antibiofouling defenses.