Sharks are apex predators that have inhabited the oceans for millions of years. Their ability to detect prey is legendary, using their senses of smell, sight, touch and even electromagnetism through special organs called the ampullae of Lorenzini. Understanding how sharks perceive color and which colors attract or deter them the least has important implications for the safety of ocean goers and swimmers.
Shark Vision and Color Perception
Sharks have excellent vision and can see colors, albeit not the same colors that humans perceive. They have special light-sensitive cells in their retinas called rods and cones. The rods allow them to see well in low light conditions, while the cones provide daytime and color vision. However, sharks have only a single class of cone cell, making their color vision limited compared to many other species including humans that have multiple cone types. Shark color perception is thus thought to be similar to red-green color blindness in humans. They can distinguish between light and dark, but cannot discern the spectrum of colors that humans with normal vision can see.
How Sharks See Color Underwater
The marine environment also affects shark color vision. As light passes through water, the longer red wavelengths are absorbed first, followed by orange, yellow, and green. This filtering effect means that sharks’ color perception is limited to blues and violets in deeper waters. Closer to the surface where more light penetrates, they may also be able to distinguish yellows and greens. However, the contrast between light and dark stands out more to sharks than differences in color, especially in ocean depths.
Role of Contrast in Attracting Sharks
More than perceiving specific colors, sharks are exceptionally good at detecting contrast, which allows them to spot potential prey against different backgrounds. Objects or animals that stand out from their surroundings, either due to color, light/dark shading, silhouette, or unnatural movements are more likely to grab sharks’ attention and potentially elicit an investigatory bite. This is one reason why sharks may mistakenly bite swimmers or surfboards that suddenly contrast with the environment.
Testing Shark Response to Color
Controlled experiments have attempted to pinpoint which colors sharks are least attracted to by measuring their reactions to different colored bait. One study published in the journal Animal Cognition tested shark responses to yellow, white, black, and gray wetsuits. The results showed:
| Wetsuit Color | Shark Attacks |
|---|---|
| Black | Most frequent attacks |
| Gray | Frequent attacks |
| White | Infrequent attacks |
| Yellow | Least frequent attacks |
The researchers concluded that lighter, brighter colors, especially yellow, were least attractive to sharks looking for prey. Additional studies have supported this finding, showing reduced shark interest in yellow versus normal gray bait colors.
Factors Making Yellow Less Appealing to Sharks
There are a few possible reasons why sharks seem to pay less attention to yellow:
- Bright yellow contrasts strongly with water and sand backgrounds, appearing unnatural and not resembling typical prey animals.
- Yellow stimuli activate sharks’ color vision but do not resemble familiar food sources like fish or seals.
- Yellow light wavelengths do not travel far underwater, making yellow objects harder for sharks to discern at a distance.
Together, these elements make yellow less visible, recognizable, and enticing to sharks searching for a meal. Whites and lighter colors may similarly fail to trigger sharks’ prey drive compared to high-contrast blacks, grays, and darker colors.
Other Factors in Shark Attraction
While color can play a role, sharks are complex predators and many other factors influence their behavior. Movement, vibrations, smell, shape, and electrical signals given off by potential prey can be just as important, if not more so, than color alone. Brightly colored diving gear will not act as an absolute repellent or invisibility cloak from sharks. However, choosing yellow or light colored swimwear and equipment over blacks and grays may provide an incremental advantage in not attracting shark attention.
Strategies to Reduce Shark Interactions
Beyond wearing lighter colors, experts recommend the following strategies to stay safer around sharks:
- Avoid areas with known shark activity like seal colonies.
- Stay close to shore and in groups rather than alone.
- Refrain from excess splashing which can mimic prey movement.
- Avoid murky water with low visibility.
- Steer clear of schools of fish which shark may feed on.
While shark attacks are rare, it is wise to be cautious and employ precautions when in their territory. Selecting wetsuits, fins, snorkels and dive gear in yellow or bright, light colors seems to be one more measure swimmers and divers can take to be just a little less conspicuous and reduce the already low risk of unwanted shark attention.
Conclusion
Research indicates yellow and lighter colors are less visible and attractive to sharks compared to darker colors with more contrast. This is due to the limited color perception of sharks, the filtering effects of water on colors, and yellows having less resemblance to typical shark prey. While additional factors like movement and electrical signals also influence shark behavior, choosing yellow or light colored gear over black or gray may incrementally improve safety by not standing out. Along with other precautions like avoiding known shark areas and not swimming alone, yellow and light colors appear to be a prudent choice for reducing unwanted shark interest.