8 Facts About the Amazing Cuttlefish

Broadclub cuttlefish on a reef in blue water and sun shining through above

Andreas Schumacher/Stocktrek Images / Getty Images

Cuttlefish are cephalopods and expert camouflagers of the sea. There are 120 cuttlefish species; all are equipped with eight arms and two extendible tentacles covered in sucker disks. Cuttlefish have one of the largest brain to body ratios of all invertebrates, and their intelligence is observed through their ability to distinguish between foods, choose the larger of two quantities, and mimic the color, texture, and patterns in their surroundings.

These bottom-dwellers live in tropical and temperate waters off of Europe, Asia, Africa, and Australia. The Australian giant cuttlefish is at risk. From remarkable vision to their ability to change their appearance in less than one second, discover the most fascinating facts about cuttlefish.

1. Cuttlefish Change Color To Match Their Surroundings

In order to blend in with their environment, cuttlefish can change their skin color in a flash — in less than one second. They can even change color as they swim through different colors of coral or rocks. What's more, the coloration doesn't have to be static. They can change color in rapid patterns that make it look like ripples of color are rolling over their bodies. The mesmerizing "light show" effect is a strategy that can help cuttlefish catch prey. This detailed color-changing ability is even more impressive when you consider that cuttlefish themselves are colorblind.

2. They Have Three Hearts

Like all cephalopods, cuttlefish have three hearts. Two of its three hearts are used to pump blood to the cuttlefish's large gills, and the third is used to circulate oxygenated blood to the rest of its body.

The circulatory system of cuttlefish is closed, unlike other mollusks, but consistent with other cephalopods and vertebrates. The blood pumped through the cuttlefish’s heart is blue-green in color because, like its cephalopod relatives, it contains a copper-based protein, hemocyanin.

3. They Can Mimic Objects Around Them

In an effort to hide from predators, cuttlefish can imitate the shape and texture of objects around them. Their close relative, the octopus, is also able to do this. Cuttlefish accomplish texture change by extending or retracting tiny bumps called papillae located across their bodies, allowing them to better match sand, bumpy rocks, or other surfaces where they're hiding.

The pharaoh cuttlefish can shape-shift itself into something closely resembling a hermit crab, to scare off predators and get more fish for itself.

4. Male Cuttlefish Disguise Themselves as Females

Cuttlefish have a few more disguise tricks up their sleeves. When male cuttlefish want to get past competing males to mate, they mimic a female. When engaging in this deception, smaller male cuttlefish use their fins for cover as they swim by larger males undiscovered.

Male cuttlefish typically reserve this behavior for instances when a single male rival is nearby. The duplicity is so advanced that male cuttlefish can display male patterns on one side of their body and female patterns on the other, keeping their rival completely unaware.

5. They Have Discerning Palates

When it comes to food, cuttlefish are intelligent enough to plan ahead. If they are aware that their favorite meal (shrimp) is on the menu, cuttlefish refrain from eating as many crabs earlier in the day. 

This ability to make choices based on the expectation of something occurring in the future led researchers to conclude that cuttlefish have complex cognitive abilities. During a study, cuttlefish that were regularly provided with shrimp in the evening consumed fewer fish and crabs during the day. Conversely, those who were given shrimp at random times did not adjust their daytime eating habits.

6. They Have Impressive Vision

cuttlefish swimming in water
Kristina Vackova / Shutterstock

For colorblind creatures, cuttlefish have remarkable vision. They have the ability to perceive polarized light, which provides them with an enhanced capacity to detect prey. Because of their W-shaped pupils, cuttlefish can see in all directions, including behind them, by simply moving their eyes.

The cuttlefish has large eyes in proportion to its body, a characteristic that is believed to boost magnification.

7. They Can Count

Cuttlefish are known for their intelligence, and when it comes to counting shrimp, they truly shine. A study found that one-month-old cuttlefish could easily tell the difference between a box with four shrimp and a box with five shrimp. When boxes contained more shrimp, the cuttlefish took longer to decide which box to eat from, which researchers considered evidence that the cuttlefish were physically counting the number of shrimp before making their decisions. Researchers concluded that the cuttlefish’s ability to compare quantities is comparable to that of 12-month-old human babies and rhesus macaques.

8. The Australian Giant Cuttlefish Is at Risk

Australian giant cuttlefish swimming over a bed of kelp
by wildestanimal / Getty Images

One species of cuttlefish, the Australian giant cuttlefish, is near threatened, primarily due to overfishing. The largest of all cuttlefish, the Australian giant cuttlefish is found throughout the coastal waters of Australia. Their population decreased from an estimated 150,000 in the late 1990s to a total of 13,492 in 2013, when the Australian government instituted a ban on fishing in their breeding area. The ban resulted in a population increase to an estimated 247,146 in 2020, and the fishing ban was lifted. 

Because the Australian giant cuttlefish only lives for two years, has a single reproductive cycle, and dies after breeding, the potential risk of increased fishing to the species may be catastrophic. Proposed industrial development in the cephalopods’ breeding area threatens the existing ecosystem and may cause additional risk to the future of the Australian giant cuttlefish.

Save the Australian Giant Cuttlefish

  • Sign the Care2 petition to support the relocation of industrial development proposed in this species’ delicate breeding area.
  • Follow and support the Scuba Divers Federation of South Australia in their efforts to protect the Australian giant cuttlefish.
  • Sign the Change.org petition for the Australian government to re-consider the lifting of the fishing ban on Australian giant cuttlefish in the Upper Spencer Gulf.
View Article Sources
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  2. Okamoto, Kohei, et al. "Unique Arm-Flapping Behavior of the Pharaoh Cuttlefish, Sepia pharaonis: Putative Mimicry of a Hermit Crab." Journal of Ethology, vol. 35, 2017, 307-311, doi:10.1007/s10164-017-0519-7

  3. Billiard, Pauline, et al. "Cuttlefish Show Flexible and Future-Dependent Foraging Cognition." Biology Letters, vol. 16, no. 2, 2020, pp. 20190743, doi:10.1098/rsbl.2019.0743

  4. Yang, Tsang-I and Chiao, Chuan-Chin, "Number Sense and State-Dependent Valuation in Cuttlefish." Proceedings of the Royal Society B, vol. 283, no. 1837, 2016, doi:10.1098/rspb.2016.1379

  5. "Giant Australian Cuttlefish." International Union for Conservation of Nature Red List of Threatened Species.

  6. "Cuttlefish Population Survey." Government of South Australia, Department of Primary Industries and Regions.