Crossing the water like sparkling arrowheads, cuttlefish are fast and safe hunters – death on eight limbs and two undulating tentacles for small creatures nearby. They transform to match the landscape, changing between a variety of tones and even textures, using tiny structures that expand and contract under your skin. They even seem to have depth perception, researchers found wearing tiny 3-D vision glasses, separating them from octopuses and squid. And his accuracy in attacking the prey is remarkable.
But for the cuttlefish, these physical feats in search of food are not everything. A new study published this month in the Royal Society Open Science magazine shows that there is even more to cuttlefish cognition than scientists may know.
Sea creatures seem to be able to perform calculations that are more complicated than simply “more food is better”. Presented with the option of choosing between one or two shrimp, they will actually choose a single shrimp when they learn from experience that they are rewarded for that choice.
Although the intelligence of their octopus cousins receives a lot of attention, researchers studying animal cognition have discovered surprising talents in cuttlefish over the years. For example, cephalopods will hunt less crabs during the day if they learn that shrimp, their favorite food, is predictably available at night. This shows that they can think about the future.
Chuan-Chin Chiao, a biologist at National Tsing Hua University in Taiwan, and author of the current article alongside his colleague Tzu-Hsin Kuo, has discovered in the past that hungry cuttlefish will choose a bigger and more difficult to catch shrimp to attack, and the who are not will choose the smallest and easiest to pick up.
But the researchers also found that animals don’t always make decisions that seem logical at first. Like humans, whose behavior rarely fits economists’ views of what an ideal, rational creature would do, animals respond to their environments using learned experiences.
In these new experiments, curious to see if they could alter the value that the cuttlefish attach to a single shrimp, the researchers gave the cuttlefish the option of entering a chamber with a shrimp or a chamber with none. Each time they entered the chamber with a shrimp, the researchers gave them a smaller shrimp as a reward.
Then, each cuttlefish took a second test. They could go into a chamber and chase two shrimp. Or they could enter another chamber that had only one.
“You would think they always choose the largest amount,” said Chiao. But that is not what happened.
In the second round, the cuttlefish chose a shrimp much more often than two. The cuttlefish that did not have the training reliably chose two shrimp instead of one, demonstrating that those who chose the smaller number were anticipating the reward and operating differently from their companions. Even waiting an hour since initial training has not completely erased the new behavior.
The process of being rewarded for choosing a shrimp appears to have given that option an extra sparkle when it comes to cuttlefish, said Chiao. This suggests that they are not simply giving basic answers to the prey they encounter – they are remembering what happened before and using it to make a choice. Even though in this situation the behavior does not result in a greater search, it increases the evidence that they are complex creatures, capable of using their brains in ways that may surprise us.