#ethology

CAN FISH RECOGNIZE INDIVIDUAL HUMANS IN THE WILD?

The ability to recognize individual humans is often associated with mammals and birds, yet research suggests that some fish are also capable of this cognitive feat. While diving in the Mediterranean Sea, a team of scientists observed something intriguing: every field season, they were followed by groups of local fish known as pargo or dorado, stealing food intended to reward other fish in their experiments.

In controlled experiments, wild saddled sea bream (Oblada melanura) and black sea bream (Spondyliosoma cantharus), were trained to follow a human diver to obtain a food reward. Remarkably, they can differentiate between dozens of individuals with high success rates, even when superficial features such as colour or brightness are altered. This suggests that their recognition is based on specific patterns rather than simple visual cues. Similar capabilities have been observed in cleaner fish (Labroides dimidiatus), which adjust their behaviour depending on whether they recognize a familiar diver, implying that this skill might have adaptive benefits in natural environments.

-Maëlan Tomasek (Max Planck Institute of Animal Behavior), one of the study's authors, next to a wild fish. The researchers found that wild fish start to follow humans for food and are able to identify individual divers by their clothing.

If fish in the wild can recognize individual humans, the implications extend beyond academic curiosity. Species frequently interacting with humans—such as those in ecotourism settings or research projects—may learn to associate specific individuals with positive or negative experiences. This has been observed in sharks, where some individuals appear to recognize divers who regularly feed or tag them, approaching more readily or avoiding interactions depending on past encounters. Understanding these cognitive abilities could inform conservation strategies by highlighting the impact of repeated human interactions on fish behaviour.

Despite these insights, much remains unknown about how fish process facial recognition and whether this ability is widespread across different taxa. Future research will need to examine whether this recognition occurs naturally in the wild without training and how it influences social interactions within fish populations. As we continue to challenge outdated assumptions about fish intelligence, it becomes increasingly clear that their cognitive world is far more complex than previously thought.

GIF: Trained fishes following diver

Horses participating in a new experiment revealed an unexpected level of smarts by appearing to strategically ignore game rules to reap the most treats for the least amount of effort. "Horses are not natural geniuses," says Carrie Ijichi, an equine scientist at Nottingham Trent University in England. "They are thought of as mediocre, but this study shows they're not average and are in fact more cognitively advanced than we give them credit for." Surprisingly few studies have been carried out on horse learning, with some research hinting at the capacity for understanding the basic consequences of their decisions.

You might have heard (correctly) that putting rabbits on their backs can induce tonic immobility, or "trancing" so you shouldn't do it. However, this is not the case every time a rabbit is flipped, or they wouldn't be able to roll around by themselves without going into a trance. Baby bunnies also tend to love to sleep on their back!

If you look at how a rabbit is shaped, the back is somewhat curved. This means when it's lying normally, the head is slightly lower than the back. Similarly, when it flips upside down, the head will be slightly higher than the back.

If a rabbit is in a state of tonic immobility you can tell this by the head dropping backwards (towards the floor). The legs will be stiff and unmoving, often appearing unnaturally straight. When the rabbit gets out of the paralysis it will be extremely stressed, and might not trust you anymore.

It's perfectly fine to hold a rabbit on its back as long as you make sure it can still move. This is usually fairly easy to do, simply by making sure the rabbit's head stays upright. A rabbit with an upright head won't go into trance.

A rabbit that can still hold its head up or move the legs is not tranced!

I'm talking about the male octopus's arm, which it uses to find the female octopus's ovary, which is hidden deep inside her mantle cavity, which is the large muscular "bag-like" body behind her head & eyes. Visually, there is no way for the male octopus to see it as it's dark, enclosed, & filled with moving tissues, gills & organs. Yet the male always finds it. How? By relying on chemical sensing & touch navigation through his specialized mating arm called the hectocotylus. The female's reproductive tract releases progesterone & related steroid signals, which diffuse into her mantle cavity. His hectocotylus suckers contain chemoreceptors that can "taste" these hormones & are drawn to them like a magnet. Octopus arms contain 10s of millions of neurons & can perform complex movements without a central brain.

Such a brilliant little kid, when I see children like this, I feel hopeful about the future, maybe we are going to witness a new wave of brilliant minds.

Channel: A Curious Birb

Video: Genius 10 Years Old's Research Shocks Scientists Around the World