Ravens Remember People for Years, Study Shows

A long-term study from the United States shows that ravens remember individual people for many years, recognise them clearly and respond to previous threats with noisy protest. The birds observe closely, communicate with one another and even pass their knowledge of “dangerous” faces to the next generation.

How it began: one man, one mask, seven ravens

In 2006, a research team at the University of Washington began an unusual experiment. Environmental scientist John Marzluff put on a distinctive rubber mask, briefly caught seven ravens on campus, marked them with leg rings and released them unharmed. From that point onwards, the mask represented danger from the birds’ perspective.

Over the years that followed, Marzluff and his colleagues repeatedly walked across the site wearing that same mask. They did not catch any more birds; they simply crossed paths and grassy areas while observing and counting the animals that reacted.

Within a short time, not only the birds originally caught but several times that number were berating the masked person.

During one of these walks, the team recorded 47 of the 53 ravens present screeching loudly, circling the mask or calling in other birds. This was far more than the seven that had ever been caught in the net. The researchers therefore concluded that ravens actively share their knowledge of dangerous people with members of their own species.

Vindictive or highly intelligent? What the study really reveals

The ravens’ responses were not random. The same pattern persisted for years: whenever the “dangerous” mask appeared, the birds kept their distance, became noisy and warned one another. Other people without the mask received little attention.

Data from the long-term observations revealed three striking phases:

• Early years: Only a small number of directly affected ravens responded to the mask.
• Peak around 2013: Aggressive calls and warning cries reached their highest level as the knowledge spread through the flock.
• Later decline: The number of scolding ravens gradually fell, presumably because the oldest birds died off over time.

In September 2023 - 17 years after the experiment began - the team found that not a single raven was still complaining about the mask. This does not mean that the birds had “forgotten”; rather, new generations had gradually replaced birds that knew of that specific event directly.

The study demonstrates that ravens can remember people for a very long time - and persistently associate a face with an earlier experience.

Good mask, bad mask: ravens make subtle distinctions

To ensure that the behaviour truly involved recognition rather than a simple fear of masks, the researchers introduced a second stimulus: a “neutral” mask that had never been linked to capture or stress for the birds. People wearing this mask fed the ravens or behaved in an entirely inconspicuous manner.

The outcome was clear. The birds largely ignored the neutral mask or behaved normally around it. Their aggressive response was directed exclusively at the “dangerous” mask. Ravens can therefore distinguish whether a particular human face represented a threat in the past.

At times, unsuspecting volunteers wore the masks without knowing what they meant to the animals. Anyone assigned the “bad” mask found themselves amid an angry flock of screeching ravens - compelling evidence of how precisely the avian brain separates different stimuli.

When ravens attack people: experiences from major cities

Reports from European cities also indicate that ravens and crows remember people. In a London suburb, residents repeatedly reported aerial attacks. Certain individuals appeared to be deliberately targeted, while other passers-by were left undisturbed.

Those affected described being swooped at repeatedly over the course of a few days, or having their hair and clothing tugged. Many suspected an earlier incident, such as driving away young birds or removing a nest. These experiences fit remarkably well with the long-term study: anyone threatening a raven or its family can easily become persona non grata within its territory.

More than merely resentful: tool-making and problem-solving

Ravens are not simply skilled “face recognisers”. Numerous studies show that they can solve complex problems, plan ahead and even make tools.

• They deliberately drop nuts onto busy roads and wait for cars to crack the shells.
• They use small sticks to fish larvae from tree bark.
• In experiments, some ravens bend wire into tiny hooks to pull food from tubes.

Such behaviour was long considered uniquely human, or at least a characteristic of primates. Today, behavioural researchers rank ravens among the highest-performing animals when it comes to flexible intelligence, memory and learning ability.

There is more processing power in the avian brain than its tiny size would suggest - especially in ravens and crows.

Social networks in the flock: knowledge passes from mind to mind

A key reason for ravens’ remarkable “memory performance” is their social organisation. The birds often live in family groups, remain with their parents for a long time and closely watch how older animals respond to situations.

When an experienced raven classifies a person as dangerous, it can spread the warning in several ways:

• It produces specific alarm calls that attract other members of its species.
• It noisily follows the threatening person, allowing others to understand the context.
• Young birds memorise the combination of face, location and the group’s behaviour.

This creates a form of “cultural memory”. Not every bird needs to have a bad experience itself in order to avoid a particular person or pattern. The information circulates through the flock, much like rumours or warnings in human neighbourhoods.

Animal culture: when behaviour is passed on without changing genes

Behavioural biologists refer to this as cultural transmission. It means knowledge that is not encoded in genes but is passed from one generation to the next through observation, imitation and learning. In ravens, this can be seen, for example, in the following areas:

Ravens therefore belong to a small group of animal species in which researchers can demonstrate something akin to culture in the broader sense: knowledge remains within the population even when individual animals die.

How not to pick a fight with ravens

Anyone living in an area where many ravens or crows breed should take their considerable memory and learning abilities seriously. A few straightforward rules can help to avoid acquiring “enemy status”:

• Do not destroy or seriously disturb nests during the breeding season.
• Do not pick up or chase away young birds when their parents are nearby.
• Dispose of rubbish and food waste in a way that prevents conflicts over food.
• If aggression is noticeable, avoid the area briefly - the situation often settles after the breeding season.

Conversely, many people report rather positive experiences. Those who feed ravens regularly, remain calm and cause no stress are eventually ignored or even expected. Sometimes the birds leave eye-catching small items, such as shiny pebbles or pieces of foil, in particular places, which some interpret as a kind of “return favour”.

What ravens teach us about animal intelligence

The University of Washington study, published in the scientific journal “Proceedings of the Royal Society B”, corrects a widespread misconception: a small brain does not automatically mean limited intelligence. What matters is how densely nerve cells are packed and how they are connected - and in this respect, many bird species perform surprisingly well.

In everyday terms, ravens are not gloomy extras in the sky but attentive observers of our towns and villages. They notice who harms them, and they do not forget. Those who treat them kindly can coexist with them more peacefully and, at best, gain a fascinating insight into the abilities of one of the most intelligent birds found in the UK.