Seattle study reveals ravens remember dangerous faces for 17 years

Anyone who crosses a raven, however, may have to contend with the bird’s anger for years.

Ravens and crows were long regarded as sinister companions in graveyards and on battlefields. Now, a long-term US study suggests that the old myths had a point: the birds recognise individual people, remember bad behaviour and even pass that information to other birds of their kind – for as long as 17 years.

How intelligent ravens really are

Ravens rank among the world’s most intelligent birds. Researchers compare some of their mental abilities to those of apes or young children. They can:

• Solve complex problems
• Make and use tools
• Recall past events in great detail
• Tell the difference between people who appear friendly and those who seem threatening

Ravens do more than memorise a person’s face. They also judge whether that person is “dangerous” or “harmless” and then act on that judgement as a flock.

The recently publicised Seattle study shows how long such memories can last and how a kind of “blacklist” spreads throughout a flock of ravens.

The mask that angered the ravens

The study began in 2006 with an unusual experiment at the University of Washington. Behavioural researcher John Marzluff put on a distinctive rubber mask and used it while catching seven ravens. The birds were tagged and released, escaping physical harm despite their fright.

Over the years that followed, Marzluff repeatedly walked around the campus wearing the same “threatening” mask. He fed the birds but did not handle them again. Even so, the ravens reacted strongly, circling him, scolding loudly and warning others with aggressive calls.

One encounter proved particularly revealing: on a walk, the researcher came across 53 ravens, 47 of which reacted with hostility to the mask. That was far more than the seven birds originally caught. Apparently, the birds had “told” one another who the dangerous person was.

Raven revenge lasting almost two decades

The researchers monitored the campus ravens’ reactions for many years. Their angry calls peaked roughly seven years after the study began. An increasing number of birds recognised the mask, even though only a very small proportion had ever been caught themselves.

The hostility then gradually declined as older birds died and new ones arrived. Even so, warning calls continued to be heard for a long time. It was not until 2023, 17 years after the experiment began, that Marzluff walked around the grounds in the mask and was met with silence. Not one raven scolded him.

The study suggests that ravens can remember a dangerous person for many years and pass that information through the flock like a rumour.

For researchers, this offers a rare glimpse into animals’ long-term and “social memory”. The birds do not rely solely on individual memories; they also use their network.

The second mask wearer: friendly rather than dangerous

To test the effect, the team also used a second mask intended to be neutral. Its wearer only fed the ravens, without catching or harassing them. The birds showed no aggression towards this person.

Later, volunteers who knew nothing about the experiment were handed the masks. They did not know that the flock had registered one of the faces as an “enemy”. Anyone wearing the dangerous mask was promptly met with a storm of croaking ravens, while those in the neutral mask were left alone.

This suggests that the birds were responding to appearance – the “face” – rather than to a particular individual or their behaviour at that moment.

Attacks from the air: when people get too close

Ravens and crows rarely attack people out of sheer malice. More often, they are defending nests or young birds. Even so, reports of targeted attacks are becoming more common, particularly in cities where people and birds live close together.

In one London suburb, for example, residents felt virtually under siege for a time. Individual ravens repeatedly swooped at the same people. One woman said she had been attacked three times as soon as she stepped out of her car. Afterwards, many people preferred to stay indoors.

Researchers say this fits the pattern: someone who has come too close to a nest or picked up a young bird may be remembered as a “danger” – and receive a clear retaliation on their next encounter.

Raven toolmakers with a sense of numbers

Their remarkable memory is only one aspect of raven intelligence. The birds display a range of cognitive tricks once thought to be typically human. In experiments, they:

• Deliberately drop nuts onto roads, wait for cars to drive over them and collect the contents when the traffic lights turn red
• Use sticks to extract insects from cracks in bark
• Bend twigs into hooks to fish food out of tubes
• Appear able to count up to a certain number and respond to differences in quantity

Such behaviour demonstrates planning, an understanding of cause and effect, and an ability to learn. These qualities put ravens in the “top class” of the bird world.

Family bonds and mourning rituals

Their social lives are as surprising as their intelligence. Ravens often live in family groups where older young birds help their parents raise the next brood. Some remain nearby for several years before seeking territories of their own.

Observations suggest that ravens take careful note when another raven dies. Dozens of birds often gather, circle the spot, call loudly and look at the body. To researchers, this looks like a mixture of grief, alarm and instruction: together, the birds learn where and how one of their kind died.

Ravens do not respond to dead members of their own species with emotion alone; they also analyse the situation, probably to understand and avoid sources of danger.

Communication within a group includes a wide variety of calls and gestures, as well as regional “dialects”. Some raven populations have characteristic sequences of sounds that differ from those heard in other regions.

Animal culture: knowledge passed on

When one raven associates a person, animal or place with danger, that knowledge does not necessarily stay with it. The bird warns others by calling, following the threat in flight or making mock attacks. Other birds watch and adopt the same assessment. Young ravens therefore grow up within an existing network of knowledge.

Researchers call this “cultural transmission”: knowledge is passed between generations without every individual having to experience something first-hand. Among ravens, examples include:

• Identifying particular faces as dangerous
• Food-finding tricks, such as cracking nuts in road traffic
• Strategic places to sleep or nest

This places ravens alongside a small number of other animal species in which such behaviour is well documented, including dolphins and some species of ape.

What people can learn from ravens

In everyday life, leaving young birds alone, avoiding disturbance to nests and not throwing stones at crows can reduce the risk of ending up on their “enemy list”. In many cases, a single negative experience is enough for the birds to register someone as a lasting problem.

In towns and cities, taking care around feeding places, nests and breeding seasons can ease tensions. Some authorities favour public education over driving the birds away: once ravens have learnt that people are dangerous, that knowledge is difficult to erase.

Parents can also use ravens and crows to make animal intelligence, respect for wildlife and the consequences of our actions tangible for children. A walk through the park can quickly become a live lesson when families pay attention to how the birds react, which ones croak at whom and which people are ignored.

The Seattle long-term study shows how close supposedly “simple” animals can come to us mentally. Ravens remember, make judgements and talk about them – just in their own language. Keep that in mind and the next black bird at the roadside may deserve a closer look.