Various types of animals have been given names for when they form groups – a school of fish, a pack of wolves, a colony of ants or penguins, a parliament of owls, a flamboyance of flamingos, a scurry of squirrels, a prickle of porcupines, and a shrewdness of apes.
But individual animals are now known to differ consistently in how much risk they are willing to take – and these personality differences directly shape how they move, behave, and ultimately survive in environments increasingly dominated by humans.
Along the bare but scintillating coastline of the Dead Sea, where desert cliffs meet one of the world’s most extreme environments, a quiet drama is unfolding in the skies above. Fan-tailed ravens –intelligent, adaptable, and ever-watchful – are making life-or-death decisions every day, and according to new research, those decisions may come down to personality.
Within populations, individuals from a wide array of species have shown consistent differences over time in risk-taking behavior when exposed to potentially threatening stimuli or situations – for example, insects, whales and dolphins, rodents, otters, cattle, giraffes, crows, and monkeys. Individuals who consistently take risks can benefit by reducing competition and increasing energy availability for survival and reproduction, but they can also be more likely to die prematurely.
By combining lab experiments with real-world tracking of these birds – officially named fan-tailed raven (Corvus rhipidurus), a medium-sized, all-black, highly aerial bird found in deserts and rocky areas of the Middle East and Africa – Hebrew University of Jerusalem (HUJI) researchers have found that risk-prone birds of this species tend to stay near human activity and face higher mortality, while more cautious individuals avoid humans and survive longer.
The study, titled “Integrating lab- and field-based approaches to decipher individuals’ response to anthropogenic change,” has been published in the journal Ecology Letters. Funded by the ISF Breakthrough Research Grants Program, this study was led by Dr. Miguel de Guinea and HUJI Prof. Ran Nathan, together with Prof. Thomas Bugnyar from the University of Vienna, and Prof. Joah Madden from the University of Exeter in South West England. They discovered that consistent individual differences in behavior, what scientists often call “animal personality,” can shape how wild animals respond to the rapidly expanding footprint of human activity.
Known for their unique “batlike” silhouette with very short tails and broad wings in flight, these intelligent birds are extremely acrobatic and ever-watchful. They often forage in large groups and roost in rocky cliffs, are curious about everything, and sometimes make acrobatic flights together, apparently for fun,” Nathan said.
There are many types of ravens, he told The Jerusalem Post in an interview. The birds seen in cities like Jerusalem that look like ravens but are quite different are crows – confusingly, the Hebrew word for both is the same – orvim.
Various species of crows, like the hooded crow (Corvus cornix), are used to people, and feed on any garbage left around in bins and on the pavement. If they see a cast-off, a near-empty bag of a Bamba snack, crows will shake it for a long time to free the last crumbs. Protective of their young, if someone tries to harm a fledgling, a crow is likely to dive down and try to attack the aggressor in the head with its beak.
Hooded crows and various other corvid species (ravens, crows, and the like) are often regarded as “winners” of the Anthropocene. Their behavioral flexibility, high cognitive skills, and pronounced curiosity appear to confer advantages in human-modified environments. In contrast, fan-tailed ravens, albeit possessing similar traits, are notable “losers.” Their native population in Israel, once distributed throughout the Arava Valley down to Eilat, is now limited to the Dead Sea coast, and has declined steadily over recent decades.
These ravens are highly social and often forage in large groups around hot spots of human activities such as Ein Gedi Nature Reserve, creating a misleading impression that this raven species is also a “winner.” Indeed, this was the initial assumption when Nathan’s team started this research a decade ago. However, it soon became evident that the population was already in a precarious state and has continued to deteriorate over time.
Evolution of animals in the Dead Sea region
Wild animals that thrive in cities tend to be bolder than their counterparts in natural habitats, allowing them to exploit rich and predictable resources in the vicinity of humans. In the Dead Sea region, however, animals have evolved under very different conditions, namely an extreme desert with scarce and unpredictable resources, and limited human presence and impact.
Yet, human-driven environmental changes have turned the original desert into a landscape with hot spots of human presence, which offer predictable and abundant resources to local wildlife. The Dead Sea coastline has seen an expansion of tourist infrastructures, including an intensively used highway that links several viewpoints, recreational “hot spots” – a resort compound, and three national parks (Qumran, Ein Gedi, and Masada).
“We sought to understand how key behavioral traits of the ravens shape their response to the rapid human-driven changes of their desert environment,” Nathan said. “Because the key change is the presence of humans at sites offering a rich and steady supply of food, we focused on examining the variation in risk-taking behavior among individuals.”
Combining controlled aviary experiments with cutting-edge GPS tracking in the wild, the research team followed the ravens living along Israel’s Dead Sea coastline. In the experimental aviary, they tested the tendency of wild ravens to take risks across different contexts – to approach unfamiliar objects, forage on unfamiliar food items and in proximity to humans, and make use of new environments. These contexts were selected as representative of the environmental changes that ravens have had to cope with in their natural habitat due to the expansion of human activities. He noted that his team used Bamba to lure them.
What emerged was striking: Individual ravens not only consistently avoided (or took) risks in the same contexts but also across all contexts set to them in an experimental aviary. Individuals who were willing to eat unfamiliar food items were willing to approach novel objects, forage near humans, and make use of new environmental structures, while others simply avoided all potential risks. But the real revelation came when these personalities were tracked in the wild.
Using high-resolution GPS data, the researchers discovered that these behavioral differences became even more pronounced in natural settings. Risk-prone ravens tended to linger near tourist areas, taking advantage of easy food sources but exposing themselves to greater danger.
In contrast, risk-averse individuals avoided human activity, ranging farther across the landscape and foraging at the edges of their home range. They were thus significantly more likely to survive than their bolder counterparts.
“Our findings show that consistent behavioral traits are not just quirks; they can determine life or death,” said post-doctoral fellow Dr. Miguel de Guinea, who led the project with Nathan. “Individuals of the same species that live in the same area might still differ in their behavioral traits; our study shows that such differences can be critical.”
The findings “reveal that animal responses to human-driven environmental change are not uniform even within a species; rather, they depend on individual behavior, suggesting that ongoing anthropogenic pressures may actively reshape wildlife populations by favoring certain personality types, with far-reaching ecological consequences.”
Following this, Nathan’s team now works together with the Israel Nature and Parks Authority on identifying the causes of the unusual mortality of fan-tailed ravens.
Eighteen years ago, Nathan launched a new field of research, called “movement ecology”, a transdisciplinary paradigm to study the movement of organisms across multiple spatial and temporal scales. The current study of ravens extends this approach, merging movement ecology and psychology, where human personality has long been explored.
Nathan concluded that “our study highlights how integrating lab-based behavioral assays with real-world movement data can reveal patterns and mechanisms we would otherwise miss. It’s a powerful approach for understanding how animals cope with human-driven environmental change.”