Do New York rats really have their own secret language?

New York City is often defined by its iconic images and landmarks: yellow taxis racing down Manhattan’s avenues, the glowing lights of Times Square, world-class Broadway performances, and the unmistakable “I ❤️ NY” logo that has become synonymous with the city itself.

But alongside these familiar symbols, there exists another, less glamorous emblem of urban life — rats.

For as long as there has been a New York City, there have been rats.

These rodents have been unwelcome but resilient cohabitants of the city for centuries, adapting to its rapid growth, changing landscape, and dense human population.

Today, researchers estimate that there are approximately three million rats living in New York, roughly one for every three residents.

A new study now offers an unprecedented glimpse into the lives of these animals.

By combining advanced technology with fieldwork in the city’s parks, sidewalks, and subway tunnels, scientists have discovered that New York’s rats not only have unique social structures and behaviours but also communicate using a complex, ultrasonic “language” that is inaudible to humans.

The findings reveal that these rodents are far more sophisticated than previously understood.

How was the study was conducted

The study, conducted by a team of neuroscientists and machine learning experts from both the US and Germany, set out to examine rats in their natural environment rather than in controlled laboratory settings.

The goal was to understand how these animals live, move, and communicate within the context of New York City, one of the most densely populated urban centres in the world.

Over the summer, researchers observed rats at three specific types of locations: a city park, a busy sidewalk, and an underground subway platform.

These sites were chosen to capture the range of environments that rats encounter daily — from relatively quiet green spaces to the deafening roar of trains beneath the city streets.

To track the animals without disturbing their natural behaviour, the team used a combination of ultrasonic recorders, thermal cameras, and artificial intelligence.

The ultrasonic devices captured high-frequency sounds beyond the range of human hearing, while thermal imaging provided clear visuals of the rats’ movements even in complete darkness.

Dmitry Batenkov, a member of the team specialising in computational modelling, later processed the video footage to create three-dimensional reconstructions.

This was a crucial step because traditional two-dimensional videos can distort the appearance of animals, making those closer to the camera seem disproportionately large.

The resulting data gave researchers a detailed and accurate picture of rat behaviour across different environments.

What the study discovered

Perhaps the most surprising discovery was that New York City rats, specifically Rattus norvegicus or brown rats, have developed a complex communication system based on ultrasonic squeaks.

These sounds are completely inaudible to humans but play a vital role in how rats interact with one another.

Emily Mackevicius, a neuroscientist involved in the study, described just how loud these vocalisations can be relative to the urban soundscape.

“There was an ambulance going by, and you could look at that in the spectrogram, and the rat vocalisations were louder than the ambulance,” she told Scientific American.

“They’re just kind of screaming to each other, but we just don’t hear it.”

The team found that the volume and structure of these ultrasonic calls varied depending on the surrounding noise level.

In the subway system, where trains and crowds create a constant din, rats communicated more forcefully than in quieter locations like parks.

This suggests that the animals are capable of adapting their “speech” to ensure they are heard in challenging environments — a behaviour not previously documented in wild urban rats.

The vocalisations also differed from those reported in laboratory studies of brown rats.

According to the research, city rats produced calls of consistently shorter duration and at frequencies that fell outside the historical ranges described in meta-analyses of the species.

This indicates that the unique conditions of New York may be influencing the evolution of rat communication.

Ralph Peterson, another co-author of the study, pointed out the importance of this discovery. “There’s this kind of secret language that rats are communicating in with each other that we don’t hear,” he said.

Peterson added that the study raises new questions about the purpose and meaning behind these sounds. “Why would you vocalise if not to some end? The fact that we don’t understand that yet—this is one of the questions that really keeps me up.”

How the rats of New York have evolved

The rats of New York today are not the same as those that first arrived centuries ago. The black rat (Rattus rattus) was the first species to establish itself in the city after being brought over on ships in the 1600s.

However, by the 1700s, the larger and more robust brown rat (Rattus norvegicus) had displaced its smaller counterpart.

Since then, approximately 500 generations of brown rats have lived and bred in New York City. Over this time, they have undergone significant genetic changes, adapting specifically to the demands of urban life.

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Researchers have found that these changes affect their metabolism, nervous systems, diet, and even the shape of their skulls.

To survive, a single rat requires only about an ounce of food and water each day. In a city that produces enormous amounts of edible waste, rats have access to a nearly limitless supply of resources.

The abundance of processed food in particular has shaped their dietary patterns and behaviour.

Peterson likened the research to a strategic endeavour, quoting a famous line from Sun Tzu’s The Art of War: “To defeat your enemy, you have to understand your enemy.”

By studying how rats have adapted to New York’s unique conditions, scientists hope to provide city planners, building managers, and public health officials with data-driven tools for managing the rodent population.

What the study revealed about how rats’ social structures and hierarchies

Beyond communication, the study shed light on the social dynamics within rat communities. The researchers observed clear patterns of group behaviour that appeared linked to age and size.

Using thermal cameras, the team frequently saw younger, smaller rats travelling in groups of up to 20 individuals.

Mackevicius explained that these were likely juveniles still learning how to find food. “The smaller ones are likely juvenile rats, so they’re kind of learning how to forage, and they tend to move a bit more slowly and a bit less in coordination, with bursts of movement,” she said.

In contrast, larger, older rats were often seen moving alone. Peterson described these solitary individuals as highly skilled and experienced. “These are big, honking, huge rats,” he said.

“This seems like some sort of role that this single rat has, to go out into the environment and assay its surroundings and bring food back or relay information back to the rest of the colony.”

Historical records support this interpretation. A 1944 article by Mitchell quoted exterminators who referred to these elder rats as “Moby Dicks,” a reference to the giant white whale in Herman Melville’s novel.

According to the exterminators, rats that live to be four years old are “the wisest and the most cynical beasts on earth.” Peterson’s modern observations echo this description. “They kind of know what they’re doing out there,” he told Scientific American.

The researchers even documented a remarkable behaviour that hinted at advanced intelligence. In one instance, a rat was seen flopping onto its side and remaining motionless after a train passed, only to jump up and run away moments later.

This could be evidence of a rat playing dead, a survival strategy known to occur in other species but rarely observed in wild rats.

How Humans fit into the story

The study was not just about rats — it also revealed how deeply intertwined these animals are with the human experience of New York City.

Throughout the research process, local residents became active participants, often approaching the scientists with tips, stories, and advice on where to find the biggest and boldest rats.

Mackevicius recalled how strangers would share their own experiences. “Oh, if you want to see rats, come to this place. I see them. They’re as big as cats. They do this. They do that. They chew through steel,” she said, describing the typical responses from curious New Yorkers.

This reflects a broader truth: rats are a constant presence in the daily lives of city residents, whether scurrying through subway stations, rummaging in trash bags, or simply existing as part of the urban ecosystem.

The infamous “pizza rat,” who went viral in 2015 for dragging a slice of pizza down a set of subway stairs, became a symbol of this enduring relationship between humans and rodents.

What this means for public health and city planning

While the study is still a preprint and has not yet been peer-reviewed, its findings could have practical applications for managing urban rat populations.

By understanding how rats move, communicate, and organise socially, city officials could improve strategies for waste management, disease control, and building design.

For example, precise data about when and where rats are most active could help determine optimal trash collection schedules or identify neighbourhoods at higher risk for infestations.

Such insights are increasingly important as cities grow. The United Nations projects that by 2050, nearly 68 per cent of the global population will live in urban areas.

As human and animal populations continue to overlap, the need to understand and manage these relationships becomes ever more urgent.

“They’re [rats] very social,” Peterson said. “They’re rugged, and they’re New Yorkers themselves: persistent and resilient and able to thrive in a very extreme environment.”

The research team hopes to continue exploring questions raised by their initial findings. What exactly are the rats saying to each other? How intelligent are they, and what can their behaviour tell us about survival in extreme urban conditions?

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With inputs from agencies