A recent study shows that hippo groups are territorial entities that behave less aggressively toward their neighbors than toward strangers. And that can have conservation consequences.

“Finding your voice.” We hear that phrase a lot, lately. It means that you know who you are at your core, and you express it.

Voices are extremely important for humans. They are the media through which we do a lot of our communicating with the outside world: release our emotions, share our ideas and show off our personalities. Voice is the emblem of its speaker, indelibly woven into the fabric of speech. In this sense, each of our utterances carries not only a message, but also—through accent, quality and tone—an audible declaration of our membership in particular regional groups, physical and psychological identities, and momentary moods. Voice is also one of the ways we recognize other humans who are important to us, such as family members or our friends.

Human babies, for example, are able to recognize the voices of their mothers. That’s hardwired into us. And research has shown that cats and dogs, who have been domesticated for centuries, can distinguish between their owner’s voice and the voices of others. They can even detect changes in tone—which is the reason why your dog looks so guilty after chewing on the couch.


Dogs can seek out their owners just by hearing their voices. They can also make use of some of the same voice properties as humans, such as noisiness and pitch.

Animals that live in proximity to people, such as crows, pigeons and even wild elephants, have also been shown to differentiate between human voices that they’re familiar with and those they aren’t. But whether other animals can recognize individual people is a bit murkier.

Now, however, new discoveries about the voices of nonhuman animals are giving us insights not only into how our own human languages developed but how “the others” give voice to their worlds.

And, with increased exposure to humans, for them that could prove to be more important than ever.


The anatomical structures that seals use for producing vocalizations—such as larynxes, mouth cavities and vocal cords—are the same ones that humans use.

Seals: unraveling the mystery of speech

Vocal learning—the ability to imitate sounds—is a rare trait among mammals. Only a few species have shown the capability to change the pitch of their voices to sound higher or lower, which is a crucial element of human speech. One of those mammals is baby seals.

In a study published in the science journal Philosophical Transactions of the Royal Society B in November 2021, researchers supported by the Max Planck Research Group in Munich, Germany, studied eight, one- to three-week-old harbor seal pups that were being held at the Seal Rehabilitation and Research Center in Pieterburen, Netherlands, before being released back into the wild.

To investigate whether the pups could change the tone of their voices in response to noises in the environment, the scientists first recorded sounds from the nearby Wadden Sea. For several days, the sea noises were then played back to the pups, in three degrees of loudness (varying from no sound to 65 decibels, or about the level of normal human conversation), but with a similar tone to that of the seal pups’ calls. The researchers also recorded the pups’ spontaneous vocalizations.


Harbor seals are one of the few species that can change the pitch of their voices to sound higher or lower, a critical element of human speech.

Surprisingly, what the scientists found was that when the seal pups heard louder sea noises, they lowered the tone of their voices. They also kept a steadier pitch. But the pups did not produce more or longer calls when they heard different levels of sea noise.

Apparently, then, the young seals were adapting to environmental noise by lowering the tone of their voices, an ability they seem to share with bats and humans. Other animals in similar experiments only raise their voices (making louder calls) in response to louder noise.

This shows that seal pups have more control over their vocalizations than assumed up until now, and it’s already present at only a few weeks of age. To date, humans had seemed to be the only mammals with direct neural connections between the cortex (the outer layer of the brain) and the larynx (what we use to produce tone of voice). Therefore, seals may be the most promising species to study for unraveling the mystery of our own speech.


Orangutan calls are believed to be the closest precursors to human language. The animals display a wide variety of vocalizations, from long-range cries and grumbles to raspberry sounds.

Orangutans: learning long-distance language

Orangutans are shining even more light onto how speech develops. Scientists have now shown that orangutan call signals—believed to be the closest precursors to human language—travel through forests over long distances without losing their meaning, throwing into question the accepted mathematical model on how human speech evolved.

The currently accepted model is based on one established 20 years ago by Harvard University mathematicians. It postulates that human ancestors strung sounds together in their calls to increase their chances of carrying a signal’s content to a recipient over distance, avoiding an error limit—the moment when a signal is received but stops being meaningful. Because signal quality degrades over longer distances, it was thought that our ancestors started linking sounds to effectively increase the chance of content traveling over distance.

So, researchers from the United Kingdom’s University of Warwick Department of Psychology set out to collect the data needed to investigate this model. They selected a range of sounds from previously collected audio recordings of orangutan communications in Indonesia. The calls of orangutans were used because they were the first species to diverge from the great ape lineage and are the only great apes who use consonant-like and vowel-like sounds in a complex way—providing a parallel with human speech that is the closest to that of our hominid ancestors.


Orangutan “kiss squeaks”—purse-lipped, consonant-like calls—could be a glimpse of how our ancestors formed the earliest words.

Specific consonant-like and vowel-like signals were played and then rerecorded across Indonesia’s rain forests at distances of 25, 50, 75 and 100 meters. After analyzing the quality and content of the signals received, the researchers found that although the quality of the signals may have degraded, the content of the signals (“packages of information”) were still intact—even at long distances. In fact, the informational characteristics of the calls remained uncompromised until the signals became inaudible.

While we still don’t know what the orangutans were referring to, what is completely clear is that the building blocks of language are present. Although the sounds of other animals can be complex, those animals are not using the same components. The research team will now be moving on to deciphering the meaning of the orangutan calls, all the ways these primates combine calls and how the apes put the consonant and vowel sounds together to get meaning. The researchers believe it will provide a parallel to the formation of human languages.

Hippos: making your voice heard

Another animal with a “long-distance” voice is the hippopotamus. Hippos’ “wheeze-honk” calls can be heard from almost a mile away, leading researchers to suspect that the calls play an important role in maintaining social groups. Now, a study published in the journal Current Biology on January 24, 2022, shows that hippos recognize each other’s voices. They also respond less aggressively to the calls of a neighbor compared to those of a stranger.


Hippos make several different vocalizations. Among these sounds are grunts, honks, roars, squeals and wheezes. As much as 80 percent of their communications happen underwater.

Working in the Maputo Special Reserve, Mozambique, an area that includes several lakes inhabited by hippos, researchers first recorded calls representative of various hippo groups. Then, they played the recordings back to the hippos to see how they’d react to the calls from their own group (familiar) versus another group from the same lake (neighbor) or a more distant group (stranger).

The researchers found that hippos respond to hearing a played-back call vocally, approaching and/or spraying dung. The overall intensity of the hippos’ response grew when they heard a stranger. The hippos were also more likely to spray dung, a territorial marking behavior, when they heard a hippo that didn’t belong to their group.

When hippos are in the water, they look inactive. But these results show that they’re paying close attention to their surroundings, communications and social groups. The findings also have important implications for conservation policy. For instance, hippos are often relocated to maintain local populations at healthy numbers. But this study suggests that precautions are needed before making that kind of move, such as broadcasting hippo voices from a loudspeaker to the groups already present so that they become accustomed to them and aggression toward them gradually decreases. Reciprocity, in which the animals to be moved become accustomed to the voices of their new neighbors before they arrive, should also be considered.


A new study indicates that these giant herbivores can identify each other by sound and that they react much more positively toward members of their own groups or neighboring groups than to strangers. ©Emily Kautz

Gorillas: distinguishing human sounds

Gorillas are taking the hippo ability to recognize individuals of their own kind a step further. These great apes can do that with another species: us.

A new study from the University of Georgia, published in the journal Animal Cognition in August 2021, is the first to show that gorillas are able to recognize familiar human voices based on their relationships with the speakers.

Working with captive gorillas at Zoo Atlanta, researchers noticed that the animals responded negatively to the presence of specific people who came into their indoor enclosure. Specifically, the gorillas seemed to grow agitated at the presence of veterinarians and one maintenance worker. But it was unclear whether they were only reacting to visually seeing the people.


Gorillas can not only recognize familiar human voices but also connect those voices to pleasant or not-so-pleasant memories.

So, over the course of six months, a research team played the apes audio recordings of three groups: long-term keepers who knew and worked with the gorillas for at least four years and had positive relationships with them; people who the apes knew and had negative interactions with, including veterinarians and the maintenance worker; and people who were unfamiliar to the animals. All the participants said the same phrase, “Good morning. Hello,” which is how keepers typically greet the gorillas.

The apes had minimal reactions to the voices of their keepers. However, when they heard the voices of people they didn’t know or with whom they’d had negative experiences, the gorillas responded with signs of distress, such as increased vigilance and vocalizations.

For example, after hearing unfamiliar voices or the voices of people with whom the gorillas had had negative interactions, the apes stopped eating their treats or whatever else they were doing and started looking toward the sound to gauge whether the voices were a threat. This kind of behavior had also been documented in the wild. It was unclear, however, whether the gorillas considered the strangers to be as threatening as the veterinarians and maintenance worker.

If it turns out that wild gorillas can distinguish between poachers versus researchers not only by sight but also by voice, it could save their lives. ©Eric Rock

This study has wider implications for the captive animals’ wild cousins. Researchers often wonder if they’re making gorillas more vulnerable to hunters by habituating them to humans. But if wild gorillas can distinguish between people who behave differently (hunters versus researchers, for example) not only by sight but also by voice, it could save their lives.

All of us: having and giving voice

For us, the phrase “finding your voice” means so much more than the sound you make when you speak. It denotes how you show up; whether you take a stand or a position on something that matters to you; it represents your authenticity, courage, determination and passion; and it’s who you are in a deeply essential way. Then, it’s using that voice to speak up and tell the world you matter, even if you feel otherwise.

And so, I think, we should start considering animal voices to be in the same vein.

Here’s to finding your true places and natural habitats,