The study was motivated by a well-established principle in mammalian development. Early adult models, particularly the mother, play an essential role in tuning a youngster’s perception so that it can build a multimodal representation of species-specific social signals. When maternal care is disrupted, social integration often suffers. In cheetahs, orphaned cubs are frequently taken in by humans, and the degree of human rearing depends on how old the cub was when it lost its mother. The researchers hypothesized that the timing of maternal loss might therefore influence whether orphaned cheetahs could build normal species-specific vocal recognition, a question made especially interesting by the cheetah’s unusual two-stage developmental schedule.

During the first two months after birth, cheetah cubs are hidden in a den while their mother hunts alone, meaning direct contact between mother and cubs is limited in this early phase. Thereafter, the cubs begin following the mother and spend increasingly long periods in contact with her. This split creates a natural experiment: cubs orphaned before the two-month mark have experienced very little exposure to an adult cheetah, while cubs orphaned after that point have had substantially more maternal interaction. If acoustic recognition depends on experience during these windows, the two groups should differ, and that is precisely what the team set out to test.

To probe this, the researchers broadcast unfamiliar human voices and unfamiliar cheetah voices to the 25 captive adult cheetahs, all of which had been orphaned before the age of six months at one of the two developmental stages. Playback experiments of this kind are a standard tool in animal cognition research, allowing scientists to present controlled acoustic stimuli and measure attention, orientation, and behavioral changes without any direct interaction. The team recorded how quickly each animal responded, how long it paid attention to the loudspeaker, and how its activity changed in reaction to the sound.

The results revealed a striking pattern that differed by sex and by the timing of orphancy. Early-orphaned male cheetahs responded more quickly, paid attention for longer, and displayed more activity changes in response to the human voice than late-orphaned males did. In contrast, early-orphaned females showed less interest in the cheetah voice than their late-orphaned counterparts. Taken together across both sexes, early-orphaned cheetahs were 5.6 times more likely to respond to a human voice than late-orphaned cheetahs, a substantial difference that persisted into adulthood long after the period of human hand-rearing had ended.

These findings suggest that the perceptual tuning normally provided by the mother, and by exposure to conspecifics more broadly, was incomplete in the early-orphaned animals. Cubs that lost their mothers before the den-exit stage had little opportunity to learn what a cheetah sounds like, and their subsequent human rearing appears to have filled that perceptual gap with the wrong acoustic model. Late-orphaned cubs, having followed their mothers for weeks or months before losing them, retained enough species-specific exposure to maintain interest in cheetah vocalizations as adults. The study is the first to demonstrate such a long-lasting effect of early versus late orphancy on acoustic perceptual development, revealing an experience-dependent perceptual plasticity that shapes species-specific representation well into adulthood.

The sex differences add an intriguing layer to the story. Why early-orphaned males should orient more strongly toward human voices while early-orphaned females disengage from cheetah voices is not fully resolved, but the divergence hints that the developmental consequences of maternal loss and human rearing may not be uniform across the sexes. In a species where females disperse and males may form coalitions, different social ecologies could make each sex differently sensitive to the identity of the acoustic models available during early life. The authors suggest that these altered perceptual representations may underlie the reduced reproductive success previously observed in hand-reared versus mother-reared cheetahs, since recognizing and responding appropriately to conspecific signals is fundamental to courtship, mating, and social tolerance.

For conservation programs, the implications are practical as well as scientific. Cheetahs are difficult to breed reliably in captivity, and hand-rearing is sometimes unavoidable when mothers die or abandon cubs. The new results indicate that the developmental stage at which a cub is orphaned matters for its long-term social perception, not merely for its immediate survival. Facilities may therefore want to consider how orphaned cubs are reared and what acoustic and social environments they are exposed to, particularly for cubs taken in before two months of age. Enriching the early soundscape of such cubs with conspecific vocalizations, or pairing them with adult cheetah models, could potentially mitigate the perceptual deficits documented here, although testing such interventions would be a logical next step.

The work also contributes to a broader scientific conversation about how mammals build their understanding of species-specific communication. Across many mammalian species, early social experience tunes auditory perception, and cross-fostering or human-rearing studies in birds and primates have shown that the models available during sensitive periods can redirect preferences toward the wrong species or even toward humans. Demonstrating the same principle in a large, endangered carnivore, using a naturally occurring gradient of maternal exposure rather than experimental deprivation, strengthens the case that these mechanisms are widespread and consequential. It also underscores the ethical weight of hand-rearing decisions: what happens in the first weeks of a cheetah’s life can echo through years of its adult social and reproductive behavior.

Methodologically, the study stands out for its use of playback experiments with adult animals whose early histories were documented, allowing a direct test of timing effects that would be difficult to arrange experimentally. By comparing responses to human and cheetah voices within the same individuals, the researchers could dissociate general responsiveness from species-specific interest, and the divergent patterns they observed indicate that the two are shaped differently by early experience. As the first evidence that early versus late orphancy leaves a measurable, long-lasting signature on acoustic perception in cheetahs, the study opens a path toward better husbandry practices, improved breeding outcomes, and a deeper understanding of how the earliest social bonds sculpt the sensory world of growing animals.

Subject of Research: The effect of early versus late maternal loss and human hand-rearing on species-specific acoustic recognition in adult cheetahs.

Article Title: Not speaking my language: playback experiments reveal early-orphaned human-reared adult cheetahs lack interest in species-specific vocalizations

Article References: Hausberger, M., Collier, K., Glaziou, A., Schmidt-Küntzel, A., Marker, L., Johnston, B., Hetem, R. S., Azuh, I. E., & Lemasson, A. (2026). Not speaking my language: playback experiments reveal early-orphaned human-reared adult cheetahs lack interest in species-specific vocalizations. Animal Cognition. https://doi.org/10.1007/s10071-026-02106-9

Image Credits: AI Generated

DOI: 10.1007/s10071-026-02106-9

Keywords: cheetahs, animal cognition, playback experiments, maternal loss, hand rearing, acoustic perception, vocal communication, early experience, species recognition, conservation, Namibia, speaking

Functionally referential signals — vocalizations that reliably inform listeners about specific external events or objects — have long fascinated comparative psychologists because they blur the boundary between animal communication and human language. Vervet monkeys emit distinct alarm calls for leopards, eagles and snakes, and recipients respond appropriately to each. Prairie dogs embed information about predator features in their calls, and some birds encode details about food quality. But the question of just how fine-grained these references can be has remained open. Most documented referential systems distinguish broad categories: predator versus non-predator, high-value versus low-value food. Whether a signal can pick out individual food types within a category — whether a chimp’s grunt for bread sounds meaningfully different from its grunt for mango — had never been empirically tested for chimpanzee food calls.

Chimpanzees produce rough grunts when finding and eating food, and earlier work had established that the acoustic structure of these calls varies with the preference value of the food that elicits them. Grunts given to highly preferred foods differ systematically from those given to less desirable items, and subsequent research showed that listening chimpanzees can use this variation to guide their own foraging decisions. That established a meaningful baseline: the calls encode relative preference. What remained unknown was whether the specificity stopped there. If two foods are both highly preferred — say, bread and mango — do the grunts they elicit sound the same to a listener, or do they carry information distinguishing one food from the other? And critically, does that fine-grained information actually matter to receivers, or is it merely acoustic noise that no chimpanzee attends to?

To answer these questions, the research team, whose work was supported by the Biotechnology and Biological Sciences Research Council and by the Swiss National Science Foundation through the NCCR Evolving Language programme, combined two complementary approaches. The first was a careful acoustic analysis of food calls recorded from chimpanzees at the Wolfgang Köhler Primate Research Centre in Leipzig, Germany, where calls elicited by foods of matched preference values could be compared. The second was a playback experiment — a technique in which recorded vocalizations are broadcast to an animal while researchers observe how it responds — allowing the team to test whether the acoustic distinctions they detected were actually meaningful to a listening chimpanzee rather than incidental by-products of arousal.

The acoustic analysis produced a strikingly layered picture. The calls differed between foods of high and low preference value, replicating and extending the earlier findings that grunts track how much a caller likes what it has found. But the analysis went further: significant acoustic differences also emerged between individual food types within each of those preference categories. In other words, grunts elicited by different high-value foods could be statistically discriminated from one another, and so could grunts elicited by different low-value foods. The calls were not simply graded along a single dimension of excitement. Instead, they appeared to encode at least two distinct dimensions of information simultaneously — the general value of the food and its specific identity — a combination that suggests a far richer encoding system than anyone had demonstrated in chimpanzee feeding vocalizations.

Statistically detectable differences, however, do not automatically translate into communicative relevance. An acoustic signature can reflect physiological differences in arousal, jaw position, or food texture in the mouth without any listener ever extracting information from it. This is where the playback design proved decisive. The researchers broadcast recorded food calls to a chimpanzee subject and measured the responses, focusing on whether the animal’s behaviour indicated that it had interpreted the calls as information about what lay hidden at the playback location. By pairing calls recorded in one context with search opportunities in another, the experiment isolated the informational content of the vocalization itself from any direct sensory experience of the food.

The results were remarkable on all three fronts. The listening chimpanzee discriminated between calls elicited by high-value and low-value foods, confirming once again that preference information is accessible to receivers. More importantly, the subject also discriminated between calls elicited by individual types of high-value food, and between calls elicited by individual types of low-value food. The fine-grained distinctions that showed up in the acoustic analysis were not lost on the audience: the receiver behaved as though it knew not just that something good had been found, but what kind of good thing it was. This represents, the authors write, an unprecedented degree of specificity in the referential food calls of our closest living relatives — a level of detail previously identified only in alarm call systems, not in feeding vocalizations.

The theoretical implications ripple outward in several directions. For theories of language evolution, the finding narrows the perceived gap between primate vocal communication and human speech. One cornerstone of linguistic meaning is the ability of a signal to pick out specific referents rather than broad emotional states, and this study shows that chimpanzee calls can do something analogous with food types, not just food categories. It also challenges the long-standing division between ‘referential’ alarm calls and ’emotional’ food calls: if food calls encode specific identities in a way receivers use, the referential-emotional dichotomy looks increasingly like a human-imposed simplification rather than a real feature of chimpanzee communication. The study adds to a growing body of evidence that the vocal repertoire of great apes is far more structured than the behaviorist traditions of the twentieth century assumed.

The methodology deserves attention too. Combining acoustic analysis with playback experiments is the gold standard for demonstrating functional reference, because each approach compensates for the other’s weaknesses. Acoustic analysis can reveal structure that receivers ignore; playback can reveal comprehension of differences the analysis missed. By requiring both — statistically discriminable calls and demonstrably different receiver responses — the researchers built a case that is difficult to dismiss. The work was approved by the School of Psychology Ethics committee at the University of St Andrews, and the authors declare no competing interests. The study was published open access, with a citable, permanent DOI, meaning anyone can examine the evidence in full.

Questions naturally remain. The playback tested a single subject, so the generality of comprehension across individuals and communities will need confirmation. It is also unclear how the specificity arises — whether callers intentionally vary their grunts to inform others, whether the acoustic differences emerge as side effects of eating different foods, or whether listeners have simply learned to exploit regularities in the sounds. None of this diminishes the central result: chimpanzees listening to a distant group member’s grunts can apparently learn both how desirable a hidden food is and what that food actually is. For a species separated from our own lineage by roughly six million years, that is a strikingly sophisticated channel of information, and it suggests that the seeds of referential specificity run far deeper in the primate lineage than the study of alarm calls alone had ever revealed.

Subject of Research: Referential specificity of chimpanzee food calls tested through acoustic analysis and playback experiments

Article Title: Chimpanzee food calls provide information about the value and type of food: a playback study

Article References: Watson, S. K., Kaller, T., Cheng, L., Wathan, J., Townsend, S. W., Zuberbühler, K., Call, J., & Slocombe, K. E. (2026). Chimpanzee food calls provide information about the value and type of food: a playback study. Animal Cognition. https://doi.org/10.1007/s10071-026-02105-w

Image Credits: AI Generated

DOI: 10.1007/s10071-026-02105-w

Keywords: chimpanzees, food calls, functional reference, rough grunts, playback experiment, vocal communication, animal cognition, primatology, language evolution, acoustic analysis, foraging behaviour, referential signalling