As the research delves deeper into this topic, it uncovers the complexities embedded within stereotypies. Common examples include pacing in captive elephants, feather-plucking in birds, and the rocking seen in some primate species. Despite the overtly maladaptive nature of these actions, it is essential to consider the underlying factors that may contribute to their occurrence. Environmental stressors, lack of enrichment, and social isolation typically exacerbate the prevalence of these behaviors, indicating that they are often symptomatic of more profound welfare issues experienced by the animals.

Exploring cortisol levels provides crucial insight into the physiological impacts of stereotypies. Cortisol, often referred to as the “stress hormone,” is released in response to stressful events, and its chronic elevation can result in adverse health outcomes, including compromised immune function and increased susceptibility to disease. Therefore, examining the relationship between cortisol and stereotypic behavior opens a window into understanding the broader implications of these maladaptive actions on the well-being of animals.

The review conducted by Hildebrand and Zaleśny presents evidence that higher cortisol levels frequently correlate with the display of stereotypic behaviors. This suggests an intriguing, albeit concerning, cycle where stress leads to stereotypies, which in turn may exacerbate stress levels due to social or environmental factors. Their findings indicate that continuous exposure to stressors can result in a state of hyperarousal, potentially linking stereotypic behavior to escalating cortisol levels, creating a vicious cycle that can become increasingly difficult to break.

However, not all stereotypies are created equal, nor do they all have the same implications for welfare. In some contexts, certain types of stereotypic behaviors may serve as coping mechanisms for animals, providing them with a sense of predictability and control in otherwise unpredictable or stressful conditions. This brings to light a vital consideration: do some stereotypies serve a beneficial purpose in alleviating stress, or are they primarily detrimental to the animal’s welfare?

The researchers argue that understanding the context in which these behaviors occur is paramount. Most importantly, the interpretation of stereotypies as mere maladaptive behaviors might overlook their potential role in stress management. For instance, when animals exhibit stereotypies in response to barren environments, these repetitive actions might fulfill a psychological need for stimulation or predictability. In such cases, modifying the environment to allow for more natural behaviors might reduce stress and, consequently, the prevalence of stereotypies.

The implications of this research extend beyond academic inquiry and touch on ethical considerations in animal husbandry practices. For those who care for animals in zoos, research facilities, or domestic settings, recognizing the signs of stress and understanding the motivations behind stereotypic behaviors are crucial steps in improving animal welfare. Practical solutions may include designing enriched environments or implementing social structures that align more closely with the species’ natural behaviors and social systems.

Importantly, the examination of cortisol levels provides a measurable biomarker for assessing animal stress and welfare. By monitoring these levels in conjunction with observations of behavior, researchers and caretakers can better discern which environmental variables are contributing to heightened stress and, subsequently, the increase in stereotypies. The findings present a call to action for those in the field; a need for holistic approaches that consider both behavior and physiological metrics when evaluating animal welfare.

By challenging preconceived notions around stereotypies, Hildebrand and Zaleśny pioneer a path toward enhanced understanding. As they unravel the complexities of animal behavior and welfare, they underscore the importance of interdisciplinary approaches that integrate behavioral science, physiology, and animal care practices. Their work encourages further research into the nuances of animal behavior and highlights the multifaceted nature of stereotypies within the greater context of animal welfare.

This exploration not only deepens our understanding of abnormal behaviors but also pushes for more humane practices within animal care environments. As we reckon with the realization that some stereotypies may be more beneficial than previously thought, it becomes imperative to reassess how we approach animal welfare and the environments in which captive animals are kept.

In summary, this groundbreaking review offers significant insights into the intricate relationship between cortisol levels and stereotypic behaviors in animals. It shines a light on the complexities of animal welfare, encouraging a shift toward more nuanced and compassionate perspectives on behaviors that were once hastily categorized as simply abnormal. As we expand our understanding, we open the door to improving the quality of life for countless animals worldwide.

Subject of Research: Relationship between cortisol levels and stereotypic behaviors in animals.

Article Title: Do stereotypies help or harm? Exploring the link between cortisol level and abnormal behaviours in animals: a review.

Article References:

Hildebrand, W.H., Zaleśny, G. Do stereotypies help or harm? Exploring the link between cortisol level and abnormal behaviours in animals: a review.
Front Zool 22, 20 (2025). https://doi.org/10.1186/s12983-025-00576-0

Image Credits: AI Generated

DOI: https://doi.org/10.1186/s12983-025-00576-0

Keywords: Stereotypies, cortisol, stress, animal behavior, animal welfare, psychological well-being, repetitive behaviors, environmental enrichment.

Nest-building in orangutans has long been recognized as a vital adaptive behavior, yet the mechanisms behind how such sophisticated construction techniques are transmitted across generations have remained elusive. For arboreal primates like orangutans, sturdy nests serve multiple survival functions—they provide protection from predators, thermal insulation during chilly nights, a safe platform for restful sleep high in the forest canopy, and even demonstrate anti-mosquito properties. Despite the importance of these nests, knowledge of how young orangutans develop these engineering feats was limited, until now.

The extensive study, published in the journal Nature Communications Biology, analyzed 17 years of observational data collected in the dense forests of Sumatra. The researchers meticulously documented the behavioral patterns of juvenile orangutans as they observed adult nest-building. They found that immatures engage in a behavior termed ‘peering’—a deliberate and focused watching of nest construction by their mothers or others. The data indicate a strong correlation between this peering behavior and the likelihood of juveniles subsequently practicing nest building themselves. Crucially, if juveniles were physically near that the time of nest construction but failed to watch attentively—perhaps due to distraction—they rarely attempted to build nests, underscoring the necessity of active visual attention in skill acquisition.

Further analysis revealed that young orangutans pay close attention to the most challenging aspects of nest construction, such as incorporating comfort features like pillows and mattresses, or building across multiple trees for structural stability. Their practice intensity increased following such observations, suggesting a nuanced learning process where juveniles prioritize and replicate complex tasks observed in adults. This finding overturns prior assumptions that nest building might be solely instinctive or innate, highlighting social learning as indispensable for mastering this multi-layered behavior.

As juveniles mature, their learning horizon broadens beyond maternal influences. Young orangutans gradually diversify their sources for observational learning, peering at the nest-building behaviors of other community members. This shift allows them to experiment with different tree species and construction techniques, expanding their practical knowledge beyond maternal traditions. This behavior mirrors cultural diversification, indicating that orangutan populations maintain and propagate cultural elements related to nest building across generations.

The study’s lead author, Dr. Ani Permana from the University of Warwick’s Department of Psychology, emphasized the significance of these findings: “Our research reveals that nest-building, a critical survival skill, is acquired through a prolonged and deliberate learning period that depends heavily on close observation and practice. This marks the first robust evidence of such social learning in wild orangutans regarding this behavior, a process that starts in infancy and continues as they mature.”

Complementing this perspective, senior author Dr. Caroline Schuppli of the Max Planck Institute highlighted the importance of material selection in nest construction. “Immature orangutans do not simply learn ‘how’ to build, but also ‘what’ to build with. Our observations demonstrate that infants predominantly mimic their mothers’ choice of tree species, indicating that the selection of nesting materials is itself a learned cultural trait,” she explained. Intriguingly, as orangutans reach adulthood, they tend to revert to their maternal preferences for nesting materials, suggesting that tried-and-tested methods have enduring value, and that cultural transmission stabilizes within populations.

This study situates nest-building within the broader context of primate cultural evolution. Though social learning has previously been documented in behaviors such as termite fishing using tools, this new evidence that orangutans learn complex nest-building skills socially carries significant implications. The complexity of nest-building—incorporating multiple stages and requiring environmental knowledge—demonstrates the powerful role of observational learning in primate cognition. Moreover, nest constructing is an ancient behavior, conserved by ape ancestors millions of years ago, indicating that social learning mechanisms may run deep in our evolutionary lineage.

The intricate nests built by orangutans vary depending on their intended use. Day nests tend to be pragmatic and minimalistic, serving as resting spots during foraging expeditions. Nighttime nests, in contrast, are elaborate platforms elevated up to 20 meters in the canopy, outfitted with multiple comfort elements and protective features to mitigate environmental hazards. The skillful assembly of these structures reflects not only physical dexterity but also complex problem-solving abilities.

The implications of this research extend beyond academic insight. Orangutan cultural diversity—expressed in nest-building traditions—represents an intangible heritage that is vulnerable to habitat loss and population declines. Protecting these intelligent primates and their environments becomes not just a matter of biodiversity conservation but also of preserving intricate social knowledge that is transmitted across generations.

This landmark study employed rigorous ethological methods, leveraging long-term field observations with detailed behavioral coding to capture the nuanced learning pathways of immature orangutans. The research provides a model for examining cultural transmission in other wild animal populations and invites renewed consideration of how complex behaviors evolve and persist in natural societies.

In synthesizing observational learning with survival-critical behaviors, the study underscores the sophistication of orangutan culture and cognition. It invites a deeper appreciation of the social fabric that shapes individual development, highlighting that knowledge in the wild is not merely passed down genetically but also transmitted through careful attention, imitation, and practice. As such, orangutan nest-building may be considered a cultural cornerstone that exemplifies the interplay between biology and social learning in evolutionary success.

Ultimately, the study opens new avenues for further research into the mechanisms and limits of social learning among great apes. It challenges scientists to unravel how behavioral traditions form, stabilize, and adapt, not only in orangutans but across the animal kingdom. The revelation that such an essential survival skill depends on cultural transmission is a resounding message about the importance of social environments and learning opportunities in shaping animal behavior and, by extension, their long-term survival.

Subject of Research: Animals

Article Title: Observational social learning of “know-how” and “know-what” in wild orangutans: evidence from nest-building skill acquisition

News Publication Date: 7-Jun-2025

Web References:
https://www.nature.com/articles/s42003-025-08217-2
https://doi.org/10.1038/s42003-025-08217-2

References:
Permana, A.L., Permana, J.J., Nellissen, L. et al. Commun Biol 8, 890 (2025).

Image Credits:
Permana, A.L., Permana, J.J., Nellissen, L. et al. Commun Biol 8, 890 (2025).

Keywords:
Orangutan, Social learning, Observational learning, Nest-building, Primate cognition, Cultural transmission, Behavioral ecology, Sumatran orangutans, Animal culture, Wildlife conservation