The IUCN Red List is the International Union for Conservation of Nature’s Red List of Threatened Species. It is the world’s most comprehensive information source on the global extinction risk status of both animal, fungus and plant species. The list is used to inform and bring about action for biodiversity conservation and policy change that are critical to protect our natural resources.

50-70% decline over the past 30 years

On 10 October 2025, the IUCN 2022 Red List conservation status for the long-tailed macaque was updated, led by AIAS Fellow Malene Friis Hansen, a primate specialist. Together with primate specialists from around the world, their studies and data collected on the macaque places the species as ‘Endangered’. In 2022, the IUCN Red List assessed the macaque population in predicted decline; in 2025, the researchers show that the decline has already taken place.

This new 2025 IUCN Red List assessment infers a 50-70% decline over the past three generations (30 years) due to habitat loss and high levels of exploitation. The assessment was reviewed and approved by the IUCN Standards and Petitions Committee and the IUCN Red List office and co-authored by the IUCN SSC Primate Specialist Group.

Moreover, as the threats and levels of exploitation that the long-tailed macaque is facing have not been mitigated and are continuing, it is suspected that the species will continue to experience a population decline at a similar rate of 50-70% over the coming three generations (30 years). This assessment is research-based on a range of data: both quantitative and qualitative, including historical and recent population estimates.

Habitat loss, Subsistence hunting, International trade and Entertainment

The long-tailed macaque is threatened due to several levels of exploitation and habitat degradation The major causes are the loss of habitat, human-wildlife conflicts, pet trade, subsistence hunting and international trade for use in research (pharmaceutical and biomedical). 

Due to the combined impact of these threats, there has been an inferred decline in population numbers and habitat area over the past three generations. As these threats have not been mitigated, it is suspected that this population decline and decline in habitat area will continue into the future.

A Call for Action in Conservation Measures

Currently, there are only a few sustainable efforts to maintain long-tailed macaque populations in Southeast Asia as the species is generally thought to be overabundant. Something this assessment shows is not the case.

Malene Friis Hansen, first-author of the study behind the update of the Red List, highlights:

“It is critical to first and foremost stop the extraction of long-tailed macaques from their habitats, and to remember that these include human landscapes. Next, we urgently need to establish wildlife management programs for long-tailed macaques based on scientific output and establish regular systematic censusing of the long-tailed macaques, as well as designing and implementing evidence-based management and protection plans throughout Southeast Asia.”

Further, Malene Friis Hansen points out the importance of creating coexistence programs for humans and long-tailed macaques led by local experts. Coexistence is also something that Malene Friis Hansen is studying in her research project at AIAS entitled ‘Towards a Cultural Biology’ that focuses on the deep current and historical relations between sympatric humans and other animals.

“When we began our research years ago, we did not expect the current findings. The long-tailed macaque utilises human resources and shares habitats with humans enabling it to adapt to anthropogenic and climate change. This is an amazing ability that we can learn from, but it also means that conflicts between humans and macaques can happen and that populations of macaques are continuously overestimated. To better understand and conserve animals that coexist and co-create behaviours with humans, so-called synanthropes, we need a novel and transdisciplinary approach to research at the human-animal interface, such as what we are attempting to define with our new project,” Malene Friis Hansen concludes.

Access the Red list for the long-tailed macaque here:https://www.iucnredlist.org/species/12551/273015436

More about the International Union for Conservation of Nature’s (IUCN) Red List of Threatened Species:
https://www.iucnredlist.org/about/background-history

More about Malene Friis Hansen’s AIAS project ‘Towards a Cultural Biology’:
https://aias.au.dk/aias-fellows/current-fellows/malene-friis-hansen

Contact

Malene Friis Hansen, AIAS-AUFF Fellow
E-mail: mfhansen@aias.au.dk

Aarhus Institute of Advanced Studies, AIAS
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DK-8000 Aarhus C
Denmark