Primate Action Blog
  • A Population Assessment of the Critically Endangered Dryas Monkey in the DRC

    dryas monkwy

    This dryas monkey was photographed with a motion-sensor
    game camera trap during the study.

    Daniel Alempijevic, Spring 2016

    Congolese forests contain some of the most diverse primate communities, yet many are poorly studied. The Lomami River basin is one of the most remote forests in DR Congo. The Lukuru Foundation documents the region's biodiversity and initiated the establishment of Lomami National Park (LNP). Two years after a new species, lesula (Cercopithecus lomamiensis), was described, the foundation had another exciting discovery: an unknown population of dryas monkeys, Cercopithecus dryas. A hunter's kill identified in the LNP buffer zone represented a range expansion of this poorly known and critically endangered species, thought to be restricted to forests around the Wamba and Kokolopori Bonobo research sites (400 km [249 mi] to the north). The Lukuru Foundation has conducted several camera trap surveys and recorded primate encounters on thousands of kilometers of park patrols but never detected dryas monkeys until 2014.

    I joined Kate Detwiler's primatology lab in 2015, tasked with studying this new population. We developed the study with the Lukuru Foundation's scientific director, John Hart, to execute a multistratum camera trap survey. Our primary goal was to develop a species-specific camera trap placement method to detect dryas monkeys. With the help of local hunters, we placed 10 vertical camera-trap columns in degraded forest in the LNP buffer zone, then moved the cameras to a mixed-mature forest site in the park. We repeated surveys at both sites, using a strategically placed camera trap grid to reduce detection bias and increase coverage within the survey area in 2017. We successfully obtained photos and video of dryas monkeys and 9 other primates. This study suggests that dryas monkeys prefer disturbed forest sites with floristically complex understories. 

    The camera trap videos gave us insight into C. dryas' diet, vocalizations, and mixed-species associations. We recorded 27 videos during the study, and we are hoping to continue the research by increasing the number of cameras in the understory to improve our detection of this rare and mysterious species. We thank PCI for its support for this study.

      David Alempijevic    
    Daniel Alempijevic (left) climbing a tree to place a camera trap in the canopy for monitoring dryas monkeys.   Project team members (from left): John Konga Bakoni, Pablo Ayali, Jean Pierre Kapale, Marten Balimu.

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  • Examining the Morphological and Behavioral Paradox of Aye-ayes in Torotorofotsy, Madagascar

      Aye-ayes feeding. Photos taken by Timothy Sefczek with a night-vision video camera

    Timothy Sefczek, Spring 2016

    With partial funding from PCI, my project studied the feeding, ranging, and positional behaviors of aye-ayes in the continuous forest of Torotorofotsy, Madagascar. Previous research on aye-aye populations suggested that either Canarium seeds (Iwano and Iwakawa 1988; Iwano 1991) or Ravenala nectar (Ancrenaz et al. 1994) is the aye-aye's critical resource. Invertebrates were said to be consumed in significant quantities only when other resources were unavailable (Sterling and McCreless 2006; Lambert 2007; Marshall and Wrangham 2007). However, all of these studies were conducted on introduced populations on the island of Nosy Mangabe (Iwano and Iwakawa 1988; Iwano 1991; Sterling 1994) or in disturbed habitats (Ancrenaz et al. 1994). Because primate behaviors can be altered by deforestation and small forest sizes (Irwin 2008; Chaves et al. 2012), it follows that these earlier-recorded aye-aye behaviors may not reflect those of naturally occurring populations in a continuous forest. My main objective was to determine the significance of invertebrates in the ecology of aye-ayes. I found that invertebrates are the aye-aye's most commonly consumed resource, especially those contained within live trees (Sefczek et al. 2017). Additionally, aye-aye home range sizes, 808 ha (1997 ac) for a female and 1586 ha (3919 ac) for a male, are larger than initially suggested (Sterling 1994), possibly due to the reliance of dispersed invertebrates as the main food source. Positional behaviors also appear to be largely adapted for invertebrate feeding, though results are still being analyzed.

        Tim Sefxzek with feild assistants  
      Timothy Sefczek (left) with his team of field assistants.

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  • Preuss’s Red Colobus Density in Northern Korup National Park, Cameroon

      One of the best photos ever taken of Piliocolobus preussi. Photo by Alexandra Hofner

    Alexandra Hofner, Spring 2016

    A Multi-faceted Approach to Understanding Arboreal Primate Abundance and Local Perceptions and Livelihoods in a Protected Area. 

    In studying Preuss’s red colobus (Piliocolobus preussi), Alexandra Hofner found that in one month 107 diurnal primates were killed by Ikenge hunters; Cerco’pithecus nictitans made up 41.9% of the reported offtake, C. mona 29.9%, C. erythrotis 12.2%, C. pogonias 12.2%, P. preussi 2.8%, and Mandrillus leucophaeus 1%. Alexandra suggests that because of steep population decreases in some primate species (such as P. preussi), Ikenge hunters may be targeting more abundant primates.

      Allie conducting an interview in Ikenge, Cameroon

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  • Socioecology of the Annamese Langur in Northeast Cambodia

      Alvaro in the field, beside a huge and very old vine. Photo by Eve Smeltzer

    Alvaro Gonzalez-Monge, Spring 2013

    Alvaro Gonzalez-Monge conducted his PhD project at Veun Sai’Siem Pang National Park, in Ratanakiri Province, Cambodia. He originally planned to study douc langurs but changed his dissertation subject to the Annamese langur (Trachypithecus margarita) because very little was known about this species in Cambodia. Initially, his focus was on the species’ socio-ecological and taxonomic placement. However, because illegal logging was rampant in the area at the time, he decided he would also study the effects that this disturbance had on the group’s behavior and habitat use. Alvaro found that these langurs were somewhat resilient toward human disturbance and were highly adaptable in their resource use, but logging had a significant impact on their ranging and habitat use. The langurs moved higher in the canopy as logging intensified. The study group even abandoned sections of their home range after heavy logging was carried out. Alvaro observed that the langurs slept and fed on the seeds and leaves of some of the tree species that are actively sought by loggers, which is cause for concern if logging remains unchecked. This study has helped increase our knowledge about one of the least-known species of Indochinese primates, but it also provides local people with an alternative livelihood as research assistants, which helps protect the natural heritage of the Annamitic region.

      Annamese langur (Trachypithecus margarita) Photo by Eve Smeltzer

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  • Understanding the Social Structure and Ecological Basis for the Formation of Supergroups in Ruwenzori Colobus Monkeys

      More than 90 individuals can be seen eating on the ground in this photo.
    Photo by Alexandra Miller

    Alexandra Miller, Spring 2016

    Alexandra Miller studies the social organization of Adolf Friedrichs’s Angolan colobus monkeys (Colobus angolensis ruwenzorii). She recently reported counting 512 individuals crossing a main road. These monkeys eat fruits, lichens, mature and new leaves, and flowers. They come to the ground to feed on terrestrial herbaceous vegetation such as Sericostachys sp. and Impatiens sp. While on the ground, they appear to stay in their family group and are often on the alert for chimpanzees, which are known to kill and eat them. In the photo at the top of the page, they look as if they are waiting for a family photo to be taken.

      Alexandra, happy to be so close to the colobus.

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  • Primate Conservation Inc. - All the World's Primates Book Giveaway to Habitat Country NGOs


    A generous donor to Primate Conservation, Inc. (PCI) has offered to subsidize the purchase and distribution of a number of All the World’s Primates books to primate habitat country conservation organizations. If you are a member of one of these organizations and could use copies of this book (for a description go to, please answer the following questions and send your information to Noel Rowe at

    Your organization's name, mailing address, and email.

    Name and CV of a principal in your organization.

    Date your organization was founded.

    URL of your website, if any.

    Are you affiliated with or primarily supported by a larger organization?

    Is your annual budget under $10,000 US, $10,000 to $100,000 US, or over $100,000?

    How many books would you like (up to 3, which can be mailed in one box)

    What primates does your organization work to protect?

    In 500 words or less, how will the book(s) be used by your organization?

    Please, do not include any information as attachments. Only material in the body of the email will be considered. The decision about which organizations will be awarded these books is up to the donor and the Board of Directors of PCI. Submissions must be made no later than August 10, 2017. Only winners will be notified. We will not share any of your information with others. You may get an annual email from PCI.

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  • Free Download: Lemurs of Ranomafana


    All The World’s Primates is sharing a free ebook, The Lemurs of Ranomafana. Created for the participants in the recent Prosimian Congress in Ranomafana National Park, Madagascar (August 2013), we thought others might like it. It’s available as either a mobi file (for Kindle) or epub for iPad, tablet, smart phone or other reader. Download link below.

    The Lemurs of Ranomafana is adapted from Pogonias Press’ new ebook  All the World’s Lemurs, Lorises, Bushbabies, and Pottos (Amazon $9.95). Planned as the first volume in a series, it illustrates the diversity of the fascinating suborder Strepsirhini, a group which contains many of our oddest, rarest, most beautiful, and least-known primate relatives. More than 100 photographers and primatologists who contributed to this website were involved.

    All the World’s Lemurs, Lorises, Bushbabies, and Pottos is a portable resource to help to introduce you to this fascinating group of primates. It has general information about each super family and family followed by profiles of 134 species. Every species profile includes a color photograph or illustration, a color range map, and information on the species’ taxonomy, distinguishing characteristics, physical characteristics, locomotion, diet, life history, social organization, behavior, habitat, IUCN conservation status, and threats the species faces in its natural habitat. The information is fully referenced (Lemurs of Ranomafana is not). Get the ebooks:

    All the World’s Lemurs, Lorises, Bushbabies, and Pottos is available at Amazon. $9.95

    The Lemurs of Ranomafana is available, free here.

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  • Three New Species of the Masked Slow Loris are Newly Recognized

      Kayan Slow Loris is new to science
    photo courtesy Chien C. Lee,

    By R. Munds, S. Ford & K.A.I. Nekaris

    An international team of scientists studying the elusive nocturnal primate the slow loris in the jungles of Borneo have discovered an entirely new species. The team’s analysis of the primate’s distinctive facial fur markings, published in the American Journal of Primatology, reveals the existence of one entirely new species, while two of species, previously considered as possible sub-species, are being officially recognized as unique.

    “Technological advances have improved our knowledge about the diversity of several nocturnal mammals,” said Rachel Munds from the University of Missouri Columbia. “Historically many species went unrecognized as they were falsely lumped together as one species. While the number of recognized primate species has doubled in the past 25 years some nocturnal species remain hidden to science.” The slow loris (Nycticebus) is found across South East Asia, from Bangladesh and China’s Yunnan province to the island of Borneo, the slow loris is rare amongst primates for having a toxic bite, and is rated as Vulnerable or Endangered on the IUCN Red List. Slow lorises are recognized by their unique fur coloration on the body and face, yet while traits such as fur patterns are often used to distinguish between species; nocturnal species are cryptic in coloration and have less obvious external differences. The team’s research focused on the distinctive colorings of Borneo’s slow loris, whose faces have an appearance of a mask, with the eyes being covered by distinct patches and their heads having varying shapes of caps on the top. Differences among these face masks resulted in recognition of four species of Bornean and Philippine lorises, N menagensis, N. bancanus, N. borneanus and N. kayan. Of these Nycticebus kayan is a new group unrecognized before as distinct. This new species is found in the central-east highland area of Borneo and is named for a major river flowing in its region, the Kayan.

    The recognition of these new species strongly suggests that there is more diversity yet to be discovered in the jungles of Borneo and on the surrounding islands, including the Philippines. However, much of this territory is threatened by human activity so the possibility that more slow loris species exist in small and fragile ranges raises urgent questions for conservation efforts.

    “The pet trade is a serious threat for slow lorises in Indonesia, and recognition of these new species raises issues regarding where to release confiscated Bornean slow lorises, as recognition by non-experts can be difficult,” said co-author Professor Nekaris, from Oxford Brookes University.

    “In the first study to quantify facial mask differences we have recognized three new species of slow loris, two of which were recognized as subspecies at some point in the past, but are now elevated to species status, and one previously unrecognized group.” concluded Ms. Munds. “This finding will assist in conservation efforts for these enigmatic primates, although survey work in Borneo suggests the new species are either very difficult to locate or that their numbers may be quite small.”

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  • Unmanned Drones Used to Count Orangutan Nests

      Lian Pin Koh and Serge Wich with drone
    photo courtesy conservationdrones

    Note that this post is a departure as the project is not presently supported by Primate Conservation, Inc. (PCI). This technology has potential in conserving primates and so is presented here. Dr. Wich is a contributor to All The World’s Primates for orangutans and Thomas’ Langur. He has also reviewed proposals on PCI’s behalf.

    Adapted from an article by Lian Pin Koh (ETH Zurich) and Serge Wich (Liverpool John Moores University) for the Orangutan Conservancy

    The distribution and density of orangutan nests, critical to conservation efforts, have traditionally been obtained by costly and time consuming ground surveys. High resolution satellite imagery that might serve the same purpose has been too costly or simply unavailable.

    But Researchers Lian Pin Koh and Serge Wich proposed what seemed at first to be a wild idea: conservation drones. The researchers have tested the conservation drones above orangutan habitat in Sumatra and Sabah (Borneo). The aim of these tests was to determine whether the system could really detect orangutan’s nests. The results are in and it can!

    Conservation Drones are inexpensive, autonomous and operator-friendly unmanned aerial vehicles for surveying and mapping forests and biodiversity. They are able to fly pre-programmed missions autonomously for a total flight time of up to ~50 minutes and over a distance of ~25 km. Depending on the camera system installed, these drones can record videos at up to 1080 pixel resolution, and acquire aerial photographs of <10 cm pixel resolution. Aerial photographs can be stitched together to produce near real-time geo-referenced land use/cover maps of surveyed areas.

    In addition the images from the drone are of a high enough resolution that one can easily distinguish land cover and land use including forests, corn fields, plantations, logging, fires, small roads, mining, banana plantings, etc. The drone approach therefore seems extremely promising as a tool in orangutan conservation and we look forward developing this further in close collaboration with our partners.

      detail of an orangutan nest as seen from the air
    photo courtesy conservationdrones

    Although Wich and Koh conceived of the idea of the conservation drone while discussing orangutan research and conservation, the drones are now being tested in various countries for a whole range of projects. As Dr. Wich explains, “A main aim of our work is to share our knowledge for building low-cost Conservation Drones to help conservation workers and researchers in developing countries do their jobs a lot more effectively and cost efficiently.” Visit the Conservation Drone Project website for more details on this high-flying project. Details from the Orangutan Conservancy here.

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  • Evaluation Begun on the Role Rare and Recently Recognized Gibbons Play in Their Environment

      The northern buff-cheeked gibbon (Nomascus annamensis)
    was first described in 2010. Photo by Jackson Frechette

    Jackson Frechette and Kathryn Sieving

    Since June, I [Jackson] have been working on my dissertation project, “The effects of crested gibbon (Nomascus annamensis) seed dispersal patterns on tree regeneration,” in the Veun Sai–Siem Pang Conservation Area, 55,000 ha managed by Conservation International and the Cambodian Forestry Administration in a remote part of northeastern Cambodia. I have been working with local ethnic minority researchers and one American volunteer (who hopes to go to graduate school) to understand the importance of northern buffed-cheek crested gibbons to trees. This is a new gibbon species that was described in 2010 using acoustic and genetic data. I am looking at seed dispersal patterns of these gibbons and how those patterns may be important for trees to regenerate. To do this, I quantified the gibbon seed dispersal pattern by mapping where every seed of a particular tree (Microcos paniculata) was defecated. Then, using that pattern, I planted 9,000 seeds of that tree, mimicking the gibbon pattern, a bird dispersal pattern (which I quantified as well), and a pattern where all the seeds just fall beneath the fruiting trees. The purpose of this is to test if there is a difference in seed germination between these dispersal patterns.

    This research explicitly tests the often theorized impact one primate species has on the patterns of seed dispersal and seed survival in its environment. The results will provide information on the importance of this endangered gibbon to tree regeneration and ecosystem health. I have been training local people on how to conduct research and to be interpretive guides for gibbon-centered community-based tourism. Increasing the local capacity develops sustainable alternatives to hunting and logging, reducing pressure on the community’s natural resources.

      Jackson (on the far left) with his team in Cambodia.
    Photo by Cheb Chanton-CI Staff

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