Bioacoustics research at Issa centred initially on chimpanzee long calls – pant hoots – and their role in chimpanzee nest site selection and mediating party reunions. Chimpanzees in savanna habitats are known to form small daily parties and aggregate in larger groups at night. Additionally, population density estimates are significantly smaller and home ranges are significantly larger than those of forested communities. Given their fission-fusion social system, how chimpanzees coordinate reunions remains poorly understood. While much is known about the function of pant hoots, the species specific chimpanzee long call, few researchers have been able to situate this behaviour in a socioecological context given the necessity to observe both caller and listener simultaneously – often a logistic challenge. To overcome this, I deployed Cornell University’s Autonomous Recording Units (ARUs) in 2006 to pilot test this method at Issa. A historically successful approach with marine mammals and birds, acoustic localization has not yet been widely used by primatologists. The 2006 pilot deployment of 3 ARUs successfully recorded (from >2km) and localized (from almost 1km) playback and wild chimpanzee pant hoots and screams from Ugalla, demonstrating the potential for this method. Additionally, numerous species of bird, six species of primate, bushbuck, and puddle frogs were among other species recorded by ARUs, revealing the potential of this method as an instrument to conduct bioacoustic surveys in remote areas that are difficult to reach on foot. Since then, with the help of Bill Sallee of Santee, California, and John Hildebrand and team at the Scripps Institute for Oceanography in La Jolla, I have developed a new, solar-powered system that records continuously and relays sounds in real-time to a central receiver. This system was deployed (2009-2010) at Issa where at one point 20 solar powered acoustic transmission units (SPATUs) were recording in an area of about 24 square kilometers. This system was later improved with the help of Paul Robertson of University of Cambridge, and was an integral component of the 2011-2012 survey of the Greater Mahale Ecosystem. Those acoustic data are still under analysis, but some sounds have been identified (thanks to David Moyer), and are below for your listening pleasure. In 2014, research continued into primate long-distance communication at Issa, with efforts focused on characterizing the heterogeneous sound environment within which Issa chimpanzees and sympatric wildlife vocalise. Specifically, Wildlife Acoustics Song Meter 3 acoustic recorders (left) are being deployed to monitor the calling behaviour of Issa’s loud calling fauna. Lucy Tibble (right), then an undergraduate student at the University of Cambridge, conducted her undergraduate dissertation research on galago (Otolemur crassicaudatus) vocalization behaviour, walking line transects during the Issa nights to compare vocal and visual encounter rates. Results comprised her honours thesis, and were presented at both Spring 2015 PSGB meeting and also the 2016 IPS meeting in Chicago. Research into animal sounds was expanded to red-tailed monkeys in June 2016, when Tifany Volle from LJMU began her undergraduate dissertation work. Tifany is studying the vocal repertoire of the focal troop, specifically how and when calls are used in various behavioural contexts. Listen below to red-tailed monkey chirping, for example!

Male B
Issa red-tailed monkey, adult male (E. McLester)
TIfany Volle - recording
Tifany Volle of LJMU recording red-tailed monkey vocalizations (July 2016)
Simon Hoggett surveying wild chimpanzees in Cameroon (September 2016)

In 2016, we collaborated with Osiris Doumbe of Bristol Zoo in a survey of chimpanzees in north-west Cameroon. We contributed SM3 recording units, whilst Osiris coordinated the survey work. Read about their preliminary results here.

It’s not just acoustic units that document vocalizations, though. A July (2014) camera trap file at Issa provided the below video and sound clip:

Waveform and spectrogram captured from the above video
Scientific Name Common Name  
Dendrohyrax arboreus Bush hyrax
Cuculus clamosus Black Cuckoo
Francolinus hildebrandti Hildebrandt’s Francolin
 Paraxerus sp. Bush (rope) squirrel  



Bryan Pijanowski of Purdue University walks Abdalla and Mashaka through SM4 (Wildlife Acoustics) song meter deployment at Issa (April 2017).

In March 2017, Bryan Pijanowski visited Issa as part of our collaboration to study Savanna Soundscapes, an attempt to capture the sounds of the mosaic ecosystem that is the Issa Valley. With Bryan, we deployed 21 SM4 sensors from Wildlife Acoustics across the study area, some which will remain for up to one year, capturing seasonal variation. Bryan presented some of his long-term work to the Wildlife Conservation/UAV Technology Msc students at LJMU, some of whom conducted passive acoustic monitoring for their own independent studies. Stay tuned for more on this work as data begin to stream in!

Listen below to a clip from the research station along with visualise the soundscape via a sonogram and photospheres taken from a couple of the deployment locations.

Miombo woodland photosphere (B. Pijanowski, March 2017) and listen below to acoustic excerpts from the 2017 recording season.

Passive Acoustic Monitoring

In an attempt to monitor chimpanzee calling behaviour in real-time, Anne-Sophie Crunchant (PhD student at LJMU) is working with Jason Isaacs (California State University, Channel Islands) to deploy an acoustic monitoring system using remotely controlled microphones, interfaced with radio transmitters to store and transmit acoustic data on not just chimpanzee, but other wildlife calls recorded in the Issa Valley.  This work is in its early stages, with Anne-Sophie and Jason shown here deploying the pilot array (June 2017).

Prof. Jason Isaacs of California State Univ, Channel Islands and Anne-Sophie Crunchant (PhD student, LJMU) work with Patrick Hassan (UPP) to deploy the radio relay station at Issa (photo: A. Henderson, June 2017)
Patrick, Jason and Anne-Sophie deploy radio sensors was part of the acoustic monitoring system at Issa (photo: A. Henderson, June 2017)