NEW MOUNTAIN GORILLA CENSUS UNDERWAY
(Posted 07th October 2015)
The wildlife management bodies in Rwanda, Uganda and Congo have embarked on a new census to reliably establish the numbers of surviving mountain gorillas in the Virunga Massif and the adjoining parks like Bwindi. Lead body will be the Greater Virunga Transboundary Collaboration, which main office is based in Rwanda.
It is expected that the number of 480, established during the 2010 census, will be substantially exceeded five years down the line as a result of sustained conservation and protection efforts. Furthermore will the census give data on the demographics of the gorilla population, i.e. silverbacks, blackbacks, females, adolescents and young born.
The recently updated treaty among the three gorilla range countries provides for closer cooperation and coordination of protection measures and has paved the way for the new census to go underway.
Maurice Twahirwa of RDB was kind enough to answer some questions in regard of the census on behalf of Rwanda’s Tourism and Conservation Department:
FREQUENTLY ASKED QUESTIONS ON MOUNTAIN GORILLA CENSUS
1. What is a mountain gorilla census?
A mountain gorilla census is a population survey used to determine the number of individual mountain gorillas within a defined area. The population survey for mountain gorillas is so intensive that it is commonly referred to as a census.
2. Why and how often is the gorilla census done?
While births and deaths are known and recorded for those mountain gorilla groups that are habituated to the presence of humans for either research or tourism, it is only during a complete survey or census that we know whether the population as a whole – both habituated and unhabituated gorillas – is stable, increasing or decreasing.
The census also provides vital information as to the demographics (age classes and sex ratios) and number and size of family groups. The spatial data from nest sites also gives scientists a snapshot of where groups are located in relation to vegetation types and in relation to other gorilla groups and park boundaries and human activities.
Illegal activities encountered and signs of other key large mammals, like elephants, are also recorded for analyses and interpretation.
Each population of mountain gorillas is surveyed every five years if conditions are conducive and human and financial resources are available.
3. How is gorilla census conducted?
The actual field work involves teams of people hiking through the forest – essentially combing the forest in search of gorilla trails and nest sites. They then collect gorilla faecal samples from every nest they encounter. Those samples are delivered to our partners at Max Planck Institute for Evolutionary Anthropology, who analyze each sample for individual DNA identifiers to ensure that each individual gorilla is counted only once.
To facilitate thorough coverage of the entire Virunga Massif, the area is divided and mapped into sectors. The field teams cover the entire Virunga Massif sector by sector. They walk reconnaissance trails that are spaced no further than 500 m apart. A complete survey of all the sectors is called a “sweep.” For this census, it is planned that two sweeps will be conducted to allow for scientists to estimate the detection probability for each effort, and more accurately estimate the total population.
4. Who is involved in the 2015 Virunga Massif mountain gorilla census?
The Virunga Massif mountain gorilla census is being conducted by the Protected Area Authorities in the DRC, Rwanda, and Uganda (l’Institut Congolais pour la Conservation de la Nature, the Rwanda Development Board and the Uganda Wildlife Authority) under the transboundary framework of the Greater Virunga Transboundary Collaboration.
The census is supported by the International Gorilla Conservation Programme (a coalition of Fauna & Flora International and WWF), Max Planck Institute for Evolutionary Anthropology, Diane Fossey Gorilla Fund International, Institute of Tropical Forest Conservation, Gorilla Doctors, and North Carolina Zoo.
The census is funded through generous contributions from Fauna & Flora International, WWF, and Partners in Conservation at the Columbus Zoo & Aquarium.
5. How is security of the teams ensured?
Teams will be accompanied by park rangers at all times throughout the exercise. In addition, the Park Authorities are working closely with security forces within the three States. This cooperation in the transboundary context is made possible through the Greater Virunga Transboundary Collaboration.
6. When was the last gorilla census and what were the findings?
Mountain gorillas exist in two isolated populations – one in the Virunga Massif and one in Uganda’s Bwindi Impenetrable National Park contiguous with DRC’s Sarambwe Nature Reserve.
The last census within the Virunga Massif was conducted in 2010 and resulted a population estimate of 480 individual gorillas in 36 groups as well as 14 lone silverbacks (solitary mature males).
The last census within Bwindi Impenetrable National Park was conducted in 2011 and resulted in a population estimate of 400 individual gorillas in 36 social groups and 16 lone silverbacks.
7. What is the gorilla population trend, is it increasing, decreasing or stable?
Both populations of mountain gorillas are demonstrating positive growth in population over the last two decades (see graphs below). It is important to note that techniques for detecting individual mountain gorillas and verifying each unique individual have been improving over time, making population estimates for these rare and elusive animals more accurate for each consecutive census.
8. What are some of the challenges encountered during gorilla census and how are they over come?
The rugged terrain of the Virunga Massif will be a challenge to teams and their movement through the area with steep slopes shrouded in dense Afromontane forest with many ravines.
The census requires a high level of coordination by multiple agencies and institutions. The logistics of rotating groups of teams in and out of the forest sometimes in remote camps on two week cycles so that the census can continue while allowing one group to rest while another continues with data collection. In addition, the logistics to keep the teams supplied with water, food, and power is a challenge.
The census is also conducted in a complex cultural landscape where there is no single dominant language and the teams communicate in a mix of English, French, Kiswahili, and Kinyarwanda/Kinyabwisha/Kifumbira.
9. What is different in the upcoming census that wasn’t done in the previous counts of the mountain gorilla?
For the first time, this census will make use of electronic devices for information and data entry by the teams in the field. The use of this new technology is expected to allow for more streamlined data collection and eliminate manual data entry. The census will also build on past advancements in terms of genetic analyses and mark recapture mathematics.
In addition, an effort to establish a DNA library for the known individual gorillas from habituated groups will serve as a reference point to the collected samples to reduce the potential to double-count individuals or under-count the overall population.
Photos are available here:
The photos should be credited to the organization indicated in the photo file name.
