Aerial counts help scientists measure the success of Gorongosa Park’s wildlife protection, restoration efforts.

A wild serval cat runs across a Gorongosa grasslands. Serval cats are native to Africa and can weigh up to 50 pounds. They have the longest legs of any cat relative to their body size. Photo – Tara Massad

By Marc Stalmans PhD, Director, Scientific Services

Why do we count animals in Gorongosa National Park and why do we use aircraft or helicopters to do it? Knowing population sizes and different wildlife trends helps us track the effectiveness of the Park’s protection and restoration efforts.  Aerial counts have many limitations, but they are the most effective way to quickly and objectively cover a large area.

The first aerial wildlife surveys in Gorongosa were undertaken using a fixed-wing aircraft. Later on, a helicopter was used. Although much more expensive, helicopter surveys are more accurate. Smaller animals can be counted too. Impala and warthog were for example not enumerated during the early fixed-wing counts.

A total of 16 wildlife counts have been undertaken in Gorongosa National Park.  A full scientific account of the wildlife numbers from 1968 through 2018 can be found online https://doi.org/10.1371/journal.pone.0212864.

Students enrolled in the Park’s Masters in Conservation Biology program participated in a simulated aerial wildlife count as part of their training in 2020.

Clockwise, starting from the upper left corner: #1 Preparing for the first aerial count of wildlife in Gorongosa Park using a Super Cub aircraft in September 1968. From left to right: Paul Dutton (ecologist and pilot), José Lobão Tello (Chief of Inspection) and Ken Tinley (ecologist). #2 Cockpit with a computer for navigation and data collection. #3 Masters students like Ana Gledis participate in an aerial count of wildlife. #4 Dr. Tara Massad, 2014 wildlife aerial count. #5 Mike Pingo (pilot) and Marc Stalmans (scientist). Photo credits – Lorraine Chittock and Marc Stalmans.

As you can see from the maps below, our survey efforts are intensifying our surveys and our animal populations are on the rise. Each dot, on average, represents more animals than the same dot a few years ago.

The lines on these maps to the right depict the flight path of each aerial survey. Each purple dot represents an aerial observation along each flight line, ranging from a single oribi to 200 or more waterbuck.

Where the buffalo roam

In 1972, an estimated 14,000 buffalo roamed through Gorongosa National Park. In 2000, there were less than 100 left.  Natural recovery would have taken too long and supplementation was therefore required. Between 2006 and 2011 a total of 210 buffalo were introduced to the Park from the Kruger National Park in South Africa and from the Limpopo National Park and Marromeu National Reserve in Mozambique.

Buffalo on the banks of the Pungue River (photo credit Marc Stalmans).

Aerial wildlife counts are critical for tracking the success of the buffalo recovery. The modeled numbers indicate a year-on-year increase of 11 percent, validated by the full counts undertaken from 2014 onward.

Gorongosa’s Park’s buffalo population are spreading across the whole Rift Valley and herds have become larger as can be seen from the GPS positions recorded during the successive aerial counts. The latest count in 2020 yielded over 1200 buffalo.

These maps show the spatial distribution and increase in buffalo herd sizes since 2010.

Buffalo running on the Gorongosa plain (photo credit Marc Stalmans).

Counting crocodiles

Crocodiles and hippo in Gorongosa National Park are strongly linked to permanent rivers, pans and Lake Urema. For this reason, a dedicated flight is undertaken during the aerial wildlife count to focus only on those two species.

Look closely and you’ll see this large hippo pod is surrounded by crocodiles. Photo – Tara Massad

The main rivers and Lake Urema are flown along their length and all hippo and crocodiles are enumerated. If we are lucky, most crocodiles are outside of the water, sunning themselves on the riverbanks. However, if it is very hot they will be mostly in the water and will be more difficult to count.

The original hippo population was over 3,000 strong but was reduced to less than 100 animals. Gorongosa’s hippo population has now recovered to over 750 individuals.

The 2020 aerial count revealed the presence of more than 2,700 crocodiles, their highest count yet, and the highest number of hippo since their decline during the Mozambican civil war.

The elusive elephant count

It may be difficult to believe, but despite their massive size, elephant can be difficult to spot from the air. In Gorongosa Park, am entire herd can remain invisible below the thick canopy of the riverine forests, especially along the Pungue River. Elephants will also bunch together when facing danger or disturbance which makes it difficult to count the smallest members that are safely tucked away in between and under the adults.

How many elephants can you count in this photograph? Can you get up to 60?

Elephant herd on a pan in 2020. Total number of elephants is 60 plus. Photo – Marc Stalmans

Elephants in Gorongosa Park were reduced by 90% during the civil war with only some 200 individuals remaining. However, they are rebounding quickly and have been enjoying a rich and productive environment for two decades. Although the latest count in 2020 yielded only 781 elephants, we suspect based on demographic work, the true count is around 1000. Whereas their numbers are recovering well, they still only occupy a relatively small portion of their former range as can be seen by comparing the historical and current distribution maps.

Some of Gorongosa’s elephants are starting to move northward again. During the 2020 aerial count, we observed elephant spoor and dung fairly close to the Nhandue River which is on the northern boundary of the Park. These signs dated from the wet season. The maps above reflect the count results which are all from the end of the dry season.  

The lighter side of an aerial count

Aerial wildlife counts offer a unique opportunity and perspective to survey a large part of Gorongosa National Park within a short period of time. Apart from the essential count of the large wildlife, there are a number of other interesting observations that are made.

A set of formal observations is made on the position of vulture nests, Marabou Stork nests, number and distribution of Ground hornbills, Yellow-billed Stork and Grey-crowned Cranes. This has led to the description of the largest known breeding colony of Marabou Stork in southern Africa.

Then there are also some informal observations where unexpected or rare sightings are made. Over the years some of the more interesting sightings included an almost white Lichtenstein hartebeest, a Zambezi Soft-Shelled Turtle with its characteristic caterpillar tracks in the mud, a Bushpig foraging in a pan, and a serval.

Lichtenstein hartebeest (left), Bushpig foraging in a pan (right). Photos – Marc Stalmans

A Zambezi Soft-Shelled Turtle with its characteristic caterpillar tracks in the mud. Photo – Marc Stalmans

Marc Stalmans, PhD, Director of Scientific Services

Dr. Marc Stalmans coordinates the scientific research studies in Gorongosa National Park. He’s been involved in the Gorongosa Restoration Project since 2006 and describes it as “A great project to be involved in because as a team, we believe in what we are doing.”

He is leading an effort to document the tremendous biodiversity of the Park through the EO Wilson Biodiversity Laboratory in Chitengo and develop the next generation of Mozambican biodiversity experts and ecologists.

Personally, I believe that the Park’s BioEducation program is one of the most important things that we do in science,” Stalmans explains. “It is immensely satisfying to see young Mozambicans discovering their passion and developing their skills as scientists.”

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