Scientists conduct hippo census at Lake Nakuru as risks increase

Researchers in Lake Nakuru to establish a baseline for the hippo population on December 10, 2022. [Kipsang Joseph, Standard]

Except for the early morning drizzles that finally fizzled out, everything else fell perfectly in place for the hippo census at the Lake Nakuru National Park.

Researchers are conducting the exercise to determine the hippo population and its distribution. The animals are under serious threat across the African continent.

The exercise also sought to determine the water quality and the lake's depth to ascertain the water levels.

"We are conducting the hippo count as part of the monitoring exercise on the species. Hippos are classified as a vulnerable species and we are doing this in Lake Nakuru to establish a baseline for the hippo population," said Judith Nyunja, the principal research scientist at the Kenya Wildlife Research and Training Institute.

Following years of increased water levels within the Rift Valley lakes, Lake Nakuru is among those that were affected. The increasing levels affected the salinity of the lake, which started exhibiting some features of a freshwater lake.

"There are increased human-hippo conflicts in Lake Nakuru as a result of the rise in the water levels that exceeded the park boundary and spilt over,” Dr Nyunja said.

Hippo in Lake Nakuru. [Kipsang Joseph, Standard]

The census involved two teams of researchers and scientists heading out in different directions on motorboats in search of the mammals.

It involved scanning the shores with binoculars to get a clear count of all visible hippo heads. Once the numbers are verified, they are entered into a datasheet. Pictures of the visible hippos are also taken during the count.

The count requires agility and patience; one can go for hours without spotting a single hippo but has to contain the excitement that comes with spotting a herd from a distance. The count is marked with fear and excitement. In a crowd, larger hippos charge forward, constantly diving and reappearing while the younger ones retreat.

This was the first ground survey at Lake Nakuru. A similar exercise had been conducted in Naivasha. In Lake Nakuru, hippo populations were common near the river mouths and springs where they could easily find fresh water and grass.

According to senior researcher Joseph Edebe, testing the water quality will determine the chemistry changes and what it means to the species within the park.

“So far, the water levels have dropped from 9.5 to 8.5m, this shows the water levels are going down. A comprehensive report from the exercise will tell us what is happening within the wetland whose chemistry has been fluctuating over time,” Edebe said.

He said although aerial surveys of the hippos in Nakuru had been conducted earlier, the ground surveys are important in enriching the survey.

Hippopotamuses in Lake Nakuru. [Kipsang Joseph, Standard]

Conducting the hippo counts, according to Everline Jeruto, a warden at the park will help the management map areas of distribution.

“There is illegal fishing within the park, which is a protected area. Knowing the distribution of hippos will ease surveillance and will also reveal the challenges these animals are facing,” Jeruto said.

In 2016, hippos were classified as vulnerable species by the International Union for Conservation and Nature Redlist.

A decline in hippo populations has been recorded in a majority of the 38 African countries where they are found.

But why are hippos important?

The animal's poop contains silica which helps algae thrive, thus ensuring the survival of aquatic plants and organisms that rely on algae.

A 2019 research on the Mara River, published in 'Science Advances' on May 1, highlights hippo poop as a source of silica, which is critical in supporting food chains in the Mara River and the lakes it drains into.

The Standard
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