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The animals of Tsavo’s rivers

Meandering eastward from the western fringes of Kenya’s Tsavo West National Park, near the Tanzanian border, the Tsavo River charts a course until it converges with the Athi River, giving rise to the Galana River in the heart of the park. Serving as a vital conduit, this waterway assumes a pivotal role in the park’s lower region watershed, its currents bustling with a profusion of diverse fish species.

This intricate network of rivers is a lifeline for hundreds of species, each intricately connected to the sustenance and flow of these waters. In the following article, we delve into the lives of some of the most crucial inhabitants, exploring their fascinating adaptations that underpin their remarkable success in these aquatic ecosystems.

Hippos: Tusked titans of the waters

A prominent inhabitant of the waterways in Tsavo is the hippopotamus, the third-largest land mammal after the elephant and rhino. Interestingly, their closest living relatives are ocean-dwelling cetaceans, including whales, dolphins, and porpoises.

Territorial bulls preside over specific water stretches with a group of 5 to 30 cows, fiercely defending their territories through loud and aggressive battles involving their sizable tusks (up to 50 cm long).

Hippos spend their days submerged in shallow water, protecting themselves from the sun to minimize energy expenditure on cooling and moving around. Adult hippos can hold their breath for about 5 minutes and can automatically surface for air while asleep.

As night falls, hippos emerge from the water, covering several kilometres predominantly to graze on grass along the plains. In Tsavo, they’ve been recorded up to 50 km away from the nearest river, residing in both man-made and natural waterholes.

The impact of hippos on the rivers they inhabit is substantial. The colossal amount of excrement they produce becomes a source of sustenance for various aquatic organisms, including insects, arthropods, mollusks, and annelids. Moreover, as hippos feed on land, they establish a robust pathway for land-based minerals and nutrients to enter the water, influencing the biogeochemistry and ecology of the river.

Nile Crocodiles: Dominance and hierarchy among reptiles

One of the most formidable inhabitants of the Tsavo River is the Nile Crocodile, with adult males reaching lengths of around 15 ft and, in some instances, recorded up to 20 ft. These creatures are highly aggressive and opportunistic apex predators, capable of catching almost all animals in their range.

Interestingly, crocodiles adhere to a strict hierarchy based on sheer size and brute force. The largest males secure prime basking spots and first rights to feeding, a hierarchy maintained with violent and aggressive reactions when challenged. Crocodiles have been observed collaborating to block migrating fish and herd them to the bank, where the older, larger males feast first, an insight into why these reptiles have been so successful for millions of years.

Many Nile crocodiles possess gastroliths, stones deliberately swallowed and stored in the stomach, thought to work as ballast, aiding in sinking to the water’s bottom, and aiding in the digestion of swallowed meat. Adding to their fearsome reputation, Nile crocodiles are known to exit the water, especially at night, concealing themselves in bushes and ambushing unsuspecting prey from the land.

African Fish Eagle: Precision predators over Tsavo’s waters

Perched in tall trees along the Galana River in Tsavo, the African Fish Eagle is a striking bird and an efficient hunter, having evolved specific features to master the waters of Tsavo. Believed to mate for life, these birds reuse the same nest annually, growing to impressive sizes, with some recorded reaching 6.5 feet across.

These large avian predators exhibit mastery in catching freshwater fish. Positioned in trees along the water’s edge, they closely observe the water’s surface with their powerful eyes. Upon spotting potential prey, they swoop down, gripping the fish with their long, sharp claws. Fish eagles have developed a rough padding on the soles of their feet, known as spiricules, aiding in gripping the slippery surface of fish.

Elephants and Egrets: The animals beyond the river

Beyond the creatures permanently residing within and along the river’s edge, numerous other animals rely on these rivers for water. Elephants, iconic in the Tsavo landscape, not only drink from the river but also spray water over their bodies, absorbing moisture into their thick skin to stay cool. These rivers are vital to hundreds of species, from egrets to lions, serving as a lifeline in Tsavo’s dry, arid environment, supporting life wherever their waters flow. In the midst of the dry arid landscape, the river becomes a vital oasis for a multitude of species.

The importance of Tsavo Rivers cannot be understated, providing a life line for many different species. The imperative to safeguard this invaluable resource has become increasingly paramount, especially in the face of mounting challenges posed by intensified development along the rivers’ upstream areas. Notably, the threat of urban pollution in the Athi River serves as a poignant reminder of the delicate balance that must be maintained to ensure the continued flourishing of this vital lifeline for the myriad inhabitants that depend on its waters.

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