A tale of four reptiles, at Nairobi National Park

An account by Washington Wachira (photos by Washington Wachira)

Many times when I am out on walks or safari drives, reptiles always entertain me. One of the most-accessible national parks in Kenya is the legendary Nairobi National Park. I have always found great reptiles here. Some of the exciting species I have found on my past trips include:-

Nile Crocodile
Nile Monitor Lizard
Tropical House Gecko
Striped Skink
Variable Skink
Long-tailed Skink
Kilimanjaro Five-toed Skink
Jackson’s Forest Lizard
Blue-headed Tree Agama
Kenya Red-headed Rock Agama
Black-lined Plated Lizard
Jackson’s Chameleon
African Rock Python
Puff Adder
Battersby’s Green Snake
Olive or Hissing Sand Snake
White-lip or White-lipped Snake
Loveridge’s Garter Snake
Marsh or Helmeted Terrapin
Serrated Hinged Terrapin
Leopard Tortoise

My list above is not exhaustive at all, and many other species have been recorded in the park by visiting guests and herpetology researchers. The park’s diversity is attributed to the great mosaic of habitats that allow the presence of great species. Nairobi National Park hosts over 46 reptile species and over 16 amphibian species.  

Some of the species who dwell in aquatic habitats, such as rivers, ponds and swamps are at home at the various wetlands around the park. Several grassland species also occupy the vast savannah grassy sections of the park. Forest-dependent and arboreal reptiles are also at home among the scattered trees in the grasslands. The forests around the Kisembe area are also a great place for arboreal reptiles. In the rocky cliffs and riverine edges, many rock-dwelling species feel at home.   

On a recent visit to Nairobi National Park, I was hoping for a similar result; but I must admit the outcome was lower than hoped for. After a very cold morning, the day warmed up slightly during the afternoon hours, and this allowed us to spot some few species. We encountered four reptiles in total.

a basking female Blue-headed Tree Agama
a displaying male Blue-headed Tree Agama for comparison

The first encounter was a female Blue-headed Tree Agama. The males of this species are phenomenal, with very bright blue heads. They also have swollen cheeks, making them look like they have loaded up food in their mouths- this is a common characteristic among Agama Lizards. Due to their bright colouration and very courageous behavior, they have been wrongly thought as being dangerous and at time venomous. This myth is more widespread around the rural areas, like in Central Kenya. However, they are pretty much harmless and only bite if hand-held, where they can offer quite a deep bite.

They live on trees, stumps, walls or sometimes on the ground. They love eating ants, but they can also consume other arthropods and at times small lizards. Males are territorial and often fight for the best territories across the Nairobi National Park. At times you find them displaying by bouncing or bobbing their heads up and down. Females are less colourful, with brown bodies, variably marked with dark patches. Most females show a dark patch around the neck, but this is sometimes invisible in the field.   

a basking Serrated Hinged Terrapin

Second on the list of encounters was a solo Serrated Hinged Terrapin, basking in the sun at a local stream, just above the Mbagathi River. This small stream drained Southwards towards the Mbagathi River and may explain why the Serrated Hinged Terrapin was basking on this patch. Unlike, the smaller Marsh Terrapin, Serrated Hinged Terrapin prefer to live along rivers at the Mbagathi River valley and its tributaries; or in large dams like Athi Dam and Hyena Dam. The Marsh Terrapins will often occur in small swamps, ponds or marshes; and other small wetlands around the park. This is probably attributed to the different threat levels the two species face from predators- Nile Crocodiles in specific. Marsh Terrapins are easier for crocodiles to crash; but again crocodiles often occur in rivers and large dams; more than small marshes. This may explain the need for Marsh Terrapins to avoid rivers and big dams. The larger Serrated Hinged Terrapins, being tougher to crash, will be safer in big dams and rivers.

The name Serrated Hinged Terrapin is very descriptive of this species; and like all the hinged terrapins, the underside of its shell has a hinged section. This hinged section can move back and forth like a door on hinges. The back of the Serrated Hinged Terrapin’s shell is usually serrated, but sometimes this feature is not obvious in the field. The underside of a terrapin’s shell is called the “plastron” while the upper side is known as the “carapace”. Terrapins are known to hide inside mud, or bury themselves underground during the dry season. They also prefer to feed on meat, and will hunt small prey species in wetlands. Sometimes they will feed on plant matter, such as fruits that fall into the water. Carrion is also another preferred meal source for terrapins, and often this allows crocodiles to hunt them when they are busy feeding.   

a Nile Crocodile basking

After a few hours of exploring the Southern sector of the park, we came across a nice Nile Crocodile at the Athi Dam. This individual seemed to be basking peacefully along the dam’s shores in close proximity to several waterbirds. It is surprising that these birds do not feel threatened by the crocodile’s presence. Nile Crocodiles are the only species of crocodile in Nairobi National Park, with good numbers occurring around the various wetlands. This species favours rivers around Kenya, and some legendary giants are known from sites such as the Mara River, Athi-Galana-Sabaki River and Tana River. The Nairobi National Park population does not grow to extreme sizes, maybe due to food availability; as compared to those in the Masai Mara, for example.

The Nile Crocodile is the top predator in the African Rivers; where they share accommodations with Nile Hippopotamuses- the latter being a vegetarian. Nile Crocodiles are pretty eclectic feeders, and they can feed on any source of meat; including scavenging on carcasses along the river or lake edges. This scavenging is often experienced during the Great Masai Mara Wildebeest Migration; where many zebras and wildebeests die crossing the rivers (Mara River, Sand River and Grumeti River).    

a non-territorial male Kenya Red-headed Rock Agama enjoying the afternoon sun
a displaying male Kenya Red-headed Rock Agama for comparison

The last reptile species we saw on our safari drive was the remarkable Kenya Red-headed Rock Agama. This individual was seen basking together with another one at the rocky cliffs above the Athi Plains. The two individuals were non-territorial males; so they missed the vigour of breeding colours. In dominant breeding colours, males of this species are stunning, with bright red heads, and blue body.

They have at times been likened to wearing a “Spider Man Suit”…… together with another Agama species, the Mwanza Flat-headed Agama (this one does not occur in Nairobi National Park- it is restricted to the South-Western Kenya and North-Western Tanzania region; with a small population reaching Rwanda and Burundi). Males of this species are territorial, and only the dominant males are “allowed” to show their beautiful colours. Non-territorial males are plainer and browner, thus looking close to the female colours- although females have red and black patches on the back; and blue spots across the head.

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