Our first stop this month is by the Rufiji River in the Selous Game Reserve. This is one of the largest game reserves in the world and the river is a great place to see the wildlife.
In some places, along the river, the banks are vertical and sandy, providing ideal nesting places for Red-throated bee-eaters. Many species of bee-eaters are communal nesters and these certainly like to have neighbours. They create tunnels, which are around a metre in length, ending in a chamber where the eggs are laid; some nesting sites may have between 50 and 100 tunnels. Like all bee-eaters these birds are strikingly colourful. They feed on flying insects caught on the wing but as their name suggests, they mainly take bees and wasps. They get rid of the sting by banging the insect on their perch and squeezing out the venom sac with their beaks. Young birds, which have been kept in captivity and have never seen other bee-eaters do this, displayed this behaviour proving that it is innate rather than learned, they are born with this instinct in place.
Herons are attracted to the river because they eat a lot of fish and one that has a unique way of getting dinner is the Black heron, also known as the ‘umbrella bird’. It will spread its wings over its head creating a shady area to which fish are immediately drawn, making it easy for the heron to catch them. Herons are clever birds; there’s one in North America, the Green heron, which uses bait to catch fish. It will take bread people have thrown to ducks and float it on the surface of the water and when the fish come to feed, snatch them up. They also use insects and the closely related Striated heron uses the same method to hunt.
Although herons tend to fish in shallow water and probably are not as much at risk from crocodiles as birds like cormorants, which will be in deeper places, they will still have to keep vigilant. Birds only make up a small part of crocodiles’ diet which is mainly fish but they are prime carnivores and will eat anything that comes their way; the river can be a dangerous place for animals when they come here to drink. A crocodile can be totally submerged with just its eyes and nostrils above the surface enabling it to see and breathe. It will launch a surprise attack and drag its victim under the water and as some of these reptiles can grow to be up to 20 feet (over 6 metres) long, they are easily capable of taking large prey, such as antelopes and wildebeest and yes, us as well! Often, not all of the animal is eaten immediately and some of the meat will be stored in an underwater larder. Unusually, for reptiles, the crocodile will care for her young. She digs a riverside nest hole and lays her eggs and, like tortoises, the temperature of the nest will determine the sex of the babies. When hatching time comes the mother will be alerted by the piping noises made by the little crocs and will often crack open the eggs to help them emerge. She will carry the young down to the water and stay with them for up to two years to protect them from predators.
The apparent lack of evolution in the crocodile has been the subject of many scientific discussions. It certainly looks much the same as it did 55 million years ago (we know this from fossilised remains) but it is evolving very slowly. The fact that it has exploited a niche that no other animal has, and the environment in which it lives has altered very little, the crocodile didn’t need to change very much.
The Nile crocodile is the main species in Tanzania and although we have visited several countries where these large reptiles live, we have never seen as many as on this trip.
Another large animal which can be taken by crocodiles is the Zebra. They live in big herds or harems with a ruling stallion, depending on the species; some males also live in bachelor herds. Zebras are equids, of the horse family, and the most common one is the Plains zebra, of which there are several sub-species, and this is the one we saw in Tanzania. Although, at a glance, they all look much the same, in fact each animal has a unique striped pattern. The stripes help with camouflage in grass and vegetation and confuse biting flies. Zebras mainly graze on grass but will eat other plants as well. As well as crocodiles, they are preyed on by lions which, as we talked about last month, hunt in groups. Hunting dogs move in packs and will take a young or injured animal and sometimes an adult. Hyenas are also a threat because, although we associate them with scavenging, they will often gang up to bring down a large animal. The Leopard is a solitary hunter and will usually only go for a young or sick Zebra; cheetahs will also take a young one. So, like many prey animals, zebras benefit from living in groups as there is always someone to keep watch even when they are resting. They mainly sleep standing up and, like horses, they are able to do this by locking their knees. This will be a dozing type of sleep but to sleep more deeply they will have to lie down when they will be more at risk from predators.
A small predator, which we will see at night, is the Tropical house gecko. There are many species of geckos but we are more aware of this one because, as the name suggests, it lives in, or on, houses. It is a patient little thing, waiting near a lamp to catch insects which are attracted to the light. It feeds on flies, moths, beetles, spiders, crickets and anything that ventures within striking distance, even baby geckos and lizards. Geckos are able to walk across walls and ceilings, they are even able to traverse glass. So how do they do this without falling? It is to do with the tiny hairs on the underside of their toes whose molecules are attracted to those on the surface of the wall or ceiling, creating adhesion. This is an electrical process known as the van der Waals force. (Don’t ask me!)
The Tropical house gecko is also known as the Wood slave because it hitched a lift on slave ships and can now be found in the Americas and the Caribbean islands.
Thank you for all your emails; I’m glad you are enjoying our safari. We’ll spend one more month in Tanzania before returning to Norfolk for the spring.
© Sheila Sims 2018. Email: firstname.lastname@example.org