Visitors to South Africa are always keen to see the country’s celebrated Big Five – neglecting a wealth of smaller wildlife. To remedy this, some clever people came up with another must-see list, the Little Five: elephant shrew, ant lion, rhinoceros beetle, buffalo weaver and leopard tortoise!
Today, Ranger Sabastion shares some fascinating background on one of the ‘Little Five’ – the leopard tortoise. This is the most common tortoise in the Lowveld and probably the whole of southern Africa. It is also the largest – reaching a maximum of 70cm and 40kg. It is the only tortoise known to be able to swim.
It can be recognised by the absence of a small tile that usually fits between the two scutes in the front of the carapace (the upper part of the shell) on a tortoise. This is called the nuchal scute.
Males have longer tails than females and a convex plastron (the lower part of the shell) that allows them to mount females during mating. Females have flat plastrons. The leopard tortoise is a slow grower and only reaches sexual maturity at between 10 and 15 years old. They weigh about 1kg at 7 years of age but then body weight doubles every second year thereafter, provided good conditions prevail. They can live up to 75 years…
The shell is divided into two halves. The upper part is called the carapace while the lower part is known as the plastron. The shell is covered in scutes (horny scales) and these show seasonal rings formed as the tortoise grows. They cannot, however, be aged accurately from these rings as they are prone to rubbing smooth in the centre. Slower growth spurts occur during winter or in times of drought as well.
The shell of the tortoise is its transportable protective body armour, a necessity to accommodate for its slow movement. The shell is formed from a modified, fused ribcage and skeleton, the most unique part of this being that the shoulder blades and hips are bourne inside the ribcage to allow the tortoise to walk. When threatened, the tortoise draws its head directly back into its dome by means of a specialised, flexible neck and then seals off the opening by pulling in its scaly legs.
To sustain their high calcium requirements necessary for shell maintenance and the production of hard-shelled eggs, leopard tortoises practise osteophagia (the chewing of bones) and a rare form of coprophagia (consumption of droppings) – they eat hyena scat to absorb the excess calcium excreted by these bone-devouring predators.
The sex of tortoise hatchlings is determined by the temperature at which they incubate in their chamber under loose sand and rotting vegetation. Those subject to temperatures between 26-30°C become males while those exposed to 31-34°C heat become females…
The leopard tortoise has a device for storing water known as a bursa sac. This stored water is needed during times of drought or to moisten soil to more easily dig a pit in which to lay eggs. If a tortoise is threatened, it will urinate profusely and dispel the contents of its bursa sac as a repellent to the predator. After such an occasion, the tortoise is at risk of desiccating.
This is a young leopard tortoise seen crossing the road on one of my bush walks recently…
Text and pics by Sabastion Wayne