Mimicry – the ability of one organism to imitate another, usually poisonous or venomous species, for their own protection is widespread across nature. Some harmless snakes resemble highly venomous ones, certain inoffensive insects resemble wasps and hornets which sting and many moths have large eyelets on their wings to look like an owl or cat.
In the savanna biome of southern Africa, including the Kalahari, Central Bushveld, Mopane and Lowveld regions, their lives an interesting lizard called the Bushveld Lizard Heliobolus lugubris. It is a medium-sized lizard measuring around 120 mm total length when adults and has closely related species further north in East, West and North Africa.
What is remarkable about this species is its colour transformation from hatchling to adult. Female lizards lay 4-6 small oval eggs inside chambers dug in loose soil or sand and these hatch from December through to March. During the late summer season hatchlings can be extremely abundant in suitable habitat.
Their colouration is striking, being jet black with a series of yellow spots across the back and usually a yellow stripe on the tail. There is a good reason for this unusual colour – it serves as an aposematic or warning colour, however, unlike other animals which exhibit aposematic colours…which are usually venomous, the bushveld lizard is harmless. However, it resembles several ground beetles in the family Carabidae which can squirt acids or quinones and are extremely distasteful to predators. This is particularly true for species like the Two-spotted Ground Beetle Thermophilum homoplatum and Yellow-spotted Ground Beetle Craspedophorus bonvouloiri and associated relatives such as Anthia ground beetles. These beetles move rapidly in a stop and go, jerky fashion, which the young lizards imitate. As a result, a potential predator perched above in a tree will think twice about snatching up one of these lizards to avoid a mouthful of bitter disappointment.
As the lizard matures the back colour transforms to a sandy brown and the yellow spots disappear altogether. At this stage, the adult lizards rely more on speed and cryptic colouration to avoid predation.
Bushveld lizards are commonly found on open sandy flats interspersed with trees, shrubs and grasses. They tend to avoid heavily vegetated areas. They emerge from burrows, or, from under rocks and logs in the morning, as soon as the sun starts heating up the substrate, and remain active throughout most of the day, running between sun and shade whilst searching for food. Prey includes termites and ants, as well as small spiders, beetles and grasshoppers. Activity decreases drastically during the cooler and dry winter months and will remain hidden from around May to August. Longevity is unknown in the wild and probably live between 3-5 years.
Bushveld Lizard 1: Bushveld lizards are commonly found on open sandy flats interspersed with trees, shrubs and grasses.
Bushveld Lizard 2: Hatchling coluration resembles several ground beetles in the family Carabidae which can squirt acids or quinones and are extremely distasteful to predators, especially Anthia beetles.
Bushveld Lizard 3: Hatchling colouration is striking, being jet black with a series of yellow spots across the back and usually a yellow stripe on the tail.
Bushveld Lizard 4: Adult lizards rely more on speed and cryptic colouration to avoid predation.
Bushveld Lizard 5: A ground beetle similar to the ones with yellow spots to which the hatchling Bushveld Lizard mimics.