The Cape dwarf chameleon (Bradypodion pumilum) is a chameleon native to the South African province of the Western Cape, where it is restricted to the region around Cape Town.
As with most chameleons, its tongue is twice the length of its body and it can be shot out of its mouth using a special muscle in the jaw. This gives the chameleon the ability to catch insects some distance away.
Description
The Cape dwarf chameleon grows to over in length, including the tail, with males and females reaching similar adult sizes. They are ovoviviparous, but examination in controlled captivity has shown the very soft egg-like membrane around the young is discarded immediately on birth. The young resemble miniature versions of the adults, with muted colours, and typically reach no more than 2 cm in length at birth. Adults can vary quite significantly in colour variety, saturation and pattern, some appearing much more vibrant than others. Like most chameleons, the tail is prehensile, and the feet are well evolved to grasping twigs, with minute claws on the end that improve grip.
Normally very slow moving, chameleons have a characteristic shake, which may make them look more like leaves to prey and predators. When provoked, they can speed up to several centimetres a second. When further provoked, they may inflate themselves, hiss, change colour dramatically, and bite. They do not have sharp teeth, so their bites rarely inflict more than a slight pinch.
Male and female are difficult to differentiate. However males tend to have brighter colours, slightly larger head crests, and slightly narrower stomach area around the hips.
The Cape dwarf chameleon is classified as a medium-sized chameleon with an average adult body size of 50–70 mm body size. This species has a restricted distribution within regions of southwestern South Africa that receive rainfall during winter months. This species is viviparous, meaning it gives live birth rather than eggs, and can have one to several clutches of about 10-15 offspring in any given year. Mortality rates of neonates are expected to be high due to an intense reproduction schedule and a high fecundity rate.Feldheim, Kevin A., Lucas F. Chauke, Kevin P. Hopkins, and Krystal A. Tolley. "Characterization of Microsatellite Loci from a South African Endemic, the Cape Dwarf Chameleon (Bradypodion Pumilum)." Conservation Genetics Resources 2.S1 (2010): 165-68. Web.
Functional consequences of morphological differentiation
Different populations within Cape dwarf chameleons were found to have different preferences regarding perch diameter. The two main populations, Kogelberg and Stellenbosch, were seen to have different behavior. Kogelberg tended to use perches that were significantly wider on average than perches used by the Stellenbosch site which chose perches by random. Hand size has a direct correlation with grip strength on both broad and narrow dowels, rod-like structures, in both populations. The longer the tail length, the greater the strength. This species prefers to sleep on perches of specific diameters that correspond to their specific morphology. Animals from habitats characterized by wider perches are also stronger than their counterparts living in habitats with narrow branches. This has led to sexual selection for chameleons with specific traits like hand size and tail length.Herrel, Anthony, G. John Measey, Bieke Vanhooydonck, and Krystal A. Tolley. "Functional Consequences of Morphological Differentiation between Populations of the Cape Dwarf Chameleon (Bradypodion Pumilum)." Biological Journal of the Linnean Society 104.3 (2011): 692-700. Web.
Bradypodion pumilum has two ecomorphs: a large, brightly coloured, ornate version often found in closed habitats, and a small, dull version with less ornamentation often found in open vegetation. Casque size is known to be used to communicate fighting ability, but it is yet to be known whether this size is an honest signal and if it is related to bite force. Bite force is significantly related to head size and the best way to tell the strength of the bite force is measuring the head width.Stuart-Fox, Devi M., David Firth, Adnan Moussalli, and Martin J. Whiting. "Multiple Signals in Chameleon Contests: Designing and Analysing Animal Contests as a Tournament." Animal Behaviour 71.6 (2006): 1263-271. Web. Open habitat males tend to have larger heads thus having stronger bite force. Larger chameleons have a high casque (parietal crest) and are brightly coloured with pink patches on their flank. The smaller chameleons found in open habitats have reduced casques and lack flank colour patches at all. Battles between males can lead to severe injuries through biting.Measey, G. John, Kevin Hopkins, and Krystal A. Tolley. "Morphology, Ornaments and Performance in Two Chameleon Ecomorphs: Is the Casque Bigger than the Bite?" Zoology 112.3 (2009): 217-26. Web.
Taxonomy In the past, most South African dwarf chameleons were considered a subspecies of the Cape species(e.g. Klaver & Böhme 1997) This is now known to be wrong, however; B. pumilum does not appear to have any particularly close living relatives. Like the Knysna dwarf chameleon, it seems to be a basal offshoot of the ancestral stock, which gave rise to all Bradypodion species.(Tolley et al. 2004)
Structure and movement Cape dwarf chameleons have a much higher survival rate in a metropolitan area if they are bigger in size. Their survival rate was dependent on body size, and the larger the size, the greater the chance that the individual would survive a ten-day period. Larger, older chameleons tend to be more sedentary compared to the smaller younger ones which means that the larger ones likely have smaller home ranges. Smaller chameleons inhabit grasses while larger chameleons are found mainly in bushes and trees. This is territorial, because it is believed that larger males would cannibalize smaller ones intruding on their territory. An alternative thought is that the smaller chameleons simply do not have big enough limbs to grasp larger branches correctly. When fighting contests occur, the outcome is influenced by the height of the ornamental casque, the relative size of the pink patch in the center of the flank, and previous experience. The ornamental casque is the protruding head piece of the chameleon, usually with a rounded end. The height of this piece is an honest signal to other male chameleons representing its total size. Similarly with the pink patch in the center of the flank, this is an honest signal showing that the chameleon has a healthy diet correlating to the strength of the individual.Arnott, Gareth, and Robert W. Elwood. "Assessment of Fighting Ability in Animal Contests." Animal Behaviour 77.5 (2009): 991-1004. Web. The turnover rate in males is thought to be higher than females.Tolley, Krystal A., Robert N.v. Raw, Res Altwegg, and G. John Measey. "Chameleons on the Move: Survival and Movement of the Cape Dwarf Chameleon, Bradypodion Pumilum, within a Fragmented Urban Habitat." African Zoology 45.1 (2010): 99-106. Web.
When it comes to foraging, males and juveniles are more active than females. Females are only equally or more active than males during the reproductive season. Males may be more active due to seeking mates and defending territories. Bradypodion pumilum is a sit-and-wait forager which means they will rarely move and wait for prey to cross their paths, only then striking out. Low rates of prey capture are often seen in this species.Butler, Marguerite A. "Foraging Mode of the Chameleon, Bradypodion Pumilum: A Challenge to the Sit-and-wait versus Active Forager Paradigm?" Biological Journal of the Linnean Society 84.4 (2005): 797-808. Web
Distribution
The Cape dwarf chameleon is restricted to the area around Cape Town, the Boland, and the mountainous coastline as far as Agulhas.
Like many other reptiles, chameleons are poikilotherms meaning their body temperature is completely dependent on environmental temperature. A large number of lizards are expected to be affected by climate change in the near future, especially in Southern Africa where this species is found. If temperatures rise by 1-3 degrees Celsius, then it is expected that Cape dwarf chameleon running speed will increase as well. Although speed would be better, bite and grip force would become worse. Chameleons are adapted to current habitat temperatures and conditions, but shifting to a higher temperature would actually benefit some of their traits and abilities. This shows that future persistence of this species is very likely even with the advancement of global warming.Segall, M., K. A. Tolley, B. Vanhooydonck, G. J. Measey, and A. Herrel. "Impact of Temperature on Performance in Two Species of South African Dwarf Chameleon, Bradypodion Pumilum and B. Occidentale." Journal of Experimental Biology 216.20 (2013): 3828-836. Web.
Habitat
Habitat in wilderness areas This species inhabits a range of different habitats and vegetation types, from fynbos and renosterveld, to indigenous Afrotemperate forest and wetlands.
It is less common in extremely fire-prone and low-growing fynbos, and in open sandy or rocky areas. It is more usually found in areas such as river valleys, which are sheltered to some degree from the region's seasonal fires, and where more dense vegetation has developed. It prefers certain plant species to reside on too, especially favouring Restios. This adaptable species has also diversified into different forms and colours, depending on their habitat. Those that live in open, low-lying fynbos vegetation tend to be smaller and dull-coloured with smaller crests. Those in denser, closed vegetation areas tend to be larger and brightly coloured, with a longer tail and larger casque.
In the wild, its predators are mainly snakes and predatory birds such as fiscal shrikes.E. Katz; K.A. Tolley; R. Altwegg: Survival and abundance of Cape dwarf chameleons, Bradypodion pumilum, inhabiting a transformed, semi-urban wetland. Herpetological Journal. Volume 23 (October 2013), 179–186.
Habitat structure differences When looking at open habitats, chameleons with smaller body sizes are favored. Differences between habitats include certain traits found in the chameleons. This includes limbs, feet, tail, and head width. Open habitats commonly see longer limbs but smaller feet compared to chameleons found in closed habitats. Smaller feet in the open habitat are more accustomed to grasping the narrower branches. Natural and sexual selection in open and closed habitats have different intensities which directly affects the morphological variation found within the species.Hopkins, Kevin P., and Krystal A. Tolley. "Morphological Variation in the Cape Dwarf Chameleon (Bradypodion Pumilum) as a Consequence of Spatially Explicit Habitat Structure Differences." Biological Journal of the Linnean Society 102.4 (2011): 878-88. Web.
Habitat loss