The tiny chameleons were discovered in a degraded mountain rainforest in northern Madagascar. Researchers believe it may be the smallest reptile species in the world at 13.5 millimeters (0.53 inches).
Until now, the smallest reptile species was the Brookesia micra, with a confirmed minimal adult male size of 15.3 mm (0.6 inches). But researchers found an even smaller relative of the former record holder, the Brookesia nana. Females of the species are slightly larger, but their total length is below 2 centimeters, as well. In contrast to larger chameleons, their miniaturized counterparts are incapable of changing their colors.
However, the most surprising feature of the B. nana is the size of the genitals on the males in proportion to their size. Reproductive organs of lizards are called hemipenes, and they usually keep it tucked in when they aren’t mating. The fully everted hemipenis of the male specimen is 2.5 mm (0.98 inches) long, which is almost 20% of its body length.
According to a comparative study of genital length in Malagasy chameleons, larger hemipenes are more likely among smaller chameleons. One possible explanation for their well-endowment may be the difference in size between the sexes – the much smaller males need relatively bigger genitals in order to successfully mate with the larger females.
Generally, they scavenge for food on the rainforest floor during the day, but they retreat to the safety of grass blades at night. Their diet is thought to be mostly comprising of mites and springtails, which they catch with their tongues.
The evolutionary reason for the miniaturization of chameleons in Madagascar is not fully understood. Some theories suggest the answer lies within the so-called island rule, which describes when isolated (like on an island), animals sometimes grow much larger or smaller than their non-isolated relatives.
The fact that scientists only found two specimens of the Brookesia nana in a single location makes it very hard to evaluate the distribution and the conservation status of this species. According to the current state of knowledge, researchers suggest that it qualifies as critically endangered. Unfortunately, deforestation and slash-and-burn-agriculture affect most forests in Madagascar, and the mountain forest where the lizards are found is already severely degraded.
The good news is that the natural habitat of the record holders was declared as a protected area!