Jaragua Dwarf Gecko: World’s smallest lizard at just 16 millimetres that can fit on a coin

A biological wonder lives in the leaf litter of the dry forests of the Dominican Republic; the Jaragua Dwarf Gecko (Sphaerodactylus ariasae) was long considered the smallest reptile on Earth and remains one of the two most extreme examples of miniaturisation in vertebrates (the adult gecko averages around 16 millimetres). According to Eurek Alert, first reported in 2001, the Jaragua Dwarf Gecko is an example of miniaturisation - the extreme lower limit of vertebrate size. However, this tiny predator lives in two locations (Jaragua National Park and Beata Island) and is facing a tremendous threat from the loss of its habitat. Learning more about this incredible animal has everything to do with saving its existence and nothing to do with understanding biology. Preserving these fragile micro-habitats ensures that such a tiny masterpiece of evolution does not vanish before we truly grasp its mystery. The Jaragua Dwarf Gecko is one of the most extreme instances of incredibly small vertebrate size (miniaturisation) recorded in the world (total length about 16 milimeters; average weight less than 0.13 grams) according to Eurek Alert. This size is so small that researchers typically use a US quarter or similar coin as an example of how small an adult specimen of this species is compared to traditional paper money.Sphaerodactylus ariasae is a species that has challenged current thinking regarding the limits of vertebrate size and its related capabilities. Scientifically, there are physical limitations to size. For example, an animal has to have enough physical space in which to contain its brain and heart, along with having enough reproductive capacity. The Jaragua Dwarf Gecko exists at the end of that continuum (or just above its limits), having evolved several characteristics that allow it to thrive in one of the many micro-habitats found on the floor of the tropical dry forest.This species is limited to a highly restricted micro-habitat - the limestone-derived dry forests of the Jaragua National Park in the Dominican Republic. The Jaragua Dwarf Gecko cannot survive without the moisture sealed in the leaf litter; therefore, if any amount of deforestation occurs, the Jaragua Dwarf Gecko has a greater chance of being locally extirpated. The IUCN Red List officially categorises Sphaerodactylus ariasae as endangered, but emphasises it is 'possibly Extinct' in specific unmonitored sub-regions due to 100 per cent habitat loss in those zones.The Jaragua Dwarf Gecko has evolved to eat ‘micro-prey’ to stay alive at its small size; larger lizards simply do not catch these creatures. The majority of the Jaragua Dwarf Gecko's food is composed of springtails (collembola) and tiny mites that live in the damp leaf litter on the forest floor. Because of their small mass, they have a very high rate of metabolism and hunting style.For twenty years, the Jaragua Dwarf Gecko was the smallest lizard on Earth. According to a research journal published in Nature which says, in 2021, scientists found the Nano-Chameleon (Brookesia nana) in Madagascar, and they are having a complicated conversation. Although the Nano-Chameleon is shorter in body length (snout-vent), the Jaragua Dwarf Gecko has been classified as one of the smallest geckos and one of the smallest vertebrates ever discovered, sitting at the absolute physical ‘floor’ of reptile evolution.