Robert Mertens’ day geckos (Phelsuma robertmertensi) are a brightly colored species endemic to Mayotte, a small island northwest of Madagascar. Because of their small range and the agricultural transformation of their habitat, this is an endangered species in the wild. Bred in captivity, however, they make beautiful pets to observe. Like all day geckos, they don’t take very well to handling, but their bright colors and diurnal nature, both characteristic of the genus, make them great geckos to observe.
Like all geckos in the genus Phelsuma, Robert Merten's day geckos exhibit bright and attractive colors. Robert Mertens’ day geckos are dark green or blueish green and may even contain light bright blue coloration. An interrupted reddish orange line descends down their back.
An 12x12x18 Exo Terra cube can house a pair of Mertens’ day geckos. Larger enclosures can house more individuals, but it is recommended that males are not housed together to avoid interspecific aggression. A variety of substrate mixtures can be used with coco fiber or peat moss as a base. Josh’s Frogs BioBedding works very well with this species; in addition to holding moisture, it will help propagate and maintain live plants and isopod populations in the setup (both highly recommended with this species).As an arboreal species, these geckos thrive in a setup filled with pieces of cork bark, branches, large bamboo sticks, and live or fake plants. It is essential to provide an enclosure with plenty of climbing material. Mertens’ day gecko can be kept at ambient temperatures ranging 72-78F. A basking area of around 85F should also be provided using a halogen light. As with all day geckos, which are diurnal, UV light is recommended.Ambient humidity for this species should remain around 60-70%. Daily misting is strongly recommended to keep the substrate moist and also provide water droplets from which the geckos can drink. There should be enough ventilation such that any water droplets on the walls of the enclosure dry out by the next day. A shallow water dish can be supplied but is not necessary if these geckos are misted every day. Both temperature and humidity can be monitored with a thermometer/hygrometer.
These day geckos will grow to be 4-5 inches as adults.
Robert Mertens’ day geckos are omnivorous. In the wild, they consume insects as well as nectar or soft fruit. In captivity, they enjoy a staple diet of small crickets and gecko diet mix. A good rule of thumb for size is to only offer insects whose length does not exceed the space in between the gecko’s eyes. Generally, hatchling Mertens’ day geckos should be fed melanogaster fruit flies and gecko diet mix, adding ⅛-inch crickets as they grow older. As adults, they can continue to be offered gecko diet mix once a week as well as ¼-inch crickets. Feeder insects should be dusted with a vitamin/mineral supplement.
Robert Mertens’ day geckos can be challenging to sex when young, but are fairly straightforward to sex when they are mature. Females are larger, and tend to have prominent calcium sacs under their chin. Males have a row of enlarged femoral pores on the underside of their thighs, flanking the cloaca. The scales around these pores are often yellow.
During the breeding season, these geckos lay a pair of eggs about once every month or two. As egg-gluers, eggs will be glued to a plant, branch, or even the walls of the enclosure; attempting to remove them will break the egg.