Captive Care of the Genus Mantella
By Devin Edmonds

Often with bright colors and contrasting patterns, frogs of the genus Mantella are frequently kept in captivity. They make excellent captives when acquired in good health and provided with the appropriate environment. The care of some species is well-understood, but for others there is still much to be learned. This article provides basic guidelines for keeping Mantella species in captivity.

Acquisition

In North America, wild-caught mantella frogs dominate the pet trade. Most species are seasonally available, usually during the winter and early spring, which coincide with the wet season in Madagascar when mantellas are active and easy to collect. They can be purchased directly from importers or other reptile and amphibian dealers, as well as retailers and pet stores. In the European Union, only captive-bred mantella frogs are available, with the exception of M. betsileo/M. ebenaui, which can still be legally imported.

With many species of Mantella having very restricted distributions, and over the half the genus considered threatened with extinction, I would discourage most from keeping wild-caught mantella frogs for private display purposes, and instead focus on using them for breeding to 1) reduce the demand for wild-caught frogs and 2) establish the species in captivity so frogs are available if imports or exports stop.

Captive-bred mantella frogs are occasionally available directly from breeders, who are the preferred source for mantellas. Frogs produced in captivity are always in better condition than those that are wild-caught, and overall seem to fair better as captives. Unfortunately, only one species (M. aurantiaca) seems to be produced in captivity with any consistency, with others being sporadically bred here and there. This can make it difficult to locate captive-bred stock of certain species which are rarely bred. The Internet is the best resource for tracking down captive-bred mantella frogs, with breeders advertising on online amphibian classifieds and forums.

Housing

Standard glass aquariums are the most common type of cage used. Alternatively, specialty reptile and amphibian cages can be used with features such as sliding front doors and side ventilation panels, both of which are desirable. Use a screen cover to prevent escapes and offer good ventilation and airflow. Over part of this cover (or sometimes all of it), plastic wrap or glass can be taped in place to restrict ventilation and increase the humidity level in the cage. During a simulated dry season, the glass or plastic wrap can be removed to allow the cage to dry. Plastic storage containers or totes are another option for housing mantella frogs, and work well when modified by having small holes drilled in the cover and sides. Because of their light weight, plastic containers can be moved around and cleaned easily, making maintenance less of a hassle.

Males of many species of Mantella behave aggressively towards each other, so ample space must be provided to reduce aggression and stress. A standard 29 gallon aquarium, which measures 30 in x 12 in x18 in (76 cm x 30 cm x 46 cm), is large enough for eight to ten individuals. Smaller cages can be used to house smaller groups of frogs. I’ve had success permanently keeping as many as five M. crocea in a standard 10 gallon aquarium, where they lived and bred well. When cages this small are used it’s important to offer plenty of hiding spots and visual barriers to reduce stress. Large species or those that have a nervous disposition in captivity should be kept in larger enclosures. On all cages, a background should be taped to all but one side of the enclosure to make the frogs feel secure. Natural backgrounds like corkbark or tree fern panels can be glued to the inside of the cage with silicone sealant as an alternative.

    

Housing in a standard aquarium, in a custom-made cage, and in a plastic storage container

Mantella frogs can be kept on a variety of substrates. Soil mixtures consisting largely of ground coconut husk fiber or peat are most often used, and work well because they look natural and provide a medium in which to grow live plants. Long-fiber sphagnum moss is a good alternative to soil mixtures, and forms a sponge-like substrate when moistened and patted down flat against the bottom of the cage. It may be helpful to place either soil mixtures or sphagnum moss over a drainage substrate, such as a layer of gravel, LECA, or a false-bottom. This allows excess water to drain through them so that they do not become waterlogged. Moist paper towels and upholstery foam rubber both work well as simple substrates, and make it easy to find eggs and monitor frogs. They must be cleaned often though, with paper towels needing to be changed at least weekly, and foam rubber requiring a good rinse or cleaning every few weeks. Whichever substrate is used, a handful of dried oak or magnolia leaves can be spread around on top of it, offering cover for the frogs.

                  

Two different drainage substrates: LECA and a false bottom

Artificial or live plants can be used to furnish the cage. When live plants are used, they can be either planted directly into a soil substrate or kept in their pots. Plan ahead when choosing which species of live plants to use, because those which grow quickly will soon dominate a tank, making it hard to observe the frogs and monitor them for breeding activity. In addition to plants, rocks, corkbark and driftwood can be used. Small, corkbark slabs are particularly useful when placed on top of piles of moist moss, forming an egg deposition site few mantella frogs can resist when conditioned properly.

A water dish should be provided so that the frogs remain hydrated. Use water that contains no chlorine, chloramines, or other chemicals which can harm amphibians. Tap water can be treated with an aquarium water conditioner to remove these chemicals, but the quality of it can vary depending on the source, and all tap water is not safe for extended use with amphibians. If the tap water in your area is of poor quality (contains nitrates, is very hard, has a high pH, etc.), consider using bottled spring water instead.

Lighting

Mantella frogs do not require any special type of lighting, but should be exposed to a natural photoperiod of between 11 and 13 hours. A single fluorescent tube set on an electrical timer is enough to provide this. If live plants are used, additional lighting may be needed. Small cages can be overheated easily when lights are set directly on top of them, so it can be helpful to suspend a light fixture above the cage if keeping a species that is particularly sensitive to warm temperatures.

Temperature

Most Mantella species do well when maintained between 18°C and 24°C (65°F and 75°F) most of the time. Some species from cooler regions of Madagascar are intolerant of warm temperatures and succumb to heat stress easily in captivity. Species reported to be sensative to warm temperature include M. aurantiaca, M. baroni, M. cowani, M. crocea, M. madagascariensis, and M. milotympanum, and temperatures at or above 25°C to 27°C (77°F to 81°F) should be avoided. It should be noted that M. baroni has a very wide distribution, and although described by some as being intolerant of warm temperatures, this may only be the case for frogs collected from certain populations originating from higher altitudes or cooler areas.

    

Three species of Mantella which are prone to heat stress in captivity

Species of Mantella that inhabit lowlands and tolerate warm temperatures in captivity include M. bernhardi, M. betsileo, M. ebenaui, M. expectata, M. leavigata, M. nigricans, and the Mantella species often referred to as the blushing mantella by hobbyists. These frogs cope well with a wide range of temperatures, and occasional days where it climbs to 27°C (81°F) don’t generally present a problem. M. expectata in particular should be kept slightly warmer than other species.

The best method for controlling the temperature is to keep the cage in a room which stays within a suitable temperature range. A cool basement or air-conditioned room works well for highland species. Often within a room there is a thermogradient between the floor and the ceiling, and keeping the terrarium on a low shelf, or even the floor, can help keep it cool on warmer days. Temporarily, ice packs can be placed on the cover of terrariums to keep them cool, but should not be relied on as a permanent method for regulating the temperature.

Heating mantella enclosures is not often required, but if necessary, reptile heat pads can be used. In terrariums with a particularly thick substrate, these may not be practical, and instead a low-wattage (15W-25W) infrared light can be used to heat the cage. Submersible aquarium heaters with thermostats also work well if there is a large enough body of water to place them in.

Humidity

In the wild, all Mantella species experience a rainy season with high humidity levels and frequent rain storms. The rest of the year, the humidity level is usually lower, and many species burrow into the leaf litter to conserve moisture until the rains return. Captive mantella frogs can be maintained year round at moderate to high humidity levels and live well, but it’s advantageous to expose them to varying levels of humidity during different times of the year to induce breeding. Humid conditions can be created by restricting ventilation and misting the terrarium with water several times each day. Use reverse osmosis or distilled water to spray down the cage to prevent water spots from developing on the glass. High humidity levels should coincide with warm temperatures, and dryer conditions should be created when the temperature is cooler.

Feeding

Captive mantella frogs should be offered a variety of live insects for food. Crickets, fruit flies, small waxworms, mini mealworms, and rice flour beetle larvae are some of the commercially available feeders which can be fed to mantellas. Insects captured from a safe location outside can be offered as well. Particularly useful are termites, which have a high fat content and can be used to bulk up thin frogs quickly or to promote egg production in females. Aphids are another good wild food source.

Crickets and fruit flies can form the majority of a captive mantella’s diet. Offer crickets which are slightly shorter than the width of the frog’s head. For large, robust species, like M. expectata and M. viridis, two to three week old crickets can be used, while smaller species, such as M. milotympanum, should be offered smaller crickets. Two species of fruit flies are commonly available – Drosophila hydei and Drosophila melanogaster. Both are readily accepted by mantella frogs, but the larger D. hydei seems to excite mantella frogs more than the smaller D. melanogaster.

To boost the nutritional content of crickets, they should be fed well for several days before being offered to the frogs. Sweet potato, dark lettuces, squash, and oranges can all be fed to crickets in addition to a dry food such as tropical fish flake or dog food. To ensure that additional nutritional requirements are met, feeder insects should be coated with high quality calcium and multivitamin powdered supplements.

The frequency with which mantella frogs are fed depends on the quantity of food offered and the conditions in which the frogs are being kept. During a cool simulated dry season, mantella frogs may only need to be fed every four to seven days in small amounts. At warmer temperatures, frogs can be fed daily. Mantella frogs will become obese if fed too heavily or too frequently, so monitor feedings carefully to ensure they are not being overfed.

Health

There are many ailments that can affect captive mantella frogs. Most are the result of improper care, and simply by keeping mantellas in proper conditions many common health problems can be avoided. It’s helpful to be familiar with a few of the more frequently encountered problems so that if they do occur, you are able to detect and treat them before they progress too far.

Stress: Often the underlying factor that allows for a mantella frog to develop a health problem is stress. Stress weakens the immune system, permitting disease to spread. Reduce stress by limiting interactions with frogs, providing adequate cover for them, and ensuring there is ample space in the cage for the amount of frogs being kept. A particularly stressful period of time for all frogs is when they are initially acquired, and special care should be taken to allow new frogs to adjust to your care as easily as possible. See Innitial Care of Wild-caught Mantella frogs for more information.

Bacterial infections: Within terrariums, mantella frogs are constantly surrounded by a variety of bacteria. When healthy, they present no problem for captive frogs, but when a frog’s immune system is compromised or the bacteria reach elevated levels, they can overwhelm the frog and take over. Fluid retention (bloating), clouded eyes, skin ulcers or sores, paralysis, and discoloration can all be symptoms of a bacterial infection, and if any are noticed, seek veterinary assistance. Antibiotics can be used to treat infections effectively provided they are caught in time, but sometimes symptoms develop only once an infection has progressed too far to successfully be treated. Prevent bacterial infections from developing by keeping the cage clean, maintaining proper environmental conditions (temperature, humidity, water quality, etc.), and keeping stressful situations to a minimum.

Parasites: Unless treated, most mantella frogs harbor a variety of internal parasites. Under normal conditions this doesn’t present a problem, but if a frog is weakened by some other factor, parasites can reach heightened levels and overcome a mantella. Recently imported frogs often have parasite problems, and are best treated prophylacticly when they arrive in your care. Established and captive-bred frogs can also run into problems with parasites. Sometimes an individual in a group may develop a problem over time, and slowly waste away while others in the colony remain healthy. If a mantella frog seems to be loosing weight, it should be isolated from the others and monitored carefully. A vet can then run fecal exams on the frog to determine if internal parasites are the problem. Treatment involved depends on the parasite(s) infecting the frog. Granular fenbendazole (Panacur) for dogs and cats can be coated onto crickets or fruit flies to treat many common parasites and is relatively safe, but is not affective against all parasites. Other drugs, such as ivermectin or metronidazole, are needed to get rid of particular types of parasites, but have a small safety margin and are easy to overdose. Consult a veterinarian prior to using any medication.

Injuries and trauma: Most often encountered with recently imported mantella frogs, injuries can include rostral abrasions, missing digits, or small scrapes or cuts. When left untreated, these wounds can open a door to a wide range of bacterial or fungal infections. Separate any injured frog away from others in a small, simple setup. A triple antibiotic ointment should then be applied to the wound. This can be used daily for a several days, but if no change is noticed in that time it may be necessary to use a different antibiotic acquired from a veterinarian.

References
Staniszewski, Marc. Mantellas. 1st ed. Frankfurt: Chimaira, 2001.