Smooth-Sided Toad

Smooth-sided toad（圖片來源：Taucce, P. P., Costa-Campos, C. E., Carvalho, T. R., & Michalski, F.，採用 CC BY 4.0 授權）

The smooth-sided toad (Rhaebo guttatus) is a large toad belonging to the family Bufonidae. It is widely distributed across the Amazon Basin in South America, including Ecuador, Colombia, Peru, Bolivia, Brazil, Venezuela, Guyana, Suriname, and French Guiana. In the wild, this species primarily inhabits tropical humid lowland rainforests, especially riparian forests and the forest floor. Individuals are often found within leaf litter or near riverbanks, and they may dig shallow burrows among decaying plant material.

In terms of body size, the smooth-sided toad is a robust species. Males typically reach around 15 cm in length, while females are larger, often exceeding 17 cm, with some records indicating females reaching up to 25 cm. Dorsal coloration varies widely, ranging from light brown and creamy tan to reddish-brown, while the ventral side is darker and commonly marked with rounded white spots. A defining feature is the preocular ridge, a prominent bony ridge located in front of the eyes, visible even in juveniles and useful for distinguishing this species from closely related taxa.

This species is nocturnal. During the day, individuals hide beneath leaf litter, soil, or other cover, emerging at night to forage. Their primary defense mechanism is the large parotoid glands located behind the eyes, which secrete a yellowish or milky substance containing bufotoxins. If ingested by predators, these toxins can cause severe poisoning or death. In humans, accidental exposure through the mouth or contact with the eyes or mucous membranes may result in cardiac disturbances or even life-threatening conditions. Therefore, handlers should avoid direct contact and wash hands thoroughly after any interaction.

In the wild, precise lifespan data are lacking, but it is estimated that they can live over 10 years. Under proper captive conditions, they may live between 10 and 15 years, making them a relatively long-lived amphibian in captivity.

Housing Requirements in Captivity

Due to their large size and relatively high activity levels, a single adult should be provided with an enclosure of at least 60 x 30 x 40 cm to 90 x 45 x 45 cm. The enclosure must have a secure, well-fitted lid with adequate ventilation, as smooth-sided toads are capable of strong movements and jumping, and may escape if openings are too large. Because of potential cannibalistic tendencies, individuals of different sizes should not be housed together. If group housing is attempted, individuals should be of similar size, with sufficient space and hiding spots provided.

Suitable substrates should retain moisture, such as coconut fiber, bark chips, sphagnum moss, or pesticide-free soil. Substrate depth should be 5 to 10 cm to allow for burrowing behavior. This species requires high humidity, ideally maintained at 70 to 80%, with misting at least once daily to prevent desiccation. However, proper ventilation is essential, as excessive moisture without airflow can promote fungal growth and skin diseases.

Temperature should be maintained between 24 and 29°C, with a slight drop at night, but not below 20°C. Additional heating is generally unnecessary, but if ambient temperatures are too low, a low-wattage heat lamp or ceramic heater may be used. Although UVB lighting is not strictly required, providing moderate UVB exposure can support calcium metabolism and overall health.

A shallow water dish should be included for soaking and maintaining skin moisture. The dish should be wide and shallow, with water depth not exceeding shoulder height to prevent drowning. Water must be clean and free of chlorine; dechlorinated water or bottled water is recommended, with changes 2 to 3 times per week.

The enclosure should also include multiple hiding places, such as overturned flower pots, bark pieces, stones, or artificial caves, to reduce stress. Artificial or live plants can increase environmental complexity and provide a more natural setting.

Smooth-sided toad（圖片來源：Bernard DUPONT from FRANCE，採用 CC BY 2.0 授權）

Feeding Conditions

The smooth-sided toad is a typical carnivore, feeding primarily on insects and small animals. In the wild, it consumes crickets, cockroaches, beetles, spiders, earthworms, and occasionally small amphibians or reptiles. It may also scavenge pet food remnants. Its hunting strategy is ambush-based, relying on keen vision to detect prey movement before rapidly extending its tongue to capture it.

In captivity, common food items include crickets, Dubia roaches, mealworms, superworms, bloodworms, earthworms, and red worms. Occasionally, appropriately sized frozen-thawed fish or pinky mice may be offered, but only in moderation.

Feeding should occur 2 to 3 times per week to prevent obesity. Juveniles require more frequent feeding, approximately every other day, while adults should be maintained at a healthy body condition. A varied diet is essential to avoid nutritional imbalance. Feeder insects should be gut-loaded with vegetables, fruits, and nutritious feeds prior to use. Additionally, insects should be dusted with calcium or vitamin supplements, especially those containing vitamin D3, 1 to 2 times per week to ensure adequate nutrition.

Feeding should be done using tweezers or feeding tongs rather than by hand, to avoid accidental bites or exposure to toxins. These toads have a strong feeding response and rapid movements, making hand-feeding potentially risky. Feeding should take place within the enclosure or in a designated feeding container to prevent escape of prey items and contamination.

Breeding Conditions

In the wild, breeding typically occurs during the rainy season, with rainfall and water flow acting as key environmental triggers. Males produce loud calls to attract females and engage in amplexus during mating. Females can lay thousands to tens of thousands of eggs at a time, which are deposited in strings attached to aquatic vegetation or near riverbanks. After hatching, tadpoles develop in water and undergo metamorphosis into juvenile toads over several weeks to months.

In captivity, breeding is highly challenging. Attempting reproduction requires simulation of rainy season conditions, such as prolonged misting or the use of sprinkler systems to mimic heavy rainfall, along with the provision of flowing water. Due to the large number of eggs produced, managing the resulting tadpoles can become extremely demanding. For most keepers, breeding is not recommended, and should not be attempted out of curiosity, as it may result in thousands of offspring without proper means of care.

If breeding occurs unexpectedly, planning for the management of large numbers of tadpoles is essential. This may include arranging placement with qualified institutions or implementing population control measures to prevent ecological impact.

Preventing Invasive Spread

The smooth-sided toad is large, highly adaptable, and equipped with effective chemical defenses, giving it a high invasive potential outside its native range. In some countries outside South America, it is classified as a regulated or prohibited species. If released into non-native environments, it may rapidly establish populations and pose serious threats to local ecosystems, including large-scale mortality of native species.

Keepers must never release these animals into the wild. Regardless of factors such as size, lifespan, or loss of interest, releasing them into non-native environments is irresponsible. Proper planning is essential before acquiring this species, including understanding its lifespan, size, and care requirements to prevent abandonment. If the animal can no longer be kept, it should be rehomed to a reliable keeper or transferred to a qualified animal care facility. Additionally, local regulations in Taiwan should be checked prior to purchase to ensure compliance with current laws.

Author: Shui-Ye You