Asian common toad

The Asian common toad, scientifically known as Duttaphrynus melanostictus, is a widespread amphibian species found across a vast swathe of South and Southeast Asia. It is also recognized by several other common names, including the Asian black-spined toad, Asian toad, black-spectacled toad, common Sunda toad, and Javanese toad. This species is notable for its size, which can reach up to 20 centimeters (8 inches) in length, and its distinctive physical characteristics, which include a warty, spiny dorsal surface and prominent parotoid glands that secrete a milky white Bufotoxin.

Habitat and Distribution

This adaptable toad thrives in a variety of disturbed lowland habitats. Its distribution spans from northern Pakistan eastward through Nepal, Bangladesh, India (including the Andaman and Nicobar Islands), Sri Lanka, Myanmar, Thailand, Laos, Vietnam, Cambodia, southern China, Taiwan, Hong Kong, and Macau, extending to Malaysia, Singapore, and various Indonesian islands such as Sumatra, Java, and Borneo. They are found from sea level up to altitudes of 1,800 meters (5,900 ft), favoring areas like upper beaches, riverbanks, agricultural land, and urban environments, while being less common in closed forests.

Characteristics and Behavior

The Asian common toad exhibits several defining features. The top of its head is adorned with several bony ridges, and its snout is short and blunt. A particularly notable characteristic is the presence of prominent, kidney-shaped or elliptical parotoid glands on its back, which are a primary source of its defensive toxin. The dorsal side is typically yellowish or brownish with black spines and ridges, contrasting with a plain or spotted underside. Males are identifiable by a subgular vocal sac and black pads on their inner fingers, which aid in grasping females during mating. These toads are terrestrial, often seeking shelter under rocks, leaf litter, or logs, and are frequently associated with human habitations. They are often observed at night, particularly when attracted to artificial lights.

Reproduction and Diet

Breeding for the Asian common toad takes place during the monsoon season. They reproduce in still or slow-flowing bodies of water, including rivers, temporary ponds, and permanent pools. Their tadpoles are distinctively black. Observations suggest a varied diet, with known prey including scorpions and various invertebrates, which they likely hunt by night. Studies have also indicated that tadpoles can recognize kin, with those raised in sibling groups metamorphosing faster than those in mixed groups.

Ecological Concerns and Introductions

The Asian common toad is considered an invasive species in several regions outside its native range, posing significant ecological risks. It was introduced to Madagascar in 2011 and has since spread around the port of Toamasina, raising concerns about its potential impact on native wildlife due to its toxicity. Similarly, introductions to islands like Bali and Sulawesi in Indonesia, and subsequent spread to New Guinea, have raised alarms. Native predators in these areas often lack resistance to the toad's toxins, mirroring the issues caused by cane toads in Australia. The species has been detected in Australia multiple times and is considered a high-priority "unwanted species" due to its potential to disrupt ecosystems through competition, disease spread, and toxicity.