Which of the following is a poisonous mammal?

Question

Accepted Answer

The correct option is 3: Male Ornithorhynchus

The male *Ornithorhynchus anatinus*, commonly known as the platypus, is one of the very few mammals in the world to be truly venomous. This fascinating characteristic is a key detail about this unique monotreme, an egg-laying mammal endemic to eastern Australia. The venom is not used for predation but primarily for defense and, more significantly, for competition during the mating season between males. A spur, which is connected to a venom-secreting crural gland, is present on the ankle of each hind leg of the male. The venom, a complex mix of at least 19 different substances, mainly defensin-like peptides, can cause excruciating, long-lasting pain and rapid swelling in humans, and can be lethal to small animals. The presence of this active, functional venom apparatus distinguishes the male platypus as a poisonous (venomous) mammal.

The incorrect option is 1: Male Guinea Pig

The Male Guinea Pig (*Cavia porcellus*) is a common domesticated species belonging to the order Rodentia. They are herbivores and lack any physiological mechanism for producing or delivering venom or poison. Guinea pigs do not possess venom glands, specialized fangs, or spurs connected to toxin-producing structures. While they may bite or scratch when feeling threatened, these actions are not associated with toxin injection, and their saliva and body fluids are non-venomous. Their inclusion in this list is to test knowledge about common non-venomous mammals against rare venomous ones.

The incorrect option is 2: Female Guinea Pig

Similar to the male, the Female Guinea Pig is entirely non-venomous and non-poisonous. The biological distinction of producing venom is not sex-dependent in this species; neither males nor females of the *Cavia porcellus* species carry or inject any form of biological toxin. They are docile social animals whose defense mechanisms rely on their hearing, speed, and seeking shelter, rather than chemical warfare. Therefore, based on established zoological classification, the female guinea pig cannot be considered a poisonous mammal.

The incorrect option is 4: Female Ornithorhynchus

While the female platypus belongs to the same venomous species as the male, she does not possess the functional venom apparatus in adulthood. Female platypuses are born with small spurs on their hind legs, just like the males, but these spurs are generally lost before they reach one year of age and are not linked to a functional venom gland. Consequently, the venom-producing and injecting capability is a trait exclusive to the adult male platypus, making the female incapable of delivering the toxin. Therefore, only the male of the species is correctly classified as a venomous mammal.