Mammals are not commonly associated with producing toxins, a trait more often found in reptiles, insects, or fish. While toxic mammals are rare, some species possess biological adaptations allowing them to produce and utilize toxins.
Clarifying Mammalian Toxicity
Understanding mammalian toxicity requires distinguishing between “poisonous” and “venomous.” A poisonous animal contains toxins within its body that cause harm when ingested, absorbed, or touched. In contrast, a venomous animal actively injects toxins into another organism, typically through a bite, sting, or spur. This injection usually serves for offense, such as subduing prey, or for defense. The mammal often cited as the “most poisonous” is actually a venomous one, delivering its toxins through a specialized mechanism.
The Solenodon: A Venomous Mammal
The solenodon is one of the few mammals known to produce venom. These nocturnal, shrew-like creatures are found on the Caribbean islands of Hispaniola and Cuba. The Cuban solenodon (Atopogale cubana) and Hispaniolan solenodon (Solenodon paradoxus) both possess a venomous bite. Their venom is produced in enlarged submaxillary salivary glands and delivered through grooves in their second lower incisors, allowing them to inject venom directly into their prey.
Solenodon venom is potent enough to subdue small prey, such as insects and small vertebrates. It causes a drop in blood pressure, paralysis, and can be lethal to smaller animals. These mammals primarily use their venom for hunting, quickly incapacitating prey. The solenodon’s reliance on venom for prey acquisition is linked to its high metabolic rate, requiring efficient hunting. Both solenodon species are endangered, facing threats from habitat loss and predation by introduced species.
Other Mammals with Toxic Capabilities
Beyond the solenodon, several other mammals exhibit toxic capabilities. Shrews, particularly certain species like the northern short-tailed shrew, Mediterranean water shrew, and Eurasian water shrew, are also known to deliver a venomous bite. Their saliva contains toxins, including proteases, which can paralyze and subdue prey such as earthworms, insects, and small mammals. While their venom can be painful to humans, it is generally not lethal.
The male platypus, a unique egg-laying mammal native to Australia, possesses a venomous spur on each hind limb. This venom, produced in femoral glands, is primarily used during mating season for competition between males. Platypus venom is known to cause excruciating pain in humans that can last for days or even months, and it does not respond well to typical painkillers. While not fatal to humans, it can incapacitate small animals.
Slow lorises, small primates found in South and Southeast Asia, also have a unique defensive toxin. They produce a secretion from brachial glands located on their forelimbs. When mixed with saliva, this secretion becomes a venom delivered by their bite. The slow loris uses this venom for defense, and it can cause allergic reactions in humans, ranging from swelling to anaphylactic shock. The patterns on their fur are thought to mimic the appearance of cobras, potentially deterring predators.