This species is a large relative of geese and shelducks but is distinct from both in a number of anatomical features and therefore is treated as its own subspecies. These birds are the largest African waterfowl and, on average, the world’s largest ‘goose’. Spur-winged geese are very fast flyers and can reach top speeds of over 130 kilometres per hour. The birds are highly territorial and have sharp spurs on their wrists, which are typically used to attack other spur-winged geese or other types of waterfowl. Some populations of these birds feed on a poisonous beetle and then sequester the beetle’s poison through their own tissues, making their flesh toxic. The beetles produce the toxin cantharidin, small amounts of which (as little at 10 milligrams) can cause death in humans, and therefore eating the goose can result in death.