A Carnivore's Contradiction
The Aguará Guazú, or Maned Wolf (Chrysocyon brachyurus), is South America's largest canid, standing up to 110 cm at the shoulder. It is a distinct species, belonging to its own genus, Chrysocyon, meaning "golden dog." Despite its common name and fox-like appearance, its diet is surprisingly omnivorous. Field studies based on scat analysis consistently show that plant matter makes up about half of its food intake. One study found vegetable material accounted for 50.5% of the total dietary mass. Another analysis of 397 food items identified 54% as plant-based.
The other half of its diet consists of small animals. The Maned Wolf is a solitary hunter, and its long legs are an adaptation for navigating the tall grasslands of its habitat. It stalks and pounces on prey like a fox. Its typical animal meals include small mammals like rodents and armadillos, as well as birds, reptiles, and insects. Unlike true wolves, its teeth are adapted for this varied diet; the upper carnassials used for shearing meat are reduced, and its molars are suited for grinding plant material. This flexible, opportunistic feeding strategy allows it to thrive in the savannas and wetlands of the Iberá Marshes.
The Wolf Apple Connection
The cornerstone of the Maned Wolf's plant-based diet is Solanum lycocarpum, a relative of the tomato and eggplant, commonly known as the "wolf apple" or fruta-do-lobo. This fruit can constitute between 40% and 90% of the Maned Wolf's entire diet, consumed year-round. The large, yellowish fruit weighs between 200 and 900 grams and is filled with soft, aromatic pulp.
The relationship between the canid and the plant is an example of mutualism. The wolf consumes the fruit and, as it travels across its large territory, disperses the seeds in its feces. Passage through the wolf’s digestive tract dramatically increases the seeds' chances of sprouting. One study found that seeds collected directly from wolf apples had a germination rate of less than 1%, while seeds from Maned Wolf scat had germination rates as high as 62%.
Maned Wolves often defecate on the nests of leafcutter ants. The ants use the dung to fertilize their fungus gardens but discard the seeds in their refuse piles, which are full of nutrients and protected, further boosting germination success. The wolf apple, in turn, may provide a health benefit to the wolf. It is widely believed that compounds in the fruit, such as the glycoalkaloids solamargine and solasonine, help protect the animal from the giant kidney worm (Dioctophyma renale), a parasite that is often fatal.