How giant anteaters duke it out


Two giant anteaters fight it out. On the left, the individuals lash out at each other with their enormous claws, and on the right they posture at each other (with the dominant animal, with the upright and puffed-out tail, on the right). From Kruetz et al 2009.

In the northern state of Roraima in Brazil, small plantations of the black wattle tree (Acacia mangium) serve up plenty of food to carpenter ants and other insects, and the variety of six-legged pests has attracted numerous giant anteaters. The trouble is that these immense xenarthrans don't typically get along very well.

As described in a brief report by Kolja Kreutz, Frauke Fischer, and K. Eduard Linsenmair in the journal Edentata, on December 5, 2005 Kreutz was observing a foraging anteater when the animal stopped in its tracks for a moment before bolting away. This was very unusual. When they perceive a threat, giant anteaters typically scent the air first before shuffling off, but this one just started running.

The reason why soon became clear. The first anteater began chasing a second through the stands of acacia trees, running a distance of almost two kilometers before stopping to grapple in a more open area. As observed by Kreutz, each anteater tried to pin the limbs of the other while slashing at sensitive areas with their free claws, and when they briefly disengaged from their bouts it was immediately apparent which was the dominant animal. The animal Kreutz had originally been observing, with its tail puffed out and carried high, was the dominant individual, while the pursued animal crouched in fear. When the fight ended, both bloody and battered anteaters walked away.

This was not like the previously-reported fights between giant anteaters. A report published in the same journal in 2006 described a more ritualized encounter, not an all-out brawl in which both animals sustained significant injuries. What might account for this difference in behavior?

It is difficult to tell. Observations of giant anteater fights in the wild are rare, and the Roraima acacia plantations are different from the more open grassland habitats giant anteaters are commonly observed in. Might the increased density of anteaters, as well as their difficulty detecting each other through the more closed-in foliage, cause them to more frequently be surprised by each other and fight? At present this question must go unanswered, but hopefully further observations in Roraima will help scientists better understand the social habits of these large, heavy-clawed mammals.

Kreutz, K., Fischer, F., & Linsenmair, K. (2009). Observations of lntraspecific Aggression in Giant Anteaters (

Edentata, 8-10, 6-7 DOI: 10.1896/020.010.0107

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Having recently read Theodore Roosevelt's "Through the Brazilian Wilderness" I'm glad to know that giant anteaters still exist, that the good Colonel & his party didn't shoot them all. Roosevelt describes their behavior when beset by dogs. Apparently they could be pretty fierce.

By darwinsdog (not verified) on 19 Apr 2010 #permalink

Individuals may escalate contests if they are unable to assess their rival (or their own) competitive ability. In the absence of such a signal, these two individuals may be establishing social dominance through aggression, whereas the more 'ritualized' encounter might have occurred between two individuals with some knowledge of each other (or of some awareness of a trait advertising competitive ability, i.e. size, scent, etc.).

A few questions. Are dominant anteaters characterized by different scent? There might be a phermonal signal at play here? Any good references on anteater social behavior? From my understanding they are mostly solitary and understudied. Given the rarity that anteaters may encounter each other, such a 'quality-signal' might be important in rapidly assessing conspecifics fighting abilities.