The Gran Chaco is a 250,000 square mile eco region encompassing parts of Bolivia, Paraguay, northern Argentina, and southwestern Brazil. The landscape consists of open palm tree savannah interspersed with thorn scrub on more xeric sites while riverine forests or marshes occur wherever there is water. The name Chaco derives from the Indian word Chacu, meaning hunting land. The name suggests various regional Indian tribes regarded the region as a neutral hunting ground, probably because the climate was too arid for productive agriculture. The region was rich in wildlife, nearly pristine, until 1970 when a major highway was constructed here. Since then, cattle ranches and irrigated lands have replaced much of the former hunting grounds.
Map of Gran Chaco ecoregion.
Like North America, the Gran Chaco lost its largest but slowest breeding species of megafauna at the end of the Pleistocene. There were 3 species of elephant-like animals–gompotheres, haplomastodons, and stegomastodons–living here until about 10,000 years ago as well as giant ground sloths, glyptodonts, pampatheres (a plant-eating giant armadillo), liptoterns (a primitive ungulate), horses, and saber-tooths. However, many of the smaller species of Pleistocene megafauna that became extinct in North America had close relatives still extant in the Gran Chaco region. The ranges of many of these species no longer overlap with each other because their populations have become fragmented following agricultural development, but an explorer traveling through the region prior to 1970 would have found a fauna very reminiscent of southeastern North America’s during the Pleistocene. Llamas shared the range with peccaries, 2 species of deer, and tapirs in the Gran Chaco, not unlike the faunal mix of southeastern North America which included 2 species of llama, 2 species of peccary, 3 species of deer, and tapirs.
A remnant population of guanacos, a type of llama, still occurs in the Gran Chaco region. Guanacos are still common in the Andes Mountains but have been largely extirpated from lowland regions.
The Chacoan peccary (Catagonys wagneri) is a close relative of the extinct flat-headed peccary (Platygonnus compressus), a species formerly common throughout North America. Scientists only knew the Chacoan peccary from fossil specimens identified in 1930, but then in 1971 western scientists “discovered” them to be still extant, though the natives were aware of their existence. This was like discovering an existing population of mammoths.
The Chacoan peccary is closely related to a species of peccary that lived in North America until about 11,000 years ago. Between 1930-1971 scientists thought they were an extinct Pleistocene species.
There are still many species of edentates in the Gran Chaco. The edentates were an important component of North America’s fauna during the Pleistocene. Several species of ground sloths, giant armadillos, pampatheres, and glyptodonts lived in North America then. The Gran Chaco still hosts 10 species of armadillos, tree sloths, and the giant eater whose raking claws resemble the formidable armament of the extinct giant ground sloths. The Gran Chaco is likely the center of armadillo evolution.
Giant armadillo (Priodontes maximus)
Giant anteater (Myrmecophaga tridactyla)
Genetic evidence suggests the pampas deer was formerly an abundant species found over a wide area of South America. Human hunting pressure has greatly fragmented and reduced the population of this species. Swamp deer live in marshy areas of the Gran Chaco as well.
Pampas deer (Ozotoceros bezoarticus). All South American species of deer share a common ancestor with North American white tailed deer.
Two important predators in the Gran Chaco, jaguars and cougars, roamed southeastern North America during the Pleistocene. The extinction of smaller species of megafauna limited the prey selection of the former, perhaps explaining its recent absence from much of the region. Studies show the prey items selected by jaguars tend to be larger than those chosen by cougars.
Jaguar and cubs in the Gran Chaco National Park.
The avifauna diversity of the Gran Chaco is astounding as well. There are over 400 species of birds native to the region, making it one of the richest bird watching sites in the world. The diversity of wildlife here suggests the region was sparsely populated by humans until very recently.
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