Posted by: Rob Viens | August 14, 2013

Riding Among Agoutis and “Villainous Banditti”

Over the next few days, Darwin traversed the pampas with his traveling companions – working his way toward Bahia Blanca via the Rìo Colorado.

“The country continued the same. — it is inhabited by very few living beings: the most common is the hare or Agouti, there are likewise some Ostriches & Guanaco. — We passed the second well, the water of which is brackish, but I think chiefly with saltpetre. — We found a good place for sleeping, the water was however so scanty that we could not take Mattee before starting the next morning. — The Gauchos when travelling only eat twice in the day, at night & before daylight in the morning; by this means one fire serves for 24 hours; an object of great consideration in many parts of this country.” (Aug 12)

The agouti is actually not a hare, as Darwin suggests, but a type of rodent (related to guinea pigs/cavies). Exactly which type of agouti he saw is not as obvious as it may sound.  Historically there were several types of rodents in the New World that were called agoutis. Ruling out acouchis (found only in the Amazon rain forests), there are two possibilities that Darwin might have encountered – the Common Agouti and the Paca. Both have a similar build and are about the same size (averaging about 2 ft (~60cm) in length. But there are some differences.

  1. Pacas have a long tail and common agoutis do not (the tail adds another 5-9 inches (~10-20 cm) to the length of the paca)
  2. The lowland paca (Cuniculus paca) – the species that could be found in Argentina – is spotted. The agouti is solid brown, black, grey or reddish.
  3. Typically the paca is found in the forest, and although it can come out into the open, it generally does not do so during the day (when Darwin was likely to see it). The common agouti is much more likely to be found in grasslands, and to be active during the day.
  4. Pacas are “meatier” with an average weight of about 20 pounds (~10 kg).  Agoutis are about have half that weight.  That puts both in the range of a medium to large house cat (with pacas being more in the range of a big Norwegian Forest Cat or Maine Coon). Meatier may be a good description, as pacas have been suggested as a good form of protein for humans.

Based on these differences, I’d suggest Darwin was observing a common agouti – specifically (based on distribution) a species called Azara’s agouti (Dasyprocta azarae).

Azara’s Agouti (a species found in Argentina) – from the 1876 Proceedings of the Zoological Society of London

azara agouti

Lowland Paca in Costa Rica (from Wikipedia Commons)

lowland paca

For more on rheas (Darwin’s ostriches) and guanacos (New World camels) see A Wish for Wing that Work and The Guanaco Family Tree.

On the 13th, Darwin was in sight of the Rio Colorado, where General Rosas’ base of operations was located. I’ll wrap up today with his colorful diary entry describing the places, plants, and people he encountered that day as he approached and then entered the military camp:

“Our distance was not more than 3 leagues from the R. Colorado; we soon left the desert sandstone plain & came to one of turf, with its flowers clover & little owls, the usual characteristic features of the Pampas. We passed a muddy swamp of considerable extent, which is occasionally overflowed by the Colorado. – It is a Salitràl that in summer is encrusted with saltpetre & hence is covered with the same species of plants which grow on the sea beach. —

We then arrived at the Colorado. The pass is about 9 leagues in a direct line from the mouth, but by water it is said to be not much less than 25. — Its width here is about 60 yards generally it must be once & half as wide as the Severn at Shrewsbury. The tortuous course of the river is marked by numerous willow trees & beds of reeds. — We were delayed crossing in the canoe by some immense troops of mares, which were swimming the river in order to follow the march of a division of troops into the interior. Mares flesh is the only food of the soldiers when thus employed. This gives them a very great facility in movement; for the distance & length of time horses can be driven over these plains is quite surprising. — I have been assured an unloaded horse will travel 100 miles for many days successively. —

The encampment of General Rosas is close to the river; it is square of 3 or 400 yards, formed by waggons, artillery, straw huts &c. — The soldiers are nearly all Cavalry. I believe such villainous Banditti-like army was never before collected together: the greater number of men are of a mixed race, between Negro, Indian & Spaniard: I know not the reason, but men of such origin seldom have good expressions. — I called on the Secretary to show my passport; he began to cross question me in a most dignified & mysterious manner. — By good luck I had a letter of recommendation from the Government of B. Ayres to the Commandante of Patagones. This was taken to General Rosas, who sent me a very obliging message & the Secretary returned all smiles & graciousness. — We took up our residence in the Rancho or hovel of a curious old Spaniard, who had served with Napoleon in the expedition against Russia.” (Aug 13)

(RJV)

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