Lake Buenos Aires / General Carrera, (46°28’ S, 71°34’ W) is shared by Argentina and Chile, and is the second largest lake in South America after Lake Titicaca. It has a surface area of 1.850 km2 (715 sq. mi).
It is a deep windswept body of water that flows into the South Pacific Ocean, 140 km (87 mi) long and 24 km (15 mi) at its widest point.
In 1899, Doctor Santiago Roth of the La Plata Museum wrote that his Tehuelche guide, chief Kánkel had told him a story that he had heard from his grandfather about a “very fierce animal at Lake Buenos Aires […] it was very dangerous to go close to it. He described it saying that when it roared all the animals ran away and that once when he was hunting ostriches [ñandú – Rhea americana] close to the lake, it had killed a whole troop of horses”.
He went on to remark that as the natives were very superstitious he paid no attention to the story until he noticed that Kánkel was terrified of going near
the lake; Roth finally forced him to go, but even so, he could not get him to go closer than 1 km [0.6 mi.] from its shores.
Roth believed that the beast was an Iemisch[*] that the natives of his time only knew about through their folklore. When he asked if they have seen the creature they would reply “no, but I have been told by such and such an Indian or chief who has seen it”.
[*] Iemisch: is a mythical aquatic creature said to live in Southern Patagonia. See our post on Iemisch.
Kánkel’s tribe camped at Senguer River just 160 km (100 mi) north of the lake. This river was also home to another terrible creature (or maybe the same one): Muster’s water tiger.
On the Chilean side, where the Lake’s name changes to General Carrera, in 2009, two locals reported “seeing the ‘lake monster’ again”. Apparently it was first sighted at the “Catedrales de Marmol”, a rock formation on the lake’s northern shore close to Puerto Tranquilo after Hudson Volcano’s 1991 eruption.
Another local, named Lautaro reported that after hearing splashing sounds in the lake, saw “a mysterious creature, about six meters [18 ft.] long […] it looked like a serpent […] had smooth skin in the front part of its body and with scales on its tail”.
 Hauthal, R., Roth, S., Lehmann-Nitsche, R. (1899). El mamifero misterioso de la Patagonia, Grypotherium domesticum. Revista del Museo de La Plata, v. ix. pp. 445.
 Irles L., (2009). El monstruo del Lago general Carrera. It has photographs (Spanish language blog) With my special thanks to Mr. Luis Irles.
Copyright 2009 by Austin Whittall ©