On boarding the Beagle, Darwin found departure delayed until the beginning of December, so he returned ashore, hired a room and spent the rest of the month in Uruguay. Complete with passport, papers and a guide, Darwin set out to explore the Rio Uruguay and its tributary, the Rio Negro. Making slow progress, he arrived at Colonia del Sacramento:
“The distance is twenty leagues, through a fine grass country, but which is very poorly stocked with cattle or inhabitants. I was invited to sleep at Colonia & to accompany on the following day a gentleman to his Estancia, where there were some rocks of recent limestone. — The town is built on a stony promontory something in the same manner as M. Video.”
At Punta Gorda, Darwin went out riding on 20th November, hoping to find a Jaguar. He “saw very fresh tracks & the trees against which they are said to sharpen their claws: the bark was cut up & grooved by scratches a yard long” but did not succeed in disturbing one.
“The low, thick woods on the coast of the Uruguay afford an excellent harbour for such animals.”
Moving north to Mercedes, Darwin rode though dense acacia woods with high pampas thistles. He found some fragments of a Megatherium, but when returning via San Jose on 26th November, he purchased a perfect head of Megatherium for a few shillings. He reached Monte Video 2 days later, having crossed some 200 miles of the Rio de la Plata plains.