Posted by: Rob Viens | November 5, 2012

The Owl and the Viscacha

On Sunday Darwin went sight-seeing around Buenos Aires – enjoying the rich history of the city.

“Walked into several of the Churches & admired the brilliancy of the decorations for which the city is celebrated.— It is impossible not to respect the fervor which appears to reign during the Catholic service as compared with the Protestant.— The effect is heightened by the equality of all ranks.— The Spanish lady with her brilliant shawl kneels by the side of her black servant in the open aisle.—

I visited the Museum, which is attached to the only remaining convent; although esteemed as second to none by the inhabitants it is very poor. In the evening went out riding with Hamond; we saw the first starting of a troop of waggons for Mendoza.” (Nov 4)

On Monday, November 5th, Darwin continued his excursions on horseback with Robert Hamond.

“Rode about 6 leagues into the camp to an English Estancia.— The country is very level & in places from Willows & Poplars being planted by the ditches much resembled Cambridgeshire.— Generally it is open & consists either of bright green turf or large tracts of a very tall Sow-thistle (8 or 9 feet high).” (Nov 5)

Along the way he discovered the holes of burrowing animals (called viscacha) which had a reputation for “tripping-up” horses and causing them to throw their riders.  He notes:

“Even the very roads were burrowed by the viscacha.— This animal is nocturnal in its habits; in structure it is allied to the Cavies, having gnawing teeth & only three toes to its hind legs; it differs in having a tail.— The holes made by this animal yearly cause the death of many of the Gauchos.— As Head mentions, every burrow is tenanted by a small owl, who, as you ride past, most gravely stares at you.” (Nov 5)

As Darwin noticed, these holes were excavated by viscachas – a type of rodent.  If you ignore their long tail, most people would probably think these animals were rabbits. But in fact, they are much more closely related to chinchillas (Family Chinchillidae) wereas rabbits are in the Family Leporidae.  And rabbits are not rodents, they belong to their own Order of life (along with pikas) – called the Lagomorpha.

Southern viscacha (Wikipedia Commons)

viscache

In this region, the viscacha that Darwin encountered were probably the plains viscacha (Lagostomus maximus). There are four additional species, but they all seem to prefer mountainous regions (so it is unlikely they would be found near Buenos Aires). The plains viscacha are the largest species of the genus, growing to upwards of 20 pounds (~9 kg).

Plains viscacha (Wikipedia Commons)

viscache

Viscacha live in colonies, collectively building complex, shared tunnel systems – the very tunnels Darwin was stepping on in his excitement to discover something new.) In general, the colony takes care of its members – sharing foraging regions and alerting others when they spot a predator.  They seem to fill the same role as prairie dogs in North America and meerkats in Africa.

When the viscacha abandon their burrows, other species take advantage of all their hard tunneling work, and move into their burrows. One of these that Darwin observes are burrowing owls – Athene cunicularia – a species found throughout the Americas. These owls often hunt in the hours of dawn or dusk, and are particularly fond of “live” prey including insects, spiders, small reptiles and small mammals.

Burrowing owls from Venezuela (from Wikipedia Commons):

burrowing owls

Interestingly the Genus name comes from the Greek Goddess Athena who was often depicted with an owl.

Coin from 400-500 BC depicting Athena’s owl (from Wikipedia Commons):

viscache

Tomorrow Darwin checks out the ladies…you don’t want to miss that 🙂 (RJV)

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