Ant rafts

The littoral of the Paraná and Uruguay rivers, forming the River Plate, has been the target of bad weather of late. We have had no sunshine for about ten days and we have suffered a tornado in the city of Dolores, located in the Soriano department -Uruguay- 100 km North of Carmelo. We had had very heavy rains in the region that, luckily, a couple of days ago have stopped and now we have sunny and cold weather.

Rains have caused havoc among people living in low areas that needed to be evacuated to refuges in order to survive while their houses were flooded and their personal effects damaged. Apart from affecting the population, the rains have damaged crops (estimates in Argentina are of about several million hectares!).

There has also been severe damage to roads and bridges that has resulted in the (relative) isolation of our town of Carmelo (Uruguay) for a couple of days. Luckily today the main roads are all passable again. Well, not all of them. The Víboras[1] stream cut the No. 21 route that connects Carmelo to the North of Uruguay via Nueva Palmira at a spot located 10 km from Carmelo.

A bridge dating from 1858 known as the “Camacho” bridge or the “Castells” bridge spans the Víboras stream. Jaime Castells made use of the watercourse to build a hydraulic mill to grind grain and he got permission to build the bridge on condition that it financed itself. This was the reason for it to become the first toll station of Uruguay. The bridge with its five stone arches is a pioneer of this building style in the country and it was declared a National Historical Monument in 1975.

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The Castells bridge photographed in the 90s.

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A view of the lovely setting near the Castells bridge in the 90s.

The news that the Víboras stream had cut the road spread like wildfire and rumours about what had taken place abounded. It was time to investigate. Driving there it was clear that the road had suffered the impact of the rain as the number of potholes had dramatically augmented!

The temporary Stop signs prior to the arrival to the bridge made us fear the worse and we were not wrong. The stream had dug a large trench on the road and taken down a few rather large trees! However, the bridge was intact, at least to the naked eye as the cut had taken place before the bridge!

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The stream cut the road before the bridge that can be seen towards the back in the centre of the picture.

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The bridge appears still intact!

Other roads were also damaged in Carmelo, including the very popular road to the beach where a trench was dug by the Municipality to drain a flooded suburb. We could appreciate the damage during one of our morning walks today, the second day of sunshine.

Apart from the road damage there was also a lot of standing water that will take a while to drain away as the rivers are still carrying a lot of water. It was while watching one of these new “lakes” that we noted some small brown floating bodies that we took for flotsam.

A better look indicated that there was some “vibrating” movement in the flotsam! It was alive and in fact these masses were made of several thousand ants.

Although we had not seen this phenomenon earlier, a quick look in the Internet indicated that it is a common event, well documented for the fire ants Solenopsis invicta in North America. I learnt that the ants link their bodies together to build these true waterproof bodies that are able to repel water through some miracle of physics and that can float for days without trouble, until the water recedes and they can reconstruct their lives!

The ants’ movement would suggest that this behaviour is a cooperative effort and that ants rotate from the more risky (wet?) periphery to the better guarded interior of the mass. I imagine that in this “wet socialism” lazy members of the society would be cast away?

 

[1] The name of the stream means “Snakes” in English.

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