One of the great things about doing fieldwork is that in addition to the focus of your visit you get to learn and see many new things. Currently I have been in Bolivia as part of a Darwin Initiative project to promote sustainable Inga based agroforest techniques with local farmers, so being in the Amazon forest, this is probably more so.
While introducing ourselves to one of collaborating community, Motucusal, in a cleared area of forest that serves as their meeting room we noticed a really strange phenomenon that none of us, including our hosts, had seen before. It was a small swarm of ants swirling around a small group of their own in a clockwise direction at speed (see the film below).
At first we thought that they could be protecting an entrance hole to their nest, or invading somebody else's nest, but on disturbing them there was no hole and they returned to what they were doing straight away. So, as far this botanist goes, it's still a complete mystery.
Completely by chance the next day, visiting the community of Palacios we several swarms of tadpoles in a large lake by their village. Again it is not really clear what they are doing but it looked as if they were skimming the surface, maybe for food?
A swarm of tadpoles in a lake at Palacios
And below is another phenomenon well known for the Amazon, white and black water rivers. Black water rivers are those where all of the water is derived from the Amazon basin itself, the water aquiring a dark tea-like colouration as a consequence of the tannins it absorbs as it filters through the leaf-litter. In a way the Amazon is a bit like am enormous tea-making facility! White water is rich in sediment derived from the weathering of the Andes and is an opaque white-coffee to orange-brown colour. This phenomenon means that wherever you are you can tell whether a river derives solely from the Amazon basin or whether it also includes water from the Andes, an incredibly powerful but simple tool for any biogeographer (which I am not). Below you can see what happens where the two mix, over several hundred metres to kilometres you get two parallel streams of dark and white water which mix very slowly. The slowness in mixing is in part because each water is at a different temperature: white water reflects more energy from the sun whilst black water absorbs it.
Mixing of white and black water rivers at the head of the Orthon river