After 3 weeks of promising me that I would get to go to Laguna Esmeralda (one of the most popular tourist hikes near Ushuaia) to collect environmental DNA samples from a beaver pond, my collaborators finally took me there on Thursday. The previous attempts to go had been canceled due to 1) a broken truck, 2) weather, and 3) lack of available institution vehicles, but the stars finally aligned and gave us a cloudy, but rain-free day, and a working, available truck.
The fieldwork we set out to do is not related to my project here. For my work, all of the samples were collected back in 2016-2018, during a pilot project to test the efficacy of eradication for beavers in 7 watersheds around the island. From that project, there are about 800 samples, of which I’ll use ~475. Instead, we were aiming to collect environmental DNA at different distances from an active beaver lodge, with the idea of testing at what distance beaver DNA can still be detected. My collaborators, Sebastian and Julieta, wanted an active beaver lodge that didn’t have any other lodges upstream of it, in order to isolate the impact of a single lodge, and there is a lodge located just upstream of Laguna Esmeralda that they thought would serve well.
In addition to the three of us, we were accompanied by a man named Julio who worked as a field technician for the Centro Austral de Investigaciones Cientificas for 41 years, before retiring a couple years ago. He’s seen many beaver researchers come and go and has helped more than a few of them with the fieldwork for their projects. Despite being 68 years old, he has not slowed down at all – literally. Sebastian, Julieta, and I were sucking wind trying to keep up with his speed. The trail was extremely muddy – we were slipping and sliding, while Julio was marching along with his hiking poles, running up hills just to prove he could.
On our way up to the Laguna, Julio pointed out old beaver ponds, new beaver ponds, which ones were currently active, and which ones were not. In addition to looking for signs that are familiar to me – things like recently cut trees or fresh branches on the dams, he had a new one for me. As we stood next to one dam, looking upstream, he pointed out how widespread the impact is. Not only are trees impacted in the inundated areas, with many dead or dying snags sticking out of the water, but the trees on either side of the pond can show signs of beaver impact as well. If the forest is open, with a few branches, such that you can see the trunk of one tree behind another tree, beavers are in the area. A healthy forest wouldn’t be so see-through, and if young trees are starting to fill in those gaps, the beavers probably aren’t active (as they would be eating the young trees).
Chatting with Julio was a delight – and also the only way to get him to slow down enough that he didn’t disappear into the distance. He reminded me of Deb, the amphibian monitoring field crew lead who retired a couple of years ago after 15+ years of monitoring. Two retired biologists who can kick my butt in the field while schooling me on my study species.
Collecting samples was a breeze – because I didn’t have to do it! We ended up collecting fewer than planned, as there wasn’t enough distance between the active lodge and the Laguna to collect as many as Julieta had thought. And…we didn’t have to filter them in the field! One of the most exhausting things about collecting eDNA samples during my fieldwork last summer was sitting with a hand-held brake bleeder, pumping the water through the filter. Here, they just hiked back out with the water to filter it later in the lab - and thankfully for our backs we weren't carrying the 15 liters initially planned!!
Some highlights:
The one downside from the day: absolutely wiping out in the mud while desperately trying to keep up with Julio.
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