This post is part of the LTER’s Short Stories About Long-Term Research (SSALTER) Blog, a graduate student driven blog about research, life in the field, and more. For more information, including submission guidelines, see lternet.edu/SSALTER
by Eric Lyons, graduate student at the Hubbard Brook LTER
Let’s paint a picture. You’re enjoying a nice day by the water. The sun is shining, the birds are chirping, and the trees are gently swaying in the wind – all the makings of your typical summer afternoon. Suddenly, you notice a man in the distance waving around what looks to be a metal detector. It beeps loudly, and he stops what he’s doing and starts excitedly digging into the rocks. You think you’ve seen this a hundred times before, expecting him to pull out a bottle or a can or maybe even that ring that someone dropped. But instead, he stands up holding a bright orange salamander. You’re not at a beach, you’re in a stream in the White Mountains of New Hampshire. Welcome to my field season at the Hubbard Brook Experimental Forest.
Credit: Eric Lyons, CC BY-SA 4.0.
Why Salamanders?
So why salamanders? It’s almost always the first question I get when I tell people about my research. Just like every sports fan will tell you about how underrated their favorite player is, I tell them how salamanders are a really underrated part of the ecosystem. For one, there are a lot more of them than you think. A study at Hubbard Brook in the 1970s found that if you added up the combined weight of all the salamanders in the forest, they would weigh twice as much as all the breeding birds put together. Second, no stream food web is complete without them. Fish rely on salamanders as a key part of their diet and often compete with larger salamanders for insects and other food resources in an area. But what you might not know is that when fish are absent, as is relatively common in small streams, salamanders are the top predator. And last, but certainly not least, salamanders can tell you a lot about the health of a stream. As amphibians, they often need suitable habitat in both land and water. They tend to be very sensitive to changes in either habitat but can live for an extremely long period of time in good quality habitat. So, if you see salamanders in an area, it is a pretty good indication of a healthy stream.
Older Than My Field Assistants
Credit: Eric Lyons, CC BY-SA 4.0.
What do I mean when I say they can live for a long time? Well, the species that I study, the northern spring salamander, can live for more than 20 years, which means that we have caught salamanders older than my field assistants. And what’s even stranger is how little they move. Their home range is only about four meters long, and around 70% of them never leave that little box. But every now and again, a salamander that has spent his entire decade in the same spot will decide he has had enough and disperse to a new habitat up to a kilometer away. My research is mainly focused on figuring out exactly why that happens. What causes a salamander to disperse?
Tagging and Tracking
Credit: Eric Lyons, CC BY-SA 4.0.
To know if a salamander dispersed, we need to catch it and be able to identify it later. As any good herpetologist will tell you, in order to catch salamanders, you need to start flipping rocks. And so we do – thousands of them in fact. When we catch one, we insert a small radio chip known as a PIT tag in its side. These tags all have a 15-digit ID number that can be read with a radio scanner. When we go back out for our next survey, we can scan the captured salamanders like barcodes to figure out exactly which one we’ve caught and compare its current location to its last known location. Spoiler alert: it is usually exactly the same location. This is where our “metal detector” comes into play. But instead of scanning for metal, we use it to scan for the radio signals given off by those PIT tags. See, the salamanders aren’t particularly active during the day and will often burrow underground to hide from predators (or biologists). By using this equipment, we can find them even when they are not actively moving around, allowing us to map out their movement patterns over an entire summer. Of course, we still search for the salamander once we detect it, both to prove it is alive and to measure how much it has grown. The biggest difference is in the efficiency of the surveys and the probability of catching any one individual. Rather than randomly flipping rocks and hoping to find salamanders, we can instead know exactly which rocks to flip and exactly which salamanders are under them.
Now What?
Credit: Eric Lyons, CC BY-SA 4.0.
Using these methods, we can now figure out exactly when a particular individual dispersed and compare the various environmental conditions in its new habitat versus its old habitat. Did it move to a nicer neighborhood, or not? The effects of ongoing climate change seem to be particularly devastating for amphibians, with as many as one in three species currently at risk of extinction. Monitoring their dispersal behavior allows us to figure out not only where these species are now, but also where they will likely go in the future, allowing us to make informed management decisions and protect key habitats before it is too late. So, the next time you see someone in the woods with a metal detector on their back, stop by and say hi. You might just get to meet one of those salamanders for yourself.
Eric Lyons is a 4th year PhD candidate in Dr. Winsor Lowe’s lab at the University of Montana. His research, conducted at the Hubbard Brook LTER, focuses on the movement and survival of salamanders within the forest. Outside of science, he loves spending time outdoors and is an avid sports fan. Reach out to eric.lyons@umontana.edu with any questions or to learn more!
