JACKSON, Wyo. — Grand Teton National Park (GTNP) boasts a number of summer swimming spots, but people won’t be the only ones in the water; leeches are present in most water sources throughout the Park and Jackson Hole.
National Park Service (NPS) biologists confirm that leeches are found during amphibian surveys, often swimming on their own or attached to frogs and salamanders, but not much additional information is known about them in GTNP.
Classified as aquatic worms, NPS biologists tell Buckrail that leeches occupy roles as prey, predators and parasites in wetland ecosystems, providing important food for birds, snakes, amphibians, fish and other invertebrates. While leeches are most frequently found in muddy and silty waters, like Two Ocean Lake in GTNP, leeches also occupy String, Jenny, Phelps and Jackson Lakes as well.
Willem Aspinall, Snake River Angler shop staff, tells Buckrail that Jackson Lake, Jenny Lake and Phelps Lake are top places to use leech flies while fishing, as fish species recognize leeches as a familiar and attractive food source.
“There’s so many of them,” Aspinall says of leeches. “We’ve got a whole box of leech patterns that we use, and we run out of leech flies in the shop” due to their effectiveness.
Jackson Hole Fly Company (JHFC) says on their website that leech-inspired flies are popular for every season, since leeches are such a common occurrence in the area.
“It’s always leech season.”
Jackson Hole Fly Company
“Whether you are fishing in winter or summer, in high or low water, it’s always leech season,” JHFC writes.
According to JHFC, leeches are most likely found in deeper waters during the day and shallower areas at night due to their light and heat sensitivity.
NPS biologists say that amphibian field crews are generally not worried about leeches, simply pulling them off fingers or gear. But they do recommend wearing waders rather than bare feet in especially muddy, silty waters.
Anna Phillips, research zoologist and the Smithsonian’s Curator of Clitellata and parasitic worms, is a driving force behind highlighting this often overlooked species and advocating for less fear around leech bites. In an interview with Smithsonian Magazine, Phillips likened leeches to mosquitoes in how they come up to a person, attach, take a little bit of blood and then leave.
In fact, leech bites are actually less dangerous than a mosquito bite; mosquitoes can transmit infectious diseases that include malaria and West Nile, but so far researchers don’t believe leeches carry any human illnesses.
“Mosquitoes are far scarier and more deadly than a leech will ever be,” Phillips tells Smithsonian Magazine.
However, burning or salting a leech that has latched onto a human can create a risk of infection for that person, due to the regurgitation of bacteria in their intestines that help them digest blood when salted or burned. This regurgitation can also include digestive tract contents and microbes that can go directly into a wound. Phillips confirms that the most effective removal method is to pull either end of the leech where its suckers are attached and break the seal.
