Castleguard Cave recognized as a globally significant Key Biodiversity Area

Thanks to a sightless, translucent creature, Canada’s most famous cave is being recognized for its unique species and harsh ecosystem

  • Mar 28, 2023
  • 890 words
  • 4 minutes
Cavers traverse through a section of Castleguard Cave named "Holes in the Floor" on the way from Camp I to Camp II. (Photo: Christian Stenner)
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Deep inside Canada’s longest cave lives a tiny translucent creature found nowhere else on Earth. Smaller than a grain of rice, this shrimp-like freshwater amphipod crustacean is known as the Castleguard Cave Amphipod (Stygobromus canadensis), and it has somehow survived for millennia in an environment that is nutrient-poor, wet, cold and dark. The unique environment combined with the unique crustacean has led to the cave system being recognized as a globally significant Key Biodiversity Area (KBA). 

Castleguard Cave, located in Banff National Park, Alta., is a 21-kilometre-long limestone cave formed by glacial drainage from the overlying Columbia Icefield. Rugged, frigid and virtually inaccessible, it’s a terrain designed to excite only the most intrepid adventurers.

The entrance to Castleguard Cave in the winter. (Photo: Christian Stenner)
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“It’s a special cave with a pretty ancient landscape,” says cave researcher and Royal Canadian Geographical Society Fellow Greg Horne. “It has interesting features, including these invertebrates, and it’s the only cave known in the world that goes underneath glaciers and an ice field.” Horne has been visiting Castleguard regularly since the mid-90s. Horne has been working to study the cave and collect data on the unique cave system, including monitoring seasonal ice levels with waterproof cameras. “There are 100 different things you could study in the cave, so you pick and choose based on your own personal interests,” he explains.

Caving, he says, is a pursuit that envelopes science, exploration and research. “When you are exploring a cave that is newly discovered, part of the ethic of exploration is to survey the cave, so you are basically mapping it,” he says. “And because it’s a three-dimensional object, you can never see in one place. A map or survey is very critical to understand a cave.”

Isotopic dating of stalagmites and other features puts the cave at least 700,000 years old with an interior that has remained intact and ice-free. Cavers have also found highly unusual, nearly cubical “cave pearls,” one of only five known examples worldwide (cave pearls are small, glossy and usually spherical formations formed by a buildup of calcium salts that form concentric layers around a nucleus).

Amphipod Stygobromus canadensis inside Castleguard Cave. (Photo: Colin Magee)
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Isopod Salmosellus steganothrix inside Castleguard Cave. (Photo: Greg Horne)
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Horne says Castleguard was discovered by Europeans in the 1920s by a horse wrangler who stumbled upon the cave entrance while searching for his horses, though it was undoubtedly known to Indigenous Peoples before then. It wasn’t until 1967, however, that members of the Karst Research Group from McMaster University in Hamilton, Ont., began formal exploration. It was a  few years later, in the late 70s and early 80s, that researchers noticed tiny invertebrates crawling around in streams and pools.

Greg Horne installing signage inside Castleguard Cave. (Photo: Kathleen Graham)
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Within Castleguard Cave, two unique species have been identified: Stygobromus canadensis, the Castleguard amphipod, and Salmasellus steganothrix, another small, blind, freshwater, cave-dwelling crustacean. Both troglobitic species, these crustaceans only live in caves and have no eyes or pigmentation. “The fact that the amphipod is only found in that cave makes that lifeform special,” says Horne. “It’s rare and unique to that point.”

Researchers speculate that the Castleguard amphipod was present in the cave during the last ice age, when zero nutrients would be entering the area. “I think it can tell us something about survival in a very austere environment,” says Horne. “Some people would say it’s just some tiny little bug. Who cares, right? But it has evolved, and it’s maybe been in that landscape long before glaciers were covering the mountain.” Researchers still have many questions about the amphipod, from its lifecycle to how often it reproduces. The KBA designation will allow them to spend more time answering these questions.

Wildlife Conservation Society pushed for the KBA designation for Castleguard Cave, which is administered by Parks Canada. Although KBAs do not provide legal protection, they are important because they identify places where stewardship and conservation efforts are necessary. The KBA will also foster collaboration between experts, traditional knowledge-holders, citizen scientists and research groups to raise awareness about the unique species and ecosystems within the cave.

Since 1996, Horne has been confirming the locations of the amphipod within Castleguard but population sizes are challenging to determine. In 2007, 40 amphipods were counted, but then in 2021, there were only eight. “This is a creature that’s small enough to accidentally drink, and it wouldn’t even tickle your throat,” says Horne. “But just because you can barely see the thing doesn’t mean that it’s not important.”

In a world that is desperately trying to find life somewhere other than Earth, the existence of the amphipod provides insight into surviving in places with little to no nutrients. “Think about a species that can live on the leftovers before the last ice age covered the mountain,” says Horne. “If we found a creature like that on another planet or moon, oh my goodness. You can imagine it would make world news forever.”

Horne explains that he wants to raise awareness of the in unique lifeforms in caves for people who may be unaware or unable to access these isolated spaces. “It’s not a beautiful, sexy kind of animal,” he says. “But it deserves to live as much as anything else does. And it might have been around on this Earth longer than we have, so let’s cherish it.”


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