Aquatic habitats – lakes, rivers, and even oceans – are surrounded by terrestrial environments. The study of aquatic ecology often involves a close look at how the terrestrial landscape affects bodies of water; for instance, a researcher might explore the pathways taken by nutrients from decomposing leaves as they wind their way through a river food web. This kind of inter-biome influence isn’t a one-way street – organisms that live on dry land are impacted by aquatic ecosystems, too (picture a grizzly bear feasting on salmon returning from the ocean, for example).
In a recent study published in The Canadian Field-Naturalist, researchers from the University of Alaska Fairbanks report a detailed account of two members of a terrestrial species, the Canada lynx, repeatedly crossing the Tanana River, a glacially fed river with channels and sloughs that range from 50 to 1,000 feet wide in the location studied, near Fairbanks, Alaska.*
Canada lynx typically weigh between 18 and 30 pounds – about the size of a large beagle. The scientists found that one of the GPS-collared lynx swam across the river at least 51 times between September and November, a window of time just before freeze-up when the water temperature dips down to near freezing and the air temperature can reach well below zero degrees Fahrenheit. The other lynx swam across at least 34 times.
As the researchers point out, “we can only speculate as to why these individuals swam across the cold river.” However, they suggest that a hunt for prey is a plausible explanation. Canada lynx depend on the snowshoe hare as their primary food, and lynx population numbers closely track those of the hare in a well-known pattern. The researchers report that the local snowshoe hare population plummeted the previous fall; perhaps the lynx were willing to take a plunge into the cold, swift waters of the Tanana in search of a suddenly more scarce meal.
The extreme athletic endeavors of these lynx can serve as a reminder that terrestrial and aquatic ecosystems are entwined in innumerable ways, from leaves falling into rivers to lynx swimming across them.
* I earned my MS in the same department where these researchers work, but I don’t know them personally and was not involved in the research reported here.