While not uncommon in the mountains of Cumbria, these terrestrial cephalopods are rarely seen by climbers or hikers since they're able to change their color and texture to perfectly blend into the jumble of strewn moss- and lichen-covered rocks that characterizes their habitat:
As can be seen, they turn a ghostly white when dead, making them easier to spot. However, their bodies are usually eaten by carrion feeders before being noticed by humans. It was only because the litter crew was carefully scouring the area near the trails that they were able to find this one before a bird made off with it.
The Cumbrian rocktopus' main predator is the black puma, endemic to Cumbria, which prowls the lower elevations looking for rocktopuses foolish enough to venture down to the relatively lush environs of the Lakelands. It's theorized that the Cumbrian rocktopus' ancestors adapted to the harsh mountain climate in an attempt to escape these big cats.
Although they lack major predators at these higher elevations, the difficulty of their existence in the barren landscape -- eking out a subsistence on arthropods and discarded bits of energy bars left by hikers -- keeps rocktopus numbers in check.
Some environmentalists fear that global warming will upset this balance, causing an explosion in the rocktopus population -- much like we're seeing with the Humboldt squid in the Pacific. If this happens, rocktopus swarms undulating down the mountains will easily overpower any pumas standing in their way, and will quickly flourish in their new environment, leading to runaway rocktopus population growth until all of Cumbria is enswarmed in their tentacles.