He's asked DoC, which manages the land up to the saddle, to install a toilet, and expects an answer by the end of next month.
"How would you feel if people were going to the loo on your property?
"We're custodians of this part of the high country, and we take our responsibilities to look after that seriously."
Perhaps surprisingly, he doesn't blame the walkers for taking a dump on the station's land.
"If you're going out for a five-hour walk, people can be expected to need to use the toilet during that time.
"If there are no facilities, or they're in the wrong place, then people have no option.
"There's probably an expectation for a popular, busy walking track that there will be toilet facilities."
Foster first noticed the issue about three years ago, and says it's getting worse as more people walk the trail.
He reckons the best location for a loo would be just below the saddle, on the Queenstown side.
About an hour's walk from the top of the Skyline gondola, "it's where everyone stops and catches their breath and takes in the view".
DoC senior ranger Susie Geh confirms it's looking at putting a self-contained toilet on the saddle, "but the reality is this has to be weighed up against visitor facility demands elsewhere".
Although DoC acknowledges the pressures from the increasing numbers, it says visitors need to behave responsibly in the outdoors.
As well as doing their business before setting out on the walk, people can take a "pocket toilet" waste bag, available from DoC's visitor centre, Geh says.
Or they can pack a compostable bag and "poo pot or poo tube" to take their number twos to the next long-drop or composting toilet.
Queenstown resident John Presto says his photo of a pile of human faeces near Ben Lomond's summit shows a toilet's badly needed.
He snapped the shot during a walk up the mountain with family members during the New Year break, and says it "paints a thousand words".
The resort's exponential growth and tourism boom is "fast turning a once beautiful and pristine corner of the world into another Venice or Barcelona", Presto says.
Clutha-Southland MP Hamish Walker says DoC needs to act and install the toilet as soon as possible to "future-proof the track and protect the natural environment".
But Federated Mountain Clubs southern convener Peter Wilson told the Otago Daily Times last month DoC is "hard-pressed" financially and, instead, Queenstown's council should apply to the Government's tourism infrastructure fund to install the toilet.
Council spokesman Jack Barlow, though, told Mountain Scene it was DoC's issue.
-Mountain Scene
