I'll try to summarise it here...
I took some more photos this morning to better illustrate what I have been trying to explain.
This animal crosses my property ,probably only at night, very regularly. (several times per week not per day)
poops on the trail , never outside it, so makes me think that he is just in transit.
The poop is always the same, it has been for almost one year.
The first photo is to show a typical spot. It is the rim of the ditch that crosses my property above the dam (dug in 1862 by Chinese gold miners..)
The next shots are of a fresh one, from last night/this morning.
It is the same ditch about 50m away from the first poop. There are others there (one can be seen at the top left of the second photo, about 2 weeks old) but NOT from the same night. Only one poop per night.
Digging into the poop reveals nothing to me, no traces of anything , looks to me that he just eats grasses.
It is very soft but, again, it has been doing them exactly like this for almost a year .