I sometimes take lunch off to go for a run around campus. Not hiking, I know, but I could do some urban hiking, I suppose. I kind of have more leeway to take my lunch time when I want to since it is my lab... I make the rules.
The gym isn't too far from my office and they have lockers and showers there that faculty and staff can use for free.
Actual hiking or any other activity that takes more than an hour is usually relegated to the weekends or a holiday off work. I am looking forward to taking my 18 month old son on hikes this spring (him in a backpack). There are some great places within an hour or so of home. I might even try him out in our tandem kayak on the gentle river that runs behind our house.
Other ideas for incorporating more physical activity into your day:
I gather that you are a scientist working on a college campus. If it is set up like my labs, you might be in a multi-level building. Use the stairs at each end of the building to get in a quick workout. Whether it is coming back from the bathroom, or just on a short break from your bench work. Go out of your way to the far end of the building, take the stairs all of the way to the top, back to the other end of the building, then all the way down. You can make a circuit of this, or just do it once per time out of the lab.
If you've got an office or semi-private space, get up from your chair do some quick air squats or lunges. Even some dips on the arms of your computer chair if that works for you.