by Dave DeGroot, Cohort 2, Feb. 23, 2022
I am fascinated by the 2,400-acre piece of raw desert northwest of Tucson called the Tortolita Preserve. The land is leased from the state by the town of Marana and its boundaries lie within the Marana city limits.
You could say that almost half of this huge piece of land – close to a thousand acres – is unexplored. The western 40% of the Preserve (shaded red in the map) lies outside of the Preserve’s well-known hiking and biking trails and beyond the utility road that most people mistakenly think is the western boundary. There are no good roads into this area. At present, this part of the Preserve is the domain of off-roaders, lots of cattle, and (illegal) target shooters. Few people even pay attention to the western border, let alone understand this area’s plants, animals, geology, and cultural history.
Ethan Fraijo and I are close to completing an amateur, preliminary biodiversity survey in the Preserve. Lately we have been stepping off the western boundary lines with a special topo map, a GPS device, compass and some temporary surveyor’s tape on tree branches, which we plan to remove later. When you add up the distance we are walking around the western border of the almost-thousand acres, it adds up to about 2 ½ miles, running through rough, trackless and virtually unexplored land.
Just a few of the interesting discoveries we have made in this western 40% of the Preserve include:
• …remains of an old aqueduct that channeled water from deep in Wild Burro Canyon eight miles to dam-like berms constructed by the U.S. Bureau of Reclamation (USBR) at the southwest corner of the Preserve. Yes, the USBR is the same government agency that is famous for constructing the Hoover Dam, Glen Canyon Dam, and dozens of other mega-dams throughout the western states during the last three-quarters of a century! Seventy-five or 100 years ago there must have been a substantial amount of water running through the Preserve – enough so the USBR was working on ways to conserve it.
• The northwest part of this area features hills of Pleistocene soil documented by State of Arizona geologists. While this particular kind of soil may not be unique around Tucson, it is fascinating to consider that it may a hundred thousand years older than all the other soils in the Preserve – land on which 14-foot tall mammoths, saber-toothed cats, camels, dire wolves, ground sloths, etc. may have roamedbefore the end of the last Ice Age.
• The southwestern grassy areas of the West Preserve could be called the Kingdom of the Ants, with huge clearings made by harvester ants and turrets constructed by leaf-cutter ants. In some washes you seea dozen or more ant hill/turrets in close proximity that are probably the home territory of several queens cooperatively ruling a massivecolony.
• The western acres (unfortunately) have many examples of dumping and destruction by irresponsible off-roaders and shooters. We foundold TVs, a bullet-riddled automobile fender, lots of shot-up beer cans, and hundreds of old shell casings. This misuse of the desert will hopefully be alleviated as the Town of Marana finalizes plans to put up fences along much the same western boundary lines now being temporarily marked by DeGroot and Fraijo.
Master Naturalists will have an opportunity for some memorable personal exploration of the Tortolita Preserve in a few months. Franklin Lane iscurrently collecting names of Master Naturalists who are interested in participating in a big BioBlitz planned by
• the Town of Marana,
• the Tortolita Alliance,
• Arizona Master Naturalists,
• the Coalition for Sonora Desert Protection, and
• the Arizona Game and Fish Dept.
Training will be provided. The big event, which could take place in November, will probably put Master Naturalists in prominent positions in a small army of citizen-scientists. PCMN Franklin Lane is gathering names of interested participants now. If you think you would like to be part of the BioBlitz, please send Franklin an email at
…and if you have a couple of hours to spare sometime, drive out to the main entrance of the Tortolita Preserve at 6250 W. Moore Road and walk a mile or two on the user-friendly 9.5-mile trail system.