The Pack Rat and the Zipline

Pack Rat at Captain Zipline in Salida, Colorado

The zip line property is home to all sorts of creatures, one of the most notable being the pack rat. During your Captain Zipline tour, you will pass by one of our most famous residents, a pack rat, tucked away in his very own penthouse inside a rocky crevice.

Pack rats are found throughout North and Central America. They belong to the genus Neotoma, and in the United States, are most commonly found in the southern and western regions. There are 22 species of pack rats; 7 of these species exist in the desert regions of North America. They live at elevations from below sea level up to 8000 feet. Here in Salida, we are situated at slightly more than 7000 feet above sea level in an outdoor paradise that is a perfect home for these and other creatures.

It is unlikely you will see our famous “Penthouse Pack rat”–or for that matter, any other pack rat–scurrying around the zip line grounds simply because they are nocturnal animals. They are most vulnerable to be preyed upon when out foraging around for food and building material and thus they seek the cover of the darkness of the night. This makes sense since they have quite a few predators, including the coyote, fox, owls, and snakes.

For those who are curious about the pack rat and want to form a mental image of this critter, here is what they look and act like: Pack rats look a bit like a squirrel, only with larger ears; they have soft fur that can be brown, buff, or gray in color and may reach a length of 18 to 20 inches, including their hairy tail. These rodents are vegetarians and thrive on seeds, nuts, berries, and wood debris such as twigs and roots. In arid places, they rely on succulent plants for hydration. They tend to build their nests in areas protected from the elements such as rocky crevices and overhangs. In dry desert environments, it is common for these animals to use pieces of cacti in the building process, creating a formidable fortress as their home.

Take a look around our high-mountain-desert zip line grounds and you will see lots of low-lying cacti all over the property…and thus, it’s not a good idea to disturb our Pack Rat Penthouse by attempting to reach inside his home.

Pack rat females are prolific breeders. They can produce a litter of two to six offspring in only 33-39 days. As many as 5 litters in 1 year may be produced by a pack rat. Sexual maturity is reached in about 60 days. And, most pack rats are polygamous.

With so many generations possible in such a short period of time, it is no wonder that pack rat predators are plentiful as well. Keep an eye out, then, for some of these animals that might be out in the light of the day, namely rattlesnakes. Rattlers are no strangers to this region, and have been spotted on the zip line property from time-to-time, however they tend to be shy creatures and want to avoid human contact at all costs. In other words, they really are not interested in “tangling” with a human.

The “Pack Rat” is also known as the “Wood Rat” or “Trade Rat” since it ‘trades’ what is in its immediate possession for shiny, more eye-catching objects it finds along the way. In return, it might leave some pebbles or other debris behind, including chunks of animal dung. So, in return for our drill bits and shiny nails that disappeared from the zip line, we found presents of tiny rocks and other bits of garbage in their place! After all, the rodent can carry only one thing at a time and the brighter, shinier objects are preferred. If you have a chance, then, to shine a light inside the zip line Pack Rat Penthouse, you’ll see the gleaming bits of metal meshed in with the pack rat’s other “construction” materials.

Such bad habits can become quite a nuisance when pack rats live in and around human habitats. It is not uncommon for them to seek refuge underneath the hood of a car, destroying the wiring and anything else they can literally sink their teeth into. The mechanical damage can be substantial, but it pales in comparison to the stench they create while making themselves comfortable in their “new home.” This is because they repeatedly urinate on whatever place and materials they claim as home turf, the urine serving as a sort of “glue” to hold the expanding structure together.

Pack rat urine is the “secret ingredient” in the matrix that holds together their ever-expanding nests. In the wild, pack rat nests can evolve into huge beaver-dam-like structures as wide as 4 feet, all of this held together by–yes, you guessed it-urine. Pack rat urine is very concentrated and viscous, especially in arid environments. When it dries, it crystallizes into a substance referred to as “amberat.” The sugar content of the urine adds to its cohesive properties, allowing structures to be built that are stable over many, many years, especially in the drier climates. Generation after generation lives in the same nest and tends to build upon this home. These nests are called “middens,” literally meaning heaps of garbage.

Pack rat middens offer much more than simple shelter to its inhabitants. Strangely enough, they are a treasure trove of artifacts lending to an understanding of the flora and fauna of past times. There are actual “midden expects” who seek out these structures as a way to understand and explain a region’s natural history. One of these scientists-or “paleoneotomologists”-is Tom Van Devender of the Arizona Sonora Desert Museum. In the process of trying to explain how the native Anasazi of Chaco Canyon, New Mexico, were able to find logs and other wood products for building their complex structures in what is now a treeless region, Van Devender looked for secrets that may be hidden in packrat middens in the area. Initially he found pinyon needles among other plant debris in the middens, suggesting that there once were pinyon trees in the immediate area since pack rats notoriously remain within several dozen yards from their homes. He then submitted samples of these fossil packrat middens for radiocarbon analysis. This analysis revealed that many of the middens were more than 1000 years old! The evidence overall supported the existence of forests in this region many, many years ago.

Van Devender is not alone, though, in his use of pack rat middens for scientific purposes. It has become quite common to look at these structures as a means of understanding some of the unknowns regarding the world around us. So when you pass by the zipline’s Pack Rat Penthouse, keep in mind that the critters inside may one day make substantial contributions to science, including insight into the ongoing concern over climate change.