by Colin Eldridge

Header photo credit: mbmceach

In the dense woodlands, coastal sage-scrub and chaparrals of California, woodrats stand out not only for their ingenious dwellings but also for their remarkable behaviors and adaptations. Meet the dusky-footed woodrat (Neotoma macrotis), big-eared woodrat (Neotoma fuscipes), and desert woodrat (Neotoma lepida) – three enigmatic creatures that often go unnoticed by humans but play crucial roles in their ecosystems.

A big-eared woodrat climbing a branch. Photo credit: randomtruth.

The woodrat family is native to North America, unlike the introduced common rat (Rattus norvegicus) that occupies our cities in masses. They are behaviorally and biologically very different from the common rat, and are part of the completely separate genus Neotoma. Woodrats are also called pack rats or trade rats, because they will take man-made objects and drop what they are holding, often looking for shiny and attractive objects to adorn their elaborate nests.

One prime location for woodrat habitat is in the oak woodlands along the Don Wimpress Trail within Cachuma Lake Recreation Area. As the trail traces the border of the lake, it dips down into a lush forested area. Hikers can see large bundles of sticks and twigs on the ground, but might pay them no attention, thinking they are merely natural accumulations of woody debris. On closer examination, these bundles of sticks are actually complex Woodrat nests that tell a story about the lives of these amazing animals.

It is a rare sight to see one of these nocturnal creatures, as they sleep deep in their nests during the day and are active at night.

Woodrat Nests: Hiding in Plain Sight

Woodrats nests are both an architectural wonder and a showcase of the woodrat’s ingenious adaptations. The nests look like large bundles of sticks, which can reach 3-6 feet high and 8 feet across. They are often intertwined within the branches of shrubs. The nest materials are held together with their urine, which contains chemicals that crystalize when dry and form a hard, sticky structure. Some nests are decades old, spanning several generations of woodrats.

While these elaborate nests may be unknown to some humans, many animals besides the woodrat know about and even utilize these nests. Woodrats are aware of this and they set up a convoluted system of tunnels which make them very hard to hunt.

Weasels, foxes, coyotes, mountain lions, bobcats, and raccoons usually have to wait outside of the nest for the woodrat to come out. Digging into the nest would likely lead to them getting lost in a dense system of tunnels or being blocked by a log or rock before reaching the inner sanctum.

Black bears, wild boars and badgers may be able to tear apart their nests, looking for either the woodrat itself, its stores of food, or both. Snakes can easily slither into the nest, but will also likely be lost in a convoluted system of tunnels.

Rattlesnakes will burrow into these nests looking for food and shelter. Once the rattlesnake enters brumation, or goes dormant when the weather is cold, woodrats will close off the snake from the rest of the nest with sticks. The smell of the brumating snake is a warning sign to many animals, and will ward off other predators.

Dusky-footed and big-eared woodrats also fumigate their nests with California bay laurel, an aromatic plant that releases powerful volatile oils capable of killing flea larvae and other parasites.

The woodrat nests are so intentionally designed that naturalists have stuck their heads into the tunnels to study them. From this process, we have learned that woodrat nests have their own separate waterproof bedrooms, nurseries, bathrooms, and separate storerooms for fungi, seeds, and leaves. Some scientists even theorize that these separate rooms are climate-controlled for optimal drying and storage conditions of their food!

The Dusky-Footed Woodrat

There are 11 sub-species identified of the dusky-footed woodrat. The dusky-footed woodrat’s native habitat ranges from Oregon down to Northern California. One subspecies native to the San Joaquin valley, the riparian woodrat (Neotoma fuscipes riparia), is federally listed as endangered.

The dusky-footed woodrat eats leaves, twigs, berries, and seeds of more than 70 plants. Their preferred food is acorns, which can be stored across seasons and can support families of woodrats. They are the only known mammal that can survive on oak leaves alone, and will also eat leaves of other plants like toyon, alder, manzanita, chamise, and elderberry.

The native habitat range of the dusky-footed woodrat. Source: googleusercontent.com

In an in-depth book by Jean Linsdale and Lloyd Tevis, the social life of dusky-footed woodrat is outlined in detail. Female woodrats each have their own nests, except during mating season. They will also occasionally let in a female roommate, usually a relative, when housing is scarce. Male woodrats will often share nests, but move around a lot in search of their mate.

Though their nests are often solitary, woodrats can live in dense communities with several nests located next to each other. Females live near their birthplace, and their villages consist mainly of family members.

A big-eared woodrat carrying its young. Photo credit: Zack Abbey.

The Big-Eared Woodrat

The big-eared woodrat used to be considered a type of dusky-footed woodrat, but scientists considered it different enough to name it as its own unique species in 2002.

Both species are found along the coast and inland along the Sierra Nevada mountain range. The Big-Eared woodrat inhabits the former southern portion of the dusky-footed woodrat’s range, south of Lake Tahoe along the Sierras and south of Monterey Bay down to northern Baja California and as far east as the Mojave Desert. This species is also native to the Santa Ynez Valley and areas surrounding Cachuma Lake.

The native habitat range of the big-eared woodrat. Source: databasin.org

There are many similarities in appearance and behavior between the dusky-footed and big-eared woodrats. They make large nests like the dusky-footed woodrat. They eat the bark and leaves from woody plants, especially coast live oaks. They can also eat fungi, flowers, grasses, and acorns. The one main differing characteristic is that the big-eared woodrat’s ears are slightly larger in comparison to their head. Some also claim that the big-eared woodrats have slightly smaller bodies on average.

Studies suggest that both male and female big-eared woodrats have multiple mates, and that the females do not seem to return to their birthplace, which may contribute to high genetic diversity within this species.

A desert woodrat (Neotoma lepida) outside of its nest. Photo credit: Tony Iwane.

Desert Woodrat

Another notable woodrat that shares much of the same habitat as the big-eared woodrat, potentially including the juniper woodlands in the valley surrounding Cachuma Lake, is the desert woodrat, but they often prefer more arid regions.

They are typically found in habitats such as sagebrush scrub, chaparral, deserts, and rocky slopes with scattered vegetation like cacti, yucca, and pine/juniper. They thrive at elevations up to 2,900 meters (9,500 feet) and prefer areas with ample rocky crevices or rock piles, which provide shelter from predators.

They consume mesquite beans and leaves, along with juniper and various parts of cacti, seemingly unaffected by the spines. Their diet also includes creosote bushes, thistles, Ephedra, mustard plants, sagebrush, and buckwheat. In addition, they eat other green vegetation, seeds, fruits, acorns, and pine nuts. In desert environments, prickly pear cacti are vital for maintaining their water balance, although they are one of the few animals that can survive on the creosote plant throughout the year.

Desert woodrats are mostly active at night and are highly territorial, living alone. They may defend water sources, like succulent plants, from other species, potentially preventing them from accessing water during droughts. Occasionally, desert woodrats take over the burrows of ground squirrels or kangaroo rats and reinforce the entrances with large piles of sticks and cactus joints from jumping and teddy-bear chollas, creating strong defenses against predators.

Their nests are often built in rock crevices, at the base of creosote bushes or cacti, or in the lower branches of trees. When available, rock crevices are preferred, but woodrats can adapt to various environments.

This picture of a coast garter snake (Thamnophis elegans ssp. terrestris) consuming a dusky-footed woodrat shows one role of this species within the interconnected web of life. Photo credit: avocat.

Ecological Importance

Despite their small size, woodrats play significant roles in their ecosystems. Their nest-building activities contribute to soil aeration and nutrient cycling, while their dietary habits, which include a wide array of vegetation, seeds, and sometimes insects, help to disperse seeds and control plant populations.

Moreover, these woodrats serve as prey for a variety of predators, including owls, snakes, and carnivorous mammals, forming an essential link in the intricate web of life. Their ability to thrive in diverse environments also makes them valuable indicators of ecosystem health, with declines in their populations often signaling broader ecological imbalances.

Many other species make the woodrat’s cool and moist nest their home, including pinyon mice, California mice, brush rabbits, salamanders, centipedes, and dozens more. For these reasons and many more, woodrats are considered a keystone species. This means that if woodrats were to go extinct, it could have a devastating cascading effect on the rest of the ecosystem.

In California, woodrat habitat is being lost at alarming rates to urbanization, logging, and clearing. Even though some woodrats can live in human-modified areas like agricultural lands and urban areas, it is imperative that we protect natural habitats for the sake of all species, including humans.

A large portion of California’s woodland and chaparral ecosystems have been segmented and/or destroyed. Photo credit: Colin Eldridge.

What You Can Do

Take action today to help protect the delicate habitats of this precious keystone woodrat species.

• Urge your California representatives to protect the remaining native shrublands and woodlands in California by restricting development, clearcutting, logging, and herbiciding, especially in the habitats of endangered and keystone species.
• Get involved with a local, regional or national nature conservation nonprofit.

Come visit our mammal exhibits at The Neal Taylor Nature Center at Cachuma Lake to learn more about these amazing creatures. If you want to help spread awareness about the wonderful biodiversity of our region, come volunteer or donate to the Nature Center.

We are a 501(c)(3) non-profit organization with the mission to encourage public understanding, enjoyment, and protection of Cachuma Lake, the Upper Santa Ynez River, and the San Rafael Mountain Range Watershed.

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Sources

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California Wildlife Habitat Relationships System. (2008). Life history account for Big-eared woodrat. California Department of Fish and Wildlife. https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=2649

Gap Analysis Project. (2018). Big-eared Woodrat (Neotoma macrotis) mBEWOx_CONUS_2001v1 Habitat Map. U.S. Geological Survey. https://doi.org/10.5066/F7CC0Z29

Kays, R. W., & Wilson, D. E. (2009). Mammals of North America (2nd ed.). Princeton University Press.

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“Genetic Variation in Multilocus Microsatellite Genotypes in Two Species of Woodrats (Neotoma Macrotis and N. Fuscipes) From California.” (n.d.). PLOS ONE. www.ncbi.nlm.nih.gov/pmc/articles/PMC2777661/.

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Thompson, S. D. (1982). Spatial utilization and foraging behavior of the desert woodrat, Neotoma lepida. Journal of Mammalogy, 63(4), 570–581. https://doi.org/10.2307/1380261

Verts, B. J., & Carraway, L. N. (2002). “Neotoma lepida.” Mammalian Species, 699, 1–12. https://doi.org/10.1644/1545-1410(2002)699<0001>2.0.CO;2