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Altered Ecosystems and their Potential Effects on the Gopher Population

Gophers! The bane of so many gardeners, farmers, landscapers, and turf managers; they are the little rodents made famous in the 1980 film Caddyshack and are at once both frustrating and amazing little animals. With over 40 species on earth, they are all native to North or Central America. With some species being narrow endemics, some endangered, and some very plentiful, they are a diverse bunch. Here in our area, the species we have is called Botta’s pocket gopher, Thomomys bottae. This widespread animal occurs in most of California and Baja California, extending east into parts of Nevada, Texas, Colorado, Utah, Arizona, New Mexico, and Mexico itself. 


Coming in 7 different genera, pocket gophers are called this because of their extensive cheek pouches they use to carry food.  Photo by Wayne Chapman.


One thing about California that Californians may find hard to truly understand, is just how much so many of the state’s original ecosystems have become altered. This is not just from the development, agriculture, and enormous human population here now, but largely due to the overwhelming prevalence of so many non-native plants in remaining natural areas. In many cases, California’s ecosystems have become either partially, or wholly, novel ecosystems. In other words, they are so thoroughly invaded by plants that never grew here before, that they are basically something “new” or novel now. But our ecosystems and landscapes are not wholly without their native organisms. Some have benefitted from the changes the last 250 years have ushered in, and some, frankly, have not. Crows, for example, seem to have expanded and benefitted. In urban areas, so too have raccoons and skunks. The inflated numbers of these animals often has negative consequences for other species, many of whom are faring far poorer. Pocket gophers, however, seem to have managed well and show no signs of disappearing anytime soon! And while data may be scarce, some have suggested that they are in higher abundance in some places than they were historically. Why might that be?


Well, for one, some of the gopher’s predators are either extinct in the state, like the California grizzly, or greatly reduced, like the American badger. True, a large variety of native fauna still makes meals of gophers regularly, including bobcats, coyotes, foxes, snakes, herons, egrets, hawks, owls, and many more. But grizzly bears and badgers don’t just wait passively for them to pop their heads up for fresh greens- they go into the ground to dig them out where they reside. It has been suggested that California grizzlies could dig up significant numbers and eat them “like popcorn”- but we don’t really know. American badgers, while very rare, are still hanging on in some places on the south coast, and they seem to be very focused and reliant on gophers in some cases. 


The result of a badger hunting gophers. These were being used by a wintering burrowing owl, another majorly declining species in the state. Photo by Wayne Chapman.


Note the bear-like claw marks left by this badger in pursuit of gophers. Photo by Wayne Chapman.


Another factor that may have influenced gopher abundance are the ubiquitous weeds and the thatch that often accompanies them. Today in Southern California, vast quantities of land are dominated by nonnative plants. Mustards, thistles, grasses, and more have become the rule, not the exception, in many herbaceous places not dominated by woody vegetation like chaparral. These areas were once dominated by native California grasses and wildflowers and were often managed with fire by native Californians. Today, many of these places are grazed, and some are not. Without some grazing to keep thatch down, its buildup smothers the surface, affecting both the function and diversity of plant life. Gophers may have benefitted from this new phenomenon, as many of these weeds provide food for them. Equally importantly, their tall stature- or the thick mats of thatch that they create above ground- provides a blanket of cover for gophers to hide beneath, making it harder or impossible for many of their natural predators to access them. Have you ever noticed a great blue heron standing in a recently mowed field? They are responding to the sudden reduction of vegetation and are looking for gophers! 



Great blue heron with a fresh gopher. Photo by Wayne Chapman.


Another recent change to hit California in the past few centuries, around 231 years to be more exact, is the prevention and suppression of fires. While the exact scope of indigenous burning is not known, it appears quite clear that a great many places were burned annually or every few years to manage grassland vegetation, among other vegetation types, and by most California Indian cultures. So where deliberate, widespread, gentler fires were once the norm, periodic, accidental, intense fires are more common. These grassland fires were integral in many processes, including recycling nutrients, reducing fuels, and invigorating the next season’s growth of native grasses and seed-bearing wildflowers. Thoroughly outlawed state-wide by then-Governor Jose Joaquin de Arrillaga on May 31, 1793, the regular burns then stopped and have only really returned in stochastic intervals that are often disastrous conflagrations. When a fire burns a grassland, the vegetation generally burns down to the mineral ground, exposing everything until regrowth occurs. While some perennial plants will resprout after fire without rain, such as wild rose and hummingbird sage, the annuals are on hold until the storms come. For centuries, vast swaths of ground would have suddenly been bare for weeks or longer every late summer or early fall, exposing gophers to more predation. Fires are so rare today that gophers no longer must contend with this “season of exposure”. It’s hard to visualize hundreds of thousands of acres burning in a managed way each year, and what that might have meant for gopher populations across those many square miles.


Ernestine Ignacio-De Soto lights the first Chumash-lit grassland fire in 230 years on the UCSB campus in September 2023. She is the daughter of the last first-speaker, Mary Yee. Photo by Wayne Chapman.


Gophers have also changed our plants and made them more biodiverse. Or, maybe put more accurately, their absence has. Among the many under-appreciated aspects of California’s floral diversity is the genetic diversity, or local genotypes, among many of its taxa. One of the best examples of this is our state flower, the California poppy. An adaptive plant that occurs naturally over a wide range of habitats and microclimates, it can be as different as apples and oranges from one to another, depending on whether the local forms are coastal, continental, wind-swept, or experience any other of the many environmental differences in their range. Unfortunately, this facet of diversity is complex, and therefore underappreciated by most, and these amazing “wild heirlooms” are being homogenized by gene flow from store bought seeds when people commonly sow them in out-of-place locations. Gophers and poppies have been coexisting in California for thousands, perhaps millions of years, and gophers like to eat them. To keep gophers moving along and not eat too much or many, California poppies have been co-evolving with gophers during all that time and produce bitter tasting secondary metabolites- alkaloids- to give themselves a fighting chance. Not surprisingly, the poppies on Santa Cruz Island have 2.5 times lower concentrations of these gopher-deterring alkaloids in their roots than mainland counterparts, making them unique from all their mainland brethren. Yet another example in California of diversity within a single species. Having never had a land bridge, the Channel Islands have never had gophers, so their floras have never had to protect themselves from their gnashing incisors. The absence of gophers on the Channel Islands has left the roots of island plants in peace, and been a great benefit to archaeologists working on the islands, as they do not tunnel through the soil stratigraphy and confound archaeology as they do elsewhere.


Today gophers in California are alive and well, and while no one would blame you for busting out the traps when they arrive in your yard, remember they are old residents of California, and they deserve admiration for their tenacity, stubbornness, ecological support, and their place in the greater picture.



Photo in Public Domain from National Parks Service.


References:


  1. Timbrook, J. et al. (1982) Vegetation Burning by the Chumash. Journal of Great Basin Anthropology https://www.jstor.org/stable/27825120

  2. Watts, S. (2011) The roots of defense: plant resistance and tolerance to belowground herbivory. https://pubmed.ncbi.nlm.nih.gov/21494690/

  3. Wikipedia: https://en.wikipedia.org/wiki/Gopher


About the Author

Wayne Chapman has worked at UCSB's Cheadle Center for 26 years doing habitat restoration as a project and nursery manager with emphasis on propagation, local genotypes, rare plants, and ethnobotany.




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