Experimental Approaches to Desert Tortoise Conservation

by Sam Easley and Tim Shields

It was my first week working for Transition Habitat Conservancy (THC), and we were enjoying a cool October morning in the desert for field orientation. The biologist handed me a dark, fibrous nugget that I promptly learned was tortoise scat. He told me that I could identify it by its shape, size, contents, and even tell the approximate the age of the dropping based on its color and sheen. I absorbed a wealth of information from Tim Shields that day in the desert, and that initial introduction has always stuck with me. His willingness to get his hands dirty, and the excitement he had for these small traces of tortoise sign showed his passion for the species and their preservation. It was the kind of inspiration that I was looking for as a business school graduate searching for a rewarding career.

THC & BLM tents during an outreach event to the OHV community. We have maps, snacks, coffee, live animals, etc. to entice folks to come over and learn about responsible recreation in tortoise habitat.

c. Pic 1

Last fall, I traveled to Sacramento with Tim to ask the Wildlife Conservation Board (WCB) of California to support a project that we have been collaborating on for the seven years since my first day as a land steward. We were successful and were awarded nearly two million dollars. Concepts that sounded wild to me at that time are now being implemented on THC land thanks to this partnership and a lot of creative problem solving. Even more importantly, these innovative solutions are being shared with others to guide more effective tortoise conservation efforts throughout the Mojave Desert.

The plight of the desert tortoise is a well-known story to conservationists. We humans have altered conditions in the desert for our own convenience in the short run, and in the process have rendered it uninhabitable to tortoises over the long run. A good example is the rapid rise of common raven populations throughout the California desert. These ultimate opportunists are happy for our handouts and hospitality, turning the readily available food, water, shade, and nest sites we provide into still more ravens to fill the skies. For tortoises, the implications of having many more ravens than were historically present means that the odds of any young tortoise surviving its soft-shelled youth to reach maturity are functionally zero across large areas. But we need to look beyond just the effects of this raven population explosion on a single species, no matter how charismatic. Burdening the desert with this many highly intelligent and mobile predators is bad news across the entire ecological spectrum. Our team has come to view ravens as agents of ecocide, as they prey on a wide variety of species while incidentally causing many problems for agricultural and industrial concerns. So, what to do?

While THC has focused on land conservation, the essential prerequisite for the survival of the tortoise and other desert wildlife, Hardshell Labs, Inc* has worked on adapting emerging technology to address ecological problems that transcend land status. Tortoises needs healthy habitat, the goal of THC’s work, but when a raven sees a young tortoise, it pays no attention to whether or not the land is in conservation status. It spirals down, assesses its prey, flips it over, and hammers through the soft spot in the middle of the underside. Land conservation is essential but insufficient to stem the decline of the tortoise.

Our joint proposal to the Wildlife Conservation Board was to combine our strengths. THC has land and among their parcels are certain areas of very high tortoise density. Hardshell has the gizmos to counter the effects, not only of ravens but of a wide variety of threats to the desert tortoise. Among these threats are the invasion of the desert by non-native grasses, which displace the native wildflowers upon which tortoises depend. We have just begun to investigate the possibilities for controlling the aggressive invasive grass Schismus arabicus. In a similar vein, we are exploring ways to increase the availability of water to desert tortoises. We are mimicking the natural basins constructed by tortoises to retain rainwater, but putting them in places where the sandy soil composition prevents tortoises' use of natural drinking sites. A large clay plate plays the role of the drinking site, retaining rainwater for a few hours after any natural storm. We then depend on the exquisitely tuned ability of tortoises to recognize and return to sites providing this vital resource. Likewise, we are working on ways to provide tortoises access to desirable food plants. This will be especially important in areas that have been taken over by Schismus. Right now, Mojave Desert Land Trust is applying its expertise in growing native food plants by fostering 1000 desert dandelion plants. We will use this crop of tortoise food in initial experiments in enhancing food availability for tortoises. Both water and food availability improvements are a hedge against the worst effects of climate change and drought on the state reptile.

We will also deploy a wide variety of tools and techniques to address the unsustainable level of predation faced by tortoises. Over the last decade, Hardshell, working with a large number of talented engineers, funders, and experienced and dedicated biologists, has developed a number of useful tools. Ravens are exceptionally sensitive to laser light, and we are using highly refined Internet connected lasers to drive these birds away from their favored subsidy sites. This denies them easy access to energy that will be turned into nestlings the following spring. Radio-tracking of previously trapped ravens is drawing us a map of their favored subsidy sites, essentially pointing the way for wide scale denial of easy subsidies to ravens.

Working with Sundance Biological, Inc. we have refined and systematized the technique of remote egg oiling (REO), birth control for ravens. A thin layer of oil prevents the hatching of the egg yet leaves it structurally undamaged. The adult ravens continue to care for eggs that will not hatch, tying up their reproductive effort, and ensuring that no fledglings leave a treated nest. This technique is now in wide use across the Mojave, and recent raven counts show that in areas where REO is intensively and consistently used, raven numbers have declined. Hooray! At least in certain areas we are helping the desert back into balance.

One very attention-grabbing option we have developed is the Techno-tortoiseTM. We use 3-D printed, highly accurate models of tortoises to attract their main predators, ravens. Early tests, which included motion capture cameras, taught us much about how ravens attack young tortoises. For the first time we could watch how the birds behaved. We applied these lessons, and working with the engineering firm Cornerstone Research Group, created a device that attracts ravens, then delivers a strong aversive experience. Once a raven has decided that the object in front of it is a scrumptious little tortoise and begins to hammer away at it, or attempt to turn it over, the Techno-tort sprays a very irritating, but non-toxic chemical in the face of the bird. Strangely enough, artificial grape flavoring, chemically called methyl anthranilate, is specifically irritating to birds. The surprise that ravens show when a delectable little tortoise suddenly fights back with a noxious spray vividly demonstrates just what an impact this experience has in the moment. Now we want to determine if it reduces the tendency of these “educated” birds to attack actual tortoises.


Tortoise or a decoy?

Photo: Tim Shields

@ William I. Boarman 2016

So far, our work on predation reduction has focused on the raven. But another highly intelligent predator is using human subsidies to increase its numbers, and thus its negative effect on the desert tortoise. We are currently considering how to adapt our devices to reduce coyote predation on tortoises. This is early stage work, but we have some promising ideas and look forward to testing them in the field.

The shared goal of THC and Hardshell is to improve the odds of the survival of the desert tortoise, but to do so using non-lethal techniques. We are counting on the intelligence of these predators to train them to either change their distribution or their behavior in desired directions.

The WCB grant, entitled Desert Tortoise Conservation Innovations (DTCI), is a boon to our efforts. The four-year span of the project, and its significant funding level, will allow us to not only deploy this wide variety of techniques and technology, but also monitor the reactions of both tortoise populations and those of their predators to assess their effectiveness.

Just as importantly, we will attempt to characterize areas of high desert tortoise density, what we call hotspots. Why this hilly area and not that low valley? What environmental factors influence the choice of area by tortoises and the capacity of that area to support that density? We are looking for the formula for tortoise success with a view toward finding as many of these hotspots as we can. Among the obvious factors are the quality of food and the availability of good soil for burrow digging. But what combination of foundational factors account for these? Topography, soil composition, degree and type of human activity come immediately to mind, and the multi-year duration of the project will certainly tell us much. The DTCI project will allow us to investigate these, with the goal of creating a template for the identification of high-quality desert tortoise habitat and active measures to maintain the tortoise populations that call them home.

For the next four years, we will be investigating the options for helping the desert tortoise to survive the next decade, the next century, and the next millennium. Humans have altered the desert ecosystem in ways that imperil this wonderful creature. Yet both THC and Hardshell are made up of optimists. We are disinclined to give up without expanding every effort to help the tortoise. And with the proliferation of powerful new tools to influence the course of ecological events, the potential for success exists.

* Hardshell Labs, Inc. is a conservation technology company from Joshua Tree, CA, specializing in applying emerging tech to ecological and resource protection problem solving.

Sam Easley graduated from James Madison University with a BBA in economics and a passion for exploring the Blue Ridge Mountains of Virginia. Sam moved West in the fall of 2014 to pursue a career in conservation, restoring habitat on the ground, leading crews, and planning projects as a BLM intern. He has been with Transition Habitat Conservancy for six years and isnow the Executive Director.

After a 35-year career in tortoise research, Tim Shields turned his attention to active interventions to save the tortoise from impending demise. In the decade since he has led and participated in a wide variety of tech development efforts with conservation in mind. He works with engineers, biologists, agency representatives and utilities. He enjoys hiking, bike riding and looking at weird bugs.