Donkeys and horses were the most highly valued animals of the ancient world. These equines were the automobiles, trucks, and trains of preindustrial times. They transported humans and carried heavy loads wherever people wanted to go, in addition to performing agricultural and martial work. Worldwide, the value of donkeys and horses as beasts of burden is still high today. People also keep them as pets and therapy animals, and for a variety of sports.

Humans value donkeys and horses so much that it is rare to find any of them living in the wild. This rarity motivated a team of eight conservationists and biologists to investigate possible roles such animals might play in enhancing wild ecosystems. The team conducted field studies over a three-year period in the Sonoran Desert where feral populations of donkeys and horses have recently been established.1 Their findings show that equines are veritable desert engineers and the animals’ propensity for digging wells carries implications for climate change.

Field Study Observations
The eight scientists observed that during periods of surface water scarcity the feral donkeys and horses would sniff out subterranean water and dig wells up to 2 meters deep (see figure 1). During summers, when temperatures would cause the water evaporation rates to soar, wells dug by donkeys and horses (known as equid wells) provided 100% of the surface water in most of the desert regions surveyed. Even in regions where perennial streams existed, equid wells provided up to 74% of surface water.


Figure 1: Donkey Digging a Well in the Sonoran Desert
Image credit: Erick Lundgren

Desert water made available by feral equines quenched the thirst of nearly all the other animals cohabitating in the Sonoran Desert. The eight scientists photographed deer, bobcats, jays, passerines, and rodents visiting equid wells. In total, they observed 57 different vertebrate species drinking from these wells.

Minus feral donkeys and horses, water features in deserts can become areas of heightened antagonistic wildlife interactions.2 They can become breeding grounds for pathogenic bacteria and biting insects. They pose increased predation risk and greater competition for both water and herbivory.

The scientists determined that equid wells reduced average nearest-neighbor distances between water features by 65% and, during the hottest times of the year, by as much as 99%. They concluded that equid wells substantially reduced antagonistic interactions near water features and greatly decreased the distances animals must travel to obtain water. In other words, with water more readily available, animals did not need to fight over water access.

Equid wells yield benefits for desert vegetation as well. The researchers observed that erosion inevitably fills in the equid wells. The seeds of fast-growing flood-adapted trees take root in these abandoned equid wells (see figure 2), where the loose soil enables the newly sprouted seeds to efficiently send roots down to the water source. Thanks to equid wells, desert vegetation is enhanced, which provides more food and shade for animals. Enhanced vegetation also increases the transpiration of water to the atmosphere, which results in more precipitation.


Figure 2: Tree Taking Root in an Abandoned Equid Well
Image credit: Erick Lundgren

Feral donkeys and horses are the only large animals that dig wells in North America but this engineering effect has been observed globally. African and Asian elephants, mountain and Grevy’s zebras, gemsbok, and khulans also dig wells in their respective ecosystems.

Climate Change Mitigation
The team of eight did not address the potential role well-digging megafauna can play in mitigating climate change. Over the past 2,000 years, anthropogenic abuse and activity have increased the size of almost all Earth’s deserts, most notably the Sahara Desert (by nearly ten times) and the Gobi Desert (by four times). Purposeful introduction of well-digging megafauna into the world’s major deserts would increase desert vegetation, which in turn would increase desert precipitation. More desert precipitation would permit more vegetation to take root and grow.

Vegetation, in its photosynthesis, draws carbon dioxide from the atmosphere and stores it in the form of carbohydrates, starches, cellulose, fats, and other hydrocarbons. If more vegetation proliferates over the world’s deserts more carbon dioxide is removed from the atmosphere, which allows vegetation to support even more animal life. More vegetation and more animals can potentially provide more income for humans inhabiting the deserts. Therefore, feral donkeys and horses can play a role in mitigating climate for the economic benefit and well-being of both humans and the rest of Earth’s life.

Donkeys and Horses as Testaments of Design
The donkey is mentioned in 93 different Bible passages and the horse in 59. In my book, Hidden Treasures in the Book of Job, I described how wonderfully and uniquely designed donkeys and horses are for making possible the launch and maintenance of global civilization and the development of a large human population.3 Apparently, I underestimated all the ways our Creator designed these animals to serve us and the rest of Earth’s life and ecosystems.

Check out more from Reasons to Believe


  1. Erick J. Lundgren et al., “Equids Engineer Desert Water Availability,” Science 372, no. 6541 (April 30, 2021): 491–495, doi:10.1126/science.abd6775.
  2. Todd C. Atwood, Tricia L. Fry, and Bruce R. Leland, “Partitioning of Anthropogenic Watering Sites by Desert Carnivores,” Journal of Wildlife Management 75, no. 7 (September 2011): 1609–1615, doi:10.1002/jwmg.225; Jared D. Rogerson, W. Sue Fairbanks, and Louis Cornicelli, “Ecology of Gastropod and Bighorn Sheep Hosts of Lungworm on Isolated, Semiarid Mountain Ranges in Utah, USA,” Journal of Wildlife Diseases 44, no. 1 (January 1, 2008): 28–44, doi:10.7589/0090-3558-44.1.28; I. Thrash, G. K. Theron, and J. du P. Bothma, “Dry Season Herbivore Densities around Drinking Troughs in the Kruger National Park,” Journal of Arid Environments 29, no. 2 (February 1995): 213–219, doi:10.1016/S0140-1963(05)80091-6.
  3. Hugh Ross, Hidden Treasures in the Book of Job (Grand Rapids: Baker, 2011), 156–157, 161–163.

About The Author

Dr. Hugh Ross

Reasons to Believe emerged from my passion to research, develop, and proclaim the most powerful new reasons to believe in Christ as Creator, Lord, and Savior and to use those new reasons to reach people for Christ. I also am eager to equip Christians to engage, rather than withdraw from or attack, educated non-Christians. One of the approaches I’ve developed, with the help of my RTB colleagues, is a biblical creation model that is testable, falsifiable, and predictive. I enjoy constructively integrating all 66 books of the Bible with all the science disciplines as a way to discover and apply deeper truths. 1 Peter 3:15–16 sets my ministry goal, "Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect, keeping a clear conscience." Hugh Ross launched his career at age seven when he went to the library to find out why stars are hot. Physics and astronomy captured his curiosity and never let go. At age seventeen he became the youngest person ever to serve as director of observations for Vancouver's Royal Astronomical Society. With the help of a provincial scholarship and a National Research Council (NRC) of Canada fellowship, he completed his undergraduate degree in physics (University of British Columbia) and graduate degrees in astronomy (University of Toronto). The NRC also sent him to the United States for postdoctoral studies. At Caltech he researched quasi-stellar objects, or "quasars," some of the most distant and ancient objects in the universe. Not all of Hugh's discoveries involved astrophysics. Prompted by curiosity, he studied the world’s religions and "holy books" and found only one book that proved scientifically and historically accurate: the Bible. Hugh started at religious "ground zero" and through scientific and historical reality-testing became convinced that the Bible is truly the Word of God! When he went on to describe for others his journey to faith in Jesus Christ, he was surprised to discover how many people believed or disbelieved without checking the evidence. Hugh's unshakable confidence that God's revelations in Scripture and nature do not, will not, and cannot contradict became his unique message. Wholeheartedly encouraged by family and friends, communicating that message as broadly and clearly as possible became his mission. Thus, in 1986, he founded science-faith think tank Reasons to Believe (RTB). He and his colleagues at RTB keep tabs on the frontiers of research to share with scientists and nonscientists alike the thrilling news of what's being discovered and how it connects with biblical theology. In this realm, he has written many books, including: The Fingerprint of God, The Creator and the Cosmos, Beyond the Cosmos, A Matter of Days, Creation as Science, Why the Universe Is the Way It Is, and More Than a Theory. Between writing books and articles, recording podcasts, and taking interviews, Hugh travels the world challenging students and faculty, churches and professional groups, to consider what they believe and why. He presents a persuasive case for Christianity without applying pressure. Because he treats people's questions and comments with respect, he is in great demand as a speaker and as a talk-radio and television guest. Having grown up amid the splendor of Canada's mountains, wildlife, and waterways, Hugh loves the outdoors. Hiking, trail running, and photography are among his favorite recreational pursuits - in addition to stargazing. Hugh lives in Southern California with his wife, Kathy, and two sons.

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