Ecosystem of the Mojave Desert
Bio/101
March 5, 2012

Ecosystem of the Mojave Desert
The Mojave Desert is 54,000 square miles of its own special brand of diversity; it is one desert - rather than a series of separate entities. By becoming aware of the combined identity, appreciation and better understanding of the issues that affect the Mojave Desert can occur on a holistic level. Generally, at the edges of the Mojave are areas where dominant plant and animal species change from one to another and both, to various degrees may be possibly found on the fringes of the other. The Mojave Desert ecosystem evolves from plants and animals which are resources within each other. Adaption to the rough temperatures and little water, these ecosystems finds many ways to survive.
This ecosystem plays host to a wide variety of plants and animals living in an environment that humans may think are harsh conditions. Many animals get their energy by eating plants, but desert plants give up the fruit of their production very reluctantly. Sharp spines, such as a cactus, discourage plant-eaters. The Mule deer avoids these obstacles by eating seeds, although safe to eat, they can be hard to find. Many are small and look like grains of sand. The plant's solar energy flows through the ecosystem as Mule deer, and other herbivores like jackrabbits, fall prey to carnivores like great horned owls, coyotes, bobcats, or snakes (Townsend, Harper & Begon, 2000).
Survival in the desert cannot occur without animals and plantsdependency on each other. Interdependence is the relationship between plants and animals. Animals look for food and shelter from desert plants and plants also need animals to help them pollinate and grow flowers. According to Desert USA, animals are instrumental in both fertilizing and spreading plant seed throughout the desert (1996-2012). These animals help to maintain diverse plant life within the desert.
Desert animals have survived with the need of small amounts of water to survive. Many animals depend on forms of desert plants that provide them with water. There are plants consumed for their sap and nectar. Some rodentspecies are capable to receive water from dry plant seeds. They can manufacture the water metabolically due to their small bodies. Rodents will not drink water even in captivity (Digital Desert, 2010).
Organisms need energy; they also need sources of nutrients like nitrogen and phosphorus. Energy flows one way through an ecosystem, whereas nutrients are recycled. Animals, plants, and bacteria all play different roles in these two basic patterns; often they depend on each other to ensure a supply of nutrients or of energy (Digital Desert, 2010)
Organisms
There are many organisms that exist in the Mojave. From plants and trees to birds and mammals, each animal serves a function in the ecosystem. Each organism, too, must adapt to the harsh environment that surrounds it. The arid, hot climate and cold nights require adaptations of all organisms that inhabit the Mojave Desert – and other deserts like it (Digital Desert, 2010).
Plants and trees that exist in the Mojave Desert include: the Joshua tree, California juniper, bitterbrush, sweet bush, sagebrush, the prickly poppy, the fan palm oases, and the pinyon pine. In addition to plants, the Mojave is alive with insect and spiders such as the Aztec pygmy grasshopper, blister beetle, Carolina wolf spider, desert tarantula, inconspicuous crab spider, Jerusalem cricket, little black ant, Mormon cricket, and the red velvet ant (2010). This list is only an abbreviated list of the plant and insect inhabitants of the Mojave; many more inhabit this arid terrain.
Reptiles, mammals, and birds are other organisms that make the Mojave home. Included are the fringe-toed lizard, western diamondback and Mojave rattlesnakes, desert iguana, horned lizard, zebra-tailed lizard, sidewinder snake, rosy boa, and the common kingsnake. Birds that make the Mojave their home include the different kind of quail (mountain quail, Gambel’s quail, and the California quail), turkey vulture, cooper’s hawk, red-tailed hawk, golden eagle, and the prairie falcon. Additionally, there are families of rails, pigeons and doves, cuckoos, owls, goatsuckers, hummingbirds, woodpeckers, flycatchers, wrens, and jays and crows. With an environment so harsh, one would think it difficult for mammals to inhabit such an ecosystem; however, there are many mammals that have adapted to the harsh environment. These would include the American badger, big free-tailed bat, cactus mouse, brush mouse, coyote, desert shrew, gray fox, long-tailed pocket mouse, mountain lion, mule deer, kangaroo mouse, porcupine, raccoon, kit fox, rock squirrel, spotted bat, striped skunk, wild horse, black-tailed jackrabbit, and the bobcat (2010). Many plants and animals have adapted physiologically to support life on the dessert.
Physiological and Structural Adaptations:
The Cholla Cactus: In desert conditions, a plant’s survival can be based on whether or not they absorb water and maintain through the dry spells. The Cholla Cactus is set up to do just that with three of their main organs that are their roots, stems, and areoles. Theses cactus have an extensive root system that lay shallow in the ground ("Desert Ecology Cacti and Other Succulents," n.d.). This is beneficial for absorbing even the slightest bit of rain water that will fall in the Mojave Desert. Once this water is absorbed, it is transferred to the stems of the cactus. These stems appear swollen, in contrast to other plants because they contain water-storage tissues, and a thick epidermis ("Desert Ecology Cacti and Other Succulents," n.d.). The stem is coated with wax from the thick epidermisand is their main prevention for water loss. Along the stems on the surface of the epidermis are rows of areoles. These are pits that grow long spines all over the cactus. These spines offer protection of the stems from herbivores, and to shade the stems from the scorching sunlight that the Mojave Desert receives. In short, the Cholla Cactus has evolved well to absorb and retain its water for survival.
Mojave Desert Tortoise: The Mojave Desert Tortoise has adapted to life in the desert by simply hiding. It will spend 95% of its life underground (Digital Desert, 2010). To aid in this tactic for survival the tortoise has developed organs such as flattened clawed front legs, a domed shell, and a large bladder. The front legs are the tools that dig the deep burrows, up to eight feet, in which they spend the majority of their lives in. Once in their burrows the domed shell acts like a plug to keep out predators as well as the hot desert air. To survive in these burrows at long lengths of time the tortoise has developed a large bladder and when filled, it can account for 40% of their body weight(Digital Desert. 2010). The tortoises can simply reabsorb the water back into their bloodstream from the bladder when needed. It has been proven a very effective way to survive in the desert.
Kangaroo Rat: The kangaroo rat is almost perfectly adapted to life in the desert. They store the seeds in their burrows, where the seeds absorb moisture from the air; the animals then receive that moisture when they eat the seeds. Kangaroo rats are even able to manufacture water as a byproduct of chemical processes involved in their digestion of seeds, and they seal their burrows to recycle the moisture released during breathing. These creatures are so efficient in their use and conservation of water that even in captivity they will not drink water when offered it (digitaldesert.net, 2010).
Without ever drinking any water, getting needed moisture from their seed diet, these rodents are able to survive in this harsh environment. They also have excellent hearing and can detect the silent sound of an owl approaching. Their large back legs enable them to jump up to 9 feet (2.75m) in one jump in order to escape predators (desertmuseum.org, 2012).
The noses of these rodents are set up in such a way that it is able to conserve and recover some of the water from its breath. Its nose works as a countercurrent heat exchanger in that the air entering and leaving the rat’s lungs has to follow a convoluted passageway. Along this passage, a heat gradient is set up. As the breath gets closer to the outside, it starts to cool. The heat gradient allows time for the water vapor to condense inside the nasal passage, allowing the kangaroo rat to recover between 50 and 80 percent of the water in its breath. This makes the kangaroo rat very water efficient (Marchetti & Moyle, 2010).
Kangaroo rats have another way to use water efficiently. They have a specialized kidney that allows the rats to remove water from their nitrogenous waste. This rodent’s urine is excreted as more as a paste than as a liquid. This process allows it save large volumes of water, making it a marvel of water conservation (2010).
Adaptations to the Mojave Desert
The fringe-toed Lizard has adapted well to life in the Mojave Desert. Some physical key characteristics of the lizards that help it survive are its coloration of brown and tan, and the scales that cover their bodies. Their coloration helps them by blending into their surroundings by resembling the sands that they live on. The fringe-toed lizard scales are used to give added traction when running across the sand, and to seal up their eyes, nose, and ears when burrowing into the sand (Digital Desert, 2010). Burrowing into the sand is a tactic they use to escape predators and the midday sun. These lizards are primarily insectivores eating insects such as ants, beetles, and grasshoppers (Digital Desert, 2010) found in the Mojave Desert. They are also known to eat plant material, which includes flower buds and stems, leaves, and seeds.
The Kangaroo Rat prefers to live in the sandy areas of the Mojave Desert because they have adapted to digging burrows to live in and to raise their young. They typically search out shrubs growing in the sand, and dig their burrows at the base of them. The shrubs offer shade as well as concealment of their burrows. These rodents are graminivorous using the seeds of plants to account for 90% of their diets (Digital Desert, 2010). In the Mojave Desert, 10% is obtained by eating leafy vegetation that is sparsely. The Kangaroo Rats biggest adaptation to the Mojave Desert is that they do not require a body of water to survive. They obtain all of the water they need metabolically from the plants and seeds they consume.
The desert Kit Fox biggest adaptation to the Mojave Desert is its ability to consume multiple food sources. They are primarily carnivores but will survive by eating just about anything. Their diet includes rabbits, rodents, insects, reptiles, birds, and plant material. Like the Kangaroo Rat, they too receive all the water they need from their food sources, so no drinking water supply is needed. They evolved into nocturnal predators for survival in the desert conditions. They hunt at night to avoid the scorching heat and to limit the amount of water their bodies will need.
The Red-tailed Hawk is a bird of prey that flourishes all across the United States. To survive in the Mojave Desert they prey mainly on small rodents, like the Kangaroo Rat, and reptiles such as rattlesnakes (Digital Desert, 2010). They use the open grasslands of the Mojave Desert to search for prey but will also rob other nests for hatchlings and their eggs to survive. The preferred nesting site of the hawks is in heavily forest areas. These are not readily available in the desert, so they have adapted to building them on the sides of cliffs, on cacti, and shrubs (Digital Desert, 2010).
The Mule Deer has adapted to life in the Mojave Desert by traversing up and down the mountains based on the time of the year. They mainly feed on the new growth of shrubs and various types of forbs. During the summer they will browse and graze in the higher elevations to feed. As winter approaches, they will descend to lower elevations so that snow cover does not hide their food sources (Digital Desert, 2010). In addition to the shrubs and forbs the Mule Deer also make use of the natural mineral licks that the Mojave Desert has to offer.
The Western Diamond-backed Rattle Snake is another species becomes most active at dusk and at night to escape the midday heat. They prefer the brushy areas of the Mojave Desert for protection as well as the numerous food sources that occupy these areas (Digital Desert, 2010). They primarily consume small to medium-sized animals such as rats and rabbits but will also consume other reptiles because of the abundance of them. Theses snakes will also find refuge under logs, rock piles, and rodent burrows (Digital Desert, 2010). The rodent burrows will double as a place to raise their young.
Ecosystem’s population growth and regulation
Resources influence ecosystem activity differently depending on whether they are essential, substitutable, or complementary. The population of species has to compete for the same resources in a limited geographical area. For a species to survive, they will require a minimum amount of food because they may need to compete with the same species or compete with other species. When populations rise, food may become limited; the population will decrease until food supplies are restored for the population to raise again. An increase in larger animals can heavily reduce smaller species when paths are crossed. When there is an increase in species, so is the spread of diseases increased. Environmental factors regulate population sizes. Weather will also have an impact on regulating population growth. The desert gets very little rain fall and if there is not enough water for all organisms, the life span of certain species can be decreased.
Human Impact on Our Environment
One of the major impacts humans have on our environment is littering. This causes the death of many animals in the desert and around the world. As an example, balloons thrown into the oceans can cause animal entanglement or choking. Trash, such as broken glass or syringes, can be very dangerous if animals were to ingest this type of waste. Trash thrown into waterways can cause blockages leading to flooding and other trash discarded from a car window (such as cigarettes) can cause fires, which can ruin the habitat for animals. Furthermore, human trash decreases the oxygen levels in water as it decays, causing yet more problems for marine environments. Overfishing is yet another problem with our current ecosystem. This problem can force animals, such as sharks, to find other sources of food, which can be potentially fatal for humans (biologicaldiversity.org, 2009).
Because of the increasing numbers of human populations more natural resources such as water, food, etc. are used. The earth can regenerate these resources but not at the amount needed to sustain our current population. Problems, such as limited water supply and limited farm land, can occur. This is also the biggest cause of deforestation today. There has been a noticeable increase in the population of other states (and also an increase in logging companies). California is the most populated state in the United States. It has soared to an astounding 38.6 million people inhabiting California alone in 2008, and it is only increasing (globalgeography.aag.org, 2011).
Pollution of our water resources not only affects the current ecosystem but also the ecosystems located downstream. Pollution of water affects plants, animals, and the entire food chain. This could pass the toxins from organism to organism to the top of the food chain (people). In 2007, the Center of Biological Diversity succeeded in increasing the standards of air pollution caused by power plants located close to Mojave Desert (environment.nsw.gov, 2011).
The destruction of forests and the ecosystem is known as deforestation. Trees provide oxygen that is vital for human survival. Deforestation occurs at a devastatingly high rate. Trees also provide shelter for many animals such as squirrels, opossums, and so on. The destruction of the earth’s forests causes these animals to find new places to live, invading other ecosystems they may not have been native to otherwise. The high human populations and their need to have natural resources to survive is the cause of deforestation (cwac.net, 2012). As previously stated, California is the most populated state in the United States.
Plant and animal extinctions has been one of the biggest human impacts on the environment. One animal is another animal’s food source. Destruction of this food source may cause an animal to find a different (maybe less healthy) food source decreasing their populations. The entire ecosystem is unstable with the destruction of a plant or an animal (environment.nsw.gov, 2011).
Humans impact all ecosystems – not just one. Polluted waters continuing downstream will also continue to impact numerous ecosystems and eventually reach the oceans. Deforestation causes animals to search for new homes, possibly in ecosystems they would not have been in otherwise, causing a disruption to that ecosystem as well. Littering affects all ecosystems bringing new dangers such as choking and chemical leaching into the environment. Underground rivers can carry the leached materials/trash to other ecosystems as well.

Conclusion
The Mojave Desert comprises an ecosystem that is unique to this type of environment. With the vast array of food sources found here, many plants and animals have been able to adapt and survive. It is a place bountiful with life with many things to discover. This can all end; however, if humans are not careful with the earth with which they were entrusted. Rapid population growth, increased pollution, and deforestation all play a vital role in keeping our ecosystems thriving with life. Plants and animals have found many ways to adapt, but these organisms need the assistance of the most advanced species on earth – humans. Ironically, humans are the biggest contributor to the ruins of ecosystems around the world. However, without the continued efforts of these same species, the ecosystems of the world may soon fall to pieces.

References

Arizona-Sonora Desert Museum. (2012). Animal fact sheet: Merriam’s kangaroo rat. Retrieved on March 2, 2012 from http://www.desertmuseum.org/kids/oz/long-fact-sheets/krat.php
Biology Online. (n.d.). Population regulation in an ecosystem. Retrieved from http://www.biology-online.org/4/5_monitoring_populations.htm
Center for Biologcal Diversity. (2009). Retrieved from http://www.biologicaldiversity.org/news/press_releases/2009/paving-offsets-11-02-2009.html CWAC.NET. (2012). Retrieved from http://www.cwac.net/population/index.html
Digital Desert. (2010). Desert ecosystem. Retrieved on March 1, 2012 from http://digital-desert.com/joshua-tree-national-park/ecosystems.html
Digital Desert. (2010). Desert mammals. Retrieved March 4, 2012 from http://digital-desert.com/wildlife/mammals.html
DesertUSA. (1996-2012). Explore the deserts of the world. Retrieved from http://www.desertusa.com/
Environment & Heritage. (2011). Retrieved from http://www.environment.nsw.gov.au/warr/litter.htm
Marchetti, M. & Moyle, P. (2010). Protecting life on earth: an introduction to the science of conservation. Berkeley, CA:
University of California Press
Population and Natural Resources case study: How does urban development affect the quality and quantity of natural resources?(2011). Retrieved from http://globalgeography.aag.org/PopulationandNaturalResources1e/CS_US_July09/CS_US_July094.html
Townsend, C. R., Harper, J. L., & Begon, M. (2000). Essentials of ecology. Blackwell science.
Retrieved from http://books.google.com/books/about/Ecology.html?id=3xklog5kVGMC

Appendix 1 Desert Food Chains
Appendix 1 Desert Food Chains
Appendix 1 Mojave Desert Food Chains
Appendix 1 Mojave Desert Food Chains

Mountain Lion
Consumer
Mountain Lion
Consumer
Fringed-toed lizard
Secondary Consumer
Fringed-toed lizard
Secondary Consumer
Kangaroo Rat
Decomposer
Kangaroo Rat
Decomposer
Prickly Poppy
Producer
Prickly Poppy
Producer
Western Diamondback
Secondary Consumer
Western Diamondback
Secondary Consumer
Mormon Cricket
Decomposer

Mormon Cricket
Decomposer

Sagebrush
Producer
Sagebrush
Producer
Sweetbush
Producer
Sweetbush
Producer
Gambel’s Quail
Decomposer
Gambel’s Quail
Decomposer
Bitter Brush
Producer
Bitter Brush
Producer
Mule Deer
Decomposer
Mule Deer
Decomposer
Red-Tailed Hawk
Consumer
Red-Tailed Hawk
Consumer
Mojave Rattlesnake
Consumer
Mojave Rattlesnake
Consumer
Desert Kit Fox
Consumer
Desert Kit Fox
Consumer

Appendix 2

Figure 2 - Mojave Desert Food Chains Mojave Desert Food Chain Examples | | Producers | Decomposers | Consumers | | Food Chain 1 | Bitterbrush | Mule Deer | Mountain Lion | | | | | | | Food Chain 2 | Sweet Bush | Gambel’s Quail | Desert Kit Fox | | | | | | | Food Chain 3 | Sagebrush | Mormon Cricket | Fringe-toed Lizard | Mojave Rattlesnake | | | | | | Food Chain 4 | Prickly Poppy | Kangaroo Rat | Western Diamond-backed | Red-tailed Hawk | *