A Natural History of the Mojave Desert by Lawrence R. Walker & Frederick H. Landau

Author:Lawrence R. Walker & Frederick H. Landau [Walker, Lawrence R. & Landau, Frederick H.]
Language: eng
Format: epub
Tags: NAT045010 Nature / Ecosystems & Habitats / Deserts, TRV025130 Travel / United States / West / Pacific (ak, Ca, Hi, Or, Wa)
Publisher: University of Arizona Press
Published: 2018-03-27T00:00:00+00:00

Figure 89. Harvester ant nest surrounded by vegetation. Photo by Lawrence Walker.

Animal Interactions

Desert animals, like organisms everywhere, are constantly interacting with their environment in their need for food, safety, health, shelter, and mates. Mule deer eat plants, mountain lions eat mule deer, foxes and ravens scavenge any carcass leftovers, but the fox also eats mice, and the mice eat plant seeds. These overlapping interactions are called food webs, and they can get quite complex. Everything really is connected to everything else, especially when you factor in the physical environment that the animals share. Just in that simple example, we see herbivory and predation. In addition, there is likely competition between the scavengers of the mule deer carcass. Less obvious, but likely present, are parasite or disease interactions (sick deer are most vulnerable to predation) and potential positive interactions (the fox cues in to the vulture circling to find the carcass).

Animal interactions are also among individuals of the same species. These include courtship and other mating rituals (perhaps the male mule deer was distracted by nearby females), territoriality (the fox might need to defend that carcass from neighboring foxes), and raising young (the fox has hungry pups to feed). Animal interactions are therefore complex and hard to study. Single interactions can be examined using binoculars, radio collars, traps, drones, and many other tools (plus a lot of patience). Understanding the larger set of food web interactions remains an ongoing challenge. Nonetheless, what is quite clear is that ecological interactions are essential. Without such interactions we would not have a recognizable world, but one filled with undecomposed dead matter without roundworms, segmented worms, and arthropods; unpollinated plants without insects; and unhealthy animal populations because a lack of predation leads to an overabundance of individuals that can then damage the environment. In the following paragraphs, we highlight a few of the better-studied examples of animal interactions in the Mojave Desert.

A politically sensitive interaction among mammals in the Mojave Desert is that between humans and feral horses and burros (see chapter 8). Humans have, of course, disrupted many food webs, and the animals that we favor (such as cattle, pets) or that benefit from our presence (ravens, coyotes) also do their share of disruption. Humans also favor certain wild animals over others, and those are the first we tend to study. For example, scientists have studied desert bighorn sheep interactions (box 8) with their predators (mountain lions, bobcats, coyotes); competitors (feral horses and burros, cattle); food (a variety of plants); and parasites (bot flies). Unlike most mammals, desert bighorn sheep can tolerate a shift of a few degrees in their body temperature and the loss of 30 percent of their body weight during hot, dry conditions. These characteristics allow them to survive in drier habitats than one of their predators, mountain lions, can tolerate. It does not allow them to escape their other main predators: bobcats, coyotes, and eagles, which prey on lambs. We once saw a desert bighorn sheep die, presumably from a bot fly infection, because it had a hole in its horn.

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