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Chapter 6: Ecological Principles and Wildlife
- University of Texas Press
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Kim Duffek Chapter 6 Ecological Principles and Wildlife Introduction to Wildlife Ecology Ecology is the pattern of relationships between organisms and their environment . An environment is everything that acts upon an individual or species to shape it, and it contains the elements that ultimately determine survival. Physical factors (such as geologic features and climate), chemical factors (such as soil makeup), and biotic factors (such as plants, animals, and microorganisms) can shape entire biotic communities. All organisms in a biotic community are interrelated in some way, in what many refer to as the web of life. Local environments are shaped by climate and topography. One need only compare the cool north side of a mountain to the warm south side to understand these forces. In doing so, contrasts in the makeup of plant and animal communities will be observed. Deserts occur primarily in the rain shadow of larger mountain ranges. In these areas, moisture-laden air rises up and over the high slopes, cools, condenses into rain, and falls at the higher elevations. Once the air reaches the far side, or rain shadow, of the mountains, it has lost most of its moisture. Within these broad environments are small local environments and even microenvironments where species that could not otherwise survive on the hot, dry desert find a place to live. Washes, or arroyos, present conditions that serve the requirements of species adapted to loose soil and higher, intermittent, sometimes violent, water availability. On rocky north-facing slopes, crevices provide shade and shelter for plants and animals not adapted to the harsh open desert.Garden designers can take advantage of shady spots to plant species with different needs than those that thrive in the hot sun. A spot near a roofline or a gutter will support plants with higher water needs. Grouping plants by their needs makes them more likely to thrive. The survival of any species depends upon the provision of food, water, shelter , and space in its habitat. Habitat is the type of place where a particular plant or animal lives. Some organisms live in a wide variety of places, while others 124 creating outdoor classrooms Ecological Principles and Wildlife have very limited habitat due to their narrow requirements for existence. At first, it does not seem advantageous for a species to occupy a narrow niche because it will be less likely to survive changes in its environment. But in a stable environment, monopolizing a certain commodity is more advantageous than being a generalist, expending energy in competition with many other species. Foranyorganism to survive in a particularenvironment it must be able to utilize the resources available. Limited nutrients, moisture, and cover must be adapted to in a harsh desert environment, through either physiological or behavioral traits. For example, the body of a Kangaroo rat (Dipodomys sp.) metabolizes the moisture it needs from dry seeds. The Kangaroo rat lives underground in a cool burrow, where it stores its seeds, coming out only at night. The seeds take up a small amount of moisture from being underground.These behavioral traits conserve and trap water. The rodent then metabolizes its food efficiently and excretes urine so concentrated it can crystallize as soon as it contacts the soil. This animal is the epitome of desert survival. Interdependence occurs when two or more species rely strongly on each other for survival. Bat-pollinated flowers open only at night, excluding daytime pollinators, and also produce the copious quantities of pollen and nectar that long-lived and far-flying nectivorous bats need for survival. Some plants have forged so tight a relationship with a particular animal species that neither could continue to survive without the other. Sometimes it is not so clear. In the northern part of their range, saguaros, which are adapted to bat pollination, keep their flowers open longer into the morning than their southern counterparts, thus attracting a second major pollinator, the white-winged dove.This is advantageous to the plant because the bat’s range is limited to the extreme southern Southwest, while the dove’s range extends throughout the range of the saguaro. The saguaro is limited in the north by frost. Studying wildlife ecology is like trying to put together a huge and complex puzzle. Often what seems obvious becomes less so when looked at more closely. An ugly caterpillar that eats garden plants, for example, will metamorphose into a beautiful butterfly that pollinates those same plants. Some scientific discoveries related to wildlife ecology can be used to benefit...