Riparian Zone Retreat and population studies Dakota Hutchinson, Honors Biology II, Period 1.
Shrew Cryptotis parva
Shrews live in forests, or weedy fields. They make nests out of leaves or dig burrows lined with leaves or grass. It is not uncommon to see Shrews sharing a burrow.
Shrews hunt for earthworms, spiders, slugs, caterpillars, insect larva, grasshoppers, crickets, centipedes, millipedes, isopods, small frogs, and small lizards. Sometimes, shrews eat carrion, seeds, and fruits. Shrews are hunted by owls, hawks, red foxes, raccoons, and snakes.
Shrews are most active during the night. They hunt for insects and bugs by digging through loose soil and leaves. Their poor eye sight and hearing forces Shrews to hunt by smell and touch. When eating insects, a shrew will bight off the insect’s head, only eating the internal organs. Some types of shrews have poisonous saliva.
Factors which Affect Birth Rate of Shrews
Shrews living in southern regions breed year round. In colder climates, breeding occurs between March and November.
Shrews can have several litters each year.
Gestation lasts between 21 to 23 days.
Shrews in captivity have been observed to have up to 9 young in each litter, but the average just under 5.
Both parents help to raise the young. Shrews nurse up to 23 days.
Shrews reach sexual maturity at 31 days in females and 36 days in males.
Factors Which Affect the Death Rate of Shrews
Shrews are preyed upon by owls, red foxes, skunks, house cats, and snakes.
On average, Shrews live for approximately 2.6 years.
Seasonal cycles of external parasites of shrews have been found. Fleas and ticks are commonly found on shrews, and a single shrew can play host to three or four large ticks.
Forests are being destroyed as the more wood and land are needed to support the growing human population. The destruction of these forests leads to the destruction of the shrew’s habitat.
Food Chain of a Shrew Producer Autotroph Primary Consumer Herbivore Secondary Consumer Carnivore Tertiary Consumer Omnivore
Food web of a Shrew Carnivore Decomposer Herbivore Herbivore Producer Producer Carnivore Carnivore Carnivore Omnivore
Population Sampling Techniques
One of the easiest ways for investigators to estimate numbers of animals without having to census an entire population is the capture-recapture method. With this method, animals are captured, marked for identification, and released into the population.
Shrew populations are typically measured by recapturing techniques at monthly intervals.
Stream Quality Data & Analysis
Since the majority of the organisms found are from Class I, Powdermill Run is pristine quality.
A great number of Class I organisms indicates good water quality because these organisms are generally pollution-intolerant. Class II organisms can exist in a wide range of water quality because they are somewhat tolerant of water pollution. A large number of Class III organisms indicates poor water quality because these organisms are generally tolerant of pollution.
A stream of good water quality offers a home for a larger variety of insects for the shrew to feed on.
If the majority of organisms found were from Class III, many organisms, including the shrew, would be unable to use the stream as a source of food.
Water Testing Data & Analysis
The nitrate and phosphate level indicates the amount of nutrients found in the stream. The oxygen level indicates the amount of dissolved oxygen found in the stream. Finally, pH is a measure of the acidity or alkalinity of the stream.
At Powdermill, the nitrate and phosphate level should be low. The oxygen level should be high and the pH level should be between 6.0 and 7.0. If the levels were to go outside this range, the organisms intolerant to pollution could die off.
If a shrew was to have a habitat near the marsh, it would have to find a source of food elsewhere because the eutrophication of the ponds would prevent any insects from living there. The pH level of the mine runoff would prevent organisms from living there as well.
The temperature can affect the level of dissolved oxygen. Streams with low temperatures have higher amounts of dissolved oxygen. High turbidity can interfere with predator-prey relationships. Cloudy water prohibits predators from seeing their prey and particles in the water can clog the gills of organisms.
Soil Testing & Analysis
Nitrogen, phosphorous, and potash play a vital role in plant growth and metabolism. The pH level controls how well plants utilize the nutrients available in the soil.
Most soils are within a range of highly acidic pH of 4 to slightly alkaline at a pH of 7.5 to 8. Nitrogen and phosphorous levels should not be excessively high or excess nitrogen and phosphorous could runoff into streams and lakes. Tomatoes, strawberries, beans, peas, and flowering plants require high levels of potash.
If the nitrogen or phosphorous level gets to high in the soil, the excess of nutrients could runoff into streams and ponds. The streams and ponds would become saturated with nitrogen and phosphorous, causing eutrophication.
Positive and Negative Factors
The current stream, marsh & mine waters would affect shrews by providing s source of food. Shrews would be able to feed on the insects around the healthy stream. The unhealthy quality of the marsh and mine water would make it more difficult for shrews to find insects to feed on.
The good quality of soil found in the riparian zone provides plants with the nutrients needed to grow. Shrews will sometimes eat the leaves and berries found on plants. Shrews will also eat the insects that feed on the plants.
The most common sources of pollution in PA streams are acid main drainage and agricultural runoff. Acid mine drainage can be limited through the use of settling ponds. Agricultural runoff can be limited by safe farming practices. Farmers can limit the amount of chemicals and fertilizers used. Buffer zones can be planted in between farms and water sources. The plants in these areas take up additional nutrients from fertilizers, limiting the amount that enters into the water.
I never knew that an excess amount of nutrients could be damaging to the environment. I was surprised to find out that if there is to much nitrogen or phosphorous in the soil, the extra amount could end up polluting streams and ponds.
I found it interesting that several shrews live together in one burrow.
I would like to research global warming in the future.
"Least Shrew." The Study of Northern Virginia Ecology. Fairfax County Public Schools, n.d. Web. 11 May 2010 http://www.fcps.edu/islandcreekes/ecology/least_shrew.htm
Tesar, Jenny. "Shrews." Reviewed by Douglas Falk. The New Book of Knowledge® . 2010. Grolier Online. 12 May 2010 <http://nbk.grolier.com/cgi-bin/article?assetid=a2026960-h>.