Environmental Stress Factors of the Shrew

Regarded as one of the world's smallest mammals, shrews are a rodent-like creature that can vary in size from 15 cm to roughly the size of a human thumbnail. There are 376 different species of the shrew, each with a unique set of dangers and environmental stress factors. For North American shrews, predators, pesticides, lack of hedgerows and loss of prey are the primary areas of stress for shrews in the wild.

  1. Predators

    • Some of the shrew's natural environmental stress factors are the animal's predators. The most common predators for North American shrews include snakes, frogs, owls, hawks and even fish. Larger mammals like foxes, weasels and bobcats also present a threat to the shrew, though some of these animals refuse to eat the shrews because of the strong odor these mammals give off. Because there is such a difference in size between the smallest shrew and the largest, sometimes larger shrews will even hunt and eat smaller species.

    Pesticides

    • For shrews that are unfortunate enough to call a populated area home, pesticides may present another potentially deadly environmental stress factor. Shrews sometimes decide to move in to human homes, which is a nuisance that human homeowners often fight to combat. Pest control companies may decide to poison or trap these unfortunate shrews. Even when shrews live outside, they could be affected or poisoned from other pesticides, particularly if they live close to farmland that undergoes chemical pesticide treatments. Thus, pesticides are another environmental danger that shrews must fight to overcome.

    Lack of Foliage

    • One of the major ways that shrews survive potential attacks from predators is to hide, particularly in long grass and deep foliage. However, humans have greatly reduced the amount of foliage in many areas of North America, making the lack of foliage another environmental stress factor for the shrew. This loss of habitat makes for fewer appealing spots for shrews to rest and reproduce, and it also makes them more vulnerable to attacks by predators. Ultimately, lack of foliage and hedgerows could contribute to depleted shrew populations.

    Loss of Prey

    • When an ecosystem suffers, all parts of that system are often damaged. Most populations are reduced, including that of bugs, birds and amphibians. This is bad news for shrews, who feed primarily on bugs like centipedes, spiders and earthworms, and who also may eat small salamanders and young birds. If shrew prey are not available, shrews become particularly stressed, forced to act recklessly in order to find enough food each day. If the shrews don't starve, this reckless search for food can lead to more exposure to predators for the shrew, further perpetuating the environmental stress cycle.