Spider Conservation in the United States By: Kevin L. Skerl Spiders, like many other invertebrates, have traditionally suffered a lack of attention from conservation professionals and the general public. As more information becomes available, however, scientists are gaining a better understanding of spiders' integral role in natural systems and of the need to improve protection efforts. Approximately 3,500 spider species, with an additional 350 yet undescribed, exist in the United States and Canada (Roth 1993). They are abundant predators in many terrestrial ecosystems, with estimates of populations in field habitats approaching one million individuals per hectare (Bristowe 1971). Almost all spiders are generalist predators, mainly eating insects and secondarily other spiders (Wise 1993); a few have become specialists (Nentwig 1986). Some larger species may even occasionally feed on small mice, birds, and lizards. Additionally, spiders are an important food source for birds, lizards, wasps and other animals. In a study of trunk arthropods, spiders provided a relatively constant food source throughout the year for bark-gleaning birds (Peterson et al. 1989). Hogstad (1984) demonstrated that spiders were a primary winter food source for goldcrests ( Regulus regulus ). Also, spider silk is important to bird species for nest building; 24 of 42 families of passerine birds and nearly all species of hummingbird depend on silk from spiders and caterpillars for nest construction (Hansel 1993). | |
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