Cofrin Center for Biodiversity

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Animals

Like the flora, the fauna of oak savannas exhibits affinities to both grasslands and forests. A study by Mierzwa (1994) in the Chicago region yielded 20 species of reptiles and amphibians and 10 species of mammals, none of which is restricted to savanna habitats. Amphibians (e.g., tiger salamander (Ambystoma tigrinum), blue-spotted salamander (Ambystoma laterale), and tree frogs (Hyla crucifer and H. versicolor) tended to be more numerous in heavily wooded savannas or woodlands, whereas reptiles (e.g., eastern garter snake (Thamnophis sirtalis), brown snake (Storeria dekayi) tended to be more numerous in open savannas. Sand savannas were inhabited by two uncommon reptiles, the six-lined racerunner (Cnemidophorus sexlineatus) and slender glass lizard (Ophisaurus attenuatus). Small mammals of oak savannas included widespread species like white-footed mouse (Peromyscus leucopus), masked shrew (Sorex cinereus), and short-tailed shrew (Blarina brevicauda). Fox squirrel (Sciurus niger), gray squirrel (Sciurus carolinensis), and Franklin's ground squirrel (Spermophilus franklinii) also were observed in Mierzwa's study

Larger animals such as American bison (Bison bison), American elk (Cervus elaphus), and white-tailed deer (Odocoileus virginiana) surely were a prominent part of presettlement oak savannas, along with woodchuck (Marmota monax), badger (Taxidea taxus), pocket gopher (Geomys bursarius), and foxes (Vulpes vulpes and Urocyon cinereoargenteus). Bison and elk are long gone from Midwestern landscapes, but most of the other savanna mammals have survived in semi-natural pastoral habitats or remnant forest/grassland mosaics.

Birds, for the most part, have adapted to alternative habitats as native oak savannas were destroyed and degraded. Species like northern flicker (Colaptes auratus), blue jay (Cyanocitta cristata), and American robin (Turdus migratorius) are familiar today in woodlands, roadsides, and even urban environments. The red-headed woodpecker (Melanerpes erythrocephalus) can still be found in oak-dominated golf courses and at the edges of woodlands, but its numbers are declining. Mississippi kite (Ictinia mississippiensis), Loggerhead shrike (Lanius ludovicianus), and Bell's vireo (Vireo bellii) might have have been widespread in Midwestern oak savannas, but today they have disappeared from much of their former ranges. Many other familiar bird species were probably part of the presettlement savanna avifauna, including orchard oriole (Icterus spurius), brown thrasher (Toxostoma rufum), and prairie warbler (Dendroica discolor). Because so few remnant savannas are present today, reconstructing the original savanna fauna is challenging. It is even possible that declining species like cerulean warbler (Dendroica cerulea), Bewick's wren (Thryomanes bewickii), Bachman's sparrow (Aimophila aestivalis), and Henslow's sparrow (Ammodramus henslowii) were regular inhabitants of presettlement oak savannas, along with the passenger pigeon (Ectopistes migratorius), which has been extinct in the wild for more than a century.

Invertebrates of oak savannas are poorly known but one species, the Karner blue butterfly (Lycaeides melissa samuelis), has become a flagship for conservation and stewardship of Midwestern oak savannas. The obligate larval host plant of Karner blues is wild lupine (Lupinus perennis), which requires fire or other disturbance for germination and persistence. Karner blues occur in habitats with a broken or scattered tree canopy, and oak savannas appear to provide ideal conditions. Today, the most significant Karner blue populations occur in Wisconsin, where more than 270 occurrences are known from about 15 large population areas (Bleser 1999). Other rare butterflies of Midwestern oak savannas include frosted elfin (Incisalia iris), Persius dusky wing (Erynnis persius), and regal fritillary (Viola pedata) (Chapman et al. 1994). The Midwestern Oak Ecosystems Recovery Plan (1994) lists 16 rare invertebrates of oak savannas, including a tiger beetle (Cicindela patruela), 7 skippers (Hesperiidae), 5 other butterfly species, and 3 species of moths.

Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects