| ... |
Amphibian and Reptile Habitat
in the Chicago Wilderness Region
Savanna and Woodland Communities
by Ken Mierzwa
|
|
Introduction Until very recently, even the most thorough and scholarly references about Midwestern amphibians and reptiles made little distinction among various types of wooded habitats. Usually any site with more than a few trees was referred to as forest. A few authors recognized that some species tended to occur only in specific situations, but did not have a classification available to adequately describe what they apparently were able to sense intuitively. For example, most of the species described as inhabitants of the ³forest edge² by Smith (1961) are now known to be associated with savannas or open woodlands. However, canopy structure is not the only influence on animal distribution. Herpetologists have recognized the critical importance of soil type for some time. Smith (1961) mapped sand areas in Illinois, and made frequent reference to the characteristic and often relict species found there. Klemens (1993) and others have noted the influence of bedrock type. Many other factors play a role.
Despite a few recent attempts to provide a framework for accurate identification of amphibian and reptile habitat (Klemens, 1993; Mierzwa, 1998a; Welsh and Lind, 1991), most habitat descriptions are still anecdotal references based on years of field experience. Because of recent advances in the understanding of plant community structure and the urgent need to restore natural areas, more detailed information is now desirable. This paper attempts to analyze available data in the context of current community classification in the Chicago Wilderness area.
While it is generally possible to assign a particular site to a plant community type, occasional disagreement by experts and inconsistencies in existing classifications highlights the need for a quantitative classification scheme similar to that used in some other states (Sawyer and Keeler-Wolf, 1995). Even more problematic is assessing animal distributions within the context of the surrounding landscape. Present distribution is determined not only by the availability of suitable habitat, but by the biogeographic history of the region and by subsequent stochastic extinction and recolonization events within metapopulations. Initial steps are taken here toward considering community level assemblages within the context of the surrounding ecosystem.
Methods Drift fence data were taken from published articles and unpublished reports (Beamer 1996; Mauger and Robeson, 1993; Mierzwa 1989, 1992, 1994; Mierzwa et al 1992; Mierzwa and Beltz 1994a, 1994b; Sliwinski 1992). Results were standardized and reported as captures per trap-night, with one trap-night = one 24 hour period per 15m of drift fence array. A few additional drift fence studies exist but were excluded from consideration, because results could not be quantified in a comparable way. Generally this was because information on array design or sampling dates was not included in available documentation, or because results collected by more than one method had been lumped for reporting purposes.
Sample sites were assigned to community types by considering both the immediate micro-environment around the drift fence arrays, and the surrounding landscape to a distance of several hundred meters. Canopy structure, tree species composition, soil type, and hydrology were key factors. Datasets from four community types are considered here: Black-soil savanna (less than 30 percent tree canopy cover, usually on soils derived from glacial till), sand savanna (less than 30 percent tree canopy cover, on predominantly sandy soils), northern flatwoods (canopy dominated by stunted oaks, cover variable, on clay soils with seasonal hydrology extremes), and mesic woodland (30 to 70 percent tree canopy cover, on moderately well-drained silt-loam soils).
Site Descriptions Of 66 Chicago Wilderness area sites with quantifiable drift fence data available at this time, 34 are in relatively intact wooded communities. Nine are within black-soil savanna sites, 10 in sand savanna sites, 10 in northern flatwoods sites, and five in woodland sites. Site locations are shown in Figure 1.
Figure 1. Locations of study sites.
Results A total of 14 amphibian and 17 reptile species (31 combined species) have been captured in drift fences within Chicago region studies considered here.
Seven species (22.6 percent) were captured in all four community types. Another seven species were captured in only one community type.
Northern flatwoods and mesic woodlands were relatively similar to each other, but both differed greatly from black-soil and sand savannas (Table 1).
| Table 1. Sorensen coefficient of similarity for savanna amphibians and reptiles |
|---|
| . |
Black-soil savanna |
Sand savanna |
Northern flatwoods |
Mesic woodland |
| Black-soil savanna | -- |
.762 | .467 |
.500 |
| Sand savanna | .762 |
-- | .451 |
.556 |
| Northern flatwoods | .467 | .421 | -- | .857 |
| Mesic woodland | .500 | .556 | .857 | -- |
Characteristics of Community Types
Black soil savanna
Black-soil savanna communities are characterized by a mix of amphibian and reptile species. Species richness is moderate at 18. Although 10 of these species are reptiles, four of the five most abundant species are amphibians often associated with dense herbaceous vegetation.
Black soil savannas support a relatively diverse herpetofauna. At the nine sites sampled, mean species richness was 6.67 species (range 3 to 12). Abundant species include Bufo americanus, Ambystoma tigrinum, Rana pipiens, and Thamnophis sirtalis. Storeria dekayi and Storeria occipitomaculata are also moderately common. Species present at two-thirds or more of the sites sampled include Ambystoma tigrinum, Bufo americanus, Pseudacris triseriata, Rana pipiens, and Thamnophis sirtalis.
The sample sites support a good mix of taxa, with two salamander species, five frogs, three turtles, and seven snakes. Good snake diversity is not surprising in savannas because of the relatively open and sunlit condition of good examples. Qualitative observations imply that snakes are most diverse and most abundant in the most open portions, including restored areas, or around the edges of savanna groves.
Characteristic species include Hyla chrysoscelis, which is moderately common in black-soil savannas in the Fox River Valley but was not noted in other community types.
One species conspicuously uncommon in savanna samples was Lampropeltis triangulum. Past qualitative field experience indicates that this species is common at some black soil savanna sites but absent at others, and also often exhibits pronounced cycles of seasonal and annual surface activity. With a larger sample size additional records of this species would be expected.
Amphibians and reptiles increased substantially in numbers at three of the sample sites after restoration activities including use of prescribed fire on a two and three year rotation (Mierzwa, 1998b). Although a few incidents of individual mortality were noted, fire is apparently beneficial at the population level for many of the species typical of black soil savannas.
Limited historical information implies that black soil savannas were once more diverse, and that some amphibian and reptile species may have been lost or become rare since the 1860s. Robert Kennicott collected a number of species in northern Cook County about 1856 which no longer occur there. Unfortunately his precise collecting locations are not known, but his residence was at the edge of an extensive savanna grove. Kennicottıs collections in Cook County were summarized by Mierzwa (1985).
Most black-soil savanna sites were inhabited by amphibian and reptile assemblages markedly different from those of other community types. However, black-soil savanna sites on the Lake Border Moraines were relatively similar to northern flatwoods sites in close geographic proximity.
Sand savanna
Sand savannas have the highest species richness of the communities sampled, at 25. Sand savannas support by far the richest reptile assemblage (16 species) of the four community types. Several unique species are present, including two lizards and a snake which are essentially restricted to sand in the Chicago Wilderness region. Mean species richness for sand savanna sites (8.3, range 4 to 17) is also relatively high.
Many sand savanna sites of good quality have been protected; these preserves usually have a relatively open tree canopy and moderate to dense herbaceous layer. Certainly many sand savanna sites have passed through successional stages much more slowly than their black soil counterparts. In any case, a number of sun-loving reptiles are present on sand savannas. Sand savannas may simply have lost fewer species within historic times than other community types.
The 10 sites sampled are all in the lake plain sand area of northwest Indiana or immediately adjacent Illinois. The most species-rich site included in this analysis (17 species) is a near-lakeshore dune complex site with extensive sand savanna habitat. This site is characterized by the presence of jack pine (Pinus banksiana) and black oak (Quercus velutina), is in general relatively open, and has extensive permanent and semi-permanent wetland swales including areas of open water. Inland sites are black oak sand savanna with wetlands typically in later successional stages.
Abundant species on sand savannas include Bufo americanus, Pseudacris triseriata, Rana pipiens, Thamnophis sirtalis, and Storeria dekayi. The same five species are known from two-thirds or more of sites sampled.
Three salamander species are present although only one (Ambystoma tigrinum) is even moderately common. Six frogs, four turtles, two lizards, and 10 snakes are also known to occur at one or more sites. Characteristic species include the lizards Cnemidophorus sexlineatus and Ophisaurus attenuatus, and the snake Heterodon platirhinos. Several other species considered characteristic of sand areas (Smith, 1961) do not occur in these lake plain sites. Terrapene ornata and Pituophis melanoleucas are known from the Kankakee sand area, while Bufo fowleri and Coluber constrictor occur there as well as in high-dune lake plain sites to the east of the area sampled. Some sand area sites are even more diverse than the set analyzed here. Several sand area species are relicts more typical of regions well to the south or west.
Amphibians and reptiles remain common and diverse at sand area sites which have been subject to prescribed fire for a number of years. A well designed burn regime at an overgrown site should in theory benefit many sand area species, especially lizards and snakes.
Northern flatwoods sites
Northern flatwoods support a herpetofaunal assemblage dramatically different than the community types discussed above. Flatwoods have relatively low species richness (13 species total; mean = 5.1, range = 2 to 8). At most sites one to a few species are abundant with other species being uncommon or rare, with correspondingly low diversity. Only two reptile species were noted, and both were uncommon.
Northern flatwoods are characterized by the presence of eastern or northern amphibians. Ambystoma laterale is usually abundant, and Ambystoma maculatum and Pseudacris crucifer are common at some sites. Another northern species, Rana sylvatica, is present at a few sites but is usually rare. In general, these species are more likely to be present at flatwoods sites which are contiguous with woodland or forest, and less likely to be present at flatwoods sites associated with more open landscapes.
Reptiles are seldom encountered at most flatwoods sites. The only species captured consistently is Thamnophis sirtalis, but even it is usually uncommon. Sistrurus catenatus may enter flatwoods seasonally, and an individual recently emerged from hibernation was observed within one of the sample sites. However this species spends the warm season in more open areas. A few other snakes have been observed in low numbers in open fields contiguous with flatwoods (Clonophis kirtlandii, Storeria dekayi) and it is possible that they might utilize very open examples.
The extreme wetness of flatwoods in the spring presumably allows use by amphibians normally typical of more mesic conditions. The dense shade of shrubs and stunted trees probably is one factor limiting summer use by reptiles.
The effect of fire on flatwoods amphibians and reptiles is not well known. In other community types, Ambystoma laterale and Pseudacris crucifer remain common after fire. Ambystoma maculatum generally decreases substantially in numbers if the tree canopy is opened (Vogt, 1981; Mierzwa, 1998b). No information is available for Rana sylvatica.
Mesic woodland sites
Woodland sites are also inhabited mostly by amphibians, although the assemblage is somewhat more diverse than in flatwoods. The blue-spotted salamander remains the most abundant species, but the dominance is not as overwhelming as in flatwoods.
A total of 15 species are known from mesic woodland sites, including three reptiles. Species richness might be slightly higher except that fewer woodland sites were sampled. Mean species richness was 6.2 (range 3-12). Three sample sites included wetlands with short hydroperiods because of partial drainage, with a clear influence on both amphibian richness and abundance. Mesic woodlands may be particularly susceptible to hydrology alteration because of moderately well drained soils.
Common species in woodlands included Ambystoma laterale, Ambystoma maculatum, Bufo americanus, and Pseudacris triseriata. As in flatwoods, four salamander species were present. Snakes were captured more frequently than in flatwoods but remained relatively uncommon.
| Table 2. Mean amphibian and reptile abundance by community type |
|---|
| Species |
Black-soil savanna |
Sand savanna |
Northern flatwoods |
Mesic woodland |
| Ambystoma laterale |
0.038 |
0.001 |
0.640 |
0.322 |
| Ambystoma maculatum |
-- |
-- |
0.330 |
0.072 |
| Ambystoma tigrinum |
0.213 |
0.017 |
0.024 |
0.014 |
| Notophthalmus viridescens |
-- |
0.001 |
0.008 |
0.022 |
| Bufo americanus |
0.342 |
0.810 |
0.019 |
0.046 |
| Acris crepitans |
-- |
0.001 |
-- |
-- |
| Pseudacris crucifer |
-- |
-- |
0.261 |
0.020 |
| Pseudacris triseriata |
0.011 |
0.220 |
0.050 |
0.080 |
| Hyla chrysoscelis |
0.001 |
-- |
-- |
-- |
| Hyla versicolor |
-- |
-- |
0.002 |
p |
| Rana catesbeiana |
p |
p |
-- |
0.004 |
| Rana clamitans |
0.003 |
0.025 |
0.003 |
p |
| Rana pipiens |
0.076 |
0.120 |
0.001 |
0.012 |
| Rana sylvatica |
-- |
-- |
p |
p |
| Chelydra serpentina |
-- |
0.003 |
-- |
-- |
| Chrysemys picta |
p |
0.005 |
-- |
-- |
| Clemmys guttata |
-- |
0.001 |
-- |
-- |
| Emydoidea blandingii |
p |
p |
-- |
-- |
| Cnemidophorus sexlineatus |
-- |
0.003 |
-- |
-- |
| Ophisaurus attenuatus |
-- |
0.004 |
-- |
-- |
| Heterodon platirhinos |
-- |
0.002 |
-- |
-- |
| Liochlorophis vernalis |
0.002 |
0.002 |
-- |
-- |
| Elaphe vulpina |
0.002 |
0.001 |
-- |
-- |
| Lampropeltis triangulum |
p |
0.001 |
-- |
-- |
| Nerodia sipedon |
-- |
p |
-- |
-- |
| Storeria dekayi |
0.004 |
0.052 |
-- |
-- |
| Storeria occipitomaculata |
0.003 |
0.044 |
-- |
p |
| Thamnophis proximus |
-- |
0.001 |
-- |
-- |
| Thamnophis radix |
0.001 |
0.001 |
-- |
-- |
| Thamnophis sirtalis |
0.029 |
0.101 |
0.001 |
0.002 |
| Sistrurus catenatus |
-- |
-- |
p |
-- |
Results expressed as captures per trap-night.
p = present but not captured in drift fences (incidental observation) |
Discussion
Sampling effectiveness
Drift fences are very effective for capturing small, secretive, relatively mobile species such as salamanders and small snakes. With properly designed funnel traps they also efficiently capture most frogs and lizards. Drift fences are also thought to be less prone to observer bias than methods such as visual encounter surveys. However, drift fences may under sample a few species which are strong climbers (tree frogs) or which have very small home ranges (Kirtlandıs snake). Large active snakes such as racers and bullsnakes may also be able to frequently evade drift fences. Drift fences are also labor intensive to install and require an initial investment in materials.
Comparing data among different studies is problematic because annual weather variation and many other factors may affect surface activity of amphibians and reptiles. Also, different investigators used slightly different methods, each with its own inherent bias. For example, most drift fences were constructed from standard 15m segments of aluminum flashing, but a few used other materials. Most studies used funnel traps but some were supplemented with pitfall traps. Finally, drift fence array placement was usually non-random and thus reflected the experience and bias of each observer.
Combining results from studies conducted over an 11-year span resulted in the availability of a large, regional dataset. Compiling this level of information over a shorter time frame might be possible but would require a very large investment and the full-time availability of several trained field teams. The largest drift fence study to date in the Midwest, part of the Missouri Forest Ecosystem Project (MOFEP),
monitored 108 drift fence arrays concurrently, but utilized 36 field technicians under the direct supervision of an experienced herpetologist (Renken, 1997). The MOFEP sites, while relatively remote and rugged, are within an area only a fraction the size of the Chicago Wilderness region and with none of the paralyzing road traffic characteristic of the urban area.
Examination of data gathered by different investigators in different years at the same Chicago region locations indicates that there is some variation in relative abundances, and some uncommon species were captured in one year but not another. However, species considered by one investigator to be common in a given community were consistently captured in large numbers by subsequent workers at those same locations. Thus, the results presented here are thought to represent, with a reasonable level of accuracy, coarse scale relative abundances of amphibians and reptiles at each location sampled. It is also the most detailed, and for some counties the only, quantitative dataset available.
Community types and landscape context
At many sample sites, vegetation community types were extensive in coverage or were relatively homogenous, simplifying classification. In a few cases sites consisted of complex mosaics of several communities. Analysis was complicated by the lack of a quantitative plant community classification (Sawyer and Keeler-Wolf, 1993) for the study region. At one site, available community maps by three different well known botanists disagreed on community boundaries and whether or not certain community types were present at all.
For this document, the coarser-scale structural environment was emphasized when assigning a community type. For example, at one site arrays in wooded areas with 30 percent and 70 percent canopy cover, as well as an array in a small prairie opening, were all considered as black-soil savanna because the structure of much of the preserve consisted of alternating oak groves and small openings. At a scale which encompasses the home range of a typical amphibian or reptile, such a site functions structurally as savanna. Results confirmed the utility of this method; at the example savanna site, true grassland amphibian and reptile species were rare and true forest species absent.
Effect of site size
All nine sample sites with amphibian and reptile species richness of eight or above were within preserves of more than 200 acres, and all but one were at sites of 500 acres or more. The most species rich site (17 species) was relatively small (220 acres, with perhaps another 100 acres of nearby high-quality land separated by roads and railroads). This sand area site is of exceptional natural quality by regional standards.
At preserves with multiple sample sites, no single location captured all species present. Overall species richness at the preserve level would be expected to be much greater at a large preserve. Several sample locations would be needed to adequately document the amphibian and reptile assemblage at a large preserve.
Effect of sample size
Of the 34 sample sites, 15 (44 percent) had an available dataset consisting of more than 200 trap-nights. Sample size alone was not a guarantee of success; the two sites with the largest datasets (938 and 954 trap-nights) had very low species richness and low relative abundance. The most species rich and most diverse site, the same high quality dune complex site discussed above, had only 72 trap-nights. However, at nine sites with species richness of eight or more, seven had more than 200 trap-nights of sampling effort. Assuming a large number of species are present at a sample site, greater sampling effort will tend to capture a greater percentage of the species pool.
It appears that most common species at a site are captured relatively quickly, as long as sampling is done in the appropriate season and under reasonable weather conditions. Considerably greater effort is usually required to capture most of the rare species at any given site. It is not unusual for one or more additional rare species to be located even after two or more years of sampling.
Effect of site quality
Because of uneven availability of plant community quality information specific to drift fence sample sites, it is not presently possible to conduct a detailed quantitative analysis of potential correlations with amphibian and reptile species richness, relative abundance, or diversity. However, a qualitative review implies that amphibian and reptile assemblages are indeed richest on the best quality sites.
All of the sites sampled retain at least moderate natural quality. No severely degraded sites were included in the dataset. All sites had predominantly native vegetation, although some suffered from hydrology alteration, invasion by exotic shrubs, or succession.
All preserves generally considered to be of high natural quality support amphibian and reptile assemblages of moderate to high species richness, relative abundance, and diversity. The few most disturbed sample sites support few species or individuals. A few examples can be cited to illustrate the general pattern.
Several references have been made above to a northwest Indiana dune complex site. Generally considered one of the highest quality Chicago region sites from a floristic standpoint, it was not acquired and protected until a few years after the sample referenced here was completed. Although no restoration had yet occurred at that time, most of the site remained in good condition. Amphibian and reptile species richness (17) and Shannon-Weiner (Hı) diversity (1.899) were the highest obtained for any sample site included here, despite a relatively small sample size and the moderate size of the preserve. Relative abundance of the three most common species (0.57) and of all species combined (0.71) was moderate. In addition to the exceptional quality of the preserve, fine-scale plant community diversity, presence of numerous wetlands, and a unique location and microclimate allowing the coexistence of species of various biogeographic affinities, all contribute.
A black-soil savanna site in the Fox River Valley includes a core area of above average but unexceptional quality where restoration is well advanced, and extensive restored buffer lands. Within the core area savanna, amphibian and reptile species richness (12) and Hı diversity (1.297) are good, and several species are abundant (relative abundance = 2.70 for the three most common species; 2.97 for all species combined). Perhaps most importantly, relative abundance improved as restoration activities progressed.
Another black-soil savanna site, this one on the Valparaiso Moraine, illustrates the other end of the spectrum. This location, described as ³scattering timber² by the 1834 surveyorıs, retains large and widely spaced bur oaks with a dense understory of sapling-sized black cherry, buckthorn, and other trees and shrubs. No restoration has yet been attempted. The only remaining dense herbaceous vegetation is associated with a marsh opening. All of the amphibians and reptiles, as well as some small mammals captured in the drift fences, are typical savanna species. However, species richness (5), Hı diversity (0.462), and relative abundance (0.47 for all species combined) are low.
Summary and Conclusions Even though savanna and woodland communities are often treated as a whole when discussing animal assemblages, various types of open wooded communities differ substantially in species richness, species composition, diversity, and abundance. More subtle variation is evident within community types depending on geographic location, physiography, degree of disturbance, and extent of restoration activities.
In general, sand savannas are most species rich and most diverse, and support more reptiles than other community types. Several reptile species are restricted to sand areas within the Chicago Wilderness region. Northern flatwoods and mesic woodlands tend to be dominated by eastern and northern amphibians, with relatively lower species richness and few reptiles. Black soil savannas are intermediate, with a good mix of amphibian and reptile species and moderately high species richness for the region. The richest black soil savanna sites are usually those which have undergone at least some restoration. Unfortunately few extensive flatwoods or woodland sites have been restored for any length of time, although several efforts are currently underway.
Only 31 species of amphibians and reptiles were captured at sites considered here, slightly under half of the species known from the region. Some species were excluded because they utilize very different habitat types (for example, several permanently aquatic species) or because they do not occur within the portion of the region studied. However, it is also an indication of the rarity and the limited number of regional occurrences for several species. Some species reported historically from savanna sites are now either seldom seen (Regina grahamii) or may even be extirpated from the region (Eumeces fasciatus).
The rapid recovery of many savanna species at restoration sites holds promise for the future. In some cases, recovery has been surprisingly rapid (Mierzwa, 1998b). At least in black soil and sand savannas, all or most of the species present are fire adapted and capable of thriving during and after restoration activity. However, as evidenced by the complexities discussed above, assemblages of amphibians and reptiles in savannas and woodlands are diverse and variable, and are influenced by a variety of factors. Careful planning, taking into account long-term objectives as well as the unique features of each site, is of critical importance.
Acknowledgements When data from multiple studies conducted over more than a decade is gathered in one place, participants and contributors are usually so numerous that it is impossible to acknowledge everyone. Some of the major contributors are mentioned below. The efforts of all, listed here or not, are greatly appreciated.
Dave Beamer, Dave Mauger, Cherie Robeson, Alan Resetar, Jacqueline Schlosser, and Robert Sliwinski graciously shared unpublished reports or raw data. Russ Hendricks, Ken Klick, Mike Redmer, Tom Anton, Brad Woodson, Sue Hayden, Steve Culberson, Kathryn King, Kathleen Strakosch-Walz, Steve Bubulka, Deb Petro, Tony Dancik, and Ellin Beltz, and many others participated in data collection over an 11 year span. Selected plant community assessments were provided by Gerould Wilhelm, Victoria Nuzzo, Jim Anderson, and Wayne Schennum. Collecting permits were provided by the Illinois Department of Natural Resources, Indiana Department of Natural Resources, Lake County Forest Preserve District, Forest Preserve District of Cook County, McHenry County Conservation District, and the Forest Preserve District of Will County. Permission to collect on private land was provided by the Indiana Chapter of The Nature Conservancy and DuPont Corporation. A few sites were sampled during larger inventories conducted by TAMS Consultants, Inc. Information gathered in 1999 was supported by a grant from the U.S. Environmental Protection Agency, and other studies were funded by the Lake County Forest Preserve District and the McHenry County Conservation District. Karen Glennemeier provided valuable review comments.
Literature Cited
-
Beamer, Dave. 1996. Herpetofauna of Oak Ridge Prairie Lake County Park. Unpublished report to the Lake County Parks and Recreation Department. 41p.
-
Klemens, Michael W. 1993. Amphibians and reptiles of Connecticut and adjacent regions. State Geological and Natural History Survey of Connecticut Bull. 112. xii + 318p.
-
Mauger, David, and Cherie Robeson. 1993. Unpublished data summary for Thorn Creek Woods. Forest Preserve District of Will County. 4p.
-
Mierzwa, Kenneth S. 1985. An introduction to Robert Kennicottıs letters to Spencer F. Baird. Bulletin of the Chicago Herpetological Society 20:61-66.
-
Mierzwa, Kenneth S. 1989. Results of the 1989 herpetofauna survey in McHenry County, Illinois, with notes on other vertebrates. Unpublished report to the McHenry County Conservation District. 26p.
-
Mierzwa, Kenneth S. 1992. An inventory of amphibians and reptiles in McHenry County, Illinois, with notes on mammals and fishes: Results of 1991 field work. Unpublished report to the McHenry County Conservation District. 20p.
-
Mierzwa, Kenneth S. 1994. An updated vertebrate inventory of the proposed South Suburban Airport site in Will County, Illinois. TAMS Consultants, Inc., Chicago.
-
Mierzwa, Kenneth S. 1998a. Amphibian habitat in the Midwestern United States. Pp. 16-23 in: M. J. Lannoo (ed.), Status and Conservation of Midwestern Amphibians. University of Iowa Press, Iowa City. xviii + 507p.
-
Mierzwa, Kenneth S. 1998b. Status of northeastern Illinois amphibians. Pp. 115-124 in: M. J. Lannoo (ed.), Status and Conservation of Midwestern Amphibians. University of Iowa Press, Iowa City. xviii + 507p.
-
Mierzwa, Kenneth S. 2001. MacArthur Woods habitat restoration project: Baseline amphibian and reptile monitoring. Unpublished report to the Lake County Forest Preserve District, Libertyville, IL. 29p.
-
Mierzwa, Kenneth S., Steven D. Culberson, Kathryn S. King, and Christine Ross. 1991. Illinois-Indiana Regional Airport Study: Biotic communities. TAMS Consultants, Inc., Chicago. 477p.
-
Mierzwa, Kenneth S., and Ellin Beltz. 1994a. Habitat associations and distribution of amphibians and reptiles at Middlefork Savanna, Lake County, Illinois. Unpublished report to the Lake Forest Open Lands Association, Lake Forest, IL.
-
Mierzwa, Kenneth S., and Ellin Beltz. 1994b. Amphibians and reptiles of Glacial Park, McHenry County, Illinois: A report on monitoring of habitat use in a restored landscape. Unpublished report to the McHenry County Conservation District.
-
Nuzzo, Victoria A., and Kenneth S. Mierzwa. 2000. The effect of forest structure on amphibian abundance and diversity in the Chicago region. Unpublished report to the U.S. Environmental Protection Agency, Great Lakes National Program Office, Chicago. 36p.
-
Renken, Rochelle B. 1997. Pre-treatment conditions of herpetofaunal communities on Missouri Ozark Forest Ecosystem Project (MOFEP) sites, 1992-1995. Pp. 289-308 in: B. L. Brookshire and S. R. Shiffley (eds.), Proceedings of the Missouri Ozark Forest Ecosystem Project Symposium: An experimental approach to landscape research. USDA Forest Service, General Technical Rept. NC-193.
-
Sawyer, John O., and Todd Keeler-Wolf. 1993. A Manual of California Vegetation. California Native Plant Society, Sacramento. 471p.
-
Schlosser, Jacqueline. 2001. Unpublished data.
-
Sliwinski, Robert P. 1992. Herpetological inventory of the Poplar Creek Forest Preserve. Unpublished report to the Illinois Chapter of The Nature Conservancy.
-
Smith, Philip W. 1961. Amphibians and reptiles of Illinois. Illinois Natural History Survey Bulletin 28:1-298.
-
Vogt, Richard C. 1981. Natural History of Amphibians and Reptiles of Wisconsin. Milwaukee Public Museum, Milwaukee.
| |