Mammals of Ohio

By John D. Harder and Guy N. Cameron

An updated, informative review of the status and biology of the fifty-five species of mammals living wild in Ohio, richly illustrated with photographs, maps, drawings, and original artwork.

This comprehensive reference illustrates how species within each of the seven orders of mammals in Ohio share modes of reproduction, locomotion, and nutrition, providing a framework for understanding the fascinating world of mammalian biology. Presentations of natural history in each account of the various species are enhanced with descriptions of intriguing adaptations for avoiding demise from predators, food shortages, and the frigid conditions of Ohio winters. The book is richly illustrated with range maps, exquisite skull drawings, beautiful photography, and engaging artwork.

Challenges to wildlife conservation are considerable in Ohio, with its vast industrialized urban centers distributed across a largely agricultural landscape. With frequent citations of scientific reports and conservation efforts of the Ohio Division of Wildlife and of other public and private entities, this book instills an appreciation for the rich mammalian fauna of Ohio, as well as knowledge on how to join efforts to protect it.

Covering all of the state’s mammals, from tiny, obscure shrews to the magnificent white-tailed deer, Mammals of Ohio is a definitive resource for professional biologists and students. The narrative style throughout the book is accessible, providing the general reader with an appreciation for the full scope of the rich mammalian diversity in the state.

• Language: English
• Publisher: Ohio University Press
• Release date: Mar 18, 2022
• ISBN: 9780821447499

John D. Harder

John D. Harder is associate professor emeritus in evolution, ecology, and organismal biology at The Ohio State University, where he taught upper-division courses in mammalogy and conservation biology. His research on the reproductive biology and ecology of mammals has focused on marsupials and involved field studies in Ohio, Venezuela, and Amazonian Peru.

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Introduction

WHAT I S A MAMMAL?

Mammals constitute the class Mammalia in the phylum Chordata, subphylum Vertebrata (animals with a vertebral column or backbone). Mammalia, with approximately 6,500 species, is small compared to other classes of vertebrates; for example, there are approximately 7,000 species of amphibians, 10,000 species of both reptiles and birds, and 32,000 species of fish. However, mammals show remarkable diversity in morphology and body size, more so than any other class of vertebrates. Consider, for instance, the structural differences evident between kangaroos, bats, seals, elephants, and antelope. Moreover, the largest mammal, the blue whale (Baleoptera musculus), at up to 190,000 kg (209 tons), is more than seven orders of magnitude larger than the smallest, the pygmy shrew (Sorex hoyi), at 3 g (0.1 oz).

Much of the diversity evident in the 29 orders of living mammals evolved following the extinction of dinosaurs at the end of the Cretaceous period, about 65 million years ago (mya), but the origin of mammals is far more ancient, stemming from an amphibian-like common ancestor to both reptiles and mammals, the amniotes of the Carboniferous period (360 mya). A descendant amniote group, the Cynodontia, with distinctive mammalian characteristics (such as three bones in the middle ear) is present in fossil deposits of the late Triassic period (220 mya). Thus, mammals diversified and coexisted with reptilian forms (birds and dinosaurs) throughout the Jurassic and Cretaceous periods. Mammals diversified rapidly during the early Cenozoic, such that most modern orders are evident in fossil deposits of the early Eocene (50 mya) (chapter 9, table 9.1).

All mammals except monotremes (duck-billed platypus and echidnas) are viviparous—that is, their embryos and fetuses are nourished from a placenta in the uterus. Nearly all are covered with hair; notable exceptions include whales, seals, hippos, and elephants. Mammary glands, unique to and present in all mammals, provide nourishment for neonates following birth. The lower jaw, or mandible, is composed of a single bone known as the dentary, which articulates with the squamosal bone at the base of the zygomatic arch of the skull. Dentary-squamosal articulation is evident in ancestral mammals from the Triassic and all their descendants. Teeth are set in sockets and arranged in a row, with differentiation in form and function from front to rear. Incisors, used in nipping, biting, or gnawing, are large in some mammals, such as rodents, but relatively small in most. Canines are typically long, pointed, and used for holding and killing prey and tearing flesh. Canines are most well developed in carnivores and absent in rodents and rabbits. Food procured by the action of incisors and canines is transferred with the tongue to the premolars and molars, where it is cut or ground into pieces appropriate for ingestion. Premolars are typically smaller but similar in morphology to molars; a prominent exception is the large, last upper premolar of carnivores, which occludes with the first lower molar in slicing flesh. Mammals have two sets of teeth, deciduous and adult. Deciduous teeth (or baby teeth), which erupt from front to back in the growing infant, are replaced by permanent teeth as the individual reaches adulthood. Molars differ from other teeth in that they erupt only in the adult form and are not replaced.

FIG. 0.1. The bones and four types of teeth in the mammalian skull are well represented in carnivores, as illustrated in the canid skull. The skull and teeth have evolved different forms and functions to meet the feeding habits of herbivores (rodents) and insectivores like shrews (from Gottschang 1981).

Mammals attract considerable attention from the public as well as the scientific community. The bond we sense with these, our closest living relatives, often begins with pets but typically extends to primates and other large, observable species in the wild, such as white-tailed deer. Scientists are intrigued by behavioral, physiological, and ecological adaptations of mammals to a wide variety of habitats and environments, including arid deserts, arctic cold, deep oceans, and subterrestrial conditions. Mammals have evolved remarkable adaptations for nearly every conceivable mode of locomotion, including walking, running, digging, burrowing, gliding, powered flight, and swimming. Their social systems and modes of communication are equally diverse, akin to those of humans in some species and very different in others. Domesticated as well as wild species of mammals are important sources of food and fiber for humans worldwide. Laboratory species play essential roles in basic biology and medical research, while wild mammals, especially tropical rain forest species, are potential sources of viral infectious diseases such as SARS and COVID-19. Finally, decades of ecological research, particularly with small mammals, provide a baseline for assessing the impact that climate change and human disturbances of the earth’s habitats have on natural communities. (Burgin et al. 2018; Feldhamer et al. 2015)

METHODS USED IN THE STUDY OF WILD MAMMALS

The majority of mammals in Ohio are small, cryptic, and nocturnal, leaving only a few species (about six) that can be studied by direct visual observation, as one might with birds. Much has been learned about the social and feeding behaviors in squirrels and white-tailed deer with this approach. The remaining species are studied through tracks and feces or, most commonly, by a variety of techniques based on trapping. Snap traps and pitfall traps, which kill, are commonly used on small, nonvolant mammals (< 100 g), such as shrews and mice. The resulting data provide evidence of relative abundance based on captures per unit effort, typically expressed as captures per trap night (TN); thus, for example, 10 traps set for 10 nights = 100 TN. A variety of box-type traps or live traps are often preferred because, when properly used, mortality is low; blood and tissue samples can be collected; and animals can be measured, marked, and released for further study. The recapture of marked animals can be used to estimate home range size (see appendix D) and provide statistical estimates of the actual number of individuals living within a study area.

Animals can be fitted with radio transmitters and released in the wild, which allows for tracking individuals over space and time and, consequently, the study of habitat use, home range size, overlap in use of habitat among individuals, and short-term survival. Here are two examples: data from radio transmitters placed on fawns captured soon after birth have given us a good understanding of postnatal survival in white-tailed deer, and mammalogists have also learned through radiotelemetry that rodents of one species are socially monogamous while a related species is polygamous. Wide-ranging animals (among them jaguars, mountain lions, moose, and black bears) whose movements are difficult to follow with radiotelemetry can be fitted with collars containing GPS-enabled tags. Then, their movement patterns over days, months, and sometimes years can be monitored by satellites or Google Earth, with the resulting data downloaded to investigators. Passive integrated transponders (PIT tags, as used on pets) inserted below the skin can be used to record (via PIT receivers) movement of individual small mammals along narrow passages or into burrows or nest sites. Infrared-triggered cameras, popularly known as game cameras or camera traps, placed along trails and feeding sites have been used for decades to study ungulates and carnivores, and more recently, they have provided data on abundance, microhabitat use, behavior, and social interactions in a variety of smaller mammals. Camera traps are particularly valuable in studies of predators, such as cats, that are rarely observed, are often nocturnal, and are difficult to capture but can be attracted to a prey carcass under surveillance by a remote camera.

Bats represent a unique challenge in small mammal ecology because they fly at night. However, their habit of roosting in large numbers at known sites (in caves and mines) and their tendency to forage in predictable habitats have facilitated research on this important component of small mammal communities. Traditional roosting sites used by hibernating bats can be surveyed and counts can be made to determine the abundance of the species that are present. Long-term data sets from such surveys enable biologists to detect changes in relative abundance related to environmental factors such as wind turbines or diseases such as white-nose syndrome. Mist nets of the sort used to capture small birds in flight are also employed for live captures of bats. Large (3 × 5 m) expanses of black, thin-filament, 2 cm mesh netting are suspended from poles set in habitats used by foraging bats—for instance, over streams, ponds, or mine and cave entrances—to capture bats on the wing. Because the frequency patterns of sound pulses emitted by echolocating bats are more or less species specific, computer analysis of such recorded emissions can be used to determine the time and location of habitats used by different species of foraging bats.

The development of polymerase chain reaction (PCR) and related techniques since the mid-1980s has revolutionized nearly all areas of biology. With PCR, a small amount of DNA from a few hair follicle cells or epithelial cells found in saliva or feces can be amplified for analysis, so that individuals or groups of individuals from a given geographic region can be identified. Because the parentage of offspring can be determined with some certainty, molecular techniques have revealed previously unknown aspects of social and breeding behaviors. Analysis of DNA in hair and fecal samples also has been used to document the presence and relative abundance of species in a given area. In a remarkable example of conservation genetics and forensic analysis, DNA extracted from elephant tusks (confiscated from poachers) revealed the specific geographic region of the Congo in which the elephants were killed.

Molecular techniques have been applied in the construction of phylogenic trees that depict evolutionary relatedness among groups of mammals and help us understand how mammalian traits evolved. DNA techniques have been instrumental over the past several decades in determining the actual number of species of living mammals, an estimate that grows each year with more and more accurate techniques. For instance, the number of extant species of mammals was 4,170 in 1982, 4,629 in 1993, and 5,416 in 2005—and it now exceeds 6,500.

Because epidermal cell morphology and patterns on plant leaves are nearly species specific, microscopic analyses of plant fragments found in animals’ stomachs or feces provide reliable estimates of the plant species composition of their diets. This information can be correlated with the nutrient content of ingested plants to estimate the quality of the diet of mammalian herbivores. Such studies have determined that some rodents, in particular, ingest certain species of plants based upon their nutritional content—similar to the way humans might select a balanced diet. A relatively new technique, stable isotope analysis, uses ratios of isotopes of carbon, nitrogen, and oxygen (isotopic signatures) applied to individual species in a food chain or food web to determine the extent to which top predators such as wolves prey on other carnivores, herbivores, and plants depending on the season and habitat. (Burgin et al. 2018; Joly et al. 2015; Oyler-McCance and Leberg 2012; Vynne et al. 2011)

CONSERVATION

The Ohio Division of Wildlife (ODW) is responsible for the welfare of all wildlife species in the state. According to their mission statement, ODW is dedicated to conserving and improving the fish and wildlife resources and their habitats, and promoting their use and appreciation by the people so that these resources continue to enhance the quality of life for all Ohioans. At approximately five-year intervals, ODW conducts an extensive review of the conservation status of state-listed wildlife, including mammals. This review considers results of recent studies and seeks input from staff biologists, noted professionals, and experienced citizens. ODW may change the conservation listing status of particular mammals depending on the outcome of this periodic review (table 0.1). Six categories of conservation status are used with regard to native species or subspecies, as defined in ODW (2019a):

Endangered—A native species or subspecies threatened with extirpation from the state. The danger may result from one or more causes, such as habitat loss, pollution, predation, interspecific competition, or disease.

Threatened—A species or subspecies whose survival in Ohio is not in immediate jeopardy but to which a threat exists. Continued or increased stress will result in it becoming endangered.

Species of Concern—A species or subspecies which might become threatened in Ohio under continued or increased stress. Also, a species or subspecies for which there is some concern but for which information is insufficient to permit an adequate status evaluation.

Special Interest—A species that occurs periodically and is capable of breeding in Ohio. It is at the edge of a larger, contiguous range with viable population(s) within the core of its range. These species have no federal endangered or threatened status, are at low breeding densities in the state, and have not been recently released to enhance Ohio’s wildlife diversity.

Extirpated—A species or subspecies that occurred in Ohio at the time of European settlement and has since disappeared from the state.

Extinct—A species or subspecies that occurred in Ohio at the time of European settlement and has since disappeared from its entire range.

Updated status information on Ohio’s listed species is available at http://wildlife.ohiodnr.gov/species-and-habitats/state-listed-species. In addition, the relative abundance of nonlisted species may be described as follows: Uncommon (localized, infrequent occurrence), Common (widespread, frequent occurrence), and/or Game (can be legally harvested), as designated in the Mammals of Ohio field guide (ODW 2016c). Copies are available from the Ohio Division of Wildlife.

Table 0.1. Checklist and conservation status of extant Ohio mammals

¹ Orders are listed according to Feldhamer et al. 2020. Families and genus species names are listed alphabetically.

² ODW 2019a.

³ Includes whales, formerly Cetacea.

GUIDE TO USING THIS BOOK

This book presents current information on the status and biology of 55 species of mammals living wild in Ohio. Of these, 3 are state-listed as Endangered, 2 as Threatened, and 18 as Species of Concern (table 0.1). Although organized around individual species accounts, our book is more than a field guide, a resource that typically focuses on identification and provides only a brief description of natural history. Species within each of the seven orders of mammals in Ohio share modes of reproduction, locomotion, and nutrition that characterize each order and offer a framework for review of the fascinating world of mammalian biology. Each species account in this book begins with descriptive information on external features and dentition, followed by sections on distribution and abundance, diet, habitat, reproduction, mortality, behavior and physiology, and conservation.

This book is intended for college students, their teachers, professional biologists in wildlife and conservation agencies, and naturalists serving in parks and nature preserves. Our book also is intended for members of the public who are interested in nature and are increasingly well informed about mammals from multiple media sources and personal experiences. It is meant to provide all readers with an informative, updated review of the wild mammals of Ohio.

Body Measurements

Standard length measurements and body mass are given in each species account or in a table for families with more than two species. These and other values are presented in metric units (e.g., millimeters [mm]), throughout this book. Standard measurements are presented in sequence from longest to shortest as follows:

Total Length: Measured from the tip of the nose to the end of the tail vertebrae when the specimen is laid on its back, excluding hairs that extend beyond the last tail vertebrae.

Tail Length: With the animal on its belly, the tail is bent at a 90° angle from the body and measured from the base of the tail to the end of the tail vertebrae.

Hind Foot Length: Measured from the heel to the tip of the claw on the longest toe.

Ear Height: Distance from the lowest notch at the base of the ear to the highest point of the pinna, excluding hairs.

Body mass: Weight of the specimen in grams (g) or kilograms (kg).

Appendix A lists dental formulas for Ohio mammals, and appendix B provides a table for converting metric weights and measurements to imperial units. The metric system is used universally in science and is in common use worldwide; the United States is the only major exception to this rule. Readers are encouraged to consult appendix B as needed to become familiar with metric units of measurement and their abbreviations and to envision the quantitative values presented. Appendix C gives the common and scientific names of plants and animals mentioned in this book, and appendix D is a glossary of terms that might not be familiar to the reader. Common expressions of time are occasionally abbreviated to conserve space, including year (yr), hour (hr), and minute (min).

Distribution and Abundance

Distribution or range maps in this book are based almost entirely on museum records of when and where, by county, specimens of a given mammalian species were collected. A county shaded dark gray, for known to occur, indicates that one or more specimens of a species have been collected in that county. Because all counties have not been sampled or received equal attention in past surveys, the absence of a museum record does not mean that a species is absent from a county. In fact, it is likely that counties bordering a county in dark gray have been occupied by the species in question. Those counties are shaded light gray and designated as probably occurs. For example, the Indiana bat is known to occur in less than half the 88 counties in Ohio, but it probably also occurs in counties bordering those in which it is known to occur. The position of Ohio in the continental distribution of each species is evident in the North American range map inserts. See page xviii for a county map of Ohio.

Abundance is a general, qualitative term that ecologists may use in reference to quantitative expressions such as a census, which provides a complete count of all individuals in a population. A census is seldom feasible with free-ranging mammals, but a statistical analysis of mark-recapture data can yield an estimate of the number of animals per unit area, often expressed as density—for instance, the number of mice per hectare (as in 20/ha). Measures of relative abundance, based on counts per unit effort, are most often used in conservation and ecological studies in which the goal is to compare abundance over time or between habitat types. Examples include the number of animals observed by bowhunters per hours of observation or the number of a given species found dead per kilometer of highway (often referred to as roadkill). The most widely used measure for small mammals is the number captured per trap nights (TN) (e.g., 10/100 TN, where 100 trap nights indicates 100 traps set out for one night, 50 traps set out for two nights, or 25 traps set out for four nights, etc.).

Classification and Nomenclature

The listing of orders in table 0.1 follows the classification of Feldhamer et al. (2020). However, we have elected to list families within orders and species within families alphabetically, rather than in any phylogenetic sequence. Genus and species, so-called scientific names, provide unique and universally accepted names for species, but they may be esoteric for the general reader. We use scientific names to introduce each species, but we most often use common names for plants and animals throughout the text. Common names can be confusing because two or more may be applied to the same species. We have used the common names of mammals from Wilson and Cole (2000), who surveyed professional mammalogists and selected the most frequently used common name for each species. Common names for other animals and plants are found in appendix C.

Sources of Information

Information presented in our species accounts is heavily based on the primary literature, and we searched for the most recent research reports to bring our species accounts up to date. However, we also relied on secondary sources such as Mammalian Species, which is published by the American Society of Mammalogists and can be accessed at www.mammalsociety.org/publications. Sources of information presented in the text are indicated by author(s) and date at the end of each section of a chapter or account (e.g., Reproduction), which will allow the interested reader to efficiently identify relevant publications in the Literature Cited section at the end of each species account. Other secondary sources that have been cited frequently are listed in the next section, References of General and Historical Interest. Greek and Latin derivations of genus and species names may be found in Mammalian Species accounts or in Greek and Latin dictionaries online. The text and literature citations follow the style of the Journal of Mammalogy.

References of General and Historical Interest

The following are general interest references and publications that are cited frequently in this book. They are not included in the Literature Cited sections of the species accounts but are provided here for easy access.

Bole, B. P., Jr., and P. N. Moulthrop. 1942. The Ohio Recent mammal collection in the Cleveland Museum of Natural History. Science Publications, Cleveland Museum of Natural History 5:83–181.

Burgin, C. J., J. P. Colella, P. L. Kahn, and N. S. Upham. 2018. How many species of mammals are there? Journal of Mammalogy 90:1–14.

Feldhamer, G. A., L. C. Drickhamer, S. H. Vessey, J. F. Merritt, and C. Krajewski. 2015. Mammalogy—adaptation, diversity, ecology. 4th ed. Johns Hopkins University Press. Baltimore, Maryland.

Feldhamer, G. A., J. F. Merritt, C. Krajewski, J. L. Rachlow, and K. M. Stewart. 2020. Mammalogy—adaptation, diversity, ecology. 5th ed. Johns Hopkins University Press. Baltimore, Maryland.

Gottschang, J. L. 1981. A guide to the mammals of Ohio. The Ohio State University Press. Columbus, Ohio.

Harder, J. D., J. K. Kotheimer, and I. M. Hamilton. 2014. A regional study of diversity and abundance of small mammals in Ohio. Northeastern Naturalist 21:210–233.

Kirtland, J. P. 1838. Report on the zoology of Ohio. Second annual report. Ohio Geological Survey 2:157–200.

Kurta, A. 2017. Mammals of the Great Lakes Region. University of Michigan Press. Ann Arbor, Michigan.

Merritt, J. F. 1987. Guide to the mammals of Pennsylvania. University of Pittsburgh Press. Pittsburgh, Pennsylvania.

ODW [Ohio Division of Wildlife, Ohio Department of Natural Resources, Columbus, Ohio]. 2006. Managing Ohio’s deer.

. 2012a. Eastern fox squirrel—wildlife population status report.

. 2012b. Coyote population status report.

. 2012c. American beaver—wildlife population status report.

. 2014a. Rural mail carrier survey.

. 2014b. Quality vs quantity, a closer look at deer herd condition trends in Oho.

. 2015. Diseases in wildlife, chronic wasting disease.

. 2016a. Ohio Wildlife Diversity Database.

. 2016b. Bowhunter survey report.

. 2016c. Mammals of Ohio field guide. Publication 5344RO216.

. 2016d. Spring 2016 furbearer roadkill survey.

. 2018a. Summary of 2017 bobcat observations in Ohio.

. 2018b. Ohio bobcat management plan.

. 2019a. Ohio’s listed species. Wildlife that are considered to be endangered, threatened, species of concern, special interest, extirpated, or extinct in Ohio. Publication 5356 (RO919).

. 2019b. Annual fur dealer report summary.

. 2019c. 2019 river otter bridge survey results.

. 2019d. River otter harvest report.

. 2019e. Ohio hunter questionnaire summary, 2018–19.

. 2019f. Ohio black bear monitoring report, 2018.

. 2019g. Summaries of Ohio deer seasons.

. 2020. Beaver population report—2019.

Reid, F. 2006. A field guide to mammals of North America. 4th ed. Houghton Mifflin Company. New York. (an auxiliary reference for body measurements)

Schwartz, C. W., and E. R. Schwartz. 2016. The wild mammals of Missouri. 3rd rev. ed. (D. K. Fantz and V. L. Jackson, eds.). University of Missouri Press and Missouri Department of Conservation. Columbia, Missouri.

Whitaker, J. O., Jr., and W. J. Hamilton Jr. 1998. Mammals of the eastern United States. 3rd ed. Comstock Publishing Associates, Cornell University Press. Ithaca, New York.

Wilson, D. E., and F. R. Cole. 2000. Common names of mammals of the world. Smithsonian Institution Press. Washington, DC. (used to select common names for all Ohio mammals)

Wilson, D. E., and S. Ruff. 1999. The Smithsonian book of North American mammals. Smithsonian Institution Press. Washington, DC.

Sources for Additional Information about Mammals

Animal Diversity Web (www.animaldiversity.org)

American Society of Mammalogists (www.mammalogy.org)

Bat Conservation International (www.batcon.org)

Merlin Tuttle’s Bat Conservation (www.merlintuttle.com)

Ohio Biological Survey (www.ohiobiologicalsurvey.org)

Ohio Division of Wildlife (www.wildlife.ohiodnr.gov)

Schupe, S. 2018. Ohio wildlife encyclopedia: an illustrated guide to birds, fish, mammals, reptiles, and amphibians. Skyhorse Publishing. New York.

Literature Cited

Joly, K., S. K. Wasser, and R. Booth. 2015. Non-invasive assessment of the interrelationships of diet, pregnancy rate, group composition, and physiological and nutritional stress of barren-ground caribou in late winter. PLoS ONE 10(6). https://doi.org/10.1371/journal.pone.0127586.

Oyler-McCance, S., and P. Leberg. 2012. Conservation genetics and molecular ecology in wildlife management. Pp. 526–546 in The wildlife techniques manual: research. 7th ed. (N. J. Silvy, ed.). Johns Hopkins University Press. Baltimore, Maryland.

Vynne, C., et al. 2011. Effectiveness of scat-detection dogs in determining species presence in a tropical savanna landscape. Conservation Biology 25:154–162.

1

Natural History of Mammals in Ohio

Ohio is home to 11.7 million people, making it the seventh most populous state in the Union. It is also industrial, with the nation’s fifth largest manufacturing workforce. Urban centers, including 6 cities with populations exceeding 100,000 and 50 with at least 25,000 residents each, are distributed across a largely agricultural landscape, which represents about 55% of the 116,096 km² of land in Ohio. Forests occupy an additional 32% of the land, nearly all of it in the eastern half of the state. The state is squarish in outline, extending approximately 335 km (208 mi) from east to west and the same from north to south between 38°27′ and 41°57′ N latitude. Elevations range from 472 m (1,549 ft) in Logan County to 139 m (456 ft) along the Ohio River. The state has a humid continental climate, with annual precipitation averaging 96 cm (38 in). Average maximum July temperature in central Ohio is 25°C (77°F); the minimum averages −5°C (23°F) in January.

GEOLOGY AND GLACIATION

Bedrock is the foundation of Ohio’s natural resources. Pulverized by glaciation, eroded by running water, and cracked by ice, rock is reduced to dust and forms the physical and mineral soil that develops over bedrock. These features along with climate and vegetation have, over eons, created a variety of soil types that have influenced the development of diverse plant associations across the state’s landscape. The bedrock in Ohio is sedimentary, contrasted with igneous materials such as granite that form from molten rock. Where bedrock is exposed by erosion along rivers or by highway construction, the layers (or strata) that were formed by sedimentation under ancient seas are clear. Limestone developed from calcareous shells of marine organisms and sandstone from fine grains of sand, compressed into rock by the pressure of overlying materials. Plants and animals became embedded in sediments as they formed, and their fossils enable geologists to age rock strata and construct a geologic calendar (table 9.1). The oldest bedrock in Ohio, formed during the Ordovician and Silurian periods some 500 million years ago, is found in the southwestern portion of the state, around Cincinnati. Younger Pennsylvanian bedrock, 320 to 280 million years old, underlies the eastern third of the state.

Glaciation, a dominant factor in shaping Ohio’s terrain, occurred in four ice ages over the last 2 million years. The most recent involved the Wisconsin Glacier, which entered what is now Ohio about 25,400 years ago, crushing and flattening everything in its path. Then, with climatic warming, it melted and retreated northward, leaving the region about 14,000 years ago. Glacial meltwater formed the Muskingum, Hocking, Scioto, and Miami drainages, which created tributaries to the Ohio River. Advancing glaciers pulverized underlying bedrock into a mixture of finely ground silt, sand, and gravel known as till. Retreating glaciers left massive deposits of boulders and till as terminal moraines, seen today as elevated ridges that stretch from east to west across northern and western Ohio. The highest point in Ohio, Campbell Hill near Bellefontaine, is a terminal moraine with an elevation of 472 m, formed by the deposition of some 107 m of glacial material over bedrock hills. Glaciation also formed the Great Lakes, including Lake Maumee, which inundated the northwestern part of the state for thousands of years before receding into what is now recognized as Lake Erie.

PHYSIOGRAPHIC REGIONS

Natural features of the earth’s surface—including terrain, geology, hydrology, climate, and vegetation—characterize continental physiographic regions or provinces. Five occur in Ohio: Lake Plains, Till Plains, Glaciated Allegheny Plateau, Unglaciated Allegheny Plateau, and the Bluegrass Section of the Interior Low Plateau.

Lake Plains

This flat, low-relief area encompasses 10 counties in northwest Ohio and extends east of Sandusky in a narrow band along the south shore of Lake Erie. The fertile soil of this region, a legacy of the Great Black Swamp, supports intensive agricultural production of corn and soybeans. This glaciated region also contains the marshes of western Lake Erie and Oak Openings in Fulton and Lucas Counties. The sandy soil of Oak Openings was formed on beaches and sand dunes of ancient lakes that preceded Lake Erie. Stands of black and white oak grow on dunes and sandy plateaus, forming openings in swamp forests of pin oak, black cherry, and aspen that grow in the hollows between the dunes. This 337 km² (130 mi²) region supports more than 100 state-listed plants and 20 rare animals, including the American badger and the endangered Karner blue butterfly. Karner blues are dependent on wild lupine, which grows in the open sandy habitats of the Oak Openings, a portion of which is protected by the Oak Openings Preserve in southern Lucas County.

Till Plains

The Till Plains is Ohio’s largest physiographic region, and with the Lake Plains, this glaciated region of western and central Ohio covers more than two-thirds of the state. Terminal moraines are abundant, but the general terrain varies from gently rolling to flat, with fertile soils well suited to agriculture. Counties bordering the Ohio River have moderate forest cover ranging from 23 to 34 ha/km², that is, forest cover per county varies from 23% to 34%. But only 3%–16% of the area in the other counties has forest cover. Roughly 95% of the region is farmland or urban developments, including Columbus, Cincinnati, and Dayton, where forest cover is limited to woodlots of < 20 ha (< 49 acres) and riparian habitats. Originally, beech-maple swamp forests occupied most of this region, with oak and sugar maple growing on drier land. The Ohio buckeye, named by the resemblance of its seed to the eye of a buck white-tailed deer, is more common here than in the hill country of southeastern Ohio.

Wet tallgrass prairies were common in the original landscape, described by early explorers as growing as high as a horse’s back for as far as the eye could see. Many of the counties here contained patches of natural prairie, with large prairies located in Erie and Marion Counties. The Darby Plains Prairie west of Columbus apparently comprised large portions of Madison, Champaign, and Clark Counties. Remnants of the original prairies persist in northern Madison County, and today there are over 650 ha of restored wetlands and prairies at Darby Creek Metro Park, which is home to a herd of bison and a high diversity of small mammals. Agricultural land includes fallow fields, pastures, and hayfields that harbor many species of small mammals, including the rare eastern harvest mouse and the thirteen-lined ground squirrel, a western prairie species. Wooded riparian habitat and small woodlots (4–10 ha) here are occupied almost exclusively by fox squirrels. Most of the 10 species of bats in Ohio are found throughout the state, but relatively few records of evening bats and the endangered Indiana bat are from counties outside of Till Plains.

Glaciated Allegheny Plateau

This region in northeast Ohio is part of the Allegheny Plateau, which extends eastward into Pennsylvania and West Virginia. The landscape is heterogeneous, with glacial moraines and abundant wetlands. When glaciers moved south into the plateau, the ice sheets encountered steep, rocky Appalachian foothills, similar to those in the Unglaciated Allegheny Plateau farther south. The advancing glaciers moved more easily through valleys between the hills, but where the ice was thick, they rode over the plateau and flattened hilltops. This glacial action left the plateau hilly, not leveled as in the Till Plains.

As the climate warmed and glaciers retreated, enormous flows of meltwater carried millions of tons of till, gravel, and rocks and huge chunks of ice southward, filling valleys and forming kettle lakes and bogs that persist today as remnant communities of the early postglacial period. A short drive south of Wooster provides a beautiful vista of the Killbuck Valley and the 2,295 ha Killbuck Marsh Wildlife Area. This area, spanning the Wayne-Holmes border, is one of Ohio’s largest remaining natural marshlands outside of western Lake Erie. The wetland is a vision of what likely was common here before the land was cleared and drained for cultivation. Killbuck is home to a diversity of birds, particularly waterfowl. Several pairs of four-foot-tall sandhill cranes nest on the area, and river otters, reintroduced to eastern Ohio between 1986 and 1992, thrive in the Killbuck.

Beech and sugar maple dominate the mature forests on much of the Glaciated Allegheny Plateau, with mixed oak forests on drier areas, particularly in southeastern parts of the region. Secondary forests that grow on abandoned farms or after windstorms and tree harvests are a mix of yellow poplar, black cherry, red maple, and white ash. Forest cover per county varies from 23% to 47%, second only to that on the Unglaciated Allegheny Plateau. The climate is cool and wet, with mean summer temperatures about 3.6°C lower than in southwestern Ohio, and the northeastern corner of the region (Geauga and Ashtabula Counties) receives 102–114 cm (40–45 in) of annual precipitation, much of it as snow. Here, the forests are similar to the woodlands of northern Pennsylvania and western New York.

Woodland mammals are well represented in this area, among them the cinereus shrew, a northern species, with capture rates for this species being four times higher in northeastern Ohio than in the southwestern region. The star-nosed mole, a hallmark of the Glaciated Allegheny Plateau, thrives in the wetlands and wet soils. Black bears frequent northeast Ohio, with confirmed sightings of up to 200 in Ashtabula, Trumbull, and Geauga Counties, compared to 1–40 confirmed sightings in 50 other counties. Most of the sightings are thought to be of dispersing juvenile males; to date, there is only limited evidence of reproduction (sows with cubs) in this region.

Unglaciated Allegheny Plateau

Southeastern Ohio is the hilliest and most densely forested part of the state. Most of this region is covered in forest, 47%–81% by county. It is home to the Wayne National Forest (98,863 ha), and most of the state forests, including the Shawnee (26,296 ha) and the Zaleski (11,270 ha). The region marks the northwestern limit of the large Allegheny Plateau, which extends east into the Appalachian highlands in Pennsylvania, West Virginia, and eastern Kentucky. Soils are diverse and generally acetic, due to parent materials derived from the weathering of sandstone and shale bedrock. With the exception of alluvial deposits in river valleys and ancient lake beds, soils in this region are thin and poorly suited for row crops, and only about 5% of the area is under cultivation (compared to 72% in the Lake Plains). The area is renowned for its scenic beauty, with high-relief hilltops reaching 183–244 m above valley floors to elevations of 366–427 m above sea level. In locales like Conkles Hollow, sandstone cliffs tower above cool, narrow valleys that harbor ferns and hemlock trees typical of more northern forests. The number of plant and animal species is probably higher in this region than in other parts of the state.

The predominant forest type on the drier hilltops and south-and southwest-facing slopes is mixed-oak, composed of white oak, black oak, and shagbark hickory. Understory species include sassafras, serviceberry, and dogwood. Mixed mesophytic (of moderate soil moisture) forests, found on north-and east-facing slopes, are more diverse, supporting 20 to 25 species of trees. Most common are white oak, red oak, beech, tulip, black walnut, shagbark hickory, and black cherry. Fewer species are found in poorly drained bottomlands, but the most prominent is sycamore, recognized by tan and white bark on the trunk and limbs. Common in riparian habitats throughout Ohio, sycamores are, by trunk diameter, the biggest tree in the eastern United States. The largest on record, near the Muskingum River in Jefferson County, measured 4.1 m in diameter.

Forests on nearly all of the plateau were removed by the early twentieth century, as were white-tailed deer. However, with the subsequent abandonment of unproductive hillside farms, a patchwork of grassland, shrubland, and young forests returned—ideal habitat for early successional plants and white-tailed deer. Deer are common today in all parts of the state, but they are most plentiful in the hill country of southeastern Ohio. Forest mammals also thrive here, including opossums, beavers, raccoons, skunks, coyotes, six species of squirrels, and the semiarboreal gray fox. White-footed mice are abundant in this habitat, and several other small mammals, including pygmy shrews, smoky shrews, and woodland voles, are restricted to or most abundant in the hill country.

Bluegrass Section of the Interior Low Plateau

The Bluegrass is a northern extension of the Kentucky Bluegrass Region, as represented in Adams County and small sections of Highland and Brown Counties. Although the region is well forested (58%) in Adams County, prairies appear as patches or openings in stands of red cedar vegetated with prairie indicator species such as big bluestem, prairie dock, and blazing star. The Lynx Prairie Preserve is managed to maintain prairie vegetation—apparent remnants of a more extensive prairie that may have occupied the area during a warmer, drier period. Sinkholes in the region mark the beginning of underground streams that flow into Ohio Brush Creek. These openings also provide access to small caverns and caves for a diversity of roosting bats. At least eight species of bats are found in the Bluegrass, including the big brown bat, red bat, silver-haired bat, small-footed myotis, little brown bat, long-eared bat, tri-colored bat, and Indiana bat.

Along the southeastern edge of the Bluegrass, an escarpment, rising 233 m above the valley of Ohio Brush Creek, provides a prominent landmark for the Edge of Appalachia Preserve. Here, the Nature Conservancy and Cincinnati Museum Center manage one of the most biologically diverse areas in the Midwest, home to over 100 species of rare plants and animals, including the endangered Allegheny woodrat. Another feature of note is the prehistoric Serpent Mound effigy located on the edge of an ancient meteor crater.

LAND USE, WILDLIFE EXPLOITATION, AND MAMMALIAN CONSERVATION IN OHIO

Settlement and Deforestation

With conclusion of the Revolutionary War and the formation of the Ohio Company in 1786, pioneers made the laborious journey over the Allegheny Mountains and down the Ohio River to establish, in 1788, Marietta, the first American village in Ohio. Early settlers encountered a vast primeval forest that covered 95% of what is now the state of Ohio. This forest, equal in grandeur to any on earth, was broken only by large open prairies, bogs, and marshes. The settlers were attracted to the favorable climate and fertile soils in the new territory. However, the region was occupied by hostile Native Americans, who limited settlements to fortified villages along the Ohio River. A confederacy of Indigenous tribes fiercely resisted American immigration, but the confederacy was finally defeated in the Battle of Fallen Timbers in 1794. With the signing of the Treaty of Greenville a year later, Native American resistance to the settlers ended, and pioneers subsequently swarmed into the region. The population of Ohio was about 50,000 when it joined the Union in 1803, and just 17 years later, it reached 230,760. By 1850, almost 2 million people lived in Ohio, making it the third most populous state in the nation.

Most of the early settlers were aspiring farmers, but the dense forests had to be cleared and in many cases drained before the land could be put into agricultural production. Trees here were enormous. Some were over 46 m tall, including thousands of white oaks with trunk diameters up to 1.5 m rising without a branch to 23–24 m. Clearing this land was a daunting task, all accomplished with ax, saw, and horsepower. Trees in southern Ohio also were cut and burned to make charcoal, which was used in the production of iron by some 40 furnaces along the Ohio River. In some areas, forests were cleared at the rate of an acre per day to meet the demand for charcoal.

About 68% of Ohio was forested in 1840, down from 95% in presettlement times, largely due to the conversion of forests to farmlands. A decade later, Ohio led the nation in agricultural production, but the Great Black Swamp was a major obstacle to the expansion of farming into the northwestern corner of the state. From 1859 to 1875, thousands of miles of ditches and drains were dug to remove water from this and other swamps, which allowed farmers to move in and clear the forest. By 1885, the Maumee Valley was fully established farmland, and by the turn of the twentieth century, all but 14% of Ohio had been cleared of forest. Gone too were large mammals, including gray wolves, black bears, white-tailed deer, elk, and bison. Deforestation progressed more slowly after the turn of the century, reaching its maximum in 1940 with only 12% of the state in forests (fig. 1.1).

FIG. 1.1. Near-maximal deforestation of Ohio was reached by 1900, with partial reforestation after 1940 to 32% of the land forested in 2016. Kingsley and Mayer 1970; Widman et al. 2009; National Land Cover Database 2016, https://www.mrlc.gov/data/nlcd-2016-land-cover-conus.

The amount of forest land in Ohio increased substantially after 1940 to about 3.7 million ha by 1991 or about 30% of the land cover, roughly equivalent to the forest cover in 1885. This increase reflects ecological succession and regrowth of forests on abandoned farmland, primarily in the hill country of southeast Ohio where soil is poorly suited for agriculture. Forests of today differ from the old-growth forests remaining in Ohio during the mid-nineteenth century. Most (88%) are younger (30 to 100 years old) and occur in patches of < 41 ha, particularly in northwestern Ohio where < 16% of the land is forested, compared to 70%–80% in some southeastern counties.

Forest cover has always had a profound effect on Ohio mammals. Rapid deforestation and the extirpation of large mammals from Ohio during the nineteenth century were followed by reforestation and a return of species such as deer, bear, and bobcat in the 1900s. This rebound illustrates the relationship between disturbance and recovery of wildlife habitat and animal abundance—a relationship that is particularly relevant in Ohio where nearly all land, whether farm or forest, is privately owned, used for commercial purposes, and is consequently in an ongoing state of disturbance and recovery.

Exploitation, Extirpation, and Recovery of Large Mammals

During the early eighteenth century, some Native American tribes moved away from military conflict, overtaxed lands, and inhospitable climate in the upper Great Lakes into the Ohio territory, where the climate was temperate and an abundance of deer and bear provided food and hides. The Wyandot, Miami, Lenape, and Shawnee tribes flourished, and when settlers arrived in Ohio, game was plentiful and diverse. Gone with the ice ages were giant ground sloths, mastodons, woolly mammoths, horses, and caribou, but cougars, wolves, bears, bison, elk, beaver, and deer were found across the landscape (see chapter 9 for details). Smaller species such as cottontail, gray squirrel, and raccoon were important sources of meat and hides for pioneers. These wildlife resources must have seemed as inexhaustible as the endless forests that were being cleared—but that was not to be.

Given the enormous effort invested by settlers in clearing forests and the threat posed by bears, wolves, and other carnivores to livestock and by squirrels, raccoons, and deer to crops, it is not surprising that wildlife was heavily hunted. The last bison known in Ohio was killed in 1803, and by the middle of the nineteenth century, elk, bobcats, and cougars were extirpated, followed by black bears in 1881. And it was not just large mammals that drew attention from hunters. Gray squirrels and fox squirrels were superabundant, and the damage they caused to corn and other crops was substantial. This prompted the Ohio General Assembly to pass legislation in 1807 requiring residents to pay part of their county taxes in squirrel scalps. Large countywide hunts were organized, and one held in Franklin County (in 1822)—promising a barrel of whiskey to the most successful district—yielded 19,666 scalps in a three-day hunt!

Wolves and bears were a problem for farmers in the early 1800s. They killed cattle, pigs, and large numbers of sheep, more than 100 per night in some areas. A war of extermination was declared against bears and wolves and executed in spectacular fashion in the Great Hinckley Hunt in northern Medina County. On the morning of 24 December 1819, more than 500 men and boys, armed with muskets, axes, and knives, were deployed around the perimeter of Hinckley Township. On command, they moved forward shooting, and with the aid of dogs, they drove game ahead of them toward the center, where a frozen stream with high banks attracted deer, wolves, bears, and other game seeking shelter. There, they fired down on the animals. By day’s end, hunters tallied over 300 deer; 21 bears; 17 wolves; and piles of squirrels, raccoons, and cottontails. Their success was celebrated with a Christmas Eve feast of barbecued bear and whiskey. The game was divided among the hunters, but there was more than the group could eat or store. As a result, many carcasses were left in the woods and attracted hungry buzzards (turkey vultures) well into spring. Local legend attributes the return of vultures to Hinckley each year for Buzzard Day, a traditional celebration on 15 March, to that initial feast in early 1819.

People today might be surprised or even appalled by stories of the wholesale slaughter of animals by early Ohioans, but these stories provide insight into the challenges facing pioneers and the social norms of the day with regard to the exploitation of wildlife. However, the ongoing loss of wildlife also fostered an interest in fish and wildlife conservation among a cadre of naturalists, scientists, and politicians. The first animal-protection law was passed early in Ohio statehood (1829), making it illegal to harvest muskrats from May to mid-October. The first legislation for the protection of fish, nongame species, and songbirds was passed in 1857. Yet, habitat loss and overhunting continued, and by 1909 deer and wild turkeys were extirpated from Ohio.

The passenger pigeon probably was, at one time, the most abundant bird on earth. Migrating flocks stretched more than 161 km in length and were so dense that they dimmed light from the sun. Some flocks were estimated in passing counts to contain more than 1 billion birds. Habitat loss contributed to the demise of passenger pigeons, but market hunting is seen as the major cause of their extinction. Hunters focused their efforts on nesting concentrations; nearly 12 million brooding pigeons were shot during the decade ending in 1876, which severely reduced the recruitment (birth and survival) of young. The last known wild passenger pigeon in Ohio was killed in 1900, and the last known individual on earth, Martha, died in the Cincinnati Zoo on 1 September 1914. However, not all was negative. The first coyote was observed in Ohio in 1919, a harbinger of changes to come in the diversity and abundance of mammals. And because of the successful return and subsequent growth of deer populations in southern Ohio, limited sport hunting of deer was initiated in 1943 and permitted statewide in 1956.

The extinction of the passenger pigeon focused public attention on conservation, particularly the need to curb market hunting for meat, hides, and feathers. A major issue was the shooting of herons and egrets for their plumage, which was used in the manufacture of women’s hats. The Lacey Act, passed by Congress in 1900, prohibited the shipment of illegally taken game, including hides and feathers, across state lines. This legislation brought the full force of the federal government to bear in support of nascent state game agencies, which were struggling to curb poaching in their woods and wetlands. Ohio was a leader in this effort with the hiring of game wardens by the newly established Fish and Game Commission in 1886, which joined the new Department of Natural Resources as the Ohio Division of Wildlife in 1949.

Revenue from hunting license sales and fines levied on poachers fueled the growth of law enforcement and habitat procurement; the first wildlife area was purchased in 1920 through a program that has established some 120 wildlife areas throughout the state. The second major piece of federal legislation, the Pittman-Robertson Act passed in 1937, made revenue from an 11% excise tax on firearms and ammunition available (through a matching-funds arrangement) to state wildlife agencies for wildlife management and research. Over $2 billion in federal aid for conservation has been generated in the 80-year history of this program. With multiple funding sources, the Division of Wildlife now manages 152,720 ha (377,380 acres) of wildlife habitat on 306 properties throughout the state.

Passage of the federal Endangered Species Act in 1973 was matched in the same year by complementary legislation in Ohio, which placed several hundred nongame and state-listed species under the care of the Division of Wildlife. Citizens have the opportunity to support this effort by purchasing the Ohio Wildlife Legacy Stamp, which generates funding for wildlife diversity programs. Interest in this program is evidenced by attendance at the annual Wildlife Diversity Conference of more than 1,000 citizen-naturalists, resource managers, and park naturalists from across Ohio.

Contributions to the natural history of Ohio have come from a long list of individuals, dating back to the explorers and pioneers of the eighteenth century. Early biologists and geologists described the flora, fauna, bedrock, and glaciation of Ohio; their work is well chronicled in Lafferty (1979). Although early zoologists in Ohio focused most of their attention on invertebrates, fishes, and birds, the Cleveland Museum of Natural History sponsored the work of Benjamin Bole and Philip Moulthrop, who published in the 1930s and early 1940s and assembled a mammal collection with more than 7,000 specimens from Ohio. Professors who made substantial contributions to mammalogy during the twentieth century include Jack Gottschang (small mammals), University of Cincinnati; Steve Vessey (white-footed mice), Bowling Green State University; and Gerald Svendsen (behavioral ecology of chipmunks and beavers), Ohio University. Beginning with research in the Department of Zoology in the 1930s, strong graduate programs in wildlife biology and conservation at The Ohio State University have greatly advanced our understanding of Ohio’s mammals.

Status of Mammals in Ohio

The decade unfolding as we write this book, the 2020s, is an exciting and challenging time for mammalogy in Ohio. Bobcats have returned, and black bears soon might reproduce in northeastern Ohio as their habitat improves. The state’s forests and open areas support viable populations of seven species of squirrels, and river otters have been successfully reintroduced. The coyote continues to thrive, but the future of its close relatives, the red fox and the gray fox, is uncertain. And all but a few of 10 species of bats are threatened by white-nose syndrome and an apparent decline in their prey, flying insects. One bat is state-listed as Endangered and another as Threatened. About 42% of the 55 species of mammals in Ohio are small rodents, shrews, or weasels. Many are difficult to monitor or study in the wild, and the current distribution and abundance are known, with any certainty, for less than a third of this group. However, preliminary evidence suggests particularly low abundance for several small mammals adapted to grassland and old-field habitats. These and other characteristics of the mammals of Ohio are described in the chapters that follow.

References

Bole, B. P., Jr., and P. N. Moulthrop. 1942. The Ohio Recent mammal collection in the Cleveland Museum of Natural History. Science Publications, Cleveland Museum of Natural History 5:83–181.

Braun, E. L. 1950. Deciduous forests of eastern North America. Hafner Publishing Company. New York.

Kern, K. F., and G. S. Wilson. 2014. Ohio—a history of the Buckeye State. John Wiley and Sons, Inc. West Sussex, United Kingdom.

Kingsley, N. P., and C. E. Mayer. 1970. The timber resources of Ohio. U.S.D.A. Forest Service Resource Bulletin NE-19. U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. Upper Darby, Pennsylvania.

Lafferty, M. B. 1979. Ohio’s natural heritage. Ohio Academy of Sciences. Columbus, Ohio.

McCormac, J., and G. Meszaros. 2009. Wild Ohio: the best of our natural heritage. Kent State University. Kent, Ohio.

Ohio Division of Forestry. 2010. Ohio’s statewide forest resource assessment—2010. Ohio Department of Natural Resources. Columbus, Ohio.

Ohio Division of Wildlife. 2015. Ohio’s state wide action plan—a comprehensive wildlife conservation strategy. Department of Natural Resources. Columbus, Ohio.

. 2019. Ohio black bear monitoring report 2018. Ohio Department of Natural Resources. Columbus, Ohio.

United States Census Bureau. 2020 census results. www.census.gov.

Widmann, R. H., et al. 2009. Ohio forests: 2006. Resource Bulletin NRS-36. U.S. Department of Agriculture, Forest Service, Northern Research Station. Newton Square, Pennsylvania.

2

Introduction to the Order Didelphimorphia

Extant mammals are placed in one of two subclasses: Prototheria, the egg-laying montoremes (echidnas and the duck-billed platypus), and Theria, the viviparous mammals. Theria is divided into two infraclasses: Metatheria, the marsupials, and Eutheria, all other viviparous mammals. The two infraclasses represent major evolutionary lines of extant mammals that diverged from a common ancestor during the early to middle Cretaceous, some 125 million years ago. Didelphimorphia is one of seven orders in Metatheria; the others include Australian taxa such as koalas, carnivores, bandicoots, opossums, wombats, and kangaroos.

Although this divergence is apparent in several morphological features, the most significant differences between the two infraclasses pertain to their modes of reproduction. Both have placentas that nourish the embryos after implantation, but marsupials devote relatively little time and energy to gestation and invest more time and energy in lactation, while the opposite is true of typical eutherians. For example, the interval from conception to birth (gestation) lasts 13 days in the opossum, but the interval from birth to weaning (lactation) is 90–100 days. Quite the opposite is seen in the woodchuck, a similar-sized eutherian in which gestation lasts 63 days and lactation 43 days. Body temperature in marsupials is 35°C (95°F) versus 38°C (100°F) in eutherians, and marsupials’ metabolic rate is about 70% of that of similar-sized eutherians. Consequently, development is slower and the interval from conception to weaning is longer in marsupials than in comparable eutherians. (Feldhamer et al. 2015; Harder et al. 1996; McNab 1978)

FAMILY DIDELPHIDAE: NEW WORLD OPOSSUMS

The order Didelphimorphia contains this single family. With 111 species distributed throughout Central and South America, Didelphidae is the largest of all marsupial families. Most members are small (< 100 g, 0.22