landscape ecology of small mammals || small mammal ecology: a landscape perspective
TRANSCRIPT
1 Small Mammal Ecology: A Landscape Perspective
GARY W. BARRETT AND JOHN D. PELES
Emergence of the Landscape Paradigm
The dictionary defines landscape as "an expanse of the scenery, usually extensive, that may be seen by the eye as one view." Landscapes have been a construction of the visual perspective for centuries. For example, in one of the older shrines at Catal Hiiyiik (presently in the country of Turkey), a painting was uncovered that has been interpreted as pure landscape (de la Croix and Tansley 1986). According to C-14 dating, it was painted soon after 6200 S.c. More recently, a special issue of Time magazine, entitled "American Visions," illustrated numerous landscape paintings, including Thomas Moran's "The Grand Canyon of the Yellowstone" (1893-1901), the first American landscape by an American artist to be bought by the U.S. government and put on display in the Capitol (Hughes 1997).
Landscapes have also been viewed as the subject matter in landscape design for centuries in which gardens and natural scenery (i.e., the mosaic of natural, agricultural, and human-built systems) were established and managed for human creativity, enjoyment, and benefit. In an ecological context, a landscape has more recently been defined as "a heterogeneous land area composed of a cluster of interacting ecosystems that are repeated in a similar form throughout" (Forman and Godron 1986). The term landscape ecology arose from the European disciplines of regional geography and vegetation science and was first used in the late 1930s (Naveh and Lieberman 1984, Turner 1989). Diverse fields, such as economics, geography, and environmental design, frequently refer to "the landscape" when describing, planning, or designing a particular space, vista, or region. Although landscape ecology became an active discipline in Europe after World War II, this field of study did not become firmly established in North America until the early 1980s.
It was not until 1983, however, that the definition of and mission statement for landscape ecology were agreed upon, resulting in this field "anchoring its roots" in the United States. A workshop, funded by the NSF, was held at
G. W. Barrett et al. (eds.), Landscape Ecology of Small Mammals© Springer Science+Business Media New York 1999
2 G.w. Barrett and 1.0. Peles
Allerton Park, Piatt County, Illinois, during April 1983. A report entitled "Landscape Ecology: Directions and Approaches" summarized the workshop (Risser et al. 1984), and landscape ecology quickly became a new integrative field of study in the United States. This mission statement recommended that landscape ecology consider the development and dynamics of spatial heterogeneity, spatial and temporal interactions and exchanges across heterogeneous landscapes, influences of spatial heterogeneity on biotic and abiotic processes, and the management of spatial heterogeneity. Following this landmark NSF workshop, landscape ecology quickly emerged as an integrative field of study and became established as an area of scientific research and education. In the United States, for example, the International Association for Landscape Ecology (US-IALE) was established and held the first annual symposium on Landscape Ecology at the University of Georgia January IS-17, 1986. The first issue of the journal Landscape Ecology was published in July 1987. It is of interest that 21 out of 261 articles published in Landscape Ecology (8%) have focused on the ecology of small mammals.
Levels-of-Organization Perspective
The landscape has increasingly been recognized as a component of the levels-of-organization concept (Forman and Godron 1981, Lidicker 1994, 1995, Barrett et al. 1997a). Ecologists initially focused more on the population, community, and ecosystem levels-of-organization. Ecologists came to recognize, however, that numerous processes, such as the transfer of materials and exchange of biota between ecosystems, occur at greater spatial scales. Ecologists now recognize that emergent properties arise when the landscape is investigated as a whole. It is important that research conducted at the landscape level of organization often permits an understanding of ecological mechanisms and processes that cannot be addressed at lower levels of organization (Turner 1989, Wiens et al. 1993, Lidicker 1995). For example, processes, such as rates of dispersal, habitat connectivity, and the transfer of materials and exchange of biota (source-sink dynamics) between habitat types or ecosystem types are best understood from a landscape perspective. It has been suggested that landscape processes can perhaps best be understood based on the levels-of-organization concept (Barrett et al. 1997a).
Small Mammals as Model Organisms
Various vertebrate groups, such as birds (Opdam 1991, Wiens 1995, Tucker et al. 1997) and amphibians (Dickman 1987, Laan and Verboom 1990, Vas and Stumpel 1996) have been used to test hypotheses at the landscape scale. We feel, however, that small mammals are the ideal taxonomic group to serve as
I. Small Mammal Ecology: A Landscape Perspective 3
models for addressing questions at this scale. We make this argument for the following reasons:
1. We know detailed information regarding the biology and natural histories of numerous species of small mammals, especially at the organismal, popUlation, and community levels of organization. We also know the roles and niches of member species functioning in old-field, grassland, and forest ecosystems.
2. We can mark (identify) small mammals and follow their lives and monitor their patterns of movement. We can determine their survivorship, reproductive success, size of home range, and trophic level dynamics at the community, ecosystem, and landscape levels. Live-trapping and radiotelemetry studies have permitted insights regarding dispersal behavior and why a particular species predominantly selects a particular ecosystem or patch type. This is the kind of information ecologists need to understand how landscape patterns affect population and community dynamics of small mammals.
3. Because small mammals live in relatively small spatial areas, have short lives, typically disperse from their natal areas on reaching adulthood, and frequently exhibit behavioral response to seasonal changes, small mammal ecologists can gain new insights into processes such as rates of colonization, extinction, dispersal, and persistence. These data and information are vital to gaining a better understanding of ecosystem and landscape processes and relationships.
In essence, we already know the many important details of the life histories of numerous species of small mammals. Because of the good work and sound research on the part of ecologists who study small mammals, it turns out that this knowledge base regarding how small mammals live their lives make them model subjects for the study of landscape-level processes. Because of this base of knowledge, it is now possible to move beyond description and into the experimental phase of science. With cleverly designed experiments, it is possible to answer questions and to test simple hypotheses, thereby gaining insights into how landscapes operate. The small mammal ecologists who contributed to this book are the first to ask these questions, and to design studies that are beginning to open this window of opportunity and understanding.
Questions regarding population-level and community-level processes in small mammals were traditionally addressed from the perspective of individual habitat patches; however, the publication of the seminal paper entitled "Spatial dynamics of field voles Microtus agrestis in heterogeneous landscapes," published in Oikos by L. Hansson of the Swedish University of Agricultural Sciences (Hansson 1977), led many mammalian ecologists to consider the importance of the surrounding landscape when investigating the
4 G.W. Barrett and J.D. Peles
relationship of ecological processes to population dynamics and survivorship in small mammals. Following the paper's publication the ecology of small mammals has increasingly been studied from a landscape perspective, especially during the 1990s. For example, landscape-level investigations involving small mammals have addressed questions such as the effects of landscape elements (e.g., corridors) on dispersal behavior (e.g., Henderson et al. 1985, Merriam and Lanoue 1990, LaPolla and Barrett 1993, Lorenz and Barrett 1993) the effects of habitat fragmentation on species success and abundance (e.g., Robinson et al. 1992, Diffendorfer et al. 1995, Collins and Barrett 1997), or the role of patch quality (as well as shape or size) on small mammal population dynamics (e.g., Harper et al. 1993, Peles and Barrett 1996).
Much large-scale (temporal and spatial) theory had fortunately been developed, and partially tested, which served as an underpinning infrastructure regarding investigations that focused on the role of small mammals at the landscape level. These "roots" for landscape ecology include island biogeography (MacArthur and Wilson, 1967), metapopulation theory (Levins 1969, 1970), hierarchy theory (Allen and Starr 1982), and patch dynamics (Pickett and Thompson 1978, Pickett and White 1985). Thus, the "time was ripe" as we entered the final decade of the twentieth century to establish a set of rigorous and robust experimental designs that focused on small mammals at the landscape scale.
Research Approaches
Typical of most emerging fields of science, the majority of studies in landscape ecology have been descriptive in nature. These studies, however, have been important because they helped to develop new technologies (GIS, systems modeling), to encourage new holistic approaches for addressing questions at greater temporal and spatial scales (hierarchy theory, cybernetics), and to provide a more integrative understanding of the total environment by the public (Ahl and Allen 1996, Barrett et al. 1997a).
Although several books have been published that describe the emerging field oflandscape ecology (Naveh and Lieberman 1984, Forman and Godron 1986, Zonneveld and Forman 1990, Lidicker 1995), as well as an array of books that focus on select components of, or changes in, the landscape, such as ecotones (Risser et al. 1984), corridors (Saunders and Hobbs 1991), habitat fragmentation (Harris 1984), or analysis of heterogeneity (Turner and Gardner 1990), few books have focused on the need for and design of experimental approaches to landscape ecology. The reasons that so few replicated, experimental studies have been conducted at this level of organization are because of funding constraints (Lubchenco et al. 1991), the problems associated with pseudoreplication (Hurlbert 1984), and/or the difficulties typically encountered with long-term, large-scale investigations (Likens 1989).
1. Small Mammal Ecology: A Landscape Perspective 5
A number of researchers have designed and conducted investigations to address questions regarding the ecology of small mammals at the landscape scale. These investigators have utilized small mammals as a model taxonomic group in which major questions have been addressed and tested to increase our understanding of landscape ecology. These investigations have illustrated both how landscape patterns and processes have impacted small mammals functioning within these landscapes as well as how small mammals have, in turn, increased our understanding oflandscape structure and function (e.g., Ostfeld et al. 1997).
Small Mammals in Landscapes
Several books have been published in the area of small mammal ecology, including those that have focused on small mammal population dynamics (Golley et al. 1975), patterns of dispersal (Chepko-Sade and Halpin 1987, Stenseth and Lidicker 1992), and social behavior (Cockburn 1988). Lidicker (1995) was the first to begin a dialogue regarding the relationship of small mammals to landscape ecology. No attempt has been made, however, to provide a comprehensive, experimental, landscape-level perspective regarding the ecology of small mammals at this scale, and how this increased knowledge has enhanced our understanding of landscape processes. That is the purpose of this book.
The focus of this book, therefore, is to describe experimental landscape approaches used to advance our understanding of small mammal ecology; to synthesize existing landscape theory regarding the role of small mammal ecology at these greater spatial scales; to challenge researchers to design new, integrative experimental studies within this new area of investigation; and to illustrate how small mammals represent a model group of organisms to advance our understanding of landscape structure and dynamics. To accomplish this objective, a group of ecologists with expertise in the area of small mammal ecology was assembled at a workshop on April 25-26, 1997, at the Conference Center at the Savannah River Ecology Laboratory, Aiken, South Carolina, to help outline this book. It was decided after extensive discussion to outline this book into the following areas of knowledge: patterns of movement and habitat use (Chapters 2-5), population and community dynamics in heterogeneous landscapes (Chapters 6-9), ecological processes at habitat edges (Chapters 10-12), experimental designs and parameter estimators at the landscape level (Chapters 13-14), and a current synthesis (Chapter 15), including recommendations regarding future investigations and transdisciplinary approaches.
The mechanisms, concepts, processes, and approaches described in this book naturally have great relevance to larger mammalian species; to advancing our theory and understanding in related fields of study such as conservation
6 G.w. Barrett and J.D. Peles
ecology, disturbance ecology, restoration ecology, and sustainable landscape management; and to challenge the next generation of ecologists, mammalogists, and resource managers to establish studies at meaningful scales, including the urgent need to recouple and better manage an integrated urban and agricultural landscape (Barrett et al. 1997b).
Whereas in the past small mammals served as a model group to advance our knowledge at the molecular and cellular (mainly in a laboratory setting) through the organismal and population levels of organization, we now encourage researchers to consider small mammals as a model experimental group to advance our knowledge and understanding at the community, ecosystem, landscape, and global levels. Small mammals represent an excellent group of organisms to investigate transcending processes across all levels of organization (Barrett et al. 1997a). We argue that the landscape level provides the least understood, but most exciting, level of organization in which to address questions that will both increase our understanding of the ecology of small mammals and how small mammals can be used to advance our understanding of landscape patterns and processes. Accepting this challenge will greatly advance our understanding both in the areas of landscape ecology and small mammal ecology, and will also illustrate how mammalian species and metapopulations function in our increasingly fragmented landscape. Biodiversity (genetic, species, niche, and habitat diversity) of small mammals, for example, must be investigated and understood based on a perspective ranging from the molecular and organismal to the landscape and global levels of organization. Such knowledge and understanding is mandatory if we are to protect biodiversity, restore landscapes in a sustainable manner, and manage our biotic and abiotic resources in an integrative manner for future generations.
Literature Cited Ahl, v., and T.F.H. Allen. 1996. Hiemrchy theory. Columbia University Press, New
York, New York. Allen, T.F.H., and T.B. Starr. 1982. Hierarchy: perspectives for ecological complexity.
University of Chicago Press, Chicago, Illinois. Barrett, G. W., J.D. Peles, and E.P. Odum. 1997a. Transcending processes and the
levels-of-organization concept. BioScience 8:531-535. Barrett, G. W., T.L. Barrett, and J.D. Peles. 1997b. Managing agroecosystems as
agrolandscapes: reconnecting agricultural and urban landscapes. Pages 197-213 in W.W. Collins and e.O. Quaslet, editors. Biodiversity in agroecosystems. CRC Press, Boca Raton, Florida.
Chepko-Sade, B.D., and Z.T. Halpin (editors). 1987. Mammalian dispersal patterns: the effects of social structure on popUlation genetics. University of Chicago Press, Chicago, Illinois.
Cockburn, A. 1988. Social behavior in fluctuating populations. Croom Helm, New York, New York.
1. Small Mammal Ecology: A Landscape Perspective 7
Collins, RJ., and G. W. Barrett. 1997. Effects of habitat fragmentation on meadow vole (Microtus pennsylvanicus) population dynamics in experiment landscape patches. Landscape Ecology 12:63-76.
de la Croix, H., and R.G. Tansley. 1986. Gardner's art through the ages: ancient, medieval, and non-European art. Harcourt Brace Jovanovich, Chicago, Illinois.
Dickman, C.R. 1987. Habitat fragmentation and vertebrate species richness in an urban environment. Journal of Applied Ecology 24:337-351.
Diffendorfer. J.E., N.A. Slade, M.S. Gaines, and R.D. Holt. 1995. Population dynamics of small mammals in fragmented and continuous old-field habitat. Pages 175-199 in W.Z. Lidicker, Jr., editor. Landscape approaches in mammalian ecology and conservation. University of Minnesota Press, Minneapolis. Minnesota.
Forman, R. T. T., and M. Godron. 1981. Patches and structural components for a landscape ecology. BioScience 31 : 733-740.
Golley, F.B., K. Petrusewicz, and L. Ryszkowski (editors). 1975. Small mammals: their productivity and population dynamics. Cambridge University Press, New York, New York.
Hansson, L. 1977. Spatial dynamics offield voles Microtus agrestis in heterogeneous landscapes. Oikos 29:539-544.
Harper, S.J., J.K. Bollinger, and G.W. Barrett. 1993. Effects of habitat patch shape on meadow vole (Microtus pennsylvanicus) population dynamics. Journal of Mammalogy 74: 1045-1055.
Harris, L.D. 1984. The fragmented forest: island biogeography theory and the preservation of biological diversity. University of Chicago Press, Chicago, Illinois.
Henderson, M.T., G. Merriam, and J. Wegner. 1985. Patchy environments and species survival: chipmunks in an agricultural mosaic. Biological Conservation 31 :95-105.
Hughes, R. 1997. American visions. Time magazine special issue, New York, New York. Hurlbert, S.H. 1984. Pseudoreplication and the design of ecological field experiments.
Ecological Monographs 54:187-211. Laan, R., and B. Verboom. 1990. Effects of pool size and isolation on amphibian
communities. Biological Conservation 54:251-262. LaPolla, V.N., and G. W. Barrett. 1993. Effects of corridor width and presence on the
population dynamics of the meadow vole (Microtus pennsylvanicus). Landscape Ecology 8:25-37.
Levins, R.A. 1969. Some demographic and genetic consequences of environmental heterogeneity for biological control. Bulletin of Entomological Society of America 15:237-240.
Levins, R.A. 1970. Extinction. Lectures in Mathematical Life Sciences 2:75-105. Lidicker, W.Z., Jr. 1994. A spatially explicit approach to vole population dynamics.
Polish Ecological Studies 20:215-225. Lidicker, W.Z., Jr. (editor). 1995. Landscape approaches in mammalian ecology. Uni
versity of Minnesota Press. Minneapolis. Minnesota. Likens, G.E. 1989. Long-term studies in ecology: approaches and alternatives. Springer
Verlag, New York, New York. Lubchenco, J., A.M. Olson, L.B. Brubaker, S.R. Carpenter. M.M. Holland. S.P. Hubbell,
S.A. Levin, J.A. MacMahon, P.A. Matson, I.M. Melillo. H.A. Mooney. C.H. Peterson. H.R. Pulliam. L.A. Real. P.J. Regal, and P.G. Risser. 1991. The sustainable biosphere initiative: an ecological research agenda. Ecology 72:371-412.
8 G.w. Barrett and J.D. Peles
MacArthur, R.H., and E.O. Wilson. 1967. The theory of island biogeography. Princeton University Press, Princeton, New Jersey.
Merriam, G., and A. Lanoue. 1990. Corridor use by small mammals: field measurements for three experimental types of Peromyscus leucopus. Landscape Ecology 4: 123-131.
Naveh, Z., and A.S. Lieberman. 1984. Landscape ecology: theory and application. Springer-Verlag, New York, New York.
Opdam, P. 1991. Metapopulation theory and habitat fragmentation: a review of hoi arctic breeding bird studies. Landscape Ecology 5 :93-1 06.
Ostfeld, R.S., e.G. Jones, and J.O. Wolff. 1997. Of mice and mast: ecological connections in eastern deciduous forests. BioScience 46:323-330.
Peles, J.D., and G.W. Barrett. 1996. Effects of vegetative cover on the population dynamics of meadow voles. Journal of Mamma logy 77:857-869.
Pickett, S.T.A., and J.N. Thompson. 1978. Patch dynamics and the design of nature reserves. Biological Conservation 13 :27-3 7.
Pickett, S.T.A., and P.S. White, eds. 1985. The ecology of natural disturbance and patch dynamics. Academic Press, New York, New York.
Risser, P.G., J.R. Karr, and R.T.T. Forman. 1984. Landscape ecology: directions and approaches. Illinois Natural Survey Special Publication Number 2, Champaign, Illinois.
Robinson, G.R., R.D. Holt, M.S. Gaines, S.T. Hamburg, M.J. Johnson, S.S. Fitch, and E.A. Martinko. 1992. Diverse and contrasting effects of habitat fragmentation. Science 257:524-526.
Saunders, D.A., and R.I. Hobbs. 1991. The role of corridors in conservation: what do we know and where do we go? Pages 421--427 in D.A. Saunders and R.I. Hobbs, editors. Nature conservation 2: the role of corridors. Surrey Beatty and Sons, Chipping Norton, Australia.
Stenseth, N.C., and W.Z. Lidicker, Jr. (editors). 1992. Animal dispersal: small mammals as a mode!. Chapman and Hall, New York, New York.
Tucker, K., S.P. Ruston, R.A. Sanderson, E.B. Martin, and J. Blaiklock. 1997. Modelling bird distributions: a combined GIS and Bayesioan based approach. Landscape Ecology 12:77-93.
Turner, M.G. 1989. Landscape ecology: the effect of pattern on process. Annual Review of Ecology and Systematics. 20: 171-198.
Turner, M.G., and R.H. Gardner. 1990. Quantitative methods in landscape ecology: the analysis and interpretation oflandscape heterogeneity. Springer-Verlag, New York, New York.
Vos, C.C., and A.H.P. Stumpe!. 1996. Comparison of habitat-isolation parameters in relation to fragmented distribution patterns in the tree frog (Hyla arborea). Landscape Ecology 11:203-214.
Wiens, J .A. 1995. Habitat fragmentation: island versus landscape perspectives on bird conservation. Ibis 137:97-104.
Wiens, J.A., N.C. Stenseth, B. Van Horne, and R.A. Ims. 1993. Ecological mechanisms and landscape ecology. Oikos 66:369-380.
Zonneveld, I.S., and R.T.T. Forman (editors). 1990. Changing landscapes: an ecological perspective. Springer-Verlag, New York, New York.