The habitat concept and a plea forstandard terminology

Linnea S. Hall, Paul R. Krausrnan, and Michael L. Morrison

Abstract We compared the uses and definitions of habitat-related terms in 50 articles from 1980 to1994 to operational definitions we derived from the literature. Only 9 (18%) of the arti-cles we reviewed defined and used habitat-related terms consistently and according toour definitions of the terms. Forty-seven articles used the term "habitat;" however, it wasonly defined and used consistent with our definition in 5 articles (I 1%) and was confusedwith vegetation association or defined incompletely in 42 papers (89%). "Habitat type"was the term most commonly used incorrectly; 16 of 17 times (94%) it was used to indi-cate vegetation association, but habitat and vegetation association are not synonymous.Authors did not provide definitions for habitat use, selection, preference, or availability23 of 28 times (82%). We concluded that habitat terminology was used vaguely in 82%of the articles we reviewed. This distorts our communication with scientists in other dis-ciplines and alienates the public because we give ambiguous, indefinite, and unstandard-ized answers to ecological questions in public and legal situations. Scientists should de-fine and use habitat terminology operationally, so that the concepts are measurable andaccurate. We must take the challenge to standardize terminology seriously, so that wecan make meaningful statements to advance science.

Key words availability, critical habitat, habitat type, operational terminology, preference, quality, se-lection, standardization

Block and Brennan (1993) discussed the conceptFirst, although several authors have recommendedof habitat in the context of ornithology, stating that itthat studies of wildlife-habitat relationships be placedcould be considered one of the few unifying theoriesin the proper spatial and temporal scales (Wiens 1981,in contemporary ecology. Their opinion was basedMorrison et al. 1992, Block and Brennan 1993, Litvaitison a wide survey of papers that related the presence,et al. 1994), this has yet to happen. Researchers needabundance, distribution, and diversity of birds to as-to recognize that their perceptions of wildlife-habitatpects of their environments, and in which habitatrelationships are scale-dependent, reflecting the differ-was invoked to explain the factors and processes thatent scales at which different animals operate and atcontributed to the evolutionary history and fitness ofwhich they operate (Wiens 1989). Johnson (1980)animals. Other authors have likewise emphasizedand Hutto (1985), for example, proposed that animalsthe importance of wildlife-habitat relationships,select habitat through a hierarchical spatial scalingSpecifically, "habitat use" by wildlife has been ad-process, with selection occurring first at the level ofdressed by numerous researchers (Verner et al. 1986,the geographic range; second, at the level where ani-Morrison et al. 1992, Bookhout 1994). However, wemals conduct their activities (i.e., in their homethink there are several problems with current studiesranges); third, at the level of specific sites or for spe-and discussions of habitat use that are the source ofcific components within their home ranges; andambiguities and inaccuracies, fourth, according to how they will procure resources

Authors’ address during this research: School of Renewable Natural Resources, 325 Biological Sciences East Building, University of Ari-zona, Tucson, AZ 85721, USA. Current address for Linnea S. Hall and Michael L. Morrison: Department of Biological Sciences, Cali-fornia State University, Sacramento, CA 95819, USA.

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within these micro-sites. Hutto (1985) proposed thatMany other papers have called for the developmentselection at the level of the geographic range is proba-of standard definitions of ecological terms (Romesbnrgbly genetically determined, and Wecker (1964) and1981, McCoy and Bell 1991, Morrison et al. 1992:11,Wiens (1972) demonstrated that selection at f’mer lev-Weckerly 1992). However, based on the variable usageels (i.e., smaller scales) may be influenced by learningand application of such terms observed in even aand experience and so is directed more intentionallysory search of the literature, it appears that the call hasby individual animals. Thus, wildlife-habitat relation-not been heeded. Inconsistent clef’tuitions lead ecolo-ships are distinctly different at different levels, and au-gists to a variety of approaches for measuring the termsthors of habitat papers need to be sure they specify the(e.g., habitat use, selection, preference; carrying capac-levels to which their studies are applicable, and not ex-ity; Wi~ns 1984:398), making it difficult to conduct in-trapolate their data beyond those levels, ter- and intra-disciplinary comparisons. The looseness

In terms of temporal scale, authors should be spe-of our ecological def’mitions has even contributed tocific about when their studies were undertaken, andprolonged court battles (e.g., def’midons of"old-growthto what time period(s) the studies apply. Morrison etforests" in the Pacific Northwest; Murphy and Noonal. (1992:163-164) stated that too many researchers1991, Orians 1993). Murphy and Noon (1991) statedignore temporal variation in resource use, or samplethat the terms "habitat" and "critical" have never beenfrom narrow time periods in which the resultingdefined precisely and independently, and that this haswildlife-habitat relationships apply only minimally toled to difficulties in determining exactly what criticalother situations. Conversely, researchers commonlyhabitat is for federally listed species. Because standardsample from across broad time periods (i.e., years;definitions are rarely used, some authors have thrownsummer or winter seasons) and then use averagedup their hands at ever trying to provide them (Verner etvalues for variables across the periods, potentiallyal. 1986~x0. We think, however, that the ubiquitousmasking differences in resource use. use of the word "habitat" in the wildlife, restoration

The second issue that authors of habitat papersecology, and conservation biology literature, and theshould consider is that if we want to advance wildlifeprevalence of words related to habitat (e.g., commu-ecology, we must be sure that the fundamental con-nity, ecosystem, and biodiversity) creates an urgentcepts with which we work are well defined, andneed for standard definitions at this time.hence, well understood. This facilitates discussionTo address some of the problems we see with def-among ecologists by forcing us to use words specifi-initions of habitat, we present information on thecally instead of loosely, but it also facilitates bettercurrent and common uses and misuses of thesepublic communication, minimizing confusion andterms. We also suggest standard def’mitions to en-ambiguity. Peters (1991) urged that environmentalcourage wildlife biologists (and others) to define andscientists "operationalize" ecological concepts. Pc-use the words less haphazardly.ters (1991:76) argued that definitions of conceptssuch as habitat should be operational, i.e., practical,measurable specifications of the ranges of the spe- Methodscific phenomena the terms represent. The defini-To evaluate how recent (i.e., 1980-1994) authorstions may change over time, but if the concepts are tohave used habitat-related terms, we reviewed 50 pa-be scientifically useful, then the original and subse-pets from prominent journals and books in thequent definitions must be measurable so that theywildlife and ecology fields that discussed wildlife-can be applied consistently, habitat relationships (Table 1). Papers and books

The third problem we see in discussions of habitat,were selected based on (1) their importance as cur-and one that underlies all of the issues we have out-rent wildlife publications (e.g., the Wildlife Tech-lined above, is that the use of habitat terminology isniques Manuals, fourth and fifth editions [Schemnitzimprecise and ambiguous. Block and Brennan (1993)1980, Booldaout 1994]), and (2) their discussion ofstated that specific definitions of the term "habitat"mammalian-habitat relationships. Block and Brennanare often vague, ranging in scope from how species(1993) recently provided a review of avian-habitat re-are associated with broad, landscape-scale vegetationlationslaips. We then recorded all uses in the papersto very detailed descriptions of the immediate physi-of terms relating to habitat, including habitat type;cal environments used by species. We recognize ahabitat use, selection, preference, or availability;similar tendency among papers in wildlife science andhabitat quality; micro- and macrohabitat; critical habi-think that the vagueness and variability is nonproduc-tat; and nonhabitat (Table 2).tive because it detracts from the ability to communi-In our reviews of each paper we noted if habitatcate effectively about habitat-related subjects, terms were defined, and evaluated the definition(s),

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Table I. Sources of literature reviewed (journals, books, sympo- migration and dispersal corridors and the land thatslum proceedings, and reports) for wildlife habitat-related fermi- animals occupy during breeding and nonbreedingnology, seasons are habitat. Habitat is therefore not equiva-

No. selections lent to "habitat type," a term coined by DaubenmireReference sources reviewed in source (1968:27-32), which refers only to the type of vegeta-

tion association in an area or to the potential of vege-Books and dictionaries tation to reach a specified climax stage. "Habitat" is

Allaby (I 992)much more than the vegetation (e.g., pine [Pinus]-Bell etal. (1991) I

Fowler and Smith (1981) 1 oak [Quercus] woodland) in an area, and so we thinkPatton (1992) I the term "habitat type" should not be used when dis-Peek(1986) 1 cussing wildlife-habitat relationships. When authors

Ioumals and series intend to refer only to the vegetation that an animalConservation Biology 2Ecological Applications 2 uses, they should use "vegetation association" or

Ecological Monographs 1 "vegetation type" instead.Ecology 2 We def’me the term "habitat use" as the way an an-EnvironmentalManagement 2 imal uses (or "consumes," in a generic sense) a col-Joumal ofMammalogy 7 lection of physical and biological components (i.e.,Journal ofWildlifeManagement 7

resources) in a habitat. "Habitat selection," as de-Research and Management Techniquesfor Wildlife and Habitats, Fifth ed. 6 fined by Hutto (1985:458), is a hierarchical process

Southwestern Naturalist 1 involving a series of innate and learned behavioral de-Wildlife Management Techniques cisions made by an animal about what habitat it

Manual, Fourth ed. 2 would use at different scales of the environment.Wildlife SocietyBulletin 2

Johnson (1980) similarly defined selection as theSymposium and forum proceedingsRodiekand Bolen (1991) 2 process by which an animal chooses which habitatVetoer et al. (1986) 3 components to use. Given the body of literature thatWilson and Peter (1988) 1 treats selection as a process, we also define selection

Agency publications this way, and furthermore, we define habitat "prefer-Brown (1994) 1

ence" as the consequence of the process, resulting inCooperrider et al. (1986) IMorrison et al. (1991) I the disproportional use of some resources over oth-Ockenfels et al. (I 991 ) I ers.U.S. Department of Agriculture (I 992) I "Habitat availability" refers to the accessibility and

procurability of physical and biological componentsof a habitat by animals. This is in contrast to the"abundance~ of these resources, which refers only to

if given. We also looked for inconsistent uses oftheir quantity in the habitat, irrespective of the or-words within a paper and recorded different uses ofganisms present (Wiens 1984:402). In theory, oneeach term. To determine if the definitions were "cot-should be able to measure the amounts and kinds ofrect," "incorrect," "weak," or "poor," we comparedresources available to animals; in practice, however,them to standard de~mitions we developed based onit is not necessarily possible to assess resource avail-def’mitions presented by Morrison et al. (1992) andability from an animal’s point of view (Litvaitis et al.Block and Brennan (1993), which were in turn drawn1994). For example, we can measure the abundancefrom ecologists such as Grinnell (1917), Leopold(by trapping) of a prey species for a particular preda-(1933), Hutchinson (1957), Daubenrnire (1968), andtor, but we cannot say that all of the prey present inOdum (1971). We therefore define "habitat" as thethe habitat are available to the predator becauseresources and conditions present in an area that pro-there may be factors that restrict their accessibility,duce occupancy--including survival and reproduc-such as presence of ample cover. Similarly, Morrisontion--by a given organism. Habitat is organism-spe-et al. (1992:139) proposed that vegetation beyondcific; it relates the presence of a species, population,the reach of an animal is unavailable for it to feed on,or individual (animal or plant) to an area’s physicaleven though the vegetation may be "preferred" for-and.biological characteristics. Habitat implies moreage. Although measuring actual resource availabilitythan vegetation or vegetation structure; it is the sumis important for understanding wildlife-habitat rela-of the specific resources that are needed by organ-tionships, in practice it is seldom measured becauseisms. Wherever an organism is provided with re-of the difficulty of determining exactly what is avail-sources that allow it to survive, that is habitat. Thus,able and what is not (Wiens 1984:406). Conse-

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Table 2. Ratings of 50 papers reviewed for their definitions and consistencies in use of habitat-related terms, as compared to our T.standard definitions of the concepts. A rating of I = a term was defined similarly to our definition and was used consistentlythroughout the article; 2 = no definition, or an incomplete one, was provided for a term, but the use of the term was similar to our use; tl3 = no definition for a term was given, or the use of the term fluctuated between being correct and incorrect in the article; and 4 = 3neither of the criteria under "I" was met. n

Reference Term used Rating Reason

Adam et al. 1994 Habitat 3 No definition; sometimes confused with vegetation association KHabitat type 4 Confused with vegetation association

Allaby 1992 Habitat IAlverson et al. 1988 Habitat 4 No definition; confused with vegetation association

Habitat type 4 No definition; confused with vegetation association ~..Unfavorable habitat 3 Implies "unsuitable" habitat

Anderson and Gutzwiller 1994 Habitat 2 Incomplete definitionBellantoni and Krausman 1993 Habitat 2 No definition; use acceptable L

Habitat use 2 No definition; use acceptableHabitat availability 2 Only defined through statistics I

Bissonette et al. 1991 Habitat 3 No definition; sometimes confused with vegetation associationHabitat preference 2 No definition; use acceptable

Boitani et al. 1994 Habitat 4 Confused with vegetation associationHabitat type 4 Confused with vegetation association

Boyd et al. 1986 Habitat 3 Gave definition; sometimes confused with vegetation associationHabitat types 4 Confused with vegetation associationHabitat preference 2 No definition; use acceptableHabitat selection 2 No definition; use acceptableHabitat suitability 2 No definition; use questionableHabitat quality 2 No definition; use questionableCritical habitat 2 No definition; use acceptable

Brown 1994 Habitat 3 No definition; sometimes confused with vegetation associationHabitat selection 2 Only defined through statistics

Brown et al. 1994 Habitat 3 No definition; sometimes confused with substrate associationHabitat use 2 No definition; use acceptableHabitat selection 2 No definition; use questionableMicro/macrohabitat 2 No definition; use acceptable

Bryant 1991 Habitat 4 Confused with vegetation associationBurkett and Thompson 1994 Habitat 3 No definition; sometimes confused with vegetation association I

Habitat use 2 No definition; use acceptable ISuitable habitat 3 Should not use; implies there is unsuitable habitat

Butynski 1990 Habitat type 4 Confused with vegetation associationClark et al. 1993 Habitat 2 No definition; use acceptable

Habitat selection IHabitat quality ISuitable habitat 3 Should not use; implies there is unsuitable habitat"Unused" habitat I Use appropriate in this case

Debinski and Brussard 1994 Habitat 3 No definition; sometimes confused with vegetation associationHabitat type 4 Confused with vegetation association

Etchberger et al. 1989 Habitat 2 No definition; use acceptableHabitat use 2 No definition; use acceptableAbandoned habitat I Use appropriate in this case

Fleming 1991 Habitat 4 Confused with vegetation associationHabitat use 2 No definition; use acceptable

Fowler and Smith 1981 Habitat 2 No definition; use acceptableFrank and McNaughton 1992 Habitat 4 No definition; confused with vegetation association

Habitat preference 2 No definition; use acceptableFranklin and Johnson 1994 Habitat 4 Confused with vegetation association

Habitat type 4 Confused with vegetation associationGoldsmith 1990 Habitat 4 No definition; confused with vegetation associationGould and Jenkins 1993 Habitat 3 No definition; sometimes confused with vegetation association

Habitat types 4 Confused with vegetation associationHabitat selection 2 Only defined through statisticsHabitat use 2 Only defined through statistics

Gysel and Lyon 1980:305-307 Habitat IHabitat type I Used according to Daubenmire’s (I 968) definition

Irwin et al. 1993 Habitat 2 No definition; use acceptableJaksic et al. 1990 Habitat 2 No definition; use acceptableKie et al. 1994 Habitat 2 No definition; use acceptable

Habitat quality 2 No definition; use acceptable

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Table 2. (continued) Ratings of 50 papers reviewed for their definitions and consistencies in use of habitat-related terms, as comparedto our standard definitions of the concepts. A rating of 1 = a term was defined similarly to our definition and was used consistentlythroughout the article; 2 = no definition, or an incomplete one, was provided for a term, but the use of the term was similar to our use;3 = no definition for a term was given, or the use of the term fluctuated between being correct and incorrect in the article; and 4 =neither of the criteria under "1" was met.

Reference Term used Rating Reason

Kissell and Kennedy 1992 Habitat 3 No definition; sometimes confused with vegetation associationHabitat utilization 2 No definition; used acceptableHabitat type 4 Confused with vegetation association

Koehler and Hornocker 1991 Habitat 2 No definition; use acceptableHabitat use 2 No definition; use acceptableHabitat type 4 Confused with vegetation association

Kondolf 1994 Habitat 3 No definition; sometimes confused with vegetation associationLaymon and Barrett 1986 Habitat 2 No definition; use acceptable

Habitat suitability .3 No definition; use questionableLitvaitis et al. 1994 Habitat

Habitat use 1Habitat selection 1Habitat preference 1

Mannan et al. 1994 Habitat 2 No definition; use acceptableMcCoy and Bell 1991 Habitat 3 No definition; said it was too difficult to define

Habitat structure 3 Provided poor definition; not species-specificHabitat type 4 Confusing meaning

Morrison et al. 1991 Habitat IHabitat use IHabitat selection 2 No definition; use acceptable

Morrison et al. 1994 Habitat 3 No definition; sometimes confused with vegetation associationMurphy 1988 Natural habitat 2 No definition; use acceptable

Microhabitat 4 Confused with vegetation associationOckenfels et al. 1991 Habitat 4 Confused with vegetation association

Habitat type 4 Confused with vegetation associationHabitat selection 2 Only defined through statisticsSuitable habitat 3 Should not use; implies there is unsuitable habitat"Less desirable" habitat 3 No definition; statement not supported

Patton 1992:43-44 Habitat IPauley et al. 1993 Habitat 2 No definition; use acceptable

Habitat type 4 Confused with vegetation associationHabitat use 2 Only defined through statistics usedHabitat selection 2 Only defined through statistics used

Peek 1986:2,82 Habitat 2 Incomplete definitionHabitat selection 2 Incomplete definitionHabitat preference IHabitat use I

Plumb and Dodd 1993 Habitat use 2 No definition; use acceptableHabitat selection 2 No definition; use acceptable

Rosenberg and Raphael 1986 Habitat 2 No definition; use acceptableSamuel and Fuller 1994 Habitat 2 Incomplete definitionSmith and Mannan 1994 Habitat 2 No definition; use acceptableSpowart and Samson 1986 Habitat 3 Incomplete definition; sometimes confused with vegetation

associationHabitat type 4 Confused with vegetation associationHabitat preference 2 No definition; use acceptableHabitat selection 2 No definition; use questionableOptimum habitat 4 No definition; is based on density of animalsAvailability of habitat 2 No definition; use acceptable

Tershy 1992 Habitat 3 No definition; sometimes confused with landscape propertiesU.S. Department of Habitat 2 No definition; use acceptable

Agriculture 1992 Occupied habitat I Use appropriate in this caseSuitable habitat 3 Should not use; implies there is unsuitable habitatHigh value habitat 2 No definition; use questionable

White and Ralls 1993 Habitat type 4 Confused with landscape propertiesWielgus and Bunnell 1994 Habitat 3 No definition; sometimes confused with vegetation association

Habitat type 4 . Confused with vegetation associationHabitat use 2 No definition; use acceptable

Yoakum et al. 1980 Habitat 2 No definition; use acceptableQuality habitat 2 No definition; use questionable

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quently, the quantification of availability usually con-for an animal at another time. We therefore thinksists of a priori or a posteriort measures of the abtm-that it is appropriate to use "nonhabitat" in some in-dance of resources in an area used by an animal,stances, but with care.rather than the availability. Thus, we think that inWe think that the terms "unused" or "unoccupied"most instances the term "availability" should behabitat (and the converse of the terms) are appropri-.avoided by biologists and the term "abundance"ate when ecologists are discussing threatened, en-should be used instead because that is what is corn-dangered, or rare species that are so reduced in num-monly measured. In situations where the accessibil-bers that they cannot use some areas of habitat, butity of a resource has been determined for an animal,would do so if their numbers were greater and theythen analyses to determine habitat preference byhad the opportunity. Additionally, the term is appro-comparing "use" versus =availability" are useful andpriate when discussing species (of any abundance)operational, that exploit patchy resources, where unused patches

We think that "habitat quality" refers to the abilityfrequently occur, at least temporarily. "Unused" andof the environment to provide conditions appropri-"unoccupied" habitat are not synonymous with "non-ate for individual and population persistence. Ithabitat."should be considered a continuous variable, rangingWe think that terms such as "macrohabitat" andfrom low to medium to high, based on resources"microhabitat" are relative and refer to the levelavailable for survival, reproduction, and population(Johnson 1980) at which a study is being conductedpersistence, respectively. Researchers commonlyfor the animal in question. Thus macro- and micro-equate high-quality habitat with vegetative featureshabitat should be de~med on a study-specific andthat may contribute to the presence (or absence) of aspecies-specific basis. Generally, macrohabitat isspecies (e.g., Habitat Suitability Index models; Lay-used to refer to landscape-scale features such as seralmort and Barrett 1986, Morrison et al. 1991). Westages or zones of specific vegetation associationsthink, however, that quality should be explicitly(Block and Brennan 1993). This would usuallylinked with demographic features if it is to be a use-equate to Johnson’s (1980) first level ("order") offul measure. For example, theoretical discussions ofhabitat selection. Microhabitat usually refers to freer-carrying capacity (Leopold 1933, Dasmann et al.scaled habitat features, such as would be important1973) have equated a high-quality habitat with onein levels 2-4 in Johnson’s (1980) hierarchy. Thus, itthat has a density of animals in balance with its re-is appropriate to use micro- and macrohahitat in a tel-sources. In practice, this has been interpreted toative sense, and the scales to which they applymean that a high-quality habitat is one with large den-should be stated explicitly.sities of animals (Laymon and Barrett 1986). How- Finally, "critical habitat" is used primarily as a legalever, Van Home (1983) demonstrated that density isterm describing the physical or biological features es-a misleading indicator of habitat quality, and thosesential to the conservation of a species, which mayconfirming source and sink habitats in nature (Pul-require special management considerations or pro-liam 1988, Wootton and Bell 1992) have persuadedtection (U.S. Fish and Wild. Serv. 1988). Critical habi-many ecologists to de-emphasize density. Thus, wetat can occur in areas within or outside the geo-propose that although carrying capacity can begraphic range of a species (Schreiner 1976, U.S. Fishequated with some level of habitat quality, habitatand Wild. Serv. 1988). We think that this det’mition isquality itself should not be based on numbers of or-not specific enough ecologically to allow for easy andganisms, but on demographics of individuals or pop-rapid delineation of critical areas for threatened andulations, endangered organisms, nor is it concrete enough to

Relatedly, the term "suitable" habitat should not besatisfy many parties concerned with U.S. Fish andused because if an organism occupies an area thatWildlife listing decisions (e.g., public interest groupssupports at least some of its needs, then it is habitat,and lawyers). Thus, we propose that critical habitatSo, by definition then, habitat is suitable. Thus, thereshould be specifically linked with the concept ofis no such thing as unsuitable habitat, because it ishigh-quality habitat, which equates to an area’s abilitythe quality that changes, not the suitability per se.to provide resources for population persistence; Mur-Terms such as "nonhabitat," especially when used tophy and Noon (1991) reached the same conclusion.identify parts of a "home range" not used by an ani-This makes it an operational and ecological termmal during a study, can be misleading. We cautionrather than a political term.that (1) home range is not necessarily equivalent toWe rated each paper (Table 2) according to howhabitat (Butt 1943) and (2) unused portions of aauthors used habitat terms compared with our defin-home range in any given study may provide habitatitions and how consistently they used the terms in

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the article. A rating of 1 ("correct") was assigned if aFinally, we identified 3 terrns--"abandoned," "un-definition similar in intention to the definition weused," and "occupied" habitat--that were all rated asprovided was given for the term and if the term wascorrect uses. The term abandoned was used cor-used consistently throughout the article. A rating ofrectly to refer to habitat that was no longer used by4 ("incorrect") was given if none of these criteriaan endangered species in Arizona, and the term oc-were met. A rating of 2 ("weak’) was given ff no de-cupied was used correctly to refer to habitat still be-finition was provided or ff the definition was incom-ing used by threatened and rare species. Unusedplete, but the use of the term was similar to our start-habitat was used to describe analyses of "used" ver-dard definition. A rating of 3 ("poor") was given ff nosus "unused" areas within home ranges, and the au-definition was provided and the use of the term flue-thors (Clark et al. 1993) correctly stated that ran-tuated between being "correct" and "incorrect" indomly selected "unused" areas often include usedthe same article, habitats.

Results DiscussionOf the 50 articles we reviewed, only 9 (18%) cot-Habitat terminology was used vaguely and impre-

rectly defined and used terms related to habitat (Tablecisely in the majority (82%) of articles we reviewed.2). Of these 9 papers, 6 contained >2 habitat-relatedSome may argue with us for ranking articles asterms; of these, only 2 correctly defined and used all"weak" if they did not provide complete definitionsof the habitat-related terms in each paper. Of the 50of terms. We counter this with several points. First,articles we reviewed, 47 used the term "habitat," andwildlife scientists have to use words correctly to com-of these articles, habitat was defined and used cot-municate with each other. We think that there is arectly in only 5 of 47 papers (11%). It was useddeep-seated problem in the ecological sciences: weweakly or poorly (e.g., no definition was given and ituse terms haphazardly, either without providing def-was sometimes confused with a vegetation associa-initions, or providing definitions that are full oftion) in 34 of 47 papers (72%), and it was used incor-vague, non-operational terms. Fortunately, "habitat"rectly (e.g., was not def’med and was confused with aand related terms are relatively straightforward to de-vegetation association) in 8 of 47 papers (17%). fine. Unfortunately, other words in the literature

The term mostcommonly used incorrectly was(e.g., carrying capacity, community, ecosystem) are"habitat type." Of the 17 times it occurred, it wasmore difficult. Peters (1991:81-82) suggested thatused incorrectly 16 times (94%) to refer to a vegeta-without clear, operational del’mitions, different userstion association. In only 1 instance was the termmay develop inconsistent def’mitions. Each new au-used as it was first defined by Daubenmire (1968); wethor in each new paper redef’mes a term, def’mitionsrated this as a correct use because of the reference toproliferate, and Finally, authors present whatever def-Daubenmire’s original definition, initions suit their own needs.

Another problem we identified was the failure toSecond, we should consider the need for effectivedefine a term except through the statistical analysiscommunication with scientists in other disciplines.used to determine its presence or absence. For ex-There are large differences in how wildlife scientists,ample, habitat use, selection, and availability were notconservation biologists, plant ecologists, theoreticaldefined conceptually in 23 of 28 papers (82%). How-ecologists, and restoration ecologists use habitat-re-ever, in 7 instances the authors concluded that ani-lated words. The schism between so-called basic andmals exhibited "use" or "selection" when there wereapplied sciences already runs deep; the misuse ofeco-significant P-values in tests of use versus measures oflogical terms among scientists makes the chasm"availability." Habitat preference was used correctlywider. There are many ecological problems to whichonly 2 of 6 times (33%) and weakly 4 times (67%).we must jointly attend (Meffe and Carroll 1994); thus,

We found several adjectives used to describe habi-we suggest that our terminology be tightened so thattat quality: "high value," "less desirable," "unfavor-scientists can cooperate effectively to solve problems.able," =quality," "optimum," and "suitable" habitats. Finally, the recent increase in the number ofscien-These were rated, collectively, as weak in 1 casetists called to be expert witnesses at court hearings(12.5%), poor in 6 cases (75%), and incorrect in 1 case(Murphy and Noon 1991) troubles many ecologists.(12.5%). We found only 1-2 references each for "crit-They wonder whether professionals in the naturalical habitat," "habitat structure," "microhabitat," andsciences are capable of providing the det’mitive an-"macrohabitat." Collectively, use of these terms wasswers sought by lawyers. Controversies such as thatrated as weak (50%), poor (25%), or incorrect (25%).over the northern spotted owl (Strix occidentalis oc-

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ctdentalts) have raised scientists’ concerns about thedeer: edge effects in northern Wisconsin. Conserv. Biol.

accuracy of their data (Thomas et al. 1990); scientists2:348-355.ANDerSON, S. H., AND K. J. GtrrzwtLLrm. 1994. Habitat evaluationshould also worry about the accuracy of their termi- methods. Pages 592-606 in T. A. Bookhout, ed. Research and "

nology. If we cannot operationalize our concepts management techniques for wildlife and habitats, Fifth ed. The .’and theories, and use habitat terms consistently, thenW’fldl. Soc., Bethesda, Md. "

we cannot blame lawyers, the media, and the publicB~L, S. S., E. D. McCoy, AND H. R. MOSttlNSKY. 1991. Habitat struc-

for being confused by our ambiguities, ture: the physical arrangement of objects in space. Chapmanand Hall, London, U.K. 438pp.

BELLmCrON~, E. S., AND P. R. ISL~AOSMAN. 1993. Habitat use by col-Recommendations lared peccaries in an urban environment. Southwest. Nat.

38:345-351.We recommend the following procedures to helpB,ssoNrrr~, J. A., R.J. FV.Z~UUCKSON, AND B. J. Tucram. 1991. Ameri-

alleviate problems in defining habitat-related and can marten: a case for landscape-level management. Pages115-134 inJ. E. Rodiek and E. G. Bolen, eds. Wildlife and habi-other terms: tats in managed landscapes. Island Press, Washington, D.C.

1. Until scientists use habitat-related terms consis-BLocr, W. M., AND L. A. BRENNAN. 1993. The habitat concept in or-tently, we should define habitat concepts in nithology: theory and applications. Pages 35-91 in D. M.

such a way as to address all of the points Power, ed. Current ornithology. Vol. 11. Plenum Press, Newstressed earlier in this paper: i.e., words used inYork, N.Y.

BO1TANt, L., L. MAa-ro, D. NoNts, ANn F. COaSL 1994. Spatial and ac-definitions should be measurable and accurate. tivity patterns of wild boars in Tuscany, Italy. J. Mammal.

2. Authors should cite references to the first in- 75:600-612.stance and use of terminology, or use a refer-Boormo~, T.A. 1994. Research and management techniques forence with definitions following the criteria we wildlife and habitats. Fifth ed. The Wildl. Soc., Bethesda, Md.

listed above. For example, Leopold (1933)740pp.

first defined and discussed carrying capacity,BovD, R. J., A. Y. COOpr.~IDE~, P. C. 12~¢r, AND J. A. BAILEY. 1986.Ungulates. Pages 519-564 in A. Y. Cooperdder, R.J. Boyd, and

but Leopold is seldom cited for coining the H.R. Stuart, eds. Inventory and monitoring of wildlife habitat.term. Authors discussing carrying capacity u.s. Dep. Inter., Bur. Land Manage. Serv. Cent., Denver, Colo.

should therefore cite Leopold as the originatorBRow~, R.L. 1994. Effects of timber management practices on elk.

of the concept, and then present operational Ariz. Game and Fish Dep. Tech. Rep. 10. 70pp. .Bt~ow~,J. S., B. P. K~rL~, AND W. A. MrrcH .~a.. 1994. Foraging the-

modifications of the concept if necessary. Dry, patch use, and the structure of a Negev Desert granivore3. Scientists must make a serious commitment tocommunity. Ecology 75:2286-2300.

standardizing terminology. It will require us toBRvta, rr, F.C. 1991. Managed habitats for deer in juniper wood-

learn definitions and to talk frankly with our lands of western Texas. Pages 57-75 tn.J.E. Rodiek and E. G.

peers about how to define nebulous terms. It Bolen, eds. Wildlife and habitats in managed landscapes. Is-

will be worth the time and effort, however, be-land Press, Washington, D.C.

Bumc_rr-r, D. W., AND B. C. THOmeSON. 1994. Wildlife associationcause we will gain a terminology that is morewith human-altered water sources in semiarid vegetation corn-science than art. munities. Conserv. Biol. 8:682-690.

BuaT, W.H. 1943. Territoriality and home range concepts as ap-

Acknowledgments. J. Heffelfmger and R. W. Man-plied to mammals. J. Mammal. 24:346-352.Bt~rrvNsm, T.M. 1990. Comparative ecology of blue monkeys (Cer-

nan reviewed earlier drafts of the manuscript andcoptthecus mitis) in high- and low-density subpopulations.made many helpful suggestions. Two anonymous re-Ecol. Monogr. 60:1-26.viewers provided us with further insightful sugges-CLam<, J. D., J. E. DUNN, AND K. G. S~trrH. 1993. A multivariatetions, and the paper was also substantially improvedmodel of female black bear habitat use for a geographic infor-

by the comments ofJ. A. Wiens. This study was sup- mation system. J. Wildl. Manage. 57:519-526.

ported by the Wildlife and Fisheries Program, SchoolCOOP~a~,DE~, A. Y., IL J. BovD, AND H. R. SaX,^RT. 1986. Inventory

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U.S. F~sn ~ W~a~u~ SwwcE. 1988. Endangered species act of Linnea ~. Hall(right) is an Assistant Professor of Avian Ecology and1973, as amended through the lO0th Congress. U.S. Dep. In- Wildlife Biology at California State University, Sacramento. She re-ter., Washington, D.C. ceived her B.S. in Biological Sciences from California Polytechnic

V~ Hova~m, B. 1983. Density as a misleading indicator of habitat State University, San Luis Obispo; her M.S. in Wildland Resourcequality. J. W’fldl. Manage. 47:893-901. Science from the University of California, Berkeley; and her Ph.D

Wx~r~, J., M. L. MomusoN, ~D C. J. P, ma,8. 1986. Introduction. in Wildlife Ecology from the University of Arizona, Tucson. Dr.

Pages xi-xv in J. Verner, M. L. Morrison, and C. J. Ralph, eds. Hall has conducted large- and small-scaled studies of habitat se-lection by bird, mammal, and herpetile species. Recent publica-W~fldLife 2000: modeling habitat relationships of terrestrial ver-tions also address breeding behavior of birds, and linking manage-

tebrates. Univ. Wisconsin Press, Madison. ment and research together for effective wildlife conservation. Lin-Wv.cmm, S. C. 1964. Habitat selection. Sci. Am. 211:109-116. nea’s professional interests lie in the development of multi-speciesWEcrawa.~, F.W. 1992. Territoriality in North American deer: a call conservation strategies and also in determining how high-quality

for a common definition. Wildl. Soc. Bull. 20:228-231. habitats ultimately relate to individual animal success. Paul R.Wmax, P. J., ~ K. P, Au.s. 1993. Reproduction and spacing pat- Krausman (center) is Professor of Wildlife and Fisheries Science

terns ofldt foxes relative to changing prey availability. J. Wildl. and Associate Director of the Arizona Agricultural Experiment Sta-Manage. 57:861-867. tion at the University of Arizona, Tucson. He received his B.S. in

Wielgus, R. B., and F. L. Bunnell. 1994. Sexual segregation and fe- Zoology from Ohio State University, his M.S. in Wildlife Manage-

male grizzly bear avoidance of males. J. Wildl. Manage. ment from New Mexico State University, and his Ph.D in WildlifeScience from the University of Idaho. His research interests have

58:405-413. revolved around large mammals in the Southwest, and more re-Whys, J. A. 1972. Anuran habitat selection: early experience and cently, in India. He teaches graduate and undergraduate classes in

substrate selection in Rana cascadae tadpoles. Anita. Behav. wildlife management, conservation, and biology. Paul has been20:218-220. actively involved with The Wildlife Society for nearly 2 decades.

wm-cs, j.A. 1981. Scale problems in avian censusing. Stud. Avian Michael L. Mordson (left) was a Professor of Wildlife B iology at theBiol. 6:513-521. University of California, Berkeley, from 1982 to 1994, and has

W~s, J. A. 1984. Resource systems, populations, and communi- been an Adjunct Associate Professor of Wildlife Biology at the Uni-

fies. Pages 397-436 in P. W. Price, C. N. Slobodchikoff, and W. versity of Arizona, Tucson, since 1994, and at California State Uni-versity, Sacramento, since May 1996. He received his B.S. in Zo-S. Gaud, eds. A new ecology: novel approaches to interactive ology from Northern Arizona University, his M.S. in Wildlife Sci-

systems. John Wiley and Sons, New York, N.Y. ence from Texas A&M University, and his Ph.D in Wildlife ScienceWu~s, J.A. 1989. Spatial scaling in ecology. Functional Ecol. from Oregon State University. Dr. Morrison has published more

3:385-397. than 100 research and commentary papers on wildlife-habitat rein-Wilson, E. O., and F. M. Peter. 1988. Biodiversity. Natl. Acad. tionships, and in 1992, he and 2 colleagues authored Wildlife-

Press, Washington, D.C. 521pp. habitat relationships: concepts and applications. Recent projectsWoo’rroN, J. T., ~ D. A. BoJ.. 1992. A metapopulation model of include studies of hantavirus in rodents in Arizona, the status of mi-

the peregrine falcon in California: viability and management grant birds along the Lower Colorado River and in the mountainsof Arizona, and involvement with several large-scale restorationstrategies. Ecol. Appl. 2:307-321.

~’OAKOM, J., W. P. DASMA.NN, H. P~. SANDERSON, C. M. N[XON, AND H.S. projects for wildlife in California.CRAWFORD. 1980. Habitat improvement techniques. Pages329-403 in S. D. Schemnitz, ed. Wildlife management tech-niques manual. Fourth ed. The Wildl. Soc., Washington, D.C. Associate Editor: Barnes

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