Conservation Biology of the Cave Bats of Mexico Author(S): Héctor T
Total Page：16
File Type：pdf, Size：1020Kb
American Society of Mammalogists Conservation Biology of the Cave Bats of Mexico Author(s): Héctor T. Arita Source: Journal of Mammalogy, Vol. 74, No. 3 (Aug., 1993), pp. 693-702 Published by: American Society of Mammalogists Stable URL: http://www.jstor.org/stable/1382291 . Accessed: 01/10/2013 17:30 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Society of Mammalogists is collaborating with JSTOR to digitize, preserve and extend access to Journal of Mammalogy. http://www.jstor.org This content downloaded from 132.248.49.122 on Tue, 1 Oct 2013 17:30:27 PM All use subject to JSTOR Terms and Conditions CONSERVATIONBIOLOGY OF THE CAVE BATS OF MEXICO HECTORT. ARITA Departmentof Wildlifeand Range Sciences, University of Florida, Gainesville,FL 32611-0304 Presentaddress: Centro de Ecologia,Universidad Nacional Aut6noma de Mexico, ApartadoPostal 70-275, 04510 M6xico,D.F., Mdxico The available informationon use of caves by Mexican bats was examined to determinethe effectivenessof a conservationstrategy based on diversity.Diversity was estimatedby species richness, or the numberof bat species present in a cave. Sixty of the 134 Mexican species of bats regularly roost in caves. Seventeen of these species tend to roost in caves with low species richness (segregationists), 14 tend to roost in caves with high species richness (integrationists), and 29 show no tendency in terms of the species richness of the caves (indifferent).Of the 215 caves includedin this study, 80% supportfew (three or less) species, whereas only 10% harbor six or more species. In general, species that share caves with many species form small or medium-sized colonies, and there is no positive correlation between species richness and total number of individuals in the caves. Few of the fragile and vulnerablespecies of Mexican bats roost in caves with high species richness or with large populations. A conservation plan based solely on diversity is not adequate for the protectionof cave bats in Mexico. Key words: conservationbiology, cave bats, Mexico Caves are essentialroosting sites for many cies that requirecaves as roosting sites, and species of bats (Dalquestand Walton, 1970; a catalogue of caves that would be impor- Kunz, 1982a; Tuttle, 1976). Of the 39 chi- tant in a conservation plan for these bats. ropteran species that occur in the United A central objective of this review is to States, at least 18 depend heavily on caves analyze the concept that the protection of for roosting sites, and many others use cav- sites with high diversity or high population erns as occasional refugia (Culver, 1986; levels assures the preservation of endan- Humphrey, 1975; McCracken, 1989). In- gered and threatenedspecies. I test such an formation is less precise for other parts of idea for Mexican cave bats by evaluating the world, but several species are known to the distributionof species of particularcon- rely completely on caves for roosting sites. cern among caves with different diversity An extreme case is Kitti's hog-nosed bat and abundance. If bats of special concern (Craseonycteris thonglongyai), which is frequently occur in caves with rich and known from only six caves in Thailand abundant communities, then the preserva- (Humphreyand Bain, 1990). For such spe- tion of these sites also would protect the cies, destruction of caves would mean in- fragile species. Conversely, if few or none evitable extinction. of the species of particularconcern roost in Mexico has a rich bat faunaof 134 species rich caves, separatestrategies would be nec- (Jones et al., 1988; Ramirez-P. et al., 1986), essary to protect the caves and the bats. many of which are known to use caves as roosts (Tuttle, 1976; Villa-R., 1967). Here, METHODS I review the available literature on use of Froma surveyof theliterature on distribution, caves by Mexican bats, provide a list of spe- naturalhistory, and taxonomyof Mexicanbats J. Mamm., 74(3):693-702, 1993 693 This content downloaded from 132.248.49.122 on Tue, 1 Oct 2013 17:30:27 PM All use subject to JSTOR Terms and Conditions 694 JOURNALOF MAMMALOGY Vol.74, No. 3 (Appendix I), I constructeda list of caves har- I developed a list of cave species of special boringpopulations of bats. For each cave, I com- concernfor conservationbased on the list of frag- piled a list of bat species, includingin some cases ile and vulnerablespecies of Mexican bats pre- informationon population size. sented by Medellin and Arita (in press). Addi- I identified the most important caves for the tionally, I included species that are endemic to conservationof Mexicancave bats based on their Middle America (Mexico and CentralAmerica) diversity and abundance. Diversity was esti- and those that virtuallyare endemic to this area, mated by species richness,or the numberof spe- barelyentering the United States(California leaf- cies reported from the cave. Abundance was nosed bat, Macrotuscalifornicus; Mexican long- quantified by the number of individuals of all nosed bat, Leptonycteris nivalis; Mexican species present at a given time in a cave. Caves long-tongued bat, Choeronycterismexicana). I of low abundancewere definedas sites sheltering included endemics in the analysis because the multispeciespopulations of < 1,000 individuals. Mexican government treats them as species of Caves with high and very high abundancewere special concern,along with rare and endangered defined as supportingmultispecies populations forms, in its ecological regulations. of > 1,000 and > 10,000 individuals, respective- The distribution of species among caves was ly. Importantsites were defined as caves with a analyzedusing "incidencefunctions." These are high species richnessand high or very high abun- graphsof the proportionof caves occupied by a dance. given species among categoriesbased on species Mexicanbats were classifiedin four categories richnessof the sites. These graphsare analogous of cave use. The first categoryincluded species to the incidencefunctions first used by Diamond for which caves are the main roost, whereasthe (1974, 1975) to study distribution of birds on second containedbats that regularlyuse caverns archipelagoesin relation to their colonization as refugia, but frequently rely on alternative ability. In caves, incidencefunctions can be used roosts. The third categoryincluded species that to analyze patterns of use by bats at different use caves occasionally,but usuallyroost in other levels of species richness. sites, and the last group comprised species not I classified Mexican species of cave bats in known to use caves as roosts. Species in the first threecategories of incidence(Fig. 1). Speciessuch two groups(caves as main or alternativeroosts) as P. davyi,which tend to occupy caves with high are treated here as cave bats, whereas those in speciesrichness, are "integrationists." Species that the last two categoriesare considered non-cave tend to be found in caves with few species, such bats. I assignedspecies to these categoriesbased as the Mexicanbig-eared bat (Plecotusmexican- on informationfrom sources in Appendix I and us) are "segregationists."Finally, species with no from personal experience. For consistency in apparentpreference for rich or poor caves, such classifyingspecies, I followed specialcriteria. For as the common vampire bat (Desmodus rotun- a few poorly known species, single or few reports dus) are "indifferent."I assignedspecies to these of use of caves in Mexico were sufficientto con- categoriesbased on the shape of their incidence sider them cave forms. For example, the trum- curves. pet-nosed bat (Musonycterisharrisoni) has been from a cave once reported only (Winkelmann, RESULTS 1962), but so little is known about its roosting habits that it was groupedwith species that use The literature survey yielded a total of cavesas alternativerefugia. Similar cases are those 215 Mexican caves with information on of Allen's big-earedbat (Idionycterisphyllotis- bats. In these caves, species richness ranges Czaplewski,1983) and free-tailedbats of the ge- from one to 13 species. The frequencydis- nus Nyctinomops(Carter and Davis, 1961;Jones tribution shows a negative exponential of the United et al., 1972). Conversely, species curve, with several caves supporting few Statesthat use caves as hibernacula,but that use species and few caves harboring many spe- other sites for summer refugia, generally were contain six or not consideredcave species in Mexico. For most cies. Only 10% of the caves of these species there are no reports of hiber- more species, whereas 80% shelter three or naculain Mexico. Examplesinclude several spe- fewer species (Fig. 2). cies of mouse-eared bats (Myotis-Humphrey, Most caves have low abundance; caves 1982; Schowalter, 1980). with high and great abundance are com- This content downloaded from 132.248.49.122 on Tue, 1 Oct 2013 17:30:27 PM All use subject to JSTOR Terms and Conditions August1993 ARITA-CONSERVATIONOFMEXICAN CAVE BATS 695 0.6 100 Pteronotus davyi a 0.5 MEXICANCAVES 80 0.4 n = 215 C 0.3 60 A 0.2 V 40 0.1 SE .:ii.i:i .. 20 ..... 1 2 3 4to6 > 6 i NUMBEROF BAT SPECIES o I+IT f i V, 1 2 3 4 5 6 7 8 9 10 11 12 13 NUMBEROF BAT SPECIES 0.6 Plecotus mexicanus b U ,<0.5 FIG.2. -Species richnessof cavebats in Mex- 0.4 ico. O 0.3 0.2 and the cave z _ stramineus), myotis (Myotis 0 0.1 velifer and Myotis peninsularis-Villa-R., Woloszin and Woloszin, a 1 2 3 4to6 > 6 1967; 1982). O NUMBEROF BATSPECIES The list of important sites for the con- 0 servation of Mexican cave bats includes 12 S0.6 --- Desmodus rotundus caves (Table 1).