Diversity of Wild Mammals in a Megalopolis: Mexico City, Mexico

Mexico City, the capital of Mexico, is located on the Southern-Central part of the country and it is one of the most important megalopolis in the world. This city lies within the Distrito Federal, bordering with the state of Mexico on the north, east and west and with the state of Morelos on the south. It is one of the 32 political divisions of Mexico and the smallest one, comprising an area of 1,485 km2 (Fig. 1). Mexico City belongs to the Basin of Mexico together with parts of the states of Hidalgo, Puebla, Tlaxcala and Mexico. Mexico City and the rest of the metropolitan area is one of the largest cities in the world with more than 30 million inhabitants (INEGI, 2010), just behind Tokyo, Japan and forward New York and the Philadelphia area, USA (34.3 and 22 respectely; Brinkhoff, 2011). The rapid growth of its population has led to the loss of original habitats and to the transformation of natural sites and therefore and in spite of being considered as a region with high levels of biodiversity to the local extinction of wildlife species. Mammals are one of the most important components of biodiversity, particularly in Mexico. Several inventories and studies have reported the occurrence of mammals in the Valley of Mexico in the past years. Some of the most remarkable contributions to this subject are by far those of Villa-R (1952) and Hall (1981). However, important mammalian information for the Valley of Mexico was also gathered by Ceballos & Galindo (1984) and Villa & Cervantes (2003). Moreover, the paper published by Ramirez-Pulido et al. (1986) more than a quarter of a century ago about mammals of the Distrito Federal contributed important information to the knowledge of the species richness of local mammals species. In addition, several papers reports on mammals collected in diverse areas of the Distrito Federal (Lopez-Forment, 1989; Sanchez et al., 1989; Negrete, 1991; Negrete & Soberon, 1994; Castro-Campillo, 1992; Chavez & Ceballos, 1992, 1994; Chavez, 1993 a, b; Alvarez et al., 1994; Monroy et al., 1999; CONANP-SEMARNAT, 2006; Navarro, et al., 2007; Barcenas & Medellin, 2007; Gomez-Jimenez, 2009). Research papers referriing especially to particular taxonomic groups (Villa-R, 1966; Alvarez & Ramirez-Pulido, 1972; Polaco et al., 2002; Carraway, 2007) also mentioned the presence of mammals in Mexico City and confirmed the outstanding contribution of mammals to the biodiversity of the Distrito Federal. Despite this large number of reports, the available information on mammals of Mexico City was scattered and incomplete. Therefore, in order to properly documents the species


Introduction
Mexico City, the capital of Mexico, is located on the Southern-Central part of the country and it is one of the most important megalopolis in the world. This city lies within the Distrito Federal, bordering with the state of Mexico on the north, east and west and with the state of Morelos on the south. It is one of the 32 political divisions of Mexico and the smallest one, comprising an area of 1,485 km 2 (Fig. 1). Mexico City belongs to the Basin of Mexico together with parts of the states of Hidalgo, Puebla, Tlaxcala and México. México City and the rest of the metropolitan area is one of the largest cities in the world with more than 30 million inhabitants (INEGI, 2010), just behind Tokyo, Japan and forward New York and the Philadelphia area, USA (34.3 and 22 respectely; Brinkhoff, 2011). The rapid growth of its population has led to the loss of original habitats and to the transformation of natural sites and therefore and in spite of being consi d e r e d a s a r e g i o n w i t h h i g h l e v e l s o f biodiversity to the local extinction of wildlife species. Mammals are one of the most important components of biodiversity, particularly in México. Several inventories and studies have reported the occurrence of mammals in the Valley of Mexico in the past years. Some of the most remarkable contributions to this subject are by far those of Villa-R (1952) and Hall (1981). However, important mammalian information for the Valley of México was also gathered by Ceballos & Galindo (1984) and Villa & Cervantes (2003). Moreover, the paper published by Ramírez-Pulido et al. (1986) more than a quarter of a century ago about mammals of the Distrito Federal contributed important information to the knowledge of the species richness of local mammals species. In addition, several papers reports on mammals collected in diverse areas of the Distrito Federal (López-Forment, 1989;Sánchez et al., 1989;Negrete, 1991;Negrete & Soberón, 1994;Castro-Campillo, 1992;Chávez & Ceballos, 1992, 1994Chávez, 1993 a, b;Álvarez et al., 1994;CONANP-SEMARNAT, 2006;Navarro, et al., 2007;Bárcenas & Medellín, 2007;Gómez-Jiménez, 2009). Research papers referriing especially to particular taxonomic groups (Villa-R, 1966;Álvarez & Ramírez-Pulido, 1972;Polaco et al., 2002;Carraway, 2007) also mentioned the presence of mammals in México City and confirmed the outstanding contribution of mammals to the biodiversity of the Distrito Federal. Despite this large number of reports, the available information on mammals of Mexico City was scattered and incomplete. Therefore, in order to properly documents the species richness of mammals in Mexico City, to make decisions about its protection, and to prevent a further loss of species due to the urban sprawl that has endangered all existing ecosystems in the Valley of Mexico, a synthesis on the subject as well as an updated inventory of the mammal fauna of this region was necessary. The result of this research will undoubtedly serve also as a tool for the development of programs aimed to the conservation and sustainable use of the biodiversity of México City and the remaining The Distrito Federal region.

Topography
The Distrito Federal topography is defined by a valley whose average altitude is 2,400 m, surrounded by high mountains whose highest elevation 3,930 m-is located on the Ajusco volcano. This city is surrounded by the mountains of Sierra de Guadalupe (2,780 m) and Cerro del Tepeyac in the northern part of the entity. In the central-eastern part is bordered by the mountains of Santa Catarina and Cerro de la Estrella, whereas the mountain range of the Sierra de las Cruces and the volcanoes Ajusco, Xitle, Chichinautzin, Teuhtli and Tláloc are located in the southern part of México City. This mountainous system belongs to the Neovolcanic Axis, also known as Sierra Ajusco-Chichinautzin. The topography of the Valley of México also includes hills such as Peñón de los Baños, Peñón Viejo and Cerro de Chapultepec.

Coniferous forests: Pines (Pinus)
This kind of vegetation is composed of pine trees: Pinus hartwegii, P. montezumae, P. pseudostrobus, P. teocote, P. rudis, besides Salix paradoxa and Juniperus monticola, along with other tree species such as Alnus jorullensis, Quercus laurina, Arbutus xalapensis and shrubs such as Buddleja cordata. There is practically no vegetation strata at high altitudes whereas at lower altitudes we have Solanum cervantesii and Barkleyanthus salicifolius wich are notorious, Alchemilla procumbens, Salvia prunelloides, Stipa ichu, Muhlenbergia quadridentata and Festuca tolucensis are abundant in places where bunch grasslands conform the herbaceous stratum, these grasslands are quite frequent, also containing dominant grasses like Muhlenbergia macroura, M. quadridentata, M. robusta, Festuca tolucensis and F. amplissima, together with the herbs Penstemon tenuiflora, Piqueria trinervia and Zephyranthes fosteri, among others. This is the most extended kind of vegetation in the Distrito Federal at altitudes between 2700 and 3800 m, and it mainly occurs in the following political delegations: Cuajimalpa, Álvaro Obregón, Magdalena Contreras, Tlalpan and Milpa Alta (Rivera & Espinosa, 2007).

Sarcocrassicaule (Xerophitic) ticket
Xerophytic thicket and say it is located in the driest areas of the Distrito Federal between 2300 and 3060 m (Rivera & Espinosa, 2007

Halophytic and gypsophytic vegetation
These are located in the southern part of the Valley of Mexico, in soil with high amounts of salt and alkaline within areas affected by constant flooding. Some of the typical species of

Materials and methods
To create an updated inventory of mammals of Mexico City we gathered data from collecting work in the field, from visiting mammalian collections in the Valley of Mexico, and from consulting the literature and databases available in web sites. Collected specimens were conventionally prepared as museum specimens and taxonomically determined following conventional identification keys (Hall, 1981;Medellín et al., 1997;Villa & Cervantes, 2003). Voucher specimens were stored and catalogued in the mammalian collection "Colección Nacional de Mamíferos (CNMA)" of Instituto de Biología, Universidad Nacional Autónoma de Mexico, at Mexico City. All resulting data were stored and managed in a database created in Microsoft Access 2003, where were incorporated 50 fields of geographical and biological information according to the guidelines of Darwin Core (Ver. 3.0) and MaNIS/HerpNet/ORNIS Georeferencing Guidelines (Wieczorek, 2001).

Updated list, distribution and conservation status
The list of the inventory was elaborated only with taxa adequately documented, at least with one voucher specimen cataloged in a biological collection. An exception to this was the coyote, Canis latrans (Aranda, 2010a;Farías, 2010) and Nasua narica (Aranda, 2010b). The nomenclature and classsification at species level we followed was that by Wilson & Reeder (2005), while for subspecies level we consulted the list of Ramírez-Pulido et al. (2005). For taxa of the family Heteromyidae and Soricomorpha we followed Hafner et al. (2007) and Carraway (2007) respectively. We reported the category of extinction risk of the taxa according to both the Norma Oficial Mexicana 059 (SEMARNAT, 2010), and the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES). The endemic condition (E) of a species and its condition as a monotypic or polytypic taxon is indicated (SEMARNAT, 2010;Carraway, 2007).

Collecting locaties
Specimens collecting locaties were verified because many were wrong, incomplete, or their names were ambiguous. Therefore, it was necessary to check maps, gazeteers, literature, field diaries and catalogues to accurately identify the localities referred. The names of the locaties were standardized and the geographic coordinates were calculated using a conventional guide for georeferencing (Wieczorek, 2001); topographic maps at scales 1:50,000 and 1:100,000 were used (INEGI, 2001;Secretaría de Comunicaciones y Transportes, 1987, respectively); in those cases when the data were taken directly from a Global Positioning System (GPS) unit (Garmin Co. Inc.). The information obtained was visualized using Arcview software and the digital map of The Distrito Federal was provided by the Unidad de Informática para la Biodiversidad (UNIBIO).

Results
The results produced 5,724 records of mammals from Mexico City in The Distrito Federal and some near localities bordering on the other states confoming the Valley of Mexico. The specimens correspond to different preservation types such as skin, skull, skeleton and alcohol cataloged in 17 mammalian collections, seven of them are domestic and ten from the United States of America. The collection name, acronym (Hafner et al., 1997;Lorenzo et al., www.intechopen.com (TTU,9); and Harvard University Provider (MCZ, 5). The database containing the whole data set will be available through the CNMA at the web site of Instituto de Biología, Universidad Nacional Autónoma de Mexico (http//unibio.ibunam.mx).

Updated list and taxonomic composition of wild mammals in The Distrito Federal
The updated list (Table 2) only registers the species that were supported by voucher specimens stored in biological collections, except Canis latrans cagotis, and Nasua narica which present footprints and photographs as evidence which are deposited at the Colección de Fotocolectas Biológicas del Instituto de Biología, UNAM. The records of probable occurrence were not mentioned in this study. The historical records were not included. Only wild species were considered, the domestic species like cats and dogs (Felis silvestres and Canis familiaris) were eliminated, as well as the exotic as rats and mice (the gray rat and the black rat; Rattus norvegicus, Rattus rattus; and the domestic mouse, Mus musculus).   (Tables 2 and 3). The best documented orders were Chiroptera (35% = 28 species) and Rodentia (35% = 28 species) followed by Carnivora (13.75% = 11species), Soricomorpha (8.75% = 7 species), and Lagomorpha (3.70% = 3 species). The orders Didelphimorphia, Cingulata and Artiodactyla are represented with one species (1.23% ) each.

Type specimens
The literature reports are 13 holotype specimens for Mexico City corresponding to 5 type localities in The Distrito Federal (Álvarez et al., 1997

Species protected by the Mexican government
We found out that 8 mammal species ocurring in México City and other localities of The Distrito Federal are within a category of extinction risk as defined by the Mexican government (SEMARNAT, 2010, Table 1). The zacatuche rabbit (Romerolagus diazi) is an endangered species; three species of phyllostomid bats (Choeronycteris mexicana, Leptonycteris yerbabuenae, cited in NOM-059, 2010 as L. curasoae), and Leptonycteris nivalis, one carnivore (Taxidea taxus berlandieri), two rodents, the kangaroo rat (Dipodomys phillipsii phillipsii), and Reithrodontomys microdon wagneri, and two species of shrews (Cyptotis alticola and Cryptotis parva) are listed under the category of special protection status ( Table 2). The kangaroo rat ocurred throughout the Valley of México.

Mammal distribution in different vegetation types
Mammal distribution in different vegetation types (CONABIO, 1999) shows that 32 % of the species are found in Oyamel coniferous forests (Abies religiosa). taylori. An analysis of records also showed that 76% of mammal species from the Distrito Federal is distributed within areas used for agriculture, cattle ranching and forest management, a fact that is not surprising if one considers that these types of area comprises much of the conservation area. A high percentage (71%) of the mammals are distributed within the urban area that comprises most of Mexico City. The Ecological Reserve of El Pedregal de San Ángel, with 33 described species, is found inside this same urban area. We compared the updated list obtained from our research with the previous published lists of wild mammals from the Distrito Federal (Table 4), including 20 regional, state, national and North American list. From the North American reports we carefully selected only those records showing that the collection site was within the boundaries of the entity. However , we did not considered publications with records for the Distrito Federal with only one or few records although they are analyzed and mentioned in our research. This paper describes almost two century of mammal records; all the specimens are housed in Mexican and North American scientific collections and the oldest records are probably hold in Europe.The taxonomic composition of wild mammals from the Distrito Federal included 80 species. The published lists vary from having 39 up to 77 species. Hall (1981) reported 77, Ceballos & Galindo (1984), and Villa & Cervantes (2003), reported 74, Ramírez-Pulido et al. (1986) reported 64 and Villa-R, 1952 reported 39. Four species were heretofore unrecognized such as the hare, Lepus callotis callotis (Hall, 1981;Ramírez-Pulido et al., 1986;López-Forment, 1989 andCervantes, 2003), two bats Dermanura azteca (Hall,1981, for the Basin of Mexico , Eumops u. underwoodi (Ceballos & Galindo,Fig. 6. Geographical distribution of mammals by vegetation type and land use. 1984;López-Forment, 1989;Álvarez et al., 1997), this last record had not been recognized in previous publications (Sánchez-H et al., 1989;Hortelano-Moncada et al., 2009). One squirrel, Sciurus occulatus (Villa-R, 1952;Hall, 1981;Ceballos & Galindo, 1984;Ramírez-Pulido et al., 1986;Villa & Cervantes, 2003) which is a specimen from Parres, Tlalpan, was wrongly identified, it is S. aureogaster indeed. Two shrews, Sorex orizabae and S, veraecrucis altoensis, are reported for the Distrito Federal in a relatively recent study (Carraway, 2007), S. veraecrucis altoensis is recorded as a new species. On the other hand, one more bat record was incorporated, Nyctinomops laticaudatus ferruginea is mentioned in previous publications as a record of probable occurrence (Hall, 1981;Polaco et al., 1992, Villa & Cervantes, 2003Bárcenas & Medellín, 2007). www.intechopen.com

Discussion
Most mammal records from the Distrito Federal are found in two Mexican collections: CNMA and UAMI, nevertheless, the type specimens and some of the oldest records are found in collections outside the country, which makes their study difficult, although access through electronic means has helped with this problem. Although there are several studies by regions and by groups, some taxa still need to be studied as a result of which there are still some poorly represented species. Another problem is that some areas have been visited only sporadically. The species accumulation graphs support this problem: in general, those periods with the higher number of collections were also the best represented regarding number of species. Some of the oldest records of the Distrito Federal belong to 4 specimens of Oryzomys couesi, collected in 1892 (Oryzomys crinitus, Merriam, 1901, NMNH: 50181), nevertheless, there is one paper reporting specimens of this species collected in Xochimilco, Distrito Federal, but it does not specify where this biological material is found theefore a verification is not possible (González-Romero, 1980 Non-invasive tools, such as photographs or prints have also contributed to species´ records (Aranda, 2010, Bárcenas & Medellín, 2007, Farías, 2010, Guevara-López, et al 2010, Ortega, 2010. This is especially useful regarding medium-and large-sized species. One of these records belongs to Procyon lotor, one of the first species recorded in the Distrito Federal in 1830, another specimen was collected 52 years later (NMNH 51151) and its presence was recently documented through prints. Several authors mention in their papers having heard Canis latrans howling, but have not provided any records, and no record of their presence has been found in biological collections. Their presence has been recently documented through prints. Recent records, prints, include those of Lynx rufus, Mustela frenata, Taxidea taxus, Conepatus leuconotus, Mephitis macroura, Bassariscus astutus, Nasua narica (Aranda, 2010), Odocoileus virginianus (Aranda, 2010, Guevara-López, 2010 Lorenzo et al., 2008). Nevertheless, the surface of Mexico´s basin must be compared with that of these last states and, also, the fact that the Distrito Federal has, within its borders, one of the cities with the largest population in the planet, not only today but historically speaking: Cuicuilco was one of the first cities in the basin with a large population (Pérez-Campa, 2007).
In this paper we also record the highest number of species for the Distrito Federal compared with previous studies of the entity: 40 species in Villa (1952), 74 species in Ceballos & Galindo (1984), 62 species in Ramírez-Pulido (1986), 78 species in Hall (1981) and 74 in Villa & Cervantes (2003). These last authors only have 29 and 44 species with their locality recorded within the borders of the Distrito Federal, the rest are potential records.
On the other hand, the highest distribution of mammals in the Distrito Federal concentrated in two delegations: Tlalpan and Coyoacán, this last one found within the border of Mexico City. Species with the largest distribution were Microtus mexicanus and Lasiurus cinereus, the first one with numerous records/delegation and the second one with one or five records/delegation. Other species with a wide distribution were: one opossum Didelphis virginiana, one rabbit Sylvilagus floridanus, seven rodents Cratogeomys merriami, Peromyscus maniculatus, Peromyscus difficilis, Neotomodon alstoni, Peromyscus gratus, Peromyscus melanotis and Reithrodontomys fulvescens, and six bats: Tadarida brasiliensis, Eptesicus fuscus, Myotis velifer, Nyctinomops macrotis, Leptonycteris yerbabuenae and Corynorhinus mexicanus. The latter analysis shows that the Distrito Federal is an entity the preserves a large mastofaunistic diversity and that in order to preserve it, it is necessary to preserve the natural habitats that still exist. Another fact to be considered is that the species with more restricted habitat requirements are also the most vulnerable to human actions such as agriculture, fires and poaching.  Table 4. Updated list and previous records of wild mammals in The Distrito Federal. One asterisk indicates that is a new record and two asterisks that are not recognized by the www.intechopen.com

Conclusions
The Distrito Federal has a great biological diversity. The best represented groups of mammals are bats and rodents and, in smaller numbers there are also groups of opossums, shrews, rabbits, armadillos, carnivores and deer. Some of these mammals are protected by International and Mexican legislation. With this study we have found species that have adapted to the new conditions of the city, and they now live in parks, buildings and green areas; some of these species are bats, opossums (Didelphis) and squirrels (Sciurus and Spermophilus), while other species, such as rodents, shrews (Sorex and Cryptotis), one rabbit (Romerolagus) and deer (Odocoileus), carnivores like (Lynx, Canis, Urocyon, Mustela, Procyon and Nasua) can only be found in protected areas. On the other hand we have found many historical records of mammals but, in this research, we did not find any evidence of their distribution in Mexico City. This study underlines the importance of updating inventories, of having them well documented and verifiable. It is of the utmost relevance to update the nomenclature. The study also demonstrates the value of the information obtained from biological collections, of the way it contributes to knowledge regarding past and present distribution of species in a region. Our study demonstrates that, for some taxa, collections are the only source of information, and this is especially useful regarding areas that have undergone drastic vegetation changes. Inventories are, undoubtedly, basic tools in the studies, monitoring, and management and conservation plans of wild fauna and, in this case, when used in Mexico City. Conservation of biodiversity is strongly linked to society´s welfare.

Acknowledgments
Sandra Mote, Vania Rivera and Gerardo Guerra helped in bench work, Gibran Hoffmann made the maps and helped in the validation of some localities. The sampling was realized with the collecting permit FAUT002 and FAUT070 expedite by SEMARNAT. We also thank curators of national collections of mammals José Ramírez-Pulido, Juan Carlos López, Livia León, Fabiola Guzmán and Gloria Magaña. The Unidad de Informática para la As everybody knows, the dynamic interactions between biotic and abiotic factors, as well as the anthropic ones, considerably affect global climate changes and consequently biology, ecology and distribution of life forms of our planet. These important natural events affect all ecosystems, causing important changes on biodiversity. Systematic and phylogenetic studies, biogeographic distribution analysis and evaluations of diversity richness are focal topics of this book written by international experts, some even considering economical effects and future perspectives on the managing and conservation plans.