Neotropical temperate grasslands comprise the Pampas ecoregion in Argentina. This region is also the center of agricultural development in Argentina, which has led to a significant simplification and homogenization of the landscape. The Tandilia Mountains, located in the Southeast of the ecoregion, house one of the last remnants of the highland grassland that acts as a refuge for several native species, including both endemic and threatened species. This work aims to present an updated inventory of mammal species that inhabit the highland grassland remnants of the Tandilia Mountains. We used several sources of information to compile the list, including museum collections, citizen science projects (i.e., iNaturalist, EcoRegistros, and Argentinian Network for Monitoring Run Over Fauna), literature, and personal observations. We recorded 40 species of mammals, which include 32 native species and eight exotic species. The richest orders were Rodentia (42.5%), Chiroptera (17.5%), and Carnivora (12.2%). The native mammals found in the Tandilia Mountains represent 44% of the mammal diversity of the Pampas ecoregion, among which there are endemic species of the ecoregion, species whose populations are declining globally, and threatened species. Unfortunately, the presence of protected areas in the system is limited to a few small ones, which highlights the urgency of increasing the number and variety of protected areas. The information presented in this work contributes to the knowledge of biodiversity and the planning of conservation actions for the last remnants of highland grasslands.

Argentina, biodiversity, checklist, conservation, Tandil Argentina, biodiversity, checklist, conservation, Tandil

With a surface larger than 700,000 km², the Río de la Plata grasslands form the largest temperate grassland in the Neotropics (Soriano et al. 1992). These grasslands comprise the Pampas ecoregion in Argentina, the Savannas of Uruguay, and a portion of northeastern Argentina and Rio Grande do Sul in Brazil (Soriano et al. 1992). In Argentina, the Pampas ecoregion extends over most of the province of Buenos Aires (except the southern portion), the south portion of Entre Ríos, southeastern Córdoba, southern Santa Fe, and the northeastern portion of La Pampa province (Burkart et al. 1999). As Argentina’s most important grassland ecosystem, its complete extension consists of approximately 398,966 km² (Matteucci 2012). This region is also the center of agricultural development in Argentina, which has led to significant simplification and homogenization of the landscape (Bilenca and Miñarro 2004). In the province of Buenos Aires, these vast plains are interrupted in their southernmost portion by the Tandilia and Ventania Mountains (Bilenca and Miñarro 2004; Matteucci 2012).

The Tandilia Mountains, located in the southeastern portion of the Buenos Aires province, consist of foothills and moderate-sloping plains that reach the Atlantic Ocean (Cingolani 2011). In this system, the native vegetation, which consists of highland grassland, is restricted to hills (cerrilladas) where rocky outcrops and shallow soils prevent cultivation (Herrera and Laterra 2008), thus limiting agricultural extension over native habitats. In these areas, the natural grasslands act as a refuge for native, endemic, and endangered species (Cantero et al. 2014; Kristensen et al. 2014; Herrera et al. 2019, 2022; Vera et al. 2021). Due to their importance, Bilenca and Miñarro (2004) proposed them as Valuable Pasture Areas.

Historically, mammals were represented in the Pampas ecoregion by large carnivores such as Puma concolor, Panthera onca and Chrysocyon brachyurus, as well as by large herbivores such as Ozotoceros bezoarticus, Blastocerus dichotomus and Lama guanicoe, in addition to rodents, armadillos, and bats (Medan et al. 2011). Changes brought about by agriculture, introduced livestock, and invasive species generated important modifications in mammal assemblages, which resulted in the local extinction of mainly large mammals and the decimation of populations of some species, while hardly affecting other mammal species (Baldi and Paruelo 2008; Bilenca et al. 2008, 2012; Medan et al. 2011). Currently, studies on the richness and distribution of mammals in the Pampas grasslands are asymmetric, and certain areas, such as the southeastern portion of the Province of Buenos Aires, contain little information (Galliari et al. 1991; Pardiñas et al. 2004). The oldest records on the diversity of mammals in the Tandilia Mountains correspond to those cited by Holmberg (1884), while the updated specific bibliography is limited to isolated studies (e.g., Velasco et al. 2013; O’Connor et al. 2019, 2020).

Wild species play an essential role in maintaining the ecosystem. From an anthropic point of view, mammals of the Pampas Ecoregion offer a wide variety of ecosystem services, mainly those related to ecosystem regulation processes, such as the biological control of species that are harmful to humans (Gorosábel et al. 2020). Studying species richness and generating inventories is of vital importance to be able to establish patterns within different groups of species and understand what has caused them (Yahnke et al. 1998; Krebs 2008). This work aims to present an updated list of mammal species present in the highland grassland remnants of the Tandilia Mountains. This work establishes a baseline for developing management and conservation strategies for the mammal species inhabiting these Neotropical grasslands.

We obtained a list of 40 mammal species inhabiting the highland grassland of the Tandilia Mountains, belonging to 7 orders, 18 families, and 35 genera. Of these species, 32 are considered native species and 8 are exotic (Table 1; Figs 2, 3; See Suppl. material 1). The orders with the largest number of species were rodents (17 species) and bats (7 species), which represented 42.5% and 17.5% of the species present, respectively (Fig. 4). The conservation statuses of two native species are currently categorized with some degree of threat.

Figure 2. 

Native mammals recorded by camera traps located within highland grassland remnants of the Tandilia Mountains: A) Capybara (Hydrochoerus hydrochaeris), B) Geoffroy’s Cat (Leopardus geoffroyi), C) Pampas Fox (Lycalopex gymnocercus), D) Melanic Geoffroy’s Cat (Leopardus geoffroyi), and E) Puma (Puma concolor).

Figure 3. 

Exotic mammal species recorded by camera traps in highland grassland remnants of the Tandilia Mountains: A) European Hare (Lepus europaeus), B) Wild Boar (Sus scrofa), and C) Fallow Deer (Dama dama).

Figure 4. 

Percentage of mammal species by order reported in the Tandilia Mountains.

From the different sources consulted to prepare the list of mammals, we obtained 33 species listed in museum collections, nine of which were found in the Museo de La Plata collection (67 records), and 33 in the GBIF database (2728 records). From the citizen science projects, 22 species were found, 19 in EcoRegistros (58 records), 18 in iNaturalist (107 records), and two in the Red Argentina de Monitoreo de Fauna Atropellada (2 records). On the other hand, 16 species were detected by camera traps and 20 species could be listed from occasional observations (our own observations and those generated by local people).

Of the 85 species of mammals that are reported for the Pampean ecoregion, 75 correspond to native species, 42.7% of which are represented in the Serrano de Tandilia System, while 80% of the 10 invasive species found in the ecoregion are present in the grassland remnants.

In this work, we present an updated inventory of the mammal species inhabiting the Tandilia Mountains. Approximately half (42.7%) of the mammal species of the Pampas ecoregion currently inhabit the Tandilia Mountains. In the recent past, the highland grassland of these mountains supported a high mammal diversity (Quintana and Mazzanti 2014). Archaeological sites within the Tandilia Mountains have reported Lama guanicoe, Ctenomys talarum and Ozotoceros bezoarticus as frequent mammal species (Quintana and Mazzanti 2014). By the end of the 19^th century, O. bezoarticus seemed to still be common, and other mammal species, such as Leopardus colocolo and Chrysocyon brachyurus, which were reported in the Tandilia Mountains (Holmberg 1884), had both become currently absent in the region.

Some species, such as Puma concolor and Hydrochoerus hydrochaeris, seem to be recolonizing the Pampas grassland (Doumecq Milieu et al. 2012; De Lucca and Chimento 2020). In the case of P. concolor, it had been experiencing population decline in the region and was considered extinct in most parts of the Pampas during the 20^th century (Cabrera and Yepes 1940). However, over the last decades, the records of P. concolor have been increasing, showing a recovery process across the Pampas ecoregion (Chimento and De Lucca 2014; De Lucca and Chimento 2020). In the Tandilia Mountains, records have become more frequent since 2011, and our recent camera trap studies have confirmed its presence in several highland grassland remnants (Chimento and De Lucca 2014). In the case of H. hydrochaeris, breeding populations were recently reported in the southern Tandilia Mountains (Doumecq Milieu et al. 2012). These grassland remnants in the Tandilia Mountains could function as corridors and refuges, facilitating the recolonization process of these species in the Pampas ecoregion.

The invasion of alien species is an increasing threat to biodiversity worldwide (Early et al. 2016). The Tandilia Mountains host 80% of the invasive mammal species reported for the Pampas region and most of these are categorized as generating high environmental risk (Sus scrofa, Cervus elaphus, Lepus europaeus, Rattus norvegicus, Rattus rattus, and Mus musculus) (Lizarralde 2016). Some of these species could be threatening native species by intertrophic or intratrophic interactions (Davis 2003). Future studies must evaluate the population size and trend, and the impact on the native biodiversity, of these invasive mammal species.

We did not find specific records in the Tandilia Mountains for three species of bats (Dasypterus ega, Molossus molossus, and Eumops patagonicus), even though the Tandilia Mountains are included in these species’ distribution maps (Barquez and Díaz 2019, 2020; Díaz and Bárquez 2019; Montani et al. 2019). Thus, we decided to exclude these three bat species from our list. However, we found records for them in nearby localities and thus consider their presence in the region highly probable.

In the case of Thylamys pallidior, the last reported ranges did not include the Tandilia Mountains (Parera 2018; Albanese and Martin 2019). However, we found several records for this species in the Tandilia Mountains, including three individuals found in Barn owl pellets (Fernández et al. 2012), one individual collected in 2015, and one photographed in 2015, both in Sierra de Los Padres (Stellatelli and Baladrón 2015; iNaturalist ID 55355680).

We excluded three collected species from our list of mammal species of the Tandilia mountains. Two of these species are far from their native ranges, so we considered them accidental records or records related to the illegal pet trade (Murray et al. 1997; Bisceglia et al. 2019). The specimen of Herpailurus yagouaroundi, collected in Tandil in 1924 (MACN-Ma 32.199) could be an accidental or extralimital record. The origin of one Leopardus pardalis collected in Balcarce (MACN-Ma 158-24) could be related to the illegal pet trade. In the case of the third excluded species (i.e., Myotis chilensis), we excluded it because the specimen (MACN-Ma 15344) was identified as Myotis levis (Velasco et al. 2013).

Regarding the conservation status of mammal species present in the Tandilia Mountains, at least six species are reported to be experiencing population declines. The populations of the Near Threatened Dasypus hybridus are declining globally, and its population status is concerning (Abba and Gozalez 2014; Abba et al. 2019). In Argentina, populations of these species have decreased by 25–30% over the last 12 years (Abba et al. 2019). The populations of Necromys obscurus, one of the four endemic mammal species of the Pampas ecoregion, are also declining, and the Argentinean Red List included the species as Near Threatened (Libardi and Gómez Villafañe 2019; Roach and Naylor 2019). In addition, four other species are also declining: Conepatus chinga, Oxymycterus rufus, Myocastor coypus, and Puma concolor (Nielsen et al. 2015; Emmons et al. 2016; Ojeda et al. 2016; Pardiñas et al. 2016). Unfortunately, only 0.15% of the Tandilia Mountains range is protected (Herrera et al. 2022). Therefore, there is an urgent need to increase the number and range of protected areas and other conservation actions (e.g., habitat restoration) aimed at preserving the last remnants of the highland grassland and its biodiversity.

Of the different methods used to enumerate species records, camera traps recorded the smallest number of species (16 species) compared to the other methods. Camera traps are a useful tool for the detection of medium and large mammals (O’Connell et al. 2011), which limits their use for the detection of species such as rodents or bats. It should also be considered that camera trap sampling is designed according to the target species, which influences the cameras’ detection capacity (O’Connell et al. 2011). In contrast, other methods, such as citizen projects, where the community participates in data collection, can make important and reliable contributions, making them a powerful tool for collecting biodiversity data at large geographic and temporal scales (Allen and Cooper 2006). On the other hand, the data provided by museum collections, of which we list 33 species, are a reliable source of records arising from numerous and diverse studies.

The information gathered contributes to the knowledge of the mammal biodiversity currently inhabiting the highland grasslands of the Tandilia Mountains. The presence of threatened and endemic species and the inclusion of newly reported species for the region highlight the importance of this grassland for conserving Pampean biodiversity.

We would like to thank field assistants and collaborators (Carmela Marin, Manuela Santiago, Celena Sarasola, Estefania Paz, Maximiliano Calcagno, Ailen Chuchuy, M. Eva Cabanellas, Claudio Santiago, Estefania Marisol Avalo, Felisa La Pescadora) for their kind assistance and support during fieldwork activities. We also appreciate the collaboration of owners and managers of highland grassland remnants for allowing us to visit their properties: Federico Juana (Estancia Las Mercedes), Paulo Mosca (Estancia Nilonil), Reina Feldman (Estancia Sanmalucon), Mario Bustillo (Estancia La Asunción), Alfonso (Valle de Los Ciervos), Emilio Milanessi (Estancia Chapaleofu), Manuel Castelar (La Argentina), Raul Eyheramendy (Sierra Alta) and Tomas Pérez Marino (Estancia El Bonete). We thank Claudio Barletta (Reserva Natural Sierra del Tigre) for his attention and collaboration. We would like to thank the assistance of the Scouts de la Ciencia program for their cooperation in fieldwork with camera traps. Also, we would like to thank Itati Olivares and the staff of the Museo de La Plata (Vertebrates division, Mammalogy section) for receiving us and providing us with the collection catalog, and Pablo Teta (Argentine Museum of Natural Sciences “Bernardino Rivadavia,” Mammalogy Collection) for attending our queries regarding the collection. We also thank Ayelén Lutz for giving us valuable suggestions for improving this manuscript. Two anonymous reviewers and one editorial board member made valuable comments that improved a previous version of this manuscript. This study was partially supported by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET PIP. 11220150100598CO), Agencia Nacional de Promoción Científica y Tecnológica (ANPCYT, PICT 2015-2281), Neotropical Grassland Conservancy (Student Grant Program 2021), IDEA WILD (IDEA WILD Equipment Support 2021). F. Aranguren, D. Vera, C. Trofino-Falasco, and M.G. Pizzarello were supported by fellowships from the Consejo Nacional de Investigaciones científicas y Técnicas de Argentina (CONICET). M.A. Velasco and I. Berkunsky are CONICET Research Fellows.