Oryx Vol 38 No 2 April 2004 Range fragmentation in the spectacled bear Tremarctos ornatus in the northern Andes Gustavo Kattan, Olga Lucía Hernández, Isaac Goldstein, Vladimir Rojas, Oscar Murillo, Carolina Gómez, Héctor Restrepo and Francisco Cuesta Abstract This paper addresses the conservation status This effect is more severe in smaller fragments, where of the spectacled bear Tremarctos ornatus in the northern internal disturbances constitute a high proportion of the Andes (Venezuela, Colombia and Ecuador) by analysing block area. We used a high population density estimate the degree of range fragmentation and estimating habitat of 0.25, a medium density of 0.11 and a low density of availability. From satellite images we constructed maps 0.04 bears per km2 to estimate population sizes. Twenty- of remnant habitat blocks, consisting of Andean forest nine populations are likely to have >500 individuals and páramo (high elevation shrublands and grassland) with the high estimate, but only nine with the medium ecosystems. This information was overlain with a road and one with the low estimate (largest estimated popula- map to determine potential isolation of populations, and tion was 9,048 bears). These estimates are much lower if a human accessibility model was used to estimate the only the core area of blocks is used. Hunting has been core area of each block. This analysis revealed that the identified as a major threat for many bear populations. species’ range is fragmented by landscape transforma- Our analyses indicate that a regional conservation tion and roads into 113 blocks >100 km2, representing strategy for spectacled bear should focus on maintaining 42% of the original extent of the bear’s distribution. Forty or increasing habitat availability in larger blocks, and percent of the blocks are <500 km2, and only nine are reducing human-induced mortality across the region. >5,000 km2. However, taking into account only core area, 56% of the blocks are <500 km2 and only six are Keywords Density, habitat availability, habitat frag- >5,000 km2. In addition, many blocks have internal mentation, northern Andes, spectacled bear, Tremarctos patches of colonization, further reducing habitat quality. ornatus. Introduction this elongated and narrow range is only 200–650 km wide but more than 4,600 km long. Throughout this The spectacled or Andean bear Tremarctos ornatus is range spectacled bears occupy a variety of ecosystems, the only extant representative of the Ursidae in South from dry areas in the coastal range of Perú to humid America. Its geographic distribution extends along the cloud forest and páramo (a high elevation grassland and tropical Andes from Venezuela to the Bolivia-Argentina shrubland ecosystem) in the northern Andes. The border. Covering 38 degrees of latitude (11° N to 27° S), geographic range of the spectacled bear coincides with some areas of high human population density, particu- Gustavo Kattan (Corresponding author), Vladimir Rojas and Carolina larly in the northern Andes (Venezuela to Ecuador). Gómez Wildlife Conservation Society, Colombia Program, Apartado 25527, Consequently, it faces various threats related to human Cali, Colombia. E-mail [email protected] presence, particularly habitat degradation and destruc- Olga Lucía Hernández World Wildlife Fund-Colombia, Carrera 35 No. 4A-25, tion, fragmentation of populations, and hunting. The Cali, Colombia. spectacled bear is categorized as Vulnerable on the IUCN Isaac Goldstein Wildlife Conservation Society, Venezuela Program, Mérida, Red List (Peyton, 1999; IUCN, 2003). Venezuela. Peyton et al. (1998) identified large habitat blocks (i.e. Oscar Murillo Departamento de Biología, Universidad del Valle, Cali, blocks of unbroken Andean forest) occupied by the Colombia. spectacled bear throughout its range, and estimated an Héctor Restrepo Unidad de Parques Nacionales Seccional Noroccidental, area of occupancy of about 260,000 km2. Assuming Medellín, Colombia. population densities similar to American black bears Francisco Cuesta Fundación EcoCiencia, Manuel Sáenz E 14-34, Quito, Ursus americanus, the total spectacled bear population Ecuador. was estimated at >20,000 adult individuals (Peyton Received 17 June 2003. Revision requested 3 September 2003. et al., 1998). This population, however, is subdivided into Accepted 24 November 2003. many smaller units, and long-term viability of the global © 2004 FFI, Oryx, 38(2), 155–163 DOI: 10.1017/S0030605304000298 Printed in the United Kingdom 155 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.22, on 24 Sep 2021 at 06:15:57, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605304000298 156 G. Kattan et al. population depends on the degree of isolation and Andes north of the Huancabamba Depression in north- viability of individual subpopulations. The range of the ern Perú, close to the Ecuadorian border. This depression spectacled bear is most fragmented in the northern half is a natural break that bisects the Andes and defines of its distribution, in Venezuela, Colombia and Ecuador two biogeographical regions (the northern and southern (Peyton et al., 1998). This fragmentation entails several Andes; Duellman, 1999), and represents the southern problems. Firstly, if populations are isolated and rela- limit of the páramo. The vegetation and land use cover tively small, their persistence is compromised, even in map was derived from a composite of satellite images the absence of hunting and further habitat loss. Secondly, (LANDSAT TM5 and TM7 for 1994–2000) that were landscape transformation in the region changes the avail- interpreted with the ER Mapper software (Earth ability of the habitat types required by bears. Spectacled Resource Mapping, San Diego, California, USA). The bears perform regional movements, using different lower elevation limit was set at 500 m. For this paper we habitat types along altitudinal gradients, but the seasonal mapped three types of cover: remnant montane forest patterns of these movements are not well known. Frag- vegetation, páramo, and transformed habitat. This last mentation disrupts these movements and restricts access category included all anthropogenic habitats such as to seasonally required habitats. Thirdly, fragmentation pasturelands, croplands and urban areas. All types of exposes bears to hunting. The smaller and more acces- Andean forest between elevations of 500 m and the sible the fragment, the higher the probability that the forest-páramo ecotone (the treeline) were considered bears will move across the fragment’s boundary and into appropriate bear habitat (present knowledge of patterns farms (Woodroffe & Ginsberg, 1998), exposing them to of habitat use does not permit a finer discrimination being killed. of bear habitat quality). Analyses were made using Peyton et al. (1998) evaluated the protection status of ArcView GIS (ESRI, Redlands, California, USA) in a grid bear populations throughout the Andes by estimating format with a 1 * 1 km cell resolution. the amount of potential bear habitat included in national On the vegetation map we overlaid the road network, parks. They estimated that c. 18.5% of the bear’s actual obtained from government cartography. Roads were range is contained within 58 protected areas. Many classified in two categories, main and secondary. Main of these areas, however, are small, particularly in the roads belong to the national road networks that connect northern Andes. Median size of 43 parks in Venezuela, major cities; these roads are paved, support heavy traffic, Colombia and Ecuador is 1,250 km2, which may be insuf- and cross highly transformed landscapes. Secondary ficient to maintain a viable population of bears (Peyton roads belong to provincial networks in rural areas, are et al., 1998). The largest protected area of bear habitat frequently unpaved, and some cut through forest and in this region is 2,050 km2. The viability of populations páramo landscapes. A buffer of 2.5 km was established in these parks depends on their degree of isolation and around main roads, and 1 km around secondary roads availability of habitat outside protected areas, which (an impact band of at least 2 km has been established for may be considerable in some cases. These unprotected spectacled bears (Peyton, 1999). Then, we recalculated habitat blocks may provide potential opportunities polygon areas and fragments of <100 km2 were elimi- for protection of bear populations. Here we present an nated. To evaluate accessibility of the areas, we used a evaluation of potential habitat availability and range model developed by the International Centre for Tropical fragmentation of the spectacled bear in the northern Agriculture, Cali, Colombia, which is based on the time it Andes. Using satellite images we mapped blocks of takes to reach different points on the map, measured in habitat potentially occupied by bears in the region. Then, hours from the nearest road or populated place; the by overlaying information on land use cover and roads, model takes into account various parameters, including we evaluated the degree of isolation of populations and topography and availability of transportation. Accessi- the accessibility of the areas to humans. This analysis bility in this model is classified into four categories: provides an overview of the status of bear populations in 1–6 hours (category 1, highly accessible), 7–24 hours the region, and can be used to help focus a conservation