FEMALE BEAR WITH THREE SECOND-YEAR CUBS FILE 1 The number of bears and where they live Cantabrian Mountains: Brown bears are found in the whole of the eastern León mountains. Cantabrian Mountains in the Some 50 individuals were estimated in autonomous communities of Asturias, this subpopulation in 2018. Castilla y León (León and Palencia provinces), Cantabria and in a small The two subpopulations are separated area of Galicia (Lugo). The population by a belt 50 to 80 km wide, known was in decline until near the end of the as the interpopulation corridor. Until 20th century, but a continuing recovery the start of the 21st century, these started from the middle of the 1990s. two subpopulations were completely separated without genetic interchange, The Cantabrian bear population however, with the increase in the bear is divided into two parts, into the population, this communication has eastern and western subpopulations. started to re-establish. The western subpopulation extends eastwards from the Ancares mountains The first “hybrid” bears (offspring from of Lugo and León as far as the centre western males and eastern females) of the Cantabrian range between León were detected in 2008 and movement and Asturias. Breeding females are of males, at least from west to east, found throughout the range of this currently appears to be regular, breaking subpopulation from south-western down the genetic isolation. In contrast, Asturias to north-eastern León. An the females tend to be philopatric, i.e. estimate of 280 bears was made for this with a tendency to settle close to where subpopulation in 2018. they were born, and perhaps because of this no females have been detected The eastern subpopulation is distributed crossing the interpopulation corridor. across the mountains of Palencia and For these reasons, given that the eastern León plus the mountains of connection between both breeding Campoo de Suso, Polaciones and nuclei is only currently made by Liébana in Cantabria, plus a few dispersing males, we can still consider individuals in eastern Asturias. The that there are two differentiated breeding females in this subpopulation Cantabrian subpopulations. are found in Cantabria and the Palencia mountains, plus the adjacent mountains in León, but do not extend over the The number of bears and where they live 1.2 An overall range of 8,600 km2 is estimated observations, enabling the registering for Cantabrian brown bears, based on and identification of a minimum definite permanent occupancy of 10x10 km number of different females which have squares, but to which we need to add given birth each year. These censuses all the other areas with sporadic bear are what have enabled the confirmation presence, which are increasing all the time. of the population increase in the species following decades of continuous decline. The population size and trend are In 2014, 34 female bears with 67 cubs calculated by counting the number of were detected, with six of these females females with cubs located each year. setting a new record for the small This method has been standardised and eastern subpopulation. In 2015, at least coordinated since 1989. These data are 40 female bears with 64 cubs were compiled by the autonomous region and detected, with six of these family groups FOP teams, with additional help locally again in the eastern nucleus, with exactly from other collaborators and interested the same number of female bears with entities. Hundreds of routes are covered cubs overall, and six family groups again to actively search for signs, watches are in the eastern subpopulation, but with 67 undertaken to observe, film and follow cubs overall. Finally, in 2018, 38 females family groups and further surveys are with cubs were detected, with 7 in the undertaken to follow up on sporadic eastern nucleus, but 64 cubs in total. Annual number of females bears with cubs of the year in the two subpopulations 36 34 32 30 28 26 24 22 20 18 16 14 Nº of female bears with cubs Nº of female 12 10 8 6 4 2 0 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 Years Western Subpopulation Eastern Subpopulation The number of bears and where they live 1.3 How do we estimate the total number of brown bears in the Cantabrian Mountains? Knowing the exactly number of animals populations, immature bears make up 50% making up a population is extremely of the total population (Swenson et al. difficult. E.g. we do not know the 2007). Consequently, the total minimum exact number of brown bears in the number of bears would be the sum of the Cantabrian Mountains, but we can make breeding females with cubs during the last a rough estimate based on the number two years, multiplied by four. of females with cubs detected each year. This figure coincides with the extreme Based on scientific research, Servheen lower limit of the range proposed by (1989) states that the females with cubs Servheen (1989), when females with cubs of the year represent 8-12% of the total represent 12% of the total population. population. Admittedly, this is true of the We can also compare the counts of N American grizzly bear, the females of females with cubs compared to the which only breed once every three years total population based on the results of at most, while the Cantabrian brown genetic analyses. Indeed, two studies of bears usually breed every other year. If this type have been undertaken for the we still take Servheen’s most conservative western subpopulation: in 2002, García- estimate (12%) to estimate the total Garitagoitia et al. (2004) estimated 107 population, we would need to multiply bears and in 2006, Pérez et al. (2014), 223 the number of females with cubs in any bears. For each of these years, totals of 8 given year by 8.33 (since 100/12= 8.33). and 18 bears with cubs were censused in this nucleus, such that the total number Our proposal is that in order to make a of bears would be equal to the number of total population estimate based on the females with cubs multiplied by 13.5 (8 x available information concerning the 13.5 = 108) and by 12.4 (18 x 12.4= 223), number of females with cubs, then we respectively. In the Apennine population, could multiply the most recent count with very similar environmental conditions of breeding females by eight, or better to the Cantabrian region, an average of 3.9 still, multiply the sum of the most recent females with cubs were detected between number of females with cubs during the 2006 and 2014, and a total population of latest two years, by four. E.g. if in 2016 51 individuals through genetic methods 40 breeding females were detected, the (Tosoni et al. 2017). A multiplying factor of minimum estimate for the population 13.1 is derived from this case. would be around 320 individuals (40x8); or better, as in 2016 and 2017 These figures fall within the highest 40 and 41 female bears with cubs were part of the range proposed by Servheen detected respectively, the total would (1989), supposing that females with be around 324 bears [(40+41) x 4]. cubs represent 8% of the population. These calculations only provide Let’s consider the logic of this estimate. approximate figures, but serve to give Mature female bears in Spain breed every an idea of the total bear population other year in a best case scenario, such that using the data from the censuses of the sum of the number of females with cubs females with young cubs carried out of the year for the last two years censuses since 1989. Of course, the number of represents the minimum number of mature females with cubs detected suffers ups female bears in the population (given that and downs due to the external factors there could be some mature females which surrounding the censusing, changes haven’t bred at some point during the in the availability of food resources – previous two years). If there are as many which influences both the detectability males as there are females (Pérez et al. of females and whether they reproduce 2014), the overall number of adult bears or not – or simply due to other random would be double the number of breeding factors, which complicate making females from the last two years. However, conclusions. Our brown bears are elusive in order to obtain the total number of bears and not prone to exhibiting their private in the population, we need to multiply this lives, but rigorous long-term monitoring figure again by two, since in European helps us to discover their secrets. The number of bears and where they live 1.4 Bibliography García-Garitagoitia JL, Rey I, Doadrio I. 2006. Variabilidad genética. En: Palomero G, Ballesteros F, Herrero J, Nores C, eds. Demografía, Distribución, Genética y Conservación del Oso Pardo Cantábrico. Madrid: Dirección General para la Biodiversidad, Ministerio de Medio Ambiente, 71–90. Pérez T, Naves J, Vázquez JF, Fernández-Gil A, Seijas J, Albornoz J, Revilla E, Delibes M, Domínguez A. 2014. Estimating the population size of the endangered Cantabrian brown bear through genetic sampling. Wildlife Biology 20(5):300–309. Servheen, C. 1989. Monitoring of bear populations. Environmental Encounters Series, Council of Europe 6: 39-45. Swenson, J. E., B. Dahle, H. Busk, O. Opseth, T. Johansen, A. Söderberg, K. Wallin and G. Cederlund. 2007. Predation on moose calves by European brown bears. Journal of Wildlife Management 71: 1993-1997.