Guillermo Palomero’s scientific contributions

Alto Sil ES0000210 y ZEC Sierra de los Ancares ES4130010. Entidad promotora de las actuaciones de restauración Fundación Oso Pardo (FOP). Entidad/es socia/s del proyecto Fundación Oso Pardo, socio coordinador. Fundación Biodiversidad, socio beneficiario. Fundación Patrimonio Natural de Castilla y León, socio beneficiario. Periodo en el que se ha desarrollado el proyecto Durante el periodo de ejecución del proyecto LIFE Osos con Futuro, entre octubre de 2020 y marzo de 2025. Las actuaciones recogen experiencias y lecciones aprendidas de otros proyectos LIFE desarrollados con anterioridad por la Fundación Oso Pardo. Origen de la perturbación/degradación del espacio Grupo I. Agricultura, silvicultura, acuicultura, ganadería y pesca. Grupo XI. Incendios (provocados, accidentales o naturales). La ganadería extensiva y los aprovechamientos forestales han supuesto una reducción histórica de la superficie ocupada por bosques en la cordillera Cantá-brica, junto con un alto grado de fragmentación de los mismos. El fuego se ha utilizado y todavía se usa como herramienta para favorecer la creación de pastos, dando lugar en muchas zonas a una recurrencia de incendios forestales que des-truye formaciones arboladas en regeneración, favorece la persistencia de breza-les y matorrales y empobrece los suelos sobre los que se asientan. Ecosistemas afectados Brezales y matorrales de zona templada. Praderas y pastizales naturales y seminaturales. Bosques. Las áreas oseras de la cordillera Cantábrica se caracterizan por un mosaico de for-maciones vegetales entre las que destacan bosques caducifolios de robles (Quer-cus robur L., Q. petraea [Matt.] Liebl., Q. pirenaica Willd.), castaños (Castanea sativa Mill.), haya (Fagus sylvatica L.) o abedul (Betula celtiberica Rothm. & Vasc.), así como extensos brezales y matorrales de montaña y formaciones herbáceas naturales y seminaturales. Brezales, matorrales y praderas seminaturales son fre-cuentemente fruto de procesos de sustitución de bosques y arbustedos tras la deforestación antrópica. Las actuaciones de restauración se realizan tanto en zonas de bosque (rodales de enriquecimiento) como en matorrales y en formaciones herbáceas de origen antrópico, vinculadas a la ganadería extensiva y en desuso por abandono de los aprovechamientos ganaderos. Motivación para desarrollar el proyecto En la cordillera Cantábrica ya se han registrado variaciones en la alimentación del oso pardo asociadas al cambio climático durante las últimas décadas. Algunas especies particularmente sensibles al cambio climático, como el arándano (Vac-cinium myrtillus L.), han reducido su importancia en la dieta de los osos cantábri-cos, posiblemente por la creciente irregularidad de sus fructificaciones, mientras que otras especies como cerezos (Prunus avium L.) o arraclanes (Frangula alnus Mill.) parecen haber aumentado su presencia en la dieta. Por otro lado, el casta-ño puede constituirse como un recurso clave en el escenario de cambio climático por su producción de cosechas más constantes que robles y hayas en el periodo de hiperfagia otoñal, y por la posibilidad de que el cambio climático favorezca su crecimiento y fructificación en nuevas áreas de la cordillera Cantábrica. Por ello, el proyecto se planteó como una estrategia de adaptación y resiliencia del oso pardo frente al cambio climático al incrementar la disponibilidad trófica para el plantígrado y otras especies de fauna silvestre, con las especies que mejor se adapten a los escenarios de cambio climático. Estas actuaciones representan un modelo de restauración ecológica del bosque templado en áreas deforestadas, principalmente afectadas por perturbaciones como incendios, y en áreas de expansión de la especie y teniendo en cuenta la incidencia presente y futura del cambio climático. Diagnóstico ecológico Las zonas a reforestar son principalmente brezales y matorrales de zona templa-da que han sufrido incendios de forma recurrente y que se encuentran parcial-mente degradadas. También se reforestan antiguas fincas agroganaderas en des-uso. Estas áreas se seleccionan por tener un alto interés para el enriquecimiento del hábitat osero, porque en el entorno hay una escasa representación de las especies con las que se va a reforestar que darán alimento al oso pardo, y por cumplir con unas condiciones ecológicas acordes a las necesidades de las dife-rentes especies a plantar en escenarios de cambio climático realizados. Objetivos de la restauración y ecosistema de referencia Las acciones de este proyecto se pueden enmarcar en la fase de «Recuperación progresiva de los ecosistemas naturales», dentro del continuo de procesos de res-tauración. Los principales objetivos de este proyecto son: • Contribuir a la mejora de la disponibilidad trófica para el oso pardo en es-cenarios de cambio climático, en espacios de la Red Natura de la cordillera Cantábrica, mediante la plantación y tratamientos selvícolas y culturales de pequeños bosquetes de especies autóctonas productoras de frutos de verano e invierno para los osos, y con baja vulnerabilidad climática, para compensar la reducción prevista en otros recursos tróficos. • Promover la mejora de la percepción social del oso pardo y la conservación de sus hábitats mediante la implicación de los actores sociales del territorio en la realización de los trabajos de restauración y en la difusión de las experiencias y su contribución al desarrollo rural. Como ecosistema de referencia se consideran tanto los bosques mixtos y arbus-tedos, con presencia de especies productoras de frutos carnosos, como los siste-mas agroforestales formados por castañares tradicionales productores de fruto.

The report Large carnivore distribution maps and population updates 2017 – 2022/23 is based on the latest information and provides the best available overview of brown bear (Ursus arctos), Eurasian lynx (Lynx lynx), wolf (Canis lupus), golden jackal (Canis aureus), and wolverine (Gulo gulo) distributions and population sizes at a European continental scale (covering 34 countries). This document has been prepared with the assistance of Istituto di Ecologia Applicata and with the contributions of the IUCN/SSC Large Carnivore Initiative for Europe (chair: Luigi Boitani) under contract N° 09.0201/2023/907799/SER/ENV.D.3 “Support for Coexistence with Large Carnivores”, “B.4 Update of the distribution maps” for the European Commission.

Brown bears (Ursus arctos) usually mate in spring throughout their global range, although a few cases of breeding activity are known in late summer and autumn. In this note, we describe four observations of courtship and copulations of brown bears in the wild in late August and September 2011, 2019, and 2021 in the Cantabrian Mountains (northwestern Spain). These cases extend the published dates on copulations in Europe and the length of the mating season. These couples showed the same behaviour as those recorded in spring. Two females interacted with three different males, but we only saw them copulating with one male. Three of the four courtship cases occurred around a concentrated and seasonal source of food that congregated a large number of bears in restricted areas for a few weeks. We discuss the advantages that these late copulations can have and the uncertainties that still exist about the late reproduction in brown bears.

During 2017, we studied knowledge, perceptions, and attitudes towards brown bears by extensive mountain sheep farmers in the Western Pyrenees, using a structured questionnaire, specifically, whether the scarce bear presence, or the administrative region, was influential. Livestock raising practices are mainly family properties and have suffered a strong decline in the last decades. Despite its low abundance (only 2 bear individuals during the study period in the area), there was a generalized negative attitude towards the presence of bears. Farmers considered bear presence as incompatible with sheep mountain herding. One third of them have experienced bear damages, although this was not the main difficulty for the viability of farming practices. They were able to change husbandry practices after wildlife and dog’s damages, increasing vigilance, hiring shepherds, and using livestock guarding dogs, whose work is perceived as satisfactory. Farmers considered that information available about bear and compensation systems for damages was insufficient, and should be improved.

Little is known about the heritable behavioural traits of attacks by large carnivores on people. During the last  years attacks by brown bears Ursus arctos on people in the Cantabrian Mountains of Spain have been disproportionately concentrated in the eastern subpopulation. Excluding factors such as the existence of a single unusually bold bear, a higher human population density, particular human activities promoting encounters, or clear habitat differences in the area of this subpopulation, we propose that a plausible explanation for the unbalanced geographical attack pattern is that this subpopulation, separated a century earlier from the western subpopulation, may harbour a higher proportion of bolder bears. In the absence of genetic analyses this explanation remains speculative, but supports the hypothesis that genetic variation on the shy-bold continuum may influence attacks of large carnivores on people.

Sexually selected infanticides (SSI) committed by male bears during the mating season has attracted a great research attention, although this type of behavior has been rarely observed in the wild. Here, we document a bear infanticide attempt in the Cantabrian Mountains in which the male killed the adult female during the fight and, subsequently, consumed the carcass for several days. Interestingly, in this case, the bear male tried to reach the cub with the apparent intention of killing it, even though the female was already dead. We complement this observation with data on documented cases of SSI events between 1996 and 2020 in the Cantabrian Mountains. We hypothesize that when females are unintentionally killed while defending their cubs in SSI events, males can benefit by feeding on the carcasses. As part of the Springer Nature SharedIt initiative, a full-text view-only version of the paper can be read in https://rdcu.be/ceReo

Monitoring of the brown bear population in the Cantabrian Mountains has been undertaken using annual counts of the number of female bears with cubs of the year. However, the increase in the bear population and its distribution range over the past 25 years make applying this technique ever less reliable, above all in the western subpopulation. Consequently, for the past few years we have been studying the viability of combining non-invasive techniques for the determination of individual genetic profiles made from bear excrement and hair samples together with spatially explicit capture-recapture models (SCR). In 2016 we evaluated the usefulness of a bank of 96 available brown bear single-nucleotide polymorphisms (SNPs) for its application to the Cantabrian brown bear population. In autumn 2017, a total of 128 excrement and 23 hair samples were collected over 148 5x5 km UTM grid squares of the eastern subpopulation to compare two distinct markers: microsatellites and SNPs. We obtained very similar density estimates independently of the marker type employed: 0.96 bears/100 km2 with microsatellites and 1.05 bears/100 km2 with SNPs. The eastern subpopulation was estimated at 48.6 individuals (95% BCI: 33.8-67.6 bears) with microsatellites. A study was carried out in 2019 with the aim of determining if it was possible to use this technique in the larger and more densely populated western subpopulation. 507 samples were collected during a total of 1,687 km of transects in 282 5x5 km UTM grid squares, resulting in an estimate of 274.7 bears (95% BCI: 222.5-338.3 bears). The results from both subpopulations are consistent with the number of females with cubs of the year and indicate that sampling along transects 2-5 km in length per 5x5 km UTM grid square between October and December are appropriate for monitoring the bear population in the Cantabrian mountain range, which we propose could be undertaken every five years. Whatever the case, the annual monitoring of females with cubs of the year should continue, at least in the eastern subpopulation.

A standardised method has been used to monitor bear families in the Cantabrian Mountains since 1989. The quantity of information gathered over this time has been remarkable, with more than 4,500 observations of females with cubs between 1989 and 2018. This information has not only allowed us to confirm the recovery of the species in the Cantabrian Mountains, but has also been fundamental in increasing our knowledge about different demographic aspects of the Cantabrian brown bear. For example, we have learned that female Cantabrian bears have between one and three cubs, with an average litter of 1.8 ± 0.7 cubs across the whole population, this being slightly higher in the western subpopulation (1.9 ± 0.7 cubs) compared to the eastern one (1.6 ± 0.6 cubs). Overall, the average monthly cub survival rate is high during the first 16 months of life, estimated at 0.839-0.994, with the most critical period being from April to June of their first year. Infanticide appears to be the principal cause of cub mortality. Family break-ups, which occur during April and May of the second year and which coincide with the mating season in the Cantabrian Mountains, mark a new stage in the cubs’ lives. Information on the causes of mortality of bears over one year old is limited, since the data are collected opportunistically, but points to human actions as the principal cause for their deaths and requires more information in the context of geographical expansion in the species.

This chapter addresses how the population recovery of the brown bear in the Cantabrian Mountains affects the consideration of its current state of conservation and its legal protection. In accordance with the criteria of the IUCN Red List of Threatened Species, the population has gone from “Critically Endangered” to “Endangered”, and it will presumably move to the category of “Vulnerable” during the course of this decade. The population viability analysis of the Cantabrian bear population suggests that it will continue to grow, provided that a high survival rate of adult females is guaranteed, which is the most relevant factor in population dynamics. However, it is still far from being considered a non-threatened population and the periodic evaluations carried out in compliance with the Habitats Directive (92/43/EEC) consider that it is still in an unfavourable state of conservation. From a legal point of view, the Cantabrian bear is considered “Endangered”, although the criteria for including species in the current Spanish Catalogue for Threatened Species contain inconsistencies which may affect the legal coverage of the brown bear and other species undergoing recovery processes, but whose populations are still low in number. The increase in the bear population poses new challenges that make it necessary to update the Recovery Plans, which are the specific legal instruments for the conservation of the bear and its habitat, as well as the expansion of the Natura 2000 Network, considering the expansion of the distribution area of the Cantabrian population. These processes must be carried out with adequate environmental governance and social participation.

This chapter explores three aspects of conflictive brown bear behaviour in the Cantabrian Mountains. Firstly, we argue the reasons of why bears approach humanised areas, what constitutes habituation and what their causes and consequences are. Secondly, we present the problem of bears and human garbage. We revise the worldwide literature of the effect of garbage on bears and present the results of a field study undertaken in 2019 in the municipalities of Somiedo (Asturias) and Villablino (León). These show that bears have easy access to garbage containers, many of which are very close to wild habitat in areas of very low night-time illumination. However, until 2019, we knew of almost no cases of bears coming to visit containers frequently, but over the past two years a few bears with this habit have appeared, reminding us that this is a significant problem affecting the majority of bear populations. We make a few suggestions of how to reduce the presence of bears in towns and villages and go over the importance of the prevention and aversive conditioning in order to dissuade bears conditioned to garbage. Finally, we summarise the characteristics of the brown bear attacks on humans in Spain which have occurred since 1989. A total of seven attacks have occurred (aggressive encounters with physical contact) in the Cantabrian Mountains and one in the Pyrenees, all of which were caused by sudden encounters, produced light to moderate injuries and lasted just a few seconds until the bear fled. All of these attacks in the Cantabrian Mountains have occurred in the eastern subpopulation, which may derive from genetic differences affecting bear behaviour between the two Cantabrian nuclei.