Abstract: Breeding biology in a population of Rufous-collared Sparrow (Zonotrichia capensis, Statius Müller, 1776) at different elevations in the Tropical Andes. Elevation strongly influences the evolution of life history traits associated with bird physiology and reproduction. Since life history traits in birds are modulated by environmental factors that vary with elevation, we expected to find changes in breeding biology traits of Z. capensis at different elevations. In this study, we compared the breeding biology (clutch size, egg volume, and reproductive activity) of a non-migratory population of Z. capensis in two localities at different elevations (low and high elevations, 1 800 m a.s.l., and 3 800 m a.s.l., respectively) and same latitude in the Colombian Tropical Andes for a one-year period. We found no differences in clutch size between the localities; however, egg volume was higher at high elevation. Furthermore, the reproductive activity differed significantly between localities. We propose that clutch size is likely conserved throughout the altitudinal distribution of Z. capensis since the species evolved in Tropical lowlands. On the other hand, the larger egg volume at high elevation could obey local environmental factors that may favor the reproductive success of the population.

Resumen: Biología reproductiva en una población de Gorrión Copetón (Zonotrichia capensis, Statius Müller, 1776) a diferente elevación en los Andes tropicales. La elevación influye fuertemente en la evolución de los rasgos de historia de vida asociados con la fisiología y reproducción de las aves. Dado que los rasgos de historia de vida en las aves están modulados por factores ambientales que varían con la elevación, esperábamos encontrar cambios en los rasgos de la biología reproductiva de Z. capensis a diferentes elevaciones. En este estudio, comparamos la biología reproductiva (tamaño de puesta, volumen del huevo y actividad reproductiva) de una población no migratoria de Z. capensis en dos localidades a diferente elevación (elevación baja 1 800 m snm, y elevación alta 3 800 m snm,) y a la misma latitud en los Andes tropicales colombianos por un período de un año. No encontramos diferencias en el tamaño de puesta entre las localidades; sin embargo, el volumen del huevo fue mayor en elevación alta. Además, la actividad reproductiva difirió entre las localidades. Proponemos que el tamaño de puesta probablemente se conserve en toda la distribución altitudinal de Z. capensis, ya que la especie evolucionó en las tierras bajas tropicales. Por otro lado, el mayor volumen del huevo a elevación alta podría obedecer a factores ambientales locales que pueden favorecer el éxito reproductivo de la población.

Abstract: The Cape Horn Biosphere Reserve is located in one of the most pristine areas on the planet. Its forest birds, some of them charismatic species, are one of the focus interests for both tourists and the local community. However, basic aspects of bird distribution in these ecosystems are still poorly understood. In this study, we characterized the distribution patterns of forest birds in the Cape Horn Biosphere Reserve. We distinguish four patterns, classifying bird species according to variations in geographic and temporal distribution within the reserve. We observed variations in the distribution of resident and migratory species related to the type of forest vegetation. We found that mixed forests of Nothofagus betuloides and N. pumilio are important for the presence of several low abundance species and of interest to birdwatchers, including the Magellanic Woodpecker (Campephilus magellanicus). These results allow us to identify priority areas for the conservation of the forest bird community of the Magellanic subantarctic ecoregion. Additionally, they highlight Isla Navarino as the area with the highest diversity of forest species, and is easily accessible, in the Cape Horn Biosphere Reserve.

Resumen: La Reserva de la Biosfera Cabo de Hornos está inserta en una de las zonas más prístinas del planeta. Sus aves de bosque, varias de ellas especies carismáticas, constituyen uno de los focos de interés tanto de los turistas como de la comunidad local en la reserva. Sin embargo, aspectos básicos sobre la distribución de las aves en estos ecosistemas son aún poco conocidos. En este estudio caracterizamos los patrones de distribución de las aves de bosque en la Reserva de la Biosfera Cabo de Hornos. Distinguimos cuatro patrones, clasificando las especies de aves según variaciones de distribución geográfica y temporal dentro de la reserva. Observamos variaciones en la distribución de especies residentes y migratorias, presumiblemente asociadas al tipo de vegetación boscosa. Encontramos que los bosques mixtos de Nothofagus betuloides y N. pumilio son importantes para la presencia de varias especies de baja abundancia y de interés para el aviturismo, entre ellas el carpintero negro (Campephilus magellanicus). Estos resultados nos permiten identificar áreas prioritarias para la conservación del ensamble de aves de los bosques de la ecorregión subantártica de Magallanes. Adicionalmente, se resalta la isla Navarino como el área con la mayor diversidad de especies de bosques presentes, y de fácil acceso, en la Reserva de la Biosfera Cabo de Hornos.

Abstract: Biosphere reserves have among their functions to support scientific research, education, training and monitoring. In the Cape Horn Biosphere Reserve (RBCH), created in 2005, this function has been fulfilled with the creation of the Omora Ethnobotanical Park in 2000, and its implementation in 2008 as a co-founder site of the Chilean Network of Studies Long-Term Socio- Ecological (LTSER-Chile). In 2016, this network has been strengthened with the addition of the new Cape Horn Long-Term Socio-Ecological Research Network (LTER-Cape Horn). The latter includes the Omora Ethnobotanical Park, and three new sites added to the monitoring of the sub-Antarctic Magellanic ecoregion. From south to north, the four sites are: (1) Gonzalo Island (56°31’S; 68°43’O), at the southern end of the Diego Ramírez Archipelago, with sub- Antarctic vegetation dominated by grasses and cryptogams, devoid of woody species; (2) Horn Island (55°58’S; 67°13’O), at the southern end of the Cape Horn Archipelago, hosting the southernmost forest ecosystems on the planet, which are dominated by the evergreen beech (Nothofagus betuloides); (3) Omora Ethnobotanical Park (54°57’S; 67°40’O), Navarino Island, an ideal site for studies on climate change and its impact on biota and sub-Antarctic ecosystems, since it protects a watershed that includes a representative mosaic of characteristic habitats of the RBCH in an altitudinal gradient with a thermal decrease analogous to that which occurs with increases in latitude; and (4) Caleta 2 de Mayo Site (54°52’S; 68°41’O), Yendegaia Bay, in an ecotonal zone between evergreen and deciduous forests (product of the local climate gradient), at a site that will be central to future connectivity between Continental Chile, Tierra del Fuego, Navarino Island, and the RBCH. In 2015, UNESCO approved the Report of the First Periodic Review of the RBCH that proposed the protection of the Diego Ramírez Archipelago and the creation of the Diego Ramírez Islands-Drake Passage Marine Park. This goal was achieved with the promulgation of this new park on February 2, 2018, and its entry into force on January 21, 2019 with the publication of the creation decree in the Diario Oficial of Chile. In this context, the new LTER-Cape Horn network acquires great local, national and global relevance. At the local scale, it covers a representative environmental heterogeneity of the great diversity of landscapes and terrestrial, freshwater and marine ecosystems of the RBCH and the sub-Antarctic Magellanic ecoregion. At the national scale, it incorporates sub-Antarctic sites, located at the southern end of South America, to LTSER-Chile and to the Monitoring Network of the Ministry of the Environment. On a global scale, the terrestrial ecosystems of the LTER-Cape Horn network stands out for two main reasons: (1) these sub-Antarctic ecosystems lack a geographical replicate in other continents of the southern hemisphere, and (2) high latitude ecosystems are especially sensitive to global climate change. Thus, the LTER-Cape Horn network helps to overcome critical geographical gaps in the implementation of the International Network for Long-Term Ecological Research (ILTER). In order to articulate these four sites and strengthen the training of technical capacities and knowledge transfer to decision makers in the area of special interest tourism and other sustainable economic activities, the LTER-Cape Horn network will be managed locally from the new Cape Horn Sub-Antarctic Center (Cape Horn Center) that will be inaugurated in Puerto Williams in 2021. The implementation of the LTER-Cape Horn network is based on a close collaboration with various public institutions: Ministry of National Assets, Ministry of the Environment, Subsecretary of Fisheries and Aquaculture of the Ministry of Economy Development and Tourism, National Forestry Service, General Water Directorate of the Ministry of Public Works, Navy of Chile, Chilean Police (Carabineros), Municipality of Cape Horn, Provincial Government of Chilean Antarctica, and the Regional Government of Magallanes and Chilean Antarctica. In the following phases, the LTER-Cape Horn network and the Cape Horn Center aim to strengthen the participation of the local community, especially the Yahgan Indigenous Community of Bahía Mejillones, artisanal fisheries, tour operators, and the educational community, including private actors. Located at the “southern summit” of the Americas, Puerto Williams, capital of the Chilean Antarctic Province emerges as a global hub for transdisciplinary sub-Antarctic research, equipped with a new center and the network of long-term socio-ecological studies. Collaboration with regional, national and international actors will allow the LTER-Cape Horn network and the Cape Horn Center to: (i) provide critical data, which will open up new opportunities for monitoring climate change and its impact on biodiversity and ecosystems in sub-Antarctic latitudes; (ii) consolidate long-term monitoring, which is an essential component to effectively design mitigation and adaptation actions; (iii) strengthen a local sustainable development model that, associated with the Cape Horn Biosphere Reserve, contributes from the south of the world, to a biocultural conservation model that meets the needs of socio-economic well-being and environmental sustainability at multiple regional and planetary scales.

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Abstract: Biocultural conservation increasingly requires transdisciplinary collaborations, which includes different disciplines, institutions and actors. The collaboration between scientists and the Chilean Navy has been an effective way to address this requirement. This inter-institutional collaboration between the Navy and the Sub-Antarctic Biocultural Conservation Program (University of Magallanes, Institute of Ecology and Biodiversity and Omora Foundation in Chile, and the University of North Texas in the US) enabled us to initiate in 2016 long term ornithological studies in the Diego Ramírez Archipelago, which includes the southernmost islands of the American continent. Until now, its avifauna has been studied exclusively during summer seasons, despite the fact that birds are one of the most sensitive and fastest responding groups of animals to climate change; modifying their periods of migration, residence and nesting, their population sizes, and their latitudinal distribution areas. In addition, subpolar regions are especially sensitive to climate change and studies in the Cape Horn Biosphere Reserve, adjacent to the Diego Ramírez Archipelago, suggest that some species could be expanding their latitudinal distribution spheres and changing their migration dates. The objective of this work is to initiate a systematic monitoring of the species composition and the nesting, migration and/or residence dates of the Diego Ramírez Archipelago birdlife at the southern tip of the Magallanes sub-Antarctic ecoregion. In this study we present an update of the avifauna records for the Gonzalo Island, Diego Ramírez Archipelago, including the first fall and winter records, and sightings at other times of year. In three expeditions, during the austral reproductive season (summer, November 29-December 1, 2016), winter (July 20-22, 2017) and fall (March 28-April 1, 2018), birds were monitored using mist-nets and creating species lists from field observations. For the observations of birds throughout the year, we used the photographic records made by José Mella (coauthor) and José Mejía (Navy petty officers at Gonzalo Island Lighthouse, years 2014-2018), and new photographic records were initiated with trained personnel of the Navy of Chile in the lighthouse of Gonzalo Island. In total, we detected 33 species belonging to 16 families. Ten of these species represent new records for the archipelago: Neotropic cormorant (Phalacrocorax brasilianus Gmelin, 1789), Western cattle egret (Bubulcus ibis (Linnaeus, 1758)), Peregrine falcon (Falco peregrinus Tunstall, 1771), Austral negrito (Lessonia rufa Gmelin, 1789), Austral thrush (Turdus falcklandii Quoy & Gaimard, 1824), Rufous-collared sparrow (Zonotrichia capensis Müller, 1776), Black-chinned siskin (Spinus barbatus Molina, 1782), Blue-and-White Swallow (Pygochelidon cyanoleuca patagonica d’Orbigny & Lafresnaye, 1837), Black-bellied storm petrel (Fregetta tropica Gould, 1844), and y Cape petrel (Daption capense capense Linnaeus, 1758). Some of these new records could be associated with global warming and a recent expansion of the latitudinal distribution areas and/or the residence periods of these birds. Among the 33 species, 26 were recorded in spring-summer, 22 in fall, and 14 in winter. However, nine were sighted only occasionally and it will be necessary in the future to determine whether they are resident or migratory species that are seldom observed, or occasional visitors. Regarding conservation status, according to the IUCN Red List of Threatened Species, the avifauna of the Diego Ramírez Archipelago includes an endangered species (Grey-headed albatross, Thalassarche chrysostoma Forster, 1785), three vulnerable species and four almost threatened. Monitoring on these islands provides a baseline to evaluate the status of bird populations under the threats of global change, among which the threat of invasive species is highlighted. It is critical to prevent the arrival of exotic invasive species that are present in other subantarctic islands, such as rats (Rattus spp.), mice (Mus musculus Linnaeus, 1758), cats (Felis catus Linnaeus, 1758), and American mink (Neovison vison Schreber, 1777), which are present in the Cape Horn Biosphere Reserve, located less than 100 km North of the Diego Ramírez Archipelago. The collaborative work with the Chilean Navy has been crucial to start these long-term ornithological studies, associated with the new Long-Term Ecological Studies Site Gonzalo Island-LTER that forms part of the Chilean Long-Term Socio-Ecological Studies Network (LTSER-Chile), and the International Long-Term Ecological Studies Network (ILTER). A main goal will be to combine avifauna monitoring with detection of potential invasive species.

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Abstract Populations that breed along steep elevation gradients show diverse physiological and morphological changes in response to the different environmental conditions. The latter has been discussed by Bergmann’s and Allen’s ecogeographic rules about body and appendage sizes and environmental temperature. We compared morphometric measures (mass, bill width, tarsus, wing, and tail length) of a Zonotrichia capensis population in two localities at different elevations with similar latitudes and photoperiods on the western slope of the Colombian Central Andes. We compared a Low Elevation locality (LE) at 1800 m a.s.l. and a High Elevation locality (HE) at 3853 m a.s.l. that have approximate wind speeds of 1.3 m/s and 8.4 m/s, respectively. During 12 months of sampling, we captured 46 adults using mist-nets; 26 in the LE and 20 in the HE. Each individual was sexed using molecular techniques at the Laboratory of Genetics of the Department of Biological Sciences of Universidad de Caldas. Individuals (males + females) from the HE had longer wings and tails than those from the LE (F1,44 = 5.93; P = 0.019). Also, wings of males in the HE were longer than those of females in both localities and tails of males in the HE were longer than those of LE males. Our results did not agree with what was expected according to Allen’s and Bergmann’s ecogeographic rules. Longer wings and tails increase sustainment, maneuverability, and balance in low atmospheric pressures and strong air currents and these conditions are found at high elevation habitats. Most likely, the longer wings found for HE males allow greater movement during territorial behavior. Further, these differences in morphological traits along elevational gradients could result from micro-evolutionary changes between localities or phenotypic plasticity of individuals exposed to different environmental conditions.

Resumen Las poblaciones que se reproducen en gradientes altitudinales, adoptan diversos cambios morfológicos para afrontar las condiciones ambientales. En el presente estudio se compararon las medidas morfológicas (peso corporal, longitud del tarso, ala, cola y culmen) de una población de Zonotrichia capensis, a diferente altitud en los Andes colombianos. Las localidades de tierra baja (TB) y alta (TA) se encuentran a 1800 m.s.n.m. y 3853 m.s.n.m., con velocidad aproximada del viento de 1.3 m/s y 8.4 m/s, respectivamente. Durante 12 meses se realizó la captura de 46 individuos (TB n=26, TA n=20) para la medición de los rasgos morfológicos. La longitud del ala de los individuos de TA fue mayor que en TB. Así mismo, en machos de TA la longitud del ala fue mayor que en hembras en general. Es posible que a las más grandes incrementen la eficiencia del vuelo en zonas ventosas y con baja presión atmosférica, como ocurre en TA. Probablemente la diferencia del tamaño del ala entre los machos de TA y las hembras, se deba a un mayor desplazamiento dentro de la conducta territorial. Estas diferencias podrían ser el resultado de cambios microevolutivos entre localidades o la plasticidad fenotípica de individuos expuestos a diferentes condiciones ambientales.

ABSTRACT In Chile, the manipulation for scientific purposes of terrestrial vertebrates from natural populations is conducted previous authorization of the Agricultural and Livestock Service and various Bioethics Committees. Obtaining such authorizations is becoming increasingly complex. The procedures do not fit the reality of scientific work, and they seem to be based on unjustified assessments of the effects of animal handling on natural populations. The aim of this commentary is to initiate a discussion in order to establish a norm of scientific manipulation of terrestrial vertebrates adjusted to biological reality and that does not interfere with scientific research.

RESUMEN La manipulación con fines científicos de vertebrados terrestres en poblaciones naturales chilenas se debe realizar previa autorización del SAG y de Comités de Bioética institucionales. Obtener dichas autorizaciones es cada vez más complejo; los trámites no se adecúan al quehacer científico ni al conocimiento sobre el efecto de la manipulación en las poblaciones naturales. El objetivo de este comentario es contribuir a una discusión en pos del establecimiento de una normativa de manipulación científica de vertebrados terrestres ajustada a la realidad biológica y que no entorpezca la investigación científica.

Senda Darwin Biological Station (SDBS) is a field research center immersed in the rural landscape of northern Chiloé island (42º S), where remnant patches of the original evergreen forests coexist with open pastures, secondary successional shrublands, Sphagnum bogs, Eucalyptus plantations and other anthropogenic cover types, constituting an agricultural frontier similar to other regions in Chile and Latin America. Since 1994, we have conducted long-term research on selected species of plants (e.g., Pilgerodendron uviferum) and animals (e.g., Aphrastura spinicauda, Dromiciops glirioides) that are considered threatened, poorly known or important for their ecological functions in local ecosystems, and on ecosystems of regional and global relevance (e.g., Sphagnum bogs, North Patagonian and Valdivian rain forests). Research has assessed the responses of species and ecosystems to anthropogenic land-use change, climate change, and the impact of management. During this period, more than 100 scientific publications in national and international journals, and 30 theses (graduate and undergraduate) have been produced by scientists and students associated with SDBS. Because of our understanding of the key role that humans play in ecological processes at this agricultural frontier, since the establishment of SDBS we have been committed to creative research on the communication of science to society and ecological education. The integration of SDBS to the nascent Chilean network of long-term socio-ecological research will consolidate and strengthen basic and applied research to project our work into the next decade.

La Estación Biológica Senda Darwin (EBSD) constituye un centro de investigación inmerso en el paisaje rural del norte de la Isla de Chiloé (42º S), donde fragmentos del bosque siempreverde original coexisten con praderas de uso ganadero, turberas de Sphagnum, matorrales sucesionales, plantaciones de Eucalyptus y otras formaciones de origen antropogénico. Desde 1994 hemos realizado estudios de largo plazo centrados en algunas especies de plantas (e.g., Pilgerodendron uviferum D. Don) y animales (e.g., Aphrastura spinicauda Gmelin, Dromiciops gliroides [Thomas]) catalogados como amenazados o escasamente conocidos y en ecosistemas nativos de importancia regional y global (e.g., turberas de Sphagnum, bosque Valdiviano y Nordpatagónico). Las investigaciones han considerado las respuestas de las especies y de los ecosistemas frente al cambio antropogénico del paisaje y cambio climático, así como los efectos de diferentes formas de manejo. Este escenario es semejante al de otras regiones de Chile y Latinoamérica lo que da generalidad a nuestros resultados y modelos. En este período, investigadores asociados a la EBSD han producido más de un centenar de publicaciones en revistas nacionales e internacionales y 30 tesis de pre y postgrado. Entendiendo el papel clave de los seres humanos en los procesos ecológicos de la zona rural, la EBSD ha desarrollado un programa de educación ecológica y vinculación del avance científico con la sociedad local y nacional. La integración de la EBSD a la naciente red de Sitios de Estudios Socio-Ecológicos de Largo Plazo en Chile consolidará y fortalecerá la investigación básica y aplicada que realizamos para proyectarla hacia la siguiente década.

Research on wild animals often involves the capture and temporary removal of individuals from their territory. Although the acute effects of such procedures are well understood in terms of stress hormone profiles, their effect on the behaviour of captured individuals after release is poorly known. Additionally, for socially-monogamous individuals captured whilst breeding, little is known regarding whether the remaining individual compensates for the temporary loss of its partner and whether offspring condition or survival ultimately decreases due to any reductions in parental provisioning. We investigated the influence of field-based experiments requiring temporary adult removal on adult provisioning behaviour and nestling mass in the thorn-tailed rayadito (Aphrastura spinicauda), a Chilean furnariid species with equal parental effort between sexes. During the absence of the removed individual, remaining individuals did not increase nestling provisioning rates while, upon their release, removed individuals did not return to nestling feeding for at least 38 minutes and typically much longer. This drastic reduction in combined parental provisioning negatively affected nestling mass, while average nestling mass increased during a control period, nestlings failed to gain weight during and subsequent to parental removal. Finally, our experiments did not affect fledging probability. Overall, our results indicate that the temporary removal of rayaditos from their territories can cause short-term reductions in parental provisioning and nestling weight, but is unlikely to lead to any long-term effects on nestling survival.

Las investigaciones en animales silvestres frecuentemente requieren la captura y remoción de individuos de sus territorios. Si bien se conocen los efectos a nivel hormonal de tales métodos, sus efectos sobre la conducta de los individuos después de la liberación son escasamente conocidos. Además, para individuos de especies monógamas que son capturados durante la época reproductiva, se desconoce si el individuo restante compensa la pérdida temporal de su compañero ni si la condición o sobrevivencia de los pichones disminuye como consecuencia del cuidado parental reducido. Investigamos la influencia de experimentos de campo que remueven temporalmente un adulto sobre las visitas de aprovisionamiento y el peso de pichones en el rayadito (Aphrastura spinicauda), un furnárido con similar cuidado parental entre los sexos. Durante la ausencia de un adulto, los individuos restantes de cada pareja no aumentaron la frecuencia de aprovisionamiento. Después de su liberación, los individuos previamente ausentes no volvieron a alimentar a sus pichones por al menos 38 minutos. Esta acentuada reducción en cuidado parental por ambos adultos de la pareja afectó negativamente el peso de los pichones. Aunque el peso medio de los pichones aumentó durante el período control, los pichones no aumentaron su peso durante y después de la remoción parental. Nuestros experimentos no afectaron el éxito de los volantones. Globalmente, los experimentos causaron reducciones de corto plazo en cuidado parental y peso de pichones, pero es improbable que causen efectos de largo plazo en la sobrevivencia de los pichones.

We present an analysis of behavioral flexibility in a day-active caviomorph rodent, the degu, Octodon degus, in response to temporal (daily and seasonal), spatial, and thermal heterogeneity of its environment. We quantified activity and foraging behavior in a population, together with thermal conditions, in an open habitat in the seasonally hot and arid matorral of central Chile. Summer activity was bimodal, with a gap of more than 8 h between the morning bout of 2.5 h of intensive foraging and the afternoon bout of 2 h. More than half of the 4.5 h of summer activity occurred in the shade of early morning or late afternoon when the sun was below the local skyline. Autumn and spring activity were also bimodal, but with greater proportions of activity under direct solar radiation, and with a shorter midday gap between the two major bouts. Winter activity was unimodal and all occurred under direct solar radiation. In summer, autumn, and spring the activity of degus was curtailed as our index of operative temperature, Te, moved above 40 ºC. We used a single measurement of Te (measured in a thermal mannequin representing degu size, shape and surface properties) as an index of the interactive effects of solar radiation and convection on body temperature. At the winter solstice (June), when degus remained fully exposed to solar radiation throughout the day, Te generally remained below 30 ºC. Flexibility in the timing of surface activity allows degus to maintain thermal homeostasis and energy balance throughout the year. Degus shift the times of daily onset and end of activity and the number of major bouts (unimodal or bimodal) over the course of the year. They remain active on the surface under a much narrower range or "window" of thermal conditions than those that occur over the entire broad range of the day and year

Presentamos un análisis de la flexibilidad conductual en la actividad diaria del degu (Octodon degus), un roedor caviomorfo, en respuesta a la heterogeneidad del ambiente temporal (diario y estacional), espacial y térmico. Junto con las condiciones térmicas, cuantificamos la conducta de actividad y forrajeo en una población que vive en un hábitat abierto en el matorral árido y estacional de Chile central. La actividad de verano fue bimodal, con 2,5 h de actividad de forrajeo intenso durante la mañana y con 2 h durante la tarde. No hubo actividad por mas de 8 h entre ambos eventos. Más de la mitad de las 4,5 h diarias de actividad de la mañana y de la tarde ocurrieron en la sombra, cuando el sol se encuentra bajo la línea local del cielo. La actividad durante el otoño y la primavera también fue bimodal pero con una mayor proporción de actividad bajo radiación solar directa y con un período de inactividad menor entre los dos eventos principales. La actividad de invierno fue unimodal y bajo radiación solar directa. En verano, otoño y primavera la actividad estuvo sesgada cuando nuestro índice de temperatura operativa, Te, superó los 40 °C. Usamos una medida de Te (registrada en un maniquí térmico que representa las propiedades de forma, tamaño y superficie de un degu) como un índice de los efectos interactivos de la radiación solar y la convección sobre la temperatura corporal. Durante el solsticio de invierno (junio), cuando los degus permanecieron todo el día totalmente expuestos al sol, Te generalmente permaneció bajo 30 °C. La flexibilidad en el tiempo de la actividad superficial le permitió a los degus mantener su homeostasis térmica y balance de energía anual. Los degus cambiaron sus períodos de inicio y término así como el número de eventos de actividad (unimodal o bimodal) durante el año. Estos roedores permanecieron activos en la superficie bajo un rango mucho más estrecho de condiciones térmicas que las que ocurren durante el largo del día y año

We present an analysis of time and energy allocation in a day-active caviomorph rodent, the degu, Octodon degus, in central Chile. We quantified components of surface activity in the field on a daily basis in individual degus near the time of the summer solstice, when conditions of heat and aridity were also at a seasonal extreme, in order to answer the following questions. Does the absolute time available for surface activity limit performance? Does the allocation of time and energy for locomotion place a functionally significant limitation on overall energy balance and performance? Degus spent about 2/3 of their above-ground time foraging; they remained stationary about 88 % of the time, walked around slowly about 10 %, and were running rapidly from one point to another only about 2 % of the time. Net locomotion costs (for walking and running combined) were computed to be only 2.2 % of total daily energy expenditure. This low net allocation of time and energy to locomotion, taken together with abundant distribution of plant food over the extremely small home range, suggests that the daily performance of degus is not limited by the absolute amount of time available under normal conditions at the summer solstice (seasonal extreme of day length, heat, and aridity). Total energy demands can be met by as little as 4.5 h surface activity per day. Our empirical observations, together with a simple computational model of time and energy expenditure, provide a useful validation of the impact of activity on the overall energy balance of a free-living rodent. The small impact of locomotion on the total energy budget is an economy of the behavior of these animals, and the rapid mode of locomotion allows them to minimize predation risks. We believe that this kind of quantitative analysis of energy expenditure associated with behavior in the field can contribute a useful basis for theoretically based time-energy modeling

Presentamos un análisis de la asignación de tiempo y energía en un roedor caviomorfo diurno el degu, Octodon degus, en Chile central. Cuantificamos los componentes de actividad superficial en el campo sobre una base diaria durante el solsticio de verano en condiciones de calor y aridez extrema, para contestar la siguiente pregunta: ¿el tiempo absoluto disponible para la actividad superficial limita el rendimiento? ¿la asignación de tiempo y energía a locomoción juega un limitación funcional significativa en el presupuesto de energía total y en el rendimiento? Los degus permanecen forrajeando cerca de 2/3 de su tiempo fuera de las cuevas; están estacionarios cerca de 88 % del tiempo, caminan cerca del 10 %, y corren rápidamente de un punto a otro solamente un 2 % del tiempo. Los costos netos de locomoción (caminando y corriendo) fueron calculados en 2,2 % del gasto energético total. Esta baja asignación neta de tiempo y energía a locomoción, junto a la abundante distribución de alimento en un ámbito de hogar pequeño, sugieren que el rendimiento diario de los degus no está limitado por el tiempo absoluto disponible bajo condiciones normales en el solsticio de verano (extremo estacional de largo del día, calor y aridez). Las demandas de energía totales se lograrían con 4,5 h de actividad superficial por día. Las observaciones empíricas, junto a un modelo simple de gasto de energía y tiempo entregan una validación simple de la actividad del balance de energía total en roedores de vida libre. El bajo impacto de la locomoción sobre el presupuesto de energía total representa una economía en la conducta de estos animales, los rápidos modos de locomoción minimizarían el riego de predación. Postulamos que estos análisis cuantitativos de gasto de energía asociados con la conducta de campo contribuirían a la modelación teórica del uso de tiempo y energía