Escape behavior in gravid and non-gravid females of Gonatodes albogularis (Squamata: Sphaerodactylidae)

Comportamento de fuga em fêmeas grávidas e não-grávidas de Gonatodes albogularis (Squamata: Sphaerodactylidae). Modelos teóricos de relações predador-presa descrevem balanços entre custos de fuga (energéticos e de outros tipos), efciência do comportamento de fuga e risco de predação. Esses modelos preveem que um animal escapará quando o custo esperado em termos de sucesso reprodutivo devido ao risco de predação quando for igual ao custo de fuga ou quando o sucesso reprodutivo após o encontro for maximizado, dependendo do modelo. Nesse cenário, demonstrou-se que diversas variáveis individuais e ecológicas afetam os padrões de fuga, mas o efeito do status reprodutivo foi estudado em poucas espécies. Nós avaliamos diferenças no comportamento de fuga entre fêmeas grávidas e não-grávidas de Gonatodes albogularis. Os lagartos foram estudados aplicando-se um método de procura livre ao longo de transectos independentes. Para cada fêmea, determinamos o status reprodutivo como grávida ou não-grávida e registramos diversas variáveis relacionadas ao comportamento de fuga. Desenvolvemos uma análise discriminante para verifcar se o estado dos indivíduos afetavam o comportamento de fuga. Nossos resultados mostram que as variáveis distância percorrida na fuga, distância fnal e distância para o refúgio diferem entre fêmeas grávidas e não-grávidas. Essas descobertas sustentam previsões baseadas em risco e custo, mas não sustentam modelos de distância de início de fuga. Tais diferenças poderiam estar relacionadas como um processo conhecido como compensação comportamental, por meio do qual alguns indivíduos (as fêmeas grávidas, no nosso caso) modifcam seu comportamento para compensar risco de predação. Estudos adicionais são necessários para verifcar se a compensação comportamental pode ser explicada em termos de processos adaptativos em G. albogularis.Escape behavior in gravid and non-gravid females of Gonatodes albogularis (Squamata: Sphaerodactylidae). Theoretical models of predator-prey relationships describe tradeoffs between energetic and other costs of escape, effectiveness of escape behavior, and predation risk. These models predict that an animal will fee when the expected ftness cost due to risk of predation becomes equal to the the cost of the escape or post-encounter ftness is maximized, depending on the model. In this framework, several individual and ecological variables have been shown to affect escape patterns, but the effect of reproductive status has been studied in few species. We assess differences in escape behavior between gravid and non-gravid females of Gonatodes albogularis. Lizards were surveyed by applying a free search method along independent transects. For each lizard, we determined reproductive status as gravid or non-gravid and recorded several variables related to escape behavior. We made a discriminant function analysis to see whether the state of individuals affect escape behavior. Our results show that the escape variables distance fed, the fnal distance and the distance to refuge differ between gravid and non-gravid females. These fndings support predictions based on risk and cost, but do not support models of fight initiation distance. Such differences could be related to a physiological process known as behavioral compensation, through which some individuals (gravid females in our case) modify their behavior to offset predation risk. Further studies are needed to see if behavioral compensation can be explained in terms of adaptive processes in G. albogularis

Occupancy and abundance of large macaws in the Beni savannahs, Bolivia

Fil: Berkunsky, Igor. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Cepeda, Rosana E.. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Marinelli, Claudia. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Simoy, María Verónica. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Daniele, Gonzalo. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Kacoliris, Federico Pablo. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Díaz Luque, José A.. Blue-throated Macaw Conservation Project. World Parrot Trust. Trinidad; BoliviaFil: Gandoy, Facundo. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Universidad Nacional del Centro de la Provincia de Buenos Aires. Tandil; ArgentinaFil: Aramburú, Rosana Mariel. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Gilardi, James D.. Blue-throated Macaw Conservation Project. World Parrot Trust. Trinidad; Bolivi

The rainbow trout is affecting the occupancy of native amphibians in Patagonia

In this work, we assessed the occupancy of two native amphibian species of the Valcheta stream in the Somuncura Plateau, northern Patagonia: the Valcheta frog, Pleurodema somuncurense and the Argentine common toad, Rhinella arenarum. We hypothesized that the occupancy of both amphibian species will be shaped by the presence of trout; we also expected a decline in occupancy assuming that the new predator in the system will affect native amphibian populations. Between December 2014 and March 2015, we conducted surveys in 148 sites along the headwaters of Valcheta stream. We modelled the occupancy by including the presence of trout, the temperature of water and the coverage of rocks and vegetation as site-habitat covariates. Models including trout were among the best ranked for both amphibian species. The presence of trout reduced the occupancy of both species and the magnitude of this reduction was much higher in the Valcheta frog than in the Argentine common toad. Overall, our results are of great relevance for land managers considering that the Valcheta frog is among the only three IUCN Critically Endangered amphibians in Argentina.Facultad de Ciencias Naturales y Muse

An individual energy balance model for greater rhea (Rhea americana) and its implication on recruitment

En este trabajo se plantearon modelos individuales del balance energético del ñandú (Rhea americana) para analizar su efecto en el reclutamiento poblacional. El modelo individual se basó en un sistema de ecuaciones que calcula diariamente el peso corporal del individuo en función de su tasa de ingesta y del costo energético de la actividad desarrollada. La tasa de ingesta se estimó a partir de resultados de ensayos en cautiverio. El costo energético diario se estimó a partir de patrones de comportamiento observados en animales silvestres, teniendo en cuenta género y factores que influyen en el comportamiento (e.g. fotoperíodo, período del año). Concatenando los resultados del modelo diario, se obtuvo la dinámica del peso a lo largo del período deseado. Una vez calibrado el modelo, se analizó la factibilidad de diferentes estrategias reproductivas para ambos sexos y se determinó la condición física (peso) que un individuo debe alcanzar para reproducirse exitosamente. Los resultados mostraron que existen pocas restricciones para que una hembra pueda reproducirse pero, en cambio, los machos dependen fuertemente de su estado nutricional para reproducirse exitosamente cada año. Los resultados obtenidos fueron contrastados con observaciones a campo que confirman el bajo éxito reproductivo en la población, a pesar de poseer esta especie un sistema de apareamiento altamente promiscuo. Adicionalmente, se estimó el impacto de poblaciones silvestres en las actividades agropecuarias de la región pampeana bonaerense.We proposed an individual based model of energy budgets of ñandú (Rhea americana) for analyzing its effect on the population recruitment. The individual model was based on a system of equations calculating the weight of an individual as a function of its ingestion rate and energetic cost of its activity pattern with daily step. The ingestion rate was calculated from field experiments. Daily energetic cost was estimated from observed activity patterns at the field, taking into account gender and factors that influence behavior (e.g., photoperiod, season). Concatenating daily model output, the weight dynamics over any period can be obtained. Once the model is calibrated, different reproductive strategies for each gender were analyzed and the minimal body weight that an individual needs to achieve for ensuring reproductive success was determined. Females exhibit low nutritional requirements to produce eggs, but reproductive success of males depends strongly on the body weight. Results obtained were compared to observations made during population censuses Additionally, the impact of wild populations on agricultural activities is assessed using the model.Fil:Simoy, María Verónica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina