How animals distribute themselves in space: energy landscapes of Antarctic avian predators

Background: Energy landscapes provide an approach to the mechanistic basis of spatial ecology and decision- making in animals. This is based on the quantification of the variation in the energy costs of movements through a given environment, as well as how these costs vary in time and for different animal populations. Organisms as diverse as fish, mammals, and birds will move in areas of the energy landscape that result in minimised costs and maximised energy gain. Recently, energy landscapes have been used to link energy gain and variable energy costs of foraging to breeding success, revealing their potential use for understanding demographic changes. Methods: Using GPS-temperature-depth and tri-axial accelerometer loggers, stable isotope and molecular analyses of the diet, and leucocyte counts, we studied the response of gentoo (Pygoscelis papua) and chinstrap (Pygoscelis antarcticus) penguins to different energy landscapes and resources. We compared species and gentoo penguin populations with contrasting population trends. Results: Between populations, gentoo penguins from Livingston Island (Antarctica), a site with positive population trends, foraged in energy landscape sectors that implied lower foraging costs per energy gained compared with those around New Island (Falkland/Malvinas Islands; sub-Antarctic), a breeding site with fluctuating energy costs of foraging, breeding success and populations. Between species, chinstrap penguins foraged in sectors of the energy landscape with lower foraging costs per bottom time, a proxy for energy gain. They also showed lower physiological stress, as revealed by leucocyte counts, and higher breeding success than gentoo penguins. In terms of diet, we found a flexible foraging ecology in gentoo penguins but a narrow foraging niche for chinstraps. Conclusions: The lower foraging costs incurred by the gentoo penguins from Livingston, may favour a higher breeding success that would explain the species’ positive population trend in the Antarctic Peninsula. The lower foraging costs in chinstrap penguins may also explain their higher breeding success, compared to gentoos from Antarctica but not their negative population trend. Altogether, our results suggest a link between energy landscapes and breeding success mediated by the physiological condition. Keywords: Antarctica, Breeding success, Chinstrap penguin Pygoscelis antarcticus, Energy costs, Energy landscapes, Gentoo penguin Pygoscelis papua, Physiological condition, Physiological stress, Population trends, Sub-Antarcti

¿Me voy o me quedo? Factores que influyen en la decisión de abandonar el lugar de nacimiento.

Múltiples factores influyen en la decisión de dispersarse y en cuándo iniciar la dispersión, y su estudio proporciona evidencias de las causas y los determinantes de la dispersión. Los animales abandonan el lugar de nacimiento para dar solución a tres problemas fundamentales: pérdida de calidad del hábitat, competencia por los recursos, y riesgo de consanguinidad. La dispersión, sin embargo, no se lleva a cabo hasta que los individuos alcanzan una condición física adecuada, que permita alcanzar con éxito un nuevo lugar de asentamiento

Lagartija colirroja – Acanthodactylus erythrurus (Schinz, 1834)

Reptiles - Orden Squamata - Familia Lacertidae en la Enciclopedia Virtual de Vertebrados Españoles, http://www.vertebradosibericos.org/. Versiones anteriores: 25-05-2006; 14-12-2006; 27-08-2009; 1-09-2009A comprehensive review of the natural history of the Spiny-footed lizard Acanthodactylus erythrurus in Spain.Peer reviewe

Red coloration in juvenile spiny-footed lizards, Acanthodactylus erythrurus, reduces adult aggression

Received 11 July 2014- Initial acceptance 19 September 2014- Final acceptance 1 December 2014In many animal taxa, coloration is a visual signal used for communication among conspecifics, for example between age classes. Juvenile coloration has been hypothesized to reduce aggression from adults in some species, in what is called the aggression avoidance hypothesis. Spiny-footed lizards are good subjects for testing this hypothesis, as juveniles develop conspicuous red coloration on their hind limbs and tails that fades in adulthood. To test the influence of juvenile coloration on adult aggressiveness, we conducted videotaped encounters in captivity between adults of both sexes and juveniles with their natural red coloration, or experimentally painted either red or white on their natural red parts. Then we recorded the number of times juveniles were bitten and attacked. In unpainted juveniles, no significant relationship was found between juvenile coloration (brightness, red chroma or hue) and adult aggressiveness. However, juveniles painted red were bitten less than those painted white when number of times bitten was controlled for number of times attacked. This result supports the aggression avoidance hypothesis, as an escalation from low-intensity (attacking) to high-intensity aggression (biting) was less probable towards red juveniles. The presence of red coloration in juveniles caused the reduction in adult aggression, while small natural variations in this red colour did not seem to have any further effect. Juvenile red coloration in this species might indicate age or sexual immaturity to adults.This study was funded by the Spanish Ministry of Education and Science and the European Regional Development Fund (grant CGL2008-00137/BOS).Peer reviewe

Parental physiological condition and reproductive success in chinstrap penguins (Pygoscelis antarctica)

Recent studies suggest that parental resource allocation may be the most important factor explaining differences in reproductive output among parents. That said at least two different hypotheses of balance between parental foraging effort and resource allocation have been proposed. First, parents with high foraging effort have high reproductive success. Second, parents with higher allocation of resources to offspring have high reproductive success. We tested the second hypothesis using chinstrap penguins (Pygoscelis antarctica) as a model. We evaluated nutritional condition of the parents using blood urea, uric acid, creatine kinase, and cholesterol levels. We evaluated reproductive success according to total mass of the brood and asymmetries inside the brood. We measured the degree of asymmetry using weight and culmen length. Generalized linear models were used to examine relationships between adult plasma urea levels with year, nest position, and degree of asymmetry in chicks. Our results demonstrate that lighter broods were more asymmetric and associated with lower values of adult plasma urea, uric acid, and creatine kinase. We interpret these findings as evidence that the birds allocate fewer resources to their chicks than adults with more symmetric broods are.The present study was supported by grant ANT91-1264 from the Spanish C.I.C.Y.T. (Plan Nacional Antartico).Peer Reviewe

Influence of heat transmission mode on heating rates and on the selection of patches for heating in a mediterranean lizard. Physiological and Biochemical Zoology 75:369–376

ABSTRACT Heliothermy (heat gain by radiation) has been given a prominent role in basking lizards. However, thigmothermy (heat gain by conduction) could be relevant for heating in small lizards. To ascertain the importance of the different heat transmission modes to the thermoregulatory processes, we conducted an experimental study where we analyzed the role of heat transmission modes on heating rates and on the selection of sites for heating in the Mediterranean lizard Acanthodactylus erythrurus (Lacertidae). The study was conducted under laboratory conditions, where two situations of different operative temperatures (38Њ and 50ЊC) were simulated in a terrarium. In a first experiment, individuals were allowed to heat up during 2 min at both temperatures and under both heat transmission modes. In a second experiment, individuals were allowed to select between patches differing in the main transmission mode, at both temperatures, to heat up. Experiences were conducted with live, nontethered lizards with a starting body temperature of 27ЊC. Temperature had a significant effect on the heating rate, with heat gain per unit of time being faster at the higher operative temperature (50ЊC). The effect of the mode of heat transmission on the heating rate was also significant: at 50ЊC, heating rate was greater when the main heat transmission mode was conduction from the substrate (thigmothermy) than when heating was mainly due to heat gain by radiation (heliothermy); at 38ЊC, heating rates did not significantly differ between transmission modes. At 38ЊC, selection of the site for heating was not significantly different from that expected by chance. However, at 50ЊC, the heating site offering the slowest heating rate (heliothermic patch) was selected. These results show that heating rates vary not only with environmental temperature but also with different predominant heat transmission modes. Lizards are able to identify and exploit this heterogeneity, selecting the source of heat gain (radiation) that minimizes the risk of overheating when temperature is high

Red tails are effective decoys for avian predators

© 2014, Springer International Publishing Switzerland. The decoy or deflection hypothesis, which states that conspicuous colouration is present in non-vital parts of the body to divert attacks from head and trunk, thus increasing survival probability, is a possible explanation for the presence of such colouration in juveniles of non-aposematic species. To test this hypothesis we made plasticine and plaster lizard models of two colour morphs, red or dark-and-light striped tails, based on the colouration of spiny-footed lizard (Acanthodactylus erythrurus) hatchlings, which naturally show a dark-and-light striped dorsal pattern and red tail. Lizard models were placed in the field and also presented to captive common kestrels (Falco tinnunculus), a common avian lizard predator. The number of attacks and the body part attacked (tail or rest-of-body) were recorded, as well as the latency to attack. Our results suggest that models of both colour morphs were recognized as prey and attacked at a similar rate, but in the field, red-tailed models were detected, and thus attacked, sooner than striped-tailed. Despite this increase in detection rate by predators, red-tailed models effectively diverted attacks to the tail from the more vulnerable body parts, thus supporting the decoy hypothesis. Greater fitness benefits of attack diversion to the tail compared to the costs of increased detection rate by predators would explain the evolution and maintenance of red tail colouration in lizards.These studies were funded by the Spanish Ministry of Education and Science and the European Regional Development Fund (Grant CGL2008-00137/BOS).Peer Reviewe

Ecophysiology of Uromastyx desert lizards and consequences for current and future distribution

Tesis doctoral por compendio de publicaciones leída en la Universidad de Madrid en la Facultad de Ciencias (Departamento de Ecología)[EN] Climate change and human disturbance are expected to impose formidable physiological and ecological challenges on terrestrial ectotherms. Lizards are a major taxonomic example of how species diversity is expected to plummet in response to a warming climate, as lizards are particularly sensitive to changes in temperature. The North African spiny-tailed lizard (Uromastyx acanthinura) is one of such examples, ranging from eastern Algeria to northwestern Libya. In Tunisia, this species occupies arid and desert areas and it is frequently poached by local people for food and traditional medicine. Thus, the focus of this thesis was to provide an overview on some ecological and physiological aspects of U. acanthinura in southern Tunisia, which may help to its conservation. My specific goals were 1) to examine the habitat requirements of the Tunisian population of this lizard, 2) to determine how this lizard can behaviorally and physiologically responds to disturbed environments and 3) to predict the potential impact of climate change on the distribution of fifteen Uromastyx species worldwide under current and future scenarios. Fieldwork was comprised of several components: a) lizards captured in live traps were morphologically characterized and subsequently released back to their capture sites, b) blood and fecal samples were collected, and c) the variables that could act as determinants of current species distribution were measured. Further, d) behavioral data were obtained from recorded videos that were analysed to assess the thermoregulatory strategy and e) plasma corticosterone and fecal corticosterone metabolites of males and females found at different distances from roads and urban areas in the study area were measured with an enzyme immunoassay kit.In addition, environmental variables and point locality data derived from several sources were used to examine the concordance between geographical distributions and environmental niches derived from occurrences for fifteen species of the genus Uromastyx and to predict the potential impact of climate change on the distribution of Uromastyx species worldwide using Ecological Niche Models (ENMs) under RCPs 2.6 and 8.5 emission scenarios for the year 2070. Morphometric analysis showed a sexual size dimorphism in U. acanthinura, with adult males reaching longer total lengths and greater weight compared to females. Diet has been described as largely herbivorous in U. acanthinura, with predominantly plant material during their active seasons. These animals prefer to set up their burrows in rocky sites close to agricultural areas and on mountain slopes facing between south west and south east and avoid living near to roads and urban areas. In the three sampling periods (spring, summer and Summary 9 autumn), the mean activity temperature of U. acanthinura (mean ±SE = 35.7 ±0.22°C) was near the range of preferred temperatures registered for other similar lizards species (34–37 °C). Results indicated that bigger individuals achieve their preferred body temperature by spending more time exposed on full sun. Furthermore, the study revealed that human disturbance may be a potential stressor for the threatened spiny-tailed lizard, which may result in increased levels of glucocortocoids. Males had higher plasma corticosterone than females, and these levels were higher in autumn than in summer and spring in both sexes. Moreover, levels of corticosterone in plasma and corticosterone metabolites in faeces were significantly higher when the capture site was closer to roads or urban areas. According to predictive models, the degree of geographical overlap is lower than the degree of environmental sharing, a pattern reinforcing the hypothesis of a speciation process within the genus Uromastyx mainly based on geographical isolation processes. Moreover, climate change could essentially threaten up to 75% of the Uromastyx species, while 25% of species may resist or even benefit from global warming. These species may lose suitable climatic conditions within protected areas and move into unprotected surroundings, making extinction rates potentially higher than expected. Understanding how free-living animals are influenced by environmental conditions and human perturbations could help direction of conservation strategies for endangered species. The results of this study are discussed in the context of management for conservation of these endangered lizards in their natural habitats

Limited effects of egg size on chick growth in the chinstrap Penguin pygoscelis antarctica

We studied the effect of egg size on chick growth in the chinstrap penguin under natural non-manipulative, conditions. The influence of egg size on chick mass at hatching, 15 and 45 days of age was analysed controlling for the effect of hatching date, as hatching date has been repeatedly associated with chick growth in this species. Egg volume explained 20% of the variation in the body mass of chicks at hatching. Its effect disappeared as chicks grew, being statistically not significant at the age of 15 and 45 days. Egg volume asymmetry also had no role in determining chicks' growth asymmetries.Peer Reviewe