Luis M. Carrascal

Climate change and outbreaks of amphibian chytridiomycosis in a montane area of Central Spain; is there a link?

Amphibian species are declining at an alarming rate on a global scale in large part owing to an infectious disease caused by the chytridiomycete fungus, Batrachochytrium dendrobatidis. This disease of amphibians has recently emerged within Europe, but knowledge of its effects on amphibian assemblages remains poor. Importantly, little is known about the environmental envelope that is associated with chytridiomycosis in Europe and the potential for climate change to drive future disease dynamics. Here, we use long-term observations on amphibian population dynamics in the Peñalara Natural Park, Spain, to investigate the link between climate change and chytridiomycosis. Our analysis shows a significant association between change in local climatic variables and the occurrence of chytridiomycosis within this region. Specifically, we show that rising temperature is linked to the occurrence of chytrid-related disease, consistent with the chytrid-thermal-optimum hypothesis. We show that these local variables are driven by general circulation patterns, principally the North Atlantic Oscillation. Given that B. dendrobatidis is known to be broadly distributed across Europe, there is now an urgent need to assess the generality of our finding and determine whether climate-driven epidemics may be expected to impact on amphibian species across the wider region.

Interactions among environmental stress, body condition, nutritional status, and dominance in great tits

Body condition and feather growth rate of Great Tits ( Parus major) were studied in relation to dominance in two contrasting Mediterranean localites during late autumn and early winter. The two localities differed in altitude, ambient temperatures (100 vs 1500 m a.s.l., and 11.7 oC vs 4.6 oC, respectively) and arthropod availability. The two study areas were similarly food supplemented (husked peanuts) throughout the study period. Percentage of time spent at feeders was higher at El Ventorrillo (the locality with colder climate and less natural food availability), and was associated with dominance only in this locality. Number of aggressive displacements per hour suffered by each individual was higher (150-fold greater) in the area with less arthropod availability and lower temperatures. Protein reserves measured as pectoralis muscle thickness was higher at El Ventorrillo, and was positively and consistently related to dominance in both localities. Growth rate of induced feathers was slower in the locality that was colder and had less natural food availability (El Ventorrillo), but was not clearly and directly related to dominance in both localities. Only dominant adult males in El Ventorrillo could compensate the higher environmental harshness of this locality attaining a higher feather growth rate than the other sex-age classes. Feather mass asymmetry during autumn was not associated with body condition, did not change between localities, and was inversely and consistently related to dominance in both localities. The covariation pattern among variables describing bird size, access to supplemented food, body condition, feather growth rate and asymmetry was different in both localities. Only in the locality with colder temperatures and lower arthropod food availability (El Ventorrillo) larger, more dominant, Great Tits spent more time foraging on feeders, had a thicker pectoralis muscle (i.e. body condition), and grew the induced feathers at a higher rate. pmajor

Covariation of Thermal Biology and Foraging Mode in Two Mediterranean Lacertid Lizards

Body temperatures, heat exchange rates, behavioral thermoregulation, and movement behavior (as an index of foraging mode) were studied in two widely distributed, medium-sized lacertid lizards (Acanthodactylus erythrurus and Psammodromus algirus). P. algirus mainly inhabits broad-leaved forests, whereas A. erythrurus prefers open, sandy areas with sparsely distributed vegetation. These habitat preferences parallel differences between the areas in which both genera presumably originated: Eurosaharian xeric steppes with high operative temperatures (T e ) for Acanthodactylus, and Mediterranean open forests with lower T e for Psammodromus. Field observations showed that percentage of time spent basking and basking rate (number of basks per minute) were negatively related to T e , although average bask duration was not. Percentage of time spent moving, moving rate (number of moves per minute), and the average duration of individual moves were inversely related to T e and were higher in P. algirus. The percentage of total locomotion time that was spent moving in the shade was also higher in P. algirus. Behavioral thermoregulation strategies differed in a laboratory thermogradient, where P. algirus basked more often and for shorter periods and selected warmer patches than did A. erythrurus. Selected body temperatures (T b ) in a laboratory thermogradient were significantly higher in A. erythrurus than in P. algirus. Shade Seeking T b was higher in A. erythrurus, but Resume Basking T b did not differ significantly between the two species. Heating and cooling rates also differed in the two species: A. erythrurus warmed more slowly and cooled faster than did P. algirus. Our data support the existence of a complex syndrome that combines aspects of the behavior, physiology, and ecology of both species. The thermal consequences of inhabiting a certain type of habitat can be counterbalanced by behavioral and physiological means that, in turn, affect movement and, hence, foraging behavior. Thus, the more active species (P. algirus) heated faster, cooled more slowly, and basked more often but for shorter periods and at warmer patches than the less active species (A. erythrurus).

Regional distribution of a Mediterranean lizard: influence of habitat cues and prey abundance

We studied the distribution of a common Medi- terranean lacertid lizard, Psammodromus algirus (L.) 1758, on nineteen sites within a regional gradient of homoge- neous yet contrasted habitats. This scale was large enough to allow line-transect estimates of lizard abundance, which were related to quantitative (and when possible multivari- ate) measurements of the structure and floristic composition of vegetation, the abundance of arthropod prey, the relative density of other lizard species, and the climatic data obtained from nearby meteorological stations. Neither the climate not the abundance of other lizards seemed to condi- tion the quantitative distribution of the species. The positive influence of broad-leaved forests on the abundance of P. more directly related to the ecology of lizards than floristic composition per se. Thus, population levels were most highly correlated with the cover of shrubs over 20 cm in height, and once this stnictural requirement was met, they increased with the abundance of potential prey (itself condi- tioned by vegetation cover at the ground leve1 and litter cover). We suggest that our results should be interpreted in the context of thermoregulatory, predator avoidance and movement minimization strategies whose influence on sur- vival, and hence abundance, could probably be applied to other insectivorous lizards from temperate zones.

Leg Morphology and Feeding Postures in Four Parus Species: An Experimental Ecomorphological Approach

.-lbstract. The foraging behavior of four Parus species feeding at artificial feeders was studied. while controlling for ecological variables related to patch characteristics (food quality. food access. and escape distance to the nearest refuge). Hindlimb morphology (osteology and myology) was analyzed and compared with foraging postures at feeders. Using the Long-Tailed Tit as an appropriate outgroup for comparison. and considering functional changes associated with morphological changes. we demonstrated the existente of clear ecomorphological patterns relating foraging postures and hindlimb morphology in the four Parus species studied. The Blue Tit uses hanging postures preferably and its hindlimb morphology is modified for helping leg flexion. The Crested Tit more often stands and its hindlimb morphology is modified to aid leg extension. Great and Coa1 Tits are ecologically and morphologically intermediate between the two former species. Our results show morphology as a determinant of locomotion mode. Since foraging postures are tightly associated with substrate use. then morphology should be considered when studying pressures determining community organization. Our proposed integrative method for dealing with ecomorphology can be valuable in demonstrating the adaptiveness of morphological structures in phylogenetically and ecologically related species. Kej. words: ~ornorpliolog~~; fec~Iirzg postures: hindlirnb; rnorpholoyl.; rnj~olo~~; ostrologj,: Parus:

Coal tits, Parus ater, lose weight in response to chases by predators

Theoretical models predict that birds should decrease their body mass in response to increased predation risk because lighter birds take off faster and are more manoeuvrable. We studied the effect of predation risk by chasing coal tits in large outdoor aviaries thus simulating an attempt to capture them. With this increase in predation risk, both perceived and actual, coal tits lost significantly more weight than in a control situation when they were not pursued. This pattern was attributable to a smaller gain in weight only during the day; nocturnal weight did not change in relation to diurnal predation risk. The lower daily weight gain was not consistent with predictions from models of interrupted foraging, but was consistent with predictions from risk adjustment models. Moreover, there was no difference in weight gain over 2-h periods that included a 1-h fast and those in which feeding was ad libitum, suggesting that coal tits could easily regain their body mass after a predator had interrupted their feeding. Our results therefore suggest that pursuit by predators leads to a decrease in the body mass of small birds. Copyright 1999 The Association for the Study of Animal Behaviour.

Hatching asynchrony, sibling hierarchies and brood reduction in the Chinstrap penguin Pygoscelis antarctica

We studied patterns of chick growth and mortality in relation to egg size and hatching asynchrony during two breeding seasons (1991 and 1992) in a colony of chinstrap penguins sited in the Vapour Col rookery, Deception Island, South Shetlands. Intraclutch variability in egg size was slight and not related to chick asymmetry at hatching. Hatching was asynchronous in 78% (1991) and 69% (1992) of the clutches, asynchrony ranging from 1 to 4 days (on average 0.9 in 1991 and 1.0 days in 1992). Chicks resulting from oneegg clutches grew better than chicks in families of two in 1991. In 1992, single chicks grew to the same size and mass at 46 days of age as chicks of broods of two, suggesting food limitation in 1991 but not in 1992. In 1991, asymmetry between siblings in mass and flipper length was significantly greater in asynchronous than in synchronous families during the initial guard stage, but these differences disappeared during the later créche phase. In 1992, asymmetry in body mass increased with hatching asynchrony and decreased with age. Only the effect of age was significant for flipper length and culmen. Asymmetries at 15 days were similar in both years, but significantly lower in 1992 than in 1991 at 46 days of age. There were relatively frequent reversals of size hierarchies during both phases of chick growth in the two years, reversals being more common in 1991 than in 1992 for small chicks. In 1991, survivors of brood reduction grew significantly worse than chicks in nonreduced broods. In both years, chicks of synchronous broods attained similarly large sizes before fledging as both A and B chicks of asynchronous broods. In 1991, chick mortality rate increased during the guard stage due to parental desertions, decreased during the transition to crèches (occurs at a mean age of 29 days) and returned to high constant levels during the crèche stage, when it is mostly due to starvation (in total 66% of hatched chicks survived to fledging). In contrast, in 1992, mortality was relatively high immediately after hatching and almost absent for chicks older than 3 weeks (87% of chicks survived to fledging). Mortality affected similarly one- and two-chick families. In 1991, asynchronous families suffered a significantly greater probability of brood reduction than synchronous families, but this probability was not significantly related to degree of asymmetry between siblings. No association between asynchrony and mortality was found in 1992. These results show that there is food limitation in this population during the crèche phase in some years, that asynchronous hatching does not facilitate early brood reduction and that it does not ensure stable size hierarchies between siblings. Brood reduction due to starvation is not associated to prior asymmetry and does not facilitate the survival or improve the growth of the surviving chick. Asynchronous hatching may be a consequence of thermal constraints on embryo development inducing incubation of eggs as soon as they are laid.

Variation in the effect of profitability on prey size selection by the lacertid lizard Psammodromus algirus

Maximizing the average rate of energy intake (profitability) may not always be the optimal foraging strategy for ectotherms with relatively low energy requirements. To test this hypothesis, we studied the feeding behaviour of captive insectivorous lizards Psammodromus algirus, and we obtained experimental estimates of prey mass, handling time, profitability, and attack distance for several types of prey. Handling time increased linearly with prey mass and differed significantly among prey types when prey size differences were controlled for, and mean profitabilities differed among prey taxa, but profitability was independent of prey size. The attack distance increased with prey length and with the mobility of prey, but it was unrelated to profitability. Thus, lizards did not seem to take account of the rate of energy intake per second as a proximate cue eliciting predatory behavior. This information was combined with pitfall-trap censuses of prey (in late April, mid-June and late July) that allowed us to compare the mass of the prey captured in the environment with that of the arthropods found in the stomachs of sacrificed free-living lizards. In April, when food abundance was low and lizards were reproducing, profitability had a pronounced effect on size selection and lizards selected prey larger than average from all taxa except the least profitable ones. As the active season progressed, and with a higher availability of food, the number of prey per stomach decreased and their mean ize increased. The effect of profitability on size selection decreased (June) and eventually vanished (July–August). This variation is probably related to seasonal changes in the ecology of lizards, e.g. time minimization in the breeding season as a means of saving time for nonforaging activities versus movement minimization by selecting fewer (but larger) prey in the postbreeding season. Thus, the hypothesis that maximizing profitability could be just an optional strategy for a terrestrial ectothermic vertebrate was supported by our data.

Species richness can decrease with altitude but not with habitat diversity.

In the paper by Allouche et al. (1), the authors suggested that species richness decreases at high levels of habitat diversity because the area available per habitat decreases [area–heterogeneity tradeoff hypothesis (AHTO)]. They showed a hump-shaped relationship between Catalonian bird richness and altitudinal range in grid cells, the authors’ surrogate for environmental heterogeneity. However, birds select habitats mainly based on vegetation structure and floristic composition (2). Catalonian high altitudes are dominated by uniform coniferous forests or simple habitats with low vegetation cover (outcrops, grasslands, and scrublands) that are known to be poor in bird richness. Furthermore, high-altitude grid cells have the largest altitudinal ranges but much fewer habitats than lower altitudes (using 48 habitat categories obtained from Inventario Nacional Forestal III, 2007–2008, Spanish Ministerio de Medio Ambiente). Elevation range in Catalonia is tightly correlated with maximum altitude (r = 0.951; P < 0.0001) and mean elevation (r = 0.858; P < 0.0001), but poorly correlated with environmental heterogeneity (number of habitats per cell: r = 0.049, P = 0.349; Shannon index across all habitat categories: r = 0.119, P = 0.024). When analyzed together (Generalized Additive Model; Fig. 1), bird-species richness shows a hump-shaped relationship with mean elevation [nonlinear P (n-Lp) = 0.003], a negative linear relationship with altitudinal range (P = 0.001; n-Lp = 0.426), and a positive, monotonic relationship with habitat diversity (P < 0.001; n-Lp = 0.336), as predicted from ecological theory (3). Thus, the unimodal relationship between altitudinal range and richness (1) merely reflects the well-known hump-shaped relationship between species richness and altitude (4), not a tradeoff between richness and environmental heterogeneity.

Reproductive Phenology and Temporal Patterns of Mate Access in Mediterranean Anurans

Acknowledgments.-We are indebted to J. H. Harding for field assistance in obtaining the specimens of Storeria occipitomaculata, to H. A. Dundee for helping to support the fieldwork, to K. M. Brown for sharing his knowledge of snail anatomy, to V. Wallach for critically reading the manuscript, and to K. K. Adler, C. P. Kofron, C. J. McCoy, and A. H. Savitzky for providing copies of some difficult-to-find refer-