Damiano Preatoni

Individual improvements and selective mortality shape lifelong migratory performance

Billions of organisms, from bacteria to humans, migrate each year and research on their migration biology is expanding rapidly through ever more sophisticated remote sensing technologies. However, little is known about how migratory performance develops through life for any organism. To date, age variation has been almost systematically simplified into a dichotomous comparison between recently born juveniles at their first migration versus adults of unknown age. These comparisons have regularly highlighted better migratory performance by adults compared with juveniles, but it is unknown whether such variation is gradual or abrupt and whether it is driven by improvements within the individual, by selective mortality of poor performers, or both. Here we exploit the opportunity offered by long-term monitoring of individuals through Global Positioning System (GPS) satellite tracking to combine within-individual and cross-sectional data on 364 migration episodes from 92 individuals of a raptorial bird, aged 1–27 years old. We show that the development of migratory behaviour follows a consistent trajectory, more gradual and prolonged than previously appreciated, and that this is promoted by both individual improvements and selective mortality, mainly operating in early life and during the pre-breeding migration. Individuals of different age used different travelling tactics and varied in their ability to exploit tailwinds or to cope with wind drift. All individuals seemed aligned along a race with their contemporary peers, whose outcome was largely determined by the ability to depart early, affecting their subsequent recruitment, reproduction and survival. Understanding how climate change and human action can affect the migration of younger animals may be the key to managing and forecasting the declines of many threatened migrants.

IDENTIFYING BATS FROM TIME-EXPANDED RECORDINGS OF SEARCH CALLS: COMPARING CLASSIFICATION METHODS

Abstract Recording ultrasonic echolocation calls of bats using bat-detectors is often used for wide-scale monitoring in studies on bat management and conservation. In Europe, the most important legal instrument for bat conservation is the Habitat Directive (43/92/EEC), which defines various levels of species (and habitat) protection for different bat species and/or genera. Thus for most management needs, the usefulness of bat-monitoring techniques depends on the possibility to determine to species/genus. We compared the discrimination performances of 4 statistical methods applied to identify bat species from their ultrasonic echolocation calls. In 3 different areas of northern Italy, we made recordings of 20 species of bat (60% of those occurring in Italy), 17 from the family Vespertilionidae and 3 from Rhinolophidae. Calls of bats identified to species level from morphological and genetic characters were time-expanded and recorded on release. We measured 7 variables from each call, and we developed classification models through both conventional tests (multiple discriminant analysis and cluster analysis) that were based on a classical statistical approach, and through 2 nonconventional classifiers (classification and regression trees, and neural networks) that relied on generalization and fuzzy reasoning. We compared the performance of the 4 techniques using the percentage of cases classified correctly in 5 classification trials at various taxonomic levels that were characterized by an increasingly difficult identification task: (1) family level (Rhinolophidae vs. Vespertilionidae), (2) species level within genus Rhinolophus, (3) genus level within Vespertilionidae, (4) species level within genus Myotis, and (5) all species. Multiple discriminant function analysis (DFA) correctly classified marginally more cases than artificial neural networks (ANN; 74–100% against 64–100%), especially at the species level (trial 4, species of genus Myotis; trial 5, all species). Both these techniques performed better than cluster analysis or classification and regression trees, the latter reaching only 56 and 41% in Myotis species and all species trials. Artificial neural networks do not yet seem to offer a major advantage over conventional multivariate methods (e.g., DFA) for identifying bat species from their ultrasonic echolocation calls.

Species Richness and Habitat Use of Small Carnivores in the Arusha National Park (Tanzania)

The carnivore community of Arusha National Park, Tanzania, was monitored using live trapping and diurnal and nocturnal visual counts and recording of tracks and signs along line transects. Nine carnivore species were recorded. Hyena (Crocuta crocuta), the most common large species, leopard (Panthera pardus) and African civet (Civettictis civetta) were detected along line transects, while the smaller species were counted and/or captured. Mungos mungo, Galerella sanguinea, and Genetta maculata were the most prevalent at transect counts, while G. sanguinea, Bdeogale crassicauda, and G. maculata were most frequently captured. Ichneumia albicauda and Ictonyx striatus were captured at only a single site. Carnivores selected natural habitat types, multilayered forest, open shrubs and herbaceous savannah, and were absent, or tended to avoid disturbed (man-made) habitats. Species of which sufficient data were gathered seemed to behave as habitat generalists (C. crocuta, G. sanguinea, G. maculata, M. mungo and I. striatus). The need for more detailed studies on small carnivore ecology and the importance of smaller protected areas for their conservation are discussed.

From mass of body elements to fish biomass: a direct method to quantify food intake of fish eating birds

The winter diet of great crested grebe (Podiceps cristatus) was studied in the major lakes of Insubria region, N Italy, in 2000–2003 by analysing stomach and oesophagus contents of birds found dead. Winter diet of cormorant (Phalacrocorax carbo) was studied using pellet analysis. Diet was expressed in terms of numerical abundance, frequency and biomass of prey. A detailed methodology is described of how to prepare a reference collection of otoliths, pharyngeal bones and chewing pads (key-elements), essential for species-specific identification of fish remains in stomachs and pellets, and to estimate ingested fish biomass. Correlations between mass (mg) of key-elements and mass of corresponding fish were significant, and exponential regression models were used to calculate biomass of each single prey item directly from the mass of its key-elements. Advantages of this method are compared with the more traditional two step approach in which size of elements is used to estimate fish length, followed by calculating fresh mass from fish length. Cyprinids formed the largest part of the diet for both predators. Great crested grebes selected small prey, feeding mainly on bleak (Alburnus alburnus alborella), while diet composition of cormorants varied significantly in relation to prey availability.

Estimating and comparing food availability for tree-seed predators in typical pulsed-resource systems: alpine conifer forests.

Abstract Alpine conifers produce pulsed resources for the community of tree‐seed consumers. Here, we describe field and statistical methods to estimate spatio‐temporal variation in seed‐crops in forests with different species composition. Annual and between‐site variation in seed production was high and characterised by occurrence of mast‐crops followed by seed‐crop failure the following year. Seed‐crops of different species did not fluctuate in parallel. Abbreviations: DLSM, differences of least square means; CED, Cedrasco; OGA, Oga; VAL, Valfurva; BOR, Bormio; RHE, Rhemes; COG, Cogne

Living on the Edge: Can Eurasian Red Squirrels (Sciurus vulgaris) Persist in Extreme High-elevation Habitats?

Abstract Studying intraspecific spatiotemporal variation in vital rates among populations over a range of environmental conditions is essential to reveal intrinsic and extrinsic factors affecting population dynamics. Mammal populations living at higher elevations often have higher adult survival, shorter breeding seasons, and lower reproductive output per season than at lower elevations. We studied dynamics of a Eurasian red squirrel (Sciurus vulgaris) population in high-elevation, mountain pine (Pinus mugo) forest with extreme winters, in the Central Italian Alps, and compared vital rates with populations in more productive habitats at lower elevations. Average density was 0.14 ± 0.07 squirrels ha−1 (range 0.07–0.30 ha−1), and numbers typically increased in summer–autumn as a result of seasonal reproduction and immigration. Mean persistence time was only 12.5 months, and there was a nearly complete population turnover in only two years. Local survival and recruitment rate were correlated with seasonal population growth rate, and partial effect of survival explained 80% of variation in growth rate. While reproductive rate in mountain pine habitat was more similar than in more productive habitats at lower elevations, density and autumn–winter survival were much lower. Thus, red squirrels did not show the adaptations observed in several other mammal species, but might invest heavily in early reproduction to compensate for short life expectancy.

The Extent of Great Crested Grebe Predation on Bleak in Lake Como, Italy

Abstract Food intake (fish biomass), during the winters of 1997-98 and 1998-99, by Great Crested Grebes (Podiceps cristatus) on a 47 km2 area of the western basin of Lake Como, North Italy, was estimated by analyzing recognizable remains of the fish prey in the stomach contents of birds found dead. Using the size of otoliths and pharyngeal bones, we showed that grebes mainly ate the younger age-classes (2-yr. old and younger) of Bleak (Alburnus alburnus), 80% of all fish prey. Monthly rates of Bleak consumption by wintering grebes were estimated by multiplying daily food intake, extrapolated from the relationship between food biomass intake and water temperature in the different winter months, with the proportion of Bleak in the diet and with the number of wintering grebes present each month. Great Crested Grebes were most numerous in the study area in January-February and there were no significant differences in numbers between the two winters. Size of Bleak eaten increased from November to February and the biomass of Bleak consumed was highest at the end of winter, when water temperature was lowest. Overall in the western basin, grebes consumed between 640 kg (conservative estimate) and 1,000 kg (maximum estimate) of Bleak per winter, which corresponded to 10% to 20% of the annual commercial Bleak harvest in that area. We suggest that grebe predation on Bleak might increase the mortality rates in the younger age-classes of the fish, and thus contribute to a decrease in the stock, but that economic impact of grebe predation on gross annual income from the local fishery is negligible.

Preventing species invasion: A role for integrative taxonomy?

Integrative taxonomy, a multi-disciplinary approach adding modern techniques to traditional morphology-based methods (e.g. molecular and morphological criteria), can play an important role in bioinvasion research to identify introduced taxa, discover pathways of introduction and inform authorities to control and prevent future introductions. The present study is the first on introduced populations of Callosciurus, Asiatic tree squirrels, known as potentially invasive species in Europe (Italy, Belgium and France). We combined molecular (mitochondrial DNA markers: CoxI, D-loop) and morphometric analysis on skulls, comparing them to the widest morphological and molecular datasets ever assembled for Callosciurus. Squirrels collected in Italy and Belgium share the same haplotypes and skull characteristics, but are conspicuously different from the French population in Antibes. Genetic data revealed close similarity between French squirrels and Pallass squirrels, Callosciurus erythraeus, from Taiwan, China. Italian and Belgian squirrels formed an independent taxonomic lineage in genetic analyses, whose taxonomic rank needs further investigation. The morphological and morphometric characteristics of these 2 populations are, however, similar to known specimens assigned to Callosciurus erythraeus. These results may indicate a common origin for the populations found in Belgium and Italy. In contrast, French specimens suggest an independent introduction event of squirrels originating from Asia.

Space use patterns of mountain hare (Lepus timidus) on the Alps.

Populations on the limits of species’ distribution can show different behavioral adaptations to strong ecological pressure than in the central part of the range. We investigated space use patterns of alpine mountain hare (Lepus timidus) at two areas on the southern edge of the species’ range. We monitored 34 hares between 2005 and 2008, estimating home range size, overlap, and site fidelity, and compared our results with space use in Scottish and North-European populations. Home ranges of mountain hares did not differ between two study areas with different habitat types. Subadult animals used larger ranges than adults and both age groups reduced home range size in autumn, a period that might be critical for hares due to changes in diet and/or high energy expenditure during the previous breeding season. Home ranges in these alpine populations were smaller than in Scandinavian populations but within the range of populations in different habitat types in Scotland. Seasonal home ranges overlapped considerably, but differed among the sexes: male–female overlap was higher than same sex (male–male and female–female) spatial overlap. Seasonal shifts of home ranges were small, and site fidelity remained high over the seasons, suggesting that resource distribution remained constant throughout the year and that the knowledge of an intensively frequented area is an important element of habitat quality. We concluded that habitat structure and availability of mates interact in affecting mountain hare space use in alpine habitats.

Poor Parasite Community of an Invasive Alien Species: Macroparasites of Pallas's Squirrel in Italy

The aim of the present study was to investigate the macroparasite fauna of Pallass squirrel, Callosciurus erythraeus, native to SE Asia, recently introduced to Italy and co-occurring with the native Eurasian red squirrel Sciurus vulgaris. A total of 161 Pallass squirrels harboured a poor macroparasite fauna, characterized by two main ectoparasite species, the flea Ceratophyllus (M.) sciurorum sciurorum (prevalence 50%, mean intensity 1.0 ± 0.1) and the tick Ixodes ricinus (prevalence 47%, mean intensity 3.0 ± 0.7), and a few helminths (Rodentoxyuris sciuri, Trichuris muris, Strongyloides callosciureus) all with prevalence below 10%. All parasites, except S. callosciureus, are native to Europe and were acquired in the invaded range. The loss of native parasites might have contributed to their successful invasion. The acquisition of local parasites C. sciurorum and Trichuris sciuri, and the introduction of the Asiatic nematode S. callosciureus may lead to spill-back and spill-over processes towards red squirrels.