Roberta Chirichella

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.

Mast seeding in deciduous forests of the northern Apennines (Italy) and its influence on wild boar population dynamics

ContextPulsed food resources may strongly affect the population dynamics of several consumer species, with consequences on the ecosystem. One of the most common pulsed resources is forest mast seeding.AimsWe analysed mast seeding in deciduous forests in a mountainous area of northern Apennines and its effect on population dynamics of wild boar (Sus scrofa L.).MethodsWe performed a quantitative, 20-year analysis on annual seed production in Turkey oak (Quercus cerris L.), beech (Fagus sylvatica L.) and chestnut (Castanea sativa Mill.) forest stands using litter traps. The wild boar population density was estimated by means of drive censuses and hunting bag records. The role of other biotic (density of predators) and abiotic (climate) factors potentially affecting wild boar mortality was also investigated.ResultsTurkey oak and chestnut showed high levels of seed production, whereas lower levels were found in beech. The pulsed resources of chestnut and Turkey oak positively affected piglet density. Analyses also highlighted the influence of snow cover and wolves on wild boar population dynamics.ConclusionWild boar can be considered a pulse rate species, the management of which can be improved by annual monitoring of seed production.

Contrasting Life Histories in Neighbouring Populations of a Large Mammal

Background A fundamental life history question is how individuals should allocate resources to reproduction optimally over time (reproductive allocation). The reproductive restraint hypothesis predicts that reproductive effort (RE; the allocation of resources to current reproduction) should peak at prime-age, whilst the terminal investment hypothesis predicts that individuals should continue to invest more resources in reproduction throughout life, owing to an ever-decreasing residual reproductive value. There is evidence supporting both hypotheses in the scientific literature. Methodology/Principal Findings We used an uncommonly large, 38 year dataset on Alpine chamois (Rupicapra rupicapra) shot at various times during the rutting period to test these two hypotheses. We assumed that body mass loss in rutting males was strongly related to RE and, using a process-based approach, modelled how male relative mass loss rates varied with age. For different regions of our study area, we provide evidence consistent with different hypotheses for reproductive allocation. In sites where RE declined in older age, this appears to be strongly linked to declining body condition in old males. In this species, terminal investment may only occur in areas with lower rates of body mass senescence. Conclusions/Significance Our results show that patterns of reproductive allocation may be more plastic than previously thought. It appears that there is a continuum from downturns in RE at old age to terminal investment that can be manifest, even across adjacent populations. Our work identifies uncertainty in the relationship between reproductive restraint and a lack of competitive ability in older life (driven by body mass senescence); both could explain a decline in RE in old age and may be hard to disentangle in empirical data. We discuss a number of environmental and anthropogenic factors which could influence reproductive life histories, underlining that life history patterns should not be generalised across different populations.

Intraseasonal Variation in Reproductive Effort: Young Males Finish Last

Age-dependent reproductive timing has been observed in females of a number of species; older females often breed earlier in the season and experience higher reproductive success as a result. However, to date, evidence for within-season variation in reproductive effort (RE) for males has been relatively weak. Males are expected to time RE in light of intraseasonal variations in the availability of receptive females and competition with other males. Young males, which are typically smaller and less experienced, might benefit from breeding later in the season, when male-male competition is less intense. Using a long-term data set of Alpine chamois Rupicapra rupicapra, we sought to evaluate the hypothesis that younger males allocate highest RE late in the breeding season, at a time when older male RE has decreased substantially. Our results support this hypothesis, which suggests that intraseasonal variation in RE may be an adaptive life-history trait for males as well as females.

Environmental change and long-term body mass declines in an alpine mammal

No abstract

Ecological drivers of group size in female Alpine chamois, Rupicapra rupicapra

Abstract In large mammalian herbivores, an increase in herd size not only reduces predation risk but also energy intake. As a consequence, the size of the groups made up by herbivores is often assumed to be the outcome of a trade-off depending on local predation risk and food availability. We studied Alpine chamois (Rupicapra rupicapra) group size in a 3660 ha wide area (central-Eastern Alps, Italy) where mouflon (Ovis gmelinii) were also present. We walked seven hiking trails (spanning a total of 33.9 km) in a high-elevation environment every 15 days from May to October in 2007–2009, and located all the groups of free-ranging ungulates within our study site. We analyzed the size variation in female groups with kids of Alpine chamois in relation to (i) forage availability (as estimated using the normalized difference vegetation index); (ii) distance from safe areas; (iii) presence of potential competitor species (i.e., mouflon); and (iv) environmental variables (elevation, slope exposure). We found that forage availability was one of the most important drivers of group size patterns. Larger groups were found in meadows with higher productivity, whereas smaller groups were located in lower quality meadows in sheltered areas, indicating how the female group size may be the outcome of both resource availability and predation risk avoidance. Interestingly, proximity of a mouflon group was able to modify the size of Alpine chamois female groups, especially if the nearest mouflon group was concurrently close and inclusive of a higher percentage of rams.

Ecological factors affecting eruption timing of mandibular teeth in roe deer

Increasing evidence suggests that conditions in early life have important consequences for body size and fitness in mammals. As regards herbivores, teeth play a central role in the long-term performance of individuals. So far, however, patterns of teeth eruption have been scarcely investigated in relation to environmental and climatic factors experienced by herbivores. We described the eruption timing of mandibular teeth in a population of roe deer (Capreolus capreolus) located in the Apennines (Central Italy), through the analysis of 2161 jaws of fawns (1176 females and 985 males) shot in their first winter of life over three hunting seasons (2013–2015). Results showed that the percentage of juveniles exhibiting permanent teeth depends on the cohort. Among the factors that may affect both incisiviform and molariform teeth replacement timing, our findings include body mass and population density. Additional factors determining the relative speed of teeth replacement are (1) food availability for the mother during the last part of gestation, the birth period and the lactation, (2) winter temperature experienced by the mother, and (3) temperature experienced by fawns during their first summer and autumn. Besides, for the first time in literature, elevation was reported to delay front teeth replacement. A greater number of climatic factors were found to shape the eruption timing of the third molar (M3) in comparison to that of incisiviform teeth. Also, a different pattern was found in males and females. The eruption of M3 is, indeed, a costly and long-lasting process requesting optimal nutritional conditions and the meeting of a threshold jaw size. Our results indicate a strong correlation between environmental conditions and eruption process, i.e., between resource availability during the gestation and rearing periods and eruption timing.

Climate, tree masting and spatial behaviour in wild boar (Sus scrofa L.): insight from a long-term study

Key messageClimate factors affect seed biomass production which in turn influences autumn wild boar spatial behaviour. Adaptive management strategies require an understanding of both masting and its influence on the behaviour of pulsed resource consumers like wild boar.ContextPulsed resources ecosystem could be strongly affected by climate. Disantangling the role of climate on mast seeding allow to understand a seed consumer spatial behaviour to design proper wildlife and forest management strategies.AimsWe investigated the relationship between mast seeding and climatic variables and we evaluated the influence of mast seeding on wild boar home range dynamics.MethodsWe analysed mast seeding as seed biomass production of three broadleaf tree species (Fagus sylvatica L., Quercus cerris L., Castanea sativa Mill.) in the northern Apennines. Next, we explored which climatic variables affected tree masting patterns and finally we tested the effect of both climate and seed biomass production on wild boar home range size.ResultsSeed biomass production is partially regulated by climate; high precipitation in spring of the current year positively affects seed biomass production while summer precipitation of previous year has an opposite effect. Wild boar home range size is negatively correlated to seed biomass production, and the climate only partially contributes to determine wild boar spatial behaviour.ConclusionClimate factors influence mast seeding, and the negative correlation between wild boar home range and mast seeding should be taken into account for designing integrated, proactive hunting management.

Capercaillie, Tetrao urogallus, monitoring in Adamello Brenta Natural Park: experimentation of new methodologies

In Adamello Brenta Natural Park (Western Trentino - Italy) a long-term study on galliformes started in 2007: its first phase regards Capercaille. The project was based on the experimentation of a methodology useful for a detailed monitoring of the species distribution during breeding period. Through a phonometer, a study for determining the sensibility of Capercaille towards human related noises was also set up.