Prey selection by an apex predator : the importance of sampling uncertainty.

The impact of predation on prey populations has long been a focus of ecologists, but a firm understanding of the factors influencing prey selection, a key predictor of that impact, remains elusive. High levels of variability observed in prey selection may reflect true differences in the ecology of different communities but might also reflect a failure to deal adequately with uncertainties in the underlying data. Indeed, our review showed that less than 10% of studies of European wolf predation accounted for sampling uncertainty. Here, we relate annual variability in wolf diet to prey availability and examine temporal patterns in prey selection; in particular, we identify how considering uncertainty alters conclusions regarding prey selection. Over nine years, we collected 1,974 wolf scats and conducted drive censuses of ungulates in Alpe di Catenaia, Italy. We bootstrapped scat and census data within years to construct confidence intervals around estimates of prey use, availability and selection. Wolf diet was dominated by boar (61.5±3.90 [SE] % of biomass eaten) and roe deer (33.7±3.61%). Temporal patterns of prey densities revealed that the proportion of roe deer in wolf diet peaked when boar densities were low, not when roe deer densities were highest. Considering only the two dominant prey types, Manly's standardized selection index using all data across years indicated selection for boar (mean = 0.73±0.023). However, sampling error resulted in wide confidence intervals around estimates of prey selection. Thus, despite considerable variation in yearly estimates, confidence intervals for all years overlapped. Failing to consider such uncertainty could lead erroneously to the assumption of differences in prey selection among years. This study highlights the importance of considering temporal variation in relative prey availability and accounting for sampling uncertainty when interpreting the results of dietary studies

TORINO, Verso la strategia territoriale metropolitana

La ricerca costituisce un documento strategico e metodologico che individua le linee guida e fornisce alcuni elementi distintivi locali per avviare il percorso di elaborazione della strategia territoriale di medio-lungo periodo per l’area metropolitana torinese. Il lavoro è stato elaborato da un gruppo di ricerca coordinato da Gabriele Pasqui del DAStU del Politecnico di Milano e da Claudio Calvaresi dell’IRS ed è stato realizzato grazie al contributo del progetto europeo CityRegions, di cui l’Associazione è partner insieme alla Città di Torino

Degradation of starch-filled polyethylene films in a composting environment

Studies were made of the microbial degradation of a series of low density polyethylene films filled with different amount of starch in the range 0-40% by weight. Biodegradability was evaluated by three different procedures of exposure of test samples to microbial attack in which the samples were either maintained in active composting piles, or aerobically incubated in the liquid obtained by pressing the initial composting material, or treated in a minimal mineral medium inoculated with a thermophilic actinomycete isolated from samples retrieved from compost. Spectroscopic analysis and optical and electron scanning microscopy, as well as dynamic-mechanical properties, molecular weight, and weight loss of the retrieved samples were utilized for a semiquantitative evaluation of microbial attack. The results indicate that the composting microbial ecosystem seems to be the most efficient degradative environment among the three systems, although this conclusion may hold only for the polymer sample containing 40% starch

Degradation of starch filled polyethylene films in a composting environment

Studies were made of the microbial degradation of a series of low density polyethylene films filled with different amount of starch in the range 0-40% by weight. Biodegradability was evaluated by three different procedures of exposure of test samples to microbial attack in which the samples were either maintained in active composting piles, or aerobically incubated in the liquid obtained by pressing the initial composting material, or treated in a minimal mineral medium inoculated with a thermophilic actinomycete isolated from samples retrieved from compost. Spectroscopic analysis and optical and electron scanning microscopy, as well as dynamic-mechanical properties, molecular weight, and weight loss of the retrieved samples were utilized for a semiquantitative evaluation of microbial attack. The results indicate that the composting microbial ecosystem seems to be the most efficient degradative environment among the three systems, although this conclusion may hold only for the polymer sample containing 40% starch

Un progetto fattibile

Presentazione del progetto di assetto paesaggistico del Lambro Milanese e delle azioni di miglioramento. Il volume raccoglie sotto il titolo ReLambro i risultati dello studio di fattibilità finanziato da Fondazione Cariplo nel 2012 nell’ambito del piano di azione “promuovere la sostenibilità ambientale a livello locale. Realizzare la connessione ecologica”. Il titolo originale del progetto, “Gli spazi aperti e gli ambiti agronaturalistici, il fiume Lambro, l’area metropolitana milanese - esempio di attivazione di rete ecologica”, nel corso del lavoro è stato precisato e orientato a rappresentare il fiume come ritrovata infrastruttura ecologica della metropoli milanese. Il progetto è stato coordinato da ERSAF (Ente Regionale per i Servizi all’Agricoltura e alle Foreste di Regione Lombardia), ente capola, e sviluppato nel corso dei due anni successivi dalla partnership costituita dallo stesso ERSAF, dal DASTU (Dipartimento di Architettura e Studi Urbani) del Politecnico di Milano, che si è avvalso del supporto di IRS (Istituto di Ricerca Sociale), dal Comune di Milano, dal Parco Locale di Interesse Sovracomunale Media Valle Lambro e da Legambiente Lombardi

Prey Selection by an Apex Predator: The Importance of Sampling Uncertainty

The impact of predation on prey populations has long been a focus of ecologists, but a firm understanding of the factors influencing prey selection, a key predictor of that impact, remains elusive. High levels of variability observed in prey selection may reflect true differences in the ecology of different communities but might also reflect a failure to deal adequately with uncertainties in the underlying data. Indeed, our review showed that less than 10% of studies of European wolf predation accounted for sampling uncertainty. Here, we relate annual variability in wolf diet to prey availability and examine temporal patterns in prey selection; in particular, we identify how considering uncertainty alters conclusions regarding prey selection. Over nine years, we collected 1,974 wolf scats and conducted drive censuses of ungulates in Alpe di Catenaia, Italy. We bootstrapped scat and census data within years to construct confidence intervals around estimates of prey use, availability and selection. Wolf diet was dominated by boar (61.5±3.90 [SE] % of biomass eaten) and roe deer (33.7±3.61%). Temporal patterns of prey densities revealed that the proportion of roe deer in wolf diet peaked when boar densities were low, not when roe deer densities were highest. Considering only the two dominant prey types, Manly's standardized selection index using all data across years indicated selection for boar (mean = 0.73±0.023). However, sampling error resulted in wide confidence intervals around estimates of prey selection. Thus, despite considerable variation in yearly estimates, confidence intervals for all years overlapped. Failing to consider such uncertainty could lead erroneously to the assumption of differences in prey selection among years. This study highlights the importance of considering temporal variation in relative prey availability and accounting for sampling uncertainty when interpreting the results of dietary studies