Diet analysis of small mammal pests: A comparison of molecular and microhistological methods

Knowledge of what pest species are eating is important to determine their impact on stored food products and to plan management strategies accordingly.In this study,we investigated the food habits of 2 rodents,Rattus rat­tus(ship rat)and Mus musculus castaneus(house mouse)as well as an insectivore,Suncus murinus(shrew),present in human dwellings.Both a microhistological approach and a DNA barcoding approach were used in the present study.Following DNA extraction,amplification was performed using group-specific primers target­ing birds,plants and invertebrates.Resulting polymerase chain reaction products were sequenced and analyzed to identify the different prey species present in the gut contents.The findings from the application of both tech­niques were in agreement,but the detection of prey type with each technique was different.The DNA barcoding approach gave greater species-level identification when compared to the microhistological method,especially for the invertebrate and avian prey.Overall,with both techniques,23 prey taxa were identified in the gut con­tents of the 3 species,including 15 plants,7 insects and a single bird species.We conclude that with a selection of suitable“barcode genes”and optimization of polymerase chain reaction protocols,DNA barcoding can pro­vide more accurate and faster results.Prey detection from either technique alone can bias the dietary informa­tion.Hence,combining prey information of both microhistological analysis and DNA barcoding is recommend­ed to study pest diet,especially if the pest is an omnivore or insectivore species.

Positive effect of spring advance on the diet quality of an alpine herbivore

Changes in vegetation phenology related to global warming are having alarming effects on the life history traits of many herbivore species.Such changes are particularly critical in alpine ecosystems,where strong climate limitations on plant growth make seasonal synchronization imperative for the growth,reproduction and survival of herbivores.However,despite the pivotal role of resource-use strategies on the performances of such species,few studies have explicitly assessed the mechanistic impact of climate change on their diets.We aimed to fill this gap by studying the effect of spring onset on the dietary composition and quality of a medium-size alpine herbivore while considering density-dependent processes and age-and sex-specific differences in foraging behavior.Using an exceptional,long-term(24 years)direct individual-based dietary monitoring of a Pyrenean chamois population(Rupicapra pyrenaica pyrenaica),we showed that ongoing earlier onsets of spring are leading to an earlier access to high-quality forage and therefore a higher diet quality at a fixed date,without apparent changes in diet composition.We also showed that at high densities,intraspecific competition reduced diet quality by driving animals to feed more on woody plants and less on nutritious forbs and graminoids.By assessing the mechanistic effects of global warming on the dietary patterns of species at the center of trophic networks,this study is an essential step for predictive models aiming at understanding the ongoing ecosystem consequences of the global climatic crisis.