A new method for assessing food quality in common vole (Microtus arvalis) populations

Abstract

Food quality is an important factor influencing the demography of small rodents. While there have been numerous studies on food supply during small mammal population cycles, studies on quality of food consumed are rare due to technical difficulties in estimating nitrogen in small samples, such as stomachs or faeces. In this study, we use a new method, near infrared reflectance spectroscopy (NIRS), for estimating nitrogenous compounds (NC) in stomachs of common voles (Microtus arvalis). Samples were taken from two populations over two 3-year periods. Vegetation cover (managed alfalfa/set-aside field), and thus also food supply, differed significantly between the two periods. In analysing the effects of food supply and individual attributes (i.e. sex, body size, reproduction) on NC in stomachs, we were able to show that nitrogen varied uniformly and that sex, body size and season had no effect. No significant difference in NC intake was observed between the two study periods, despite individuals being smaller and the population less abundant during the second period. During the peak densities, however, reproducing females consumed food with a significantly higher level of nitrogen than all other individuals. Our results indicate that changes in food supply do not affect the overall quality of food consumed but that maintenance of nutritional quality may require higher energetic release, which may affect body condition. We confirm that NIRS represents a useful new tool opening new possibilities in small-mammal ecology studies.

Losing seasonal patterns in a hibernating omnivore? Diet quality proxies and faecal cortisol metabolites in brown bears in areas with and without artificial feeding

“…Seasonal and spatial variations of FN are found in wild large herbivore populations, with values peaking in spring in response to higher digestibility and protein content in growing vegetation [ 10 – 12 ]. A similar pattern has been observed in primates [ 13 , 14 ] and rodents [ 15 , 16 ], and several free-ranging omnivore species [ 17 ]. The percentage of nitrogen content in faeces represents the protein content of the food consumed, and, thus, it is considered as a biomarker for diet quality and shifts in diet composition [ 7 , 8 , 13 , 18 ], while faecal carbon (FC) indicates changes in energy consumption and shifts in energy intake from digested food items [ 7 ].…”

Relevance of body weight effects for the population development of common voles and its significance in regulatory risk assessment of pesticides in the European Union

“…The common vole (Microtus arvalis) is one of the best studied small mammals in Europe, inhabiting agricultural landscapes [3,[5][6][7], but the relevance of body weight for their survival and reproduction has not been specifically analysed. For such purpose, field studies provide very useful information when body weights are taken and the fate of individuals can be followed.…”

The pygmy field mouse – what does influence food quality?

“…Twenty independent stomach samples were used for calibration validation and verification. For further details on calibration and verification, see Janova et al (2015) and Cepelka et al (2017). Food quality was expressed as the percentage of total NC (NC = N*6.25) in total stomach content dry matter (according to AOAC, 1990).…”

“…For this, infrared reflectance spectroscopy (NIRS) was used. This method was originally developed and validated for the estimation of nitrogen content (NC) in rodent stomachs (Cepelka et al 2014, Janova et al 2015.…”