Anonymous fecal sampling and NIRS studies of diet quality: Problem or opportunity?

Abstract

Investigating the drivers of diet quality is a key issue in wildlife ecology and conservation. Fecal near infrared reflectance spectroscopy (f‐NIRS) is widely used to assess dietary quality since it allows for noninvasive, rapid, and low‐cost analysis of nutrients. Samples for f‐NIRS can be collected and analyzed with or without knowledge of animal identities. While anonymous sampling allows to reduce the costs of individual identification, as it neither requires physical captures nor DNA genotyping, it neglects the potential effects of individual variation. As a consequence, regression models fitted to investigate the drivers of dietary quality may suffer severe issues of pseudoreplication. I investigated the relationship between crude protein and ecological predictors at different time periods to assess the level of individual heterogeneity in diet quality of 22 marked chamois Rupicapra rupicapra monitored over 2 years. Models with and without individual grouping effect were fitted to simulate identifiable and anonymous fecal sampling, and model estimates were compared to evaluate the consequences of anonymizing data collection and analysis. The variance explained by the individual random effect and the value of diet repeatability varied with seasons and peaked in winter. Despite the occurrence of individual variation in dietary quality, ecological parameter estimates under identifiable or anonymous sampling were consistently similar. This study suggests that anonymous fecal sampling may provide robust estimates of the relationship between dietary quality and ecological correlates. However, since the level of individual heterogeneity in dietary quality may vary with species‐ or study‐specific features, inconsequential pseudoreplication should not be assumed in other taxa. When individual differences are known to be inconsequential, anonymous sampling allows to optimize the trade‐off between sampling intensity and representativeness. When pseudoreplication is consequential, however, no conclusive remedy exists to effectively resolve nonindependence.

Season‐dependent impact of forage quality on stress in alpine chamois

“…Anderwald et al, 2021 ). Additionally, in Alpine environments, forage quality in the winter months is generally ubiquitously poor, and the little variation in crude protein observed in our study site in this period (see Corlatti, 2020 ), reduces the possibility to detect significant relationships. When compared to the results of Anderwald et al ( 2021 ), unknown ecological differences between study sites might contribute to explaining the contrasting patterns in the summer months.…”

“…The percentage of CP was determined by near‐infrared reflectance spectroscopy (NIRS): first, about 20 g of wet samples were homogenized, dried, and ground with a grinder A11 basic (Ika, Staufen, Germany). A subsample ( n = 86, see Corlatti, Bassano, et al, 2013 ) was chemically analyzed for calibration to establish a standard reference for physical analysis (Nehring, 1960 ); the remaining samples were then analyzed using an FT‐NIR Spectrometer MPA and validated based on calibration values (details in Corlatti, 2020 ). FCM concentrations were analyzed with an 11‐oxoetiocholanolone enzyme immunoassay (EIA) measuring metabolites with a 5ß‐3α‐hydroxy‐11‐oxo structure (Möstl et al, 2002 ; validated for chamois: Anderwald et al, 2021 ), in 0.5 g of homogenized fecal samples, extracted and mixed with 5 mL of aqueous methanol (80%), shaken and then centrifuged (Palme et al, 2013 ).…”

“…), while data from GPS collars provided the elevation (in meters a.s.l.) of the day before feces collection (Corlatti, 2020 ).…”

The Application of NIRS to Determine Animal Physiological Traits for Wildlife Management and Conservation

“…Pseudoreplication is a process whereby samples from the same individual are treated as independent data points. Models from these data can be very good at predicting traits from the individuals used for model development but may be limited in their ability to predict the same traits from other individuals [116]. A number of studies utilizing NIRS to determine traits from wildlife have had extensive pseudoreplication in their datasets [10,82].…”

Are they both the same shit? Winter faeces of roe and red deer show no difference in nutritional components

“…The nutritional quality of the feed ingested determines wild ungulate populations' performance and well-being, which is, at the same time, essential for maintaining healthy forest habitats (Parker et al 1999(Parker et al , 2009Christianson, Creel 2007;Felton et al 2017). Understanding the ungulates' feeding behaviour and the drivers of diet selection regarding nu-tritional quality, chemical defence, and availability has been of high interest to scientists (Naiman 1988;Hodgman et al 1996;Barboza et al 2009;Lambert, Rothman 2015;Corlatti 2020) but is often overlooked during management and conservation decision-making (Morgan et al 2021). After Raymond (1948) and Lancester (1949) described how the or-https://doi.org/10.17221/19/2023-JFS ganic matter digestibility of pasture could be calculated from the nitrogen content of the faeces, the use of faecal nitrogen (fN) as a research proxy has been extensively applied in ecological research, and especially in studies related to the nutrition of wild ruminants (Putman 1984;Leslie Jr, Starkey 1987;Osborn, Jenks 1998;Dryden 2003;Leslie Jr et al 2008).…”