New data on fish diet and bone digestion of the Eurasian otter (Lutra lutra) (Mammalia: Mustelidae) in central France

Abstract

Fish remains are abundant and easily recognizable in many archaeological sites. The origin of such assemblages is generally poorly known. The ability to create small fish bone accumulations is restricted to a small number of predators (including raptors, carnivores and humans). In order to recognize the agents responsible for these concentrations in archaeological sites, we have investigated the taphonomy of the fish remains from otter spraints to determine the potential role of the Eurasian otter, Lutra lutra, in the formation of fossil assemblages as a piscivorous mammal. Currently, few data are available to characterize the accumulation of otter remains in natural or archaeological sites. We analyzed a collection of 29 otter spraints from Bugeat (Corrèze) in central France. We identified the remains of eight fish species: brown trout (Salmo trutta, Salmonidae), perch (Perca fluviatilis, Percidae), pumpkinseed (Lepomis gibbosus, Centrarchidae), and several Cyprinidae, rudd (Scardinius erythrophthalmus), minnow (Phoxinus phoxinus), bullhead (Cottus gobio), and the indeterminate pair chub/ dace (Squalius cephalus/Leuciscus leuciscus). The species and the body parts present, along with the reconstruction of the fish weight and observations of any modifications, such as deformation, rounding and polishing, give us insight into otter prey categories and their transformation after digestion. Among the ca. 200 bones constituting the whole fish skeleton, only between six and 39 bones survived depending on the different species. Cyprinids display a high-moderate digestion grade and seem to be the taxon most affected by digestion (64.67%). Based on surface modifications, such as breakage and digestion traces, as well as bone element representation, we produced a set of criteria as a new tool to be applied to the fossil record.

Taphonomic signature of Eurasian eagle owl (Bubo bubo) on fish remains

“…Five categories of digestion were distinguished: null (0); light (1); moderate (2); heavy (3); and extreme (4-5). For fish bones, the digestion degrees have been illustrated in Guillaud et al (2017). The action of gastric juices results in a smooth and polished surface (Andrews 1990); and although the prolonged transportation of bones in water can also produce this result, only digestion could have caused these effects in our study.…”

“…Prey sizes were estimated by direct comparison with specimens from the osteological reference collection of the MNHN. Following the methodology used in a previous study (Guillaud et al 2017), surface modification was classified following Nicholson (1991). The percentage of visible surface was adapted from Villa & Mahieu (1991).…”

Review of the Actualistic Taphonomy of Small Mammals Ingested by South American Predators. Its Importance in the Interpretation of the Fossil Record

“…There are numerous papers on actualistic studies for the northern hemisphere; thus, there is currently a fairly broad picture of the modifications that different predators produce on the bones of small mammals (e.g., Andrews, 1990; Fernández-Jalvo and Andrews, 1992;Laudet and Selva, 2005;Lloveras et al, 2008;Esteban-Nadal et al, 2010;Denys, 2011;Souttou et al, 2012;Fernández-Jalvo et al, 2016;Campmas et al, 2018;Denys et al, 2018;Royer et al, 2019). Samples of small fish, amphibians, reptiles and birds were only occasionally evaluated; in those cases, an alternative methodology was used to better fit the morphology of the bones of these microvertebrates (Bochenski et al, 1993(Bochenski et al, , 2009Bochenski and Tomek, 1994;Pinto Llona and Andrews, 1999;Castillo et al, 2001;Bochenski and Tornberg, 2003;Bochenski, 2005;Broughton et al, 2006;Bailon, 2011;Russ and Jones, 2011;Guillaud et al, 2017). Andrews (1990) and Fernández-Jalvo and Andrews (1992) suggested that the most relevant criterion to distinguish the effects produced during predation on small mammal bones is the evaluation of the modifications of their surface caused by the digestive acids of the predator.…”

DNA metabarcoding-based diet survey for the Eurasian otter (Lutra lutra): Development of a Eurasian otter-specific blocking oligonucleotide for 12S rRNA gene sequencing for vertebrates

“…The otters’ feces (spraints) are useful for their diet analyses [3, 4, 6] and individual identification [7, 8]. Morphological observation of undigested food remains, such as bones, shells, and hair, in spraints provides information regarding the otters’ diets [3, 6]. Previous studies reported fishes as the otters’ main preys followed by amphibians, crabs, birds, and insects [3, 4].…”