Feeding ecology and habitat preferences of top predators from two Miocene carnivore-rich assemblages

Abstract

Carnivore-rich fossil sites are uncommon in the fossil record and, accordingly, provide valuable opportunities to study predators from vantages that are rarely applied to ancient faunas. Through stable isotopes of carbon and a Bayesian mixing model, we analyze time-successive (nearly contemporaneous), late Miocene carnivoran populations from two fossil sites (Batallones-1 and Batallones-3) from central Spain. Stable isotopes of carbon in tooth enamel provide a reliable and direct methodology to track ancient diets. These two carnivoran-dominated fossil sites display differences in the composition and abundance of the carnivoran species, with some species present at both sites and some present only at one site. This disparity has been interpreted as the consequence of habitat differences between Batallones-1, the older site, and Batallones-3, the younger site. However, carbon isotope values of carnivore and herbivore tooth enamel suggest a common habitat of C3 woodland originally present at both sites. The differences in the carnivoran faunas rather may be the consequence of the dynamics of species entrance and exit from the Madrid Basin during the time elapsed between Batallones-1 and Batallones-3 and changes in population densities due to biotic factors. We infer higher levels of interspecific competition in Batallones-3 than in Batallones-1 because of the larger number of similar-sized, sympatric predators; the clear overlap in their δ13C values (except for the amphicyonid Magericyon anceps); and similarity of their preferred prey: the hipparionine horses. Finally, carbon stable isotopic composition of Indarctos arctoides teeth implies that this ursid was a carnivorous omnivore rather than a herbivorous omnivore. This work demonstrates the insights that stable isotopes can provide in characterizing the feeding ecology and trophic interactions of ancient carnivoran taxa.

Carnivoran resource and habitat use in the context of a Late Miocene faunal turnover episode

“…In the case of BAT, we have included the ursid Indarctos arctoides in the predator analysis since M. S. Domingo et al . () observed that the tooth enamel δ 13 C offset between BAT‐3 Indarctos and BAT‐3 herbivore (i.e. Δδ 13 C Indarctos ‐herbivore ) was −1.42‰, comparable to the tooth enamel Δδ 13 C carnivore–herbivore of value −1.3‰, determined by Clementz et al .…”

“…This is supported by statistical tests that reveal no differences in their isotopic values when comparing BAT sites (Domingo, M. S. et al . ). These fossil sites show subtle differences in age (0.30 myr at most, with BAT‐10 being the oldest and BAT‐3 the youngest) as evidenced by micro‐mammal biochronology (López‐Antoñanzas et al .…”

“…hipparionine horses) make it feasible to perform a valid predator dietary analysis (Domingo, M. S. et al . ). Carbon and oxygen isotope composition on the carbonate fraction of 63 carnivore tooth enamel samples and 46 herbivore tooth enamel samples from BAT were analysed, including six carnivore species and eight herbivore species (four small to medium‐sized species and four large species) (Table ; Domingo, L. et al .…”

“…Based on this result, M. S. Domingo et al . () concluded that BAT‐3 Indarctos arctoides would have been a carnivorous omnivore ursid that incorporated a significant proportion of meat to its diet and therefore, a plausible competitor for the rest of carnivore taxa from this fossil assemblage. Although the Late Miocene Indarctos has no modern counterpart, by analogy with modern ursids (Bocherens et al .…”

Application of artificially intelligent systems for the identification of discrete fossiliferous levels

“…Full-size  DOI: 10.7717/peerj.8767/ fig-1 Palaeoecological, palaeoenvironmental and taphonomical studies carried out at Batallones Butte (Antón & Morales, 2000;Domingo et al, 2011Domingo et al, , 2013aDomingo et al, , 2013bDomingo et al, , 2016 have treated the upper and lower part of the hourglass-shaped cavities separately based on their different depth and their different taxonomical composition (herbivores vs. carnivores, respectively). Due to the challenges posed by the structure of the deposits that filled the Batallones Butte cavities, such as lateral facies changes, deformations, depositional asymmetries, collapse structures, slickensides and/or local tilting typical of cave deposits (Calvo et al, 2013), geological sub-levels have not been identified within each of these parts.…”