Higher δ15N values in bone collagen of mammoth (Mammuthus primigenius) compared with coeval large herbivores is a classic trait of the mammoth steppe. An exception applies to the Epigravettian site of Mezhyrich (ca. 18–17.4 ka cal BP) in the central East European plains, where mammoth bones have δ15N values equivalent to or in a lower range than those of horse specimens (Equus sp.). We expanded our preliminary dataset to a larger sampling size of mammoth, other large herbivores, and carnivores from contemporaneous and nearby sites of Buzhanka 2, Eliseevichi, and Yudinovo. The unusual low mammoth δ15N values were confirmed at Buzhanka 2 and for some specimens from Eliseevichi, while most individuals from Yudinovo displayed the expected high δ15N values, meaning similar to those of the large canids. The possibility of a contrast in migration pattern is not supported since the δ34S values, a marker of mobility, do not correlate with the δ15N values of mammoth bone collagen. No clear chronological tendency could be revealed, at least not at the scale of radiocarbon dating. The low range in δ15N values is likely to reflect a change in the specific niche of the mammoth in the southern part of its distribution.

Understanding the dietary needs of syntopic species is essential for examining species coexistence and resource partitioning. We analysed stable isotopes of carbon (δ13C) and nitrogen (δ15N) to estimate the diet of two putative nectarivorous bats on Puerto Rico, the brown flower bat (Erophylla bombifrons) and the Greater Antillean long-tongued bat (Monophyllus redmani). Isotopic ratios of δ13C and δ15N were obtained from whole blood of both species of bat and tissues of available plant foods and insect prey over 15 wk at the same locality. We used a concentration-dependent Bayesian mixing model to determine probability distributions of feasible dietary contributions for major potential foods used by each species of bat. Additionally, separate dietary estimates were conducted for males and non-reproductive, pregnant and lactating females to determine differences due to reproductive condition. Insects were an important source of protein for M. redmani, whereas E. bombifrons obtained most of its protein from plants. In both species of bat, lactating females had lower assimilated nitrogen than males, suggesting more reliance on plants for protein. We observed no intraspecific differences in assimilated carbon among reproductive conditions. Flight and lactation are energetically expensive and may explain the increased consumption of high-energy foods, such as fruit or nectar, in lactating female bats. Comparison of isotopes between E. bombifrons and M. redmani illustrate the differential use of food resources by these insular syntopic species of bat.

Fractionation of N isotopes occurs in many metabolic reactions which causes tissue proteins to become enriched in 15N while urea (urine) is depleted in 15N relative to the diet. We investigated 15N enrichment of whole plasma and its relationship with feed conversion efficiency (FCE) in growing beef heifers (n 84) offered 2 kg/d of concentrates with grass silage ad libitum. Heifers were on average 299 (sd 48·3) d old and weighed 311 (sd 48·8) kg. Plasma was obtained on day 79 (n 84) of the experiment and from a subset of animals (n 20) on four occasions between days 16 and 79. Silage DM intake (DMI) averaged 4·1 (sd 0·74) kg/d and concentrate DMI was 1·72 kg/d. Mean mid-test live weight was 333 (sd 47·6) kg, daily gain was 0·53 (sd 0·183) kg, FCE (g live-weight gain/g DMI) was 0·09 (sd 0·028) and residual feed intake (RFI) was 0 (sd 0·428). N isotopic fractionation (Δ15N; plasma δ15N − diet δ15N) averaged 3·58 ‰ on day 79 (n 84) and 3·90 ‰ for the subset of heifers. There was no relationship between Δ15N and RFI. Plasma δ15N and Δ15N were related to both FCE (negative) and animal weight (positive) for the whole population, and repeatable for the subset of animals over four time points. These relationships of Δ15N with FCE and animal weight are consistent with the anticipated negative relationship with N-use efficiency. There is potential to use Δ15N to provide rapid, low-cost estimates of FCE in cattle.

Only a small proportion of the marine nutrients brought ashore by breeding colonial seabirds is retained in colony soils. However, means by which these marine nutrients can be dispersed to the wider terrestrial ecosystem have rarely been identified. In this study, moulted feathers from Hemiphaga novaeseelandiae (an endemic pigeon; n=9) and Gallirallus australis (an endemic flightless rail; n=3) and from a Procellaria westlandica (Westland petrel) colony were analysed for 13C and 15N enrichment. Potential diet items from both the colony and a control location were also analysed, and their contributions to the diets of H. novaeseelandiae and G. australis calculated. Hemiphaga novaeseelandiae assimilated marine N but not marine C, and showed a wide range in the significance of different diet sources. Food for most H. novaeseelandiae came from within the colony, implying minimal transport of marine nutrients to the wider terrestrial environment. All G. australis food came from within the colony, but 29–39% was from petrel tissue, or invertebrates feeding on petrel material. Thus, both H. novaeseelandiae and G. australis assimilated nutrients brought ashore by P. westlandica, but neither was shown to disperse the nutrients much beyond the petrel colony. However, birds that are now locally extinct may have dispersed marine nutrients more widely. Future research should focus on the consequences of restoring these species to petrel colonies as part of attempts to re-establish the functioning of pre-human ecosystems in New Zealand.