Quantifying marine reservoir effect variability along the Northwest Coast of North America

Recognition of marine reservoir effect (MRE) spatial and temporal variability must be accounted for in any radiocarbon-based paleoclimate, geomorphological, or archaeological reconstruction in a coastal setting. ΔR values from 37 shell-wood pairs across southern Southeast Alaska provide a robust local evaluation of the MRE, reporting a local Early Holocene weighted ΔR average of 265 ± 205, with a significantly higher ΔR average of 410 ± 60 for samples near limestone karst. Integration with our synthesis of extant MRE calibrations for the Northwest Coast of North America suggests that despite local variability, regional ΔR averages echo proxies for coastal upwelling: regional weighted averages were at their highest in the Bølling-Allerød interstade (575 ± 165) and their lowest in the Younger Dryas stade (−55 ± 110). Weighted ΔR averages across the Northwest Coast rose to a Holocene high during the Early Holocene warm period (245 ± 200) before settling into a stable Holocene average ΔR of 145 ± 165, which persisted until the late Holocene. Our quantification of local and regional shifts in the MRE shines a light on present methodological issues involved in MRE corrections in mixed-feeder, diet-based calibrations of archaeological and paleontological specimens.

Seasonal dietary changes increase the abundances of savanna herbivore species

African savannas are home to the world’s last great megafaunal communities, but despite ongoing population declines, we only poorly understand the constraints on savanna herbivore abundances. Seasonal diet shifts (except migration) have received little attention, despite a diversity of possible dietary strategies. Here, we first formulate two theoretical models that predict that both mixed feeding and migratory grazing increase population sizes. These predictions are borne out in comprehensive data across African savanna parks: Mixed feeders are the most abundant herbivores in Africa, alongside a few migratory grazer populations. Overall, clear mixed-feeder dominance may reflect a historical pattern or may instead mirror a general global decline in specialists. Regardless, mixed feeders dominate the savannas of the present and future.

Habitat use by a mixed feeder: impala Aepyceros melampus in a heterogeneous protected area

Although large herbivore habitat use has been extensively studied, more information is still required on the use of heterogeneous vegetation types. Over 3 y we carried out monthly road transects in the Zambezi National Park (ZNP), Zimbabwe, to determine the impala density in each of five vegetation types. In addition we determined grass and browse chemical composition to test if at the time the impala switches from grass to browse, grass nutritive quality had declined below that of browse. Furthermore, grass height was measured in the five vegetation types. The impala used mixed, acacia and terminalia vegetation types, which constituted 37% of the protected area and avoided grassland and the predominant Zambezi teak (60% of ZNP) vegetation types. At the time of the diet switch by the impala from grass to browse, woody plant leaf nutritive quality was higher than grass in terms of nitrogen, calcium and acid detergent fibre content. The three vegetation types used by the impala had short to medium grass height. We concluded that when the impala switched from grass to browse the grass nutritive quality was lower than that of the browse.

Diet and habitat of unique individuals of Dinohippus mexicanus and Neohipparion eurystyle (Equidae) from the late Hemphillian (Hh3) of Guanajuato and Jalisco, central Mexico: stable isotope studies

Stable carbon and oxygen isotopes were determined in molar enamel from fossil Pliocene equids from Rancho El Ocote in the San Miguel Allende basin, Guanajuato, and from Santa María, Tecolotlán basin, Jalisco. At each locality, the source was one molar from an individual Dinohippus mexicanus and one molar from an individual Neohipparion eurystyle. Results indicated that the N. eurystyle individuals from both localities had been C3/C4 mixed feeders, and had lived in open-zone vegetation (δ13C: -3.1‰ to -1.3‰; δ18O: -4.9‰ to -6.4‰). On the other hand, the D. mexicanus from Rancho El Ocote had fed upon C4 plants and lived in open zones (δ13C: -1.3‰; δ18O: -4.9‰), whereas the D. mexicanus from Santa María was a C3/C4 mixed feeder with considerable consumption of C3 plants (δ13C: -7.7‰; δ18O: -6.4‰). These results could be contrast to suggestions from previous isotopic work that D. mexicanus in Mexico predominantly fed on C4 plants and further samples analyses are warranted. This study contributes to the understanding of the Pliocene equid taxa from central Mexico and emphasizes the presence of different diets, ranging from exclusive C4 to mixed C3/C4 plants.

Differing influences of resource availability on the demographics and habitat selection of wildebeest compared with impala

Although what drives the abundance and habitat selection of ungulates is a long-standing question, coherent datasets investigating the influences of rainfall, competition and fire on ungulates are unusual. Over 4 y we carried out extensive monthly road transects in Ithala Game Reserve, South Africa, to determine the demographics and habitat occupancy of the region's prevalent grazer (wildebeest) and mixed-feeder (impala). Habitat occupancy was determined using a GIS-based approach. We obtained 8742 sighting records, encompassing 8400 wildebeest and 10071 impala. Annual rainfall did not significantly correlate with population sizes of either species. Fecundity of wildebeest, but not of impala, showed a significant positive relationship with rainfall specifically over the perinatal period (November–December), whilst no significant relationships were found for either species between fecundity and rainfall over the previous year, 2 y, rut (February–April) or height of the dry season (June–August). Impala unexpectedly favoured browse habitats to grassland year round, probably consequent on competition for grass with wildebeest. Dry-season grass flushes attracted both wildebeest and impala. The study emphasized how rainfall, competition and fire regimes may affect differently grazers compared with mixed-feeders.

Dietary innovations spurred the diversification of ruminants during the Caenozoic

Global climate shifts and ecological flexibility are two major factors that may affect rates of speciation and extinction across clades. Here, we connect past climate to changes in diet and diversification dynamics of ruminant mammals. Using novel versions of Multi-State Speciation and Extinction models, we explore the most likely scenarios for evolutionary transitions among diets in this clade and ask whether ruminant lineages with different feeding styles (browsing, grazing and mixed feeding) underwent differential rates of diversification concomitant with global temperature change. The best model of trait change had transitions from browsers to grazers via mixed feeding, with appreciable rates of transition to and from grazing and mixed feeding. Diversification rates in mixed-feeder and grazer lineages tracked the palaeotemperature curve, exhibiting higher rates during the Miocene thermal maxima. The origination of facultative mixed diet and grazing states may have triggered two adaptive radiations—one during the Oligocene–Miocene transition and the other during Middle-to-Late Miocene. Our estimate of mixed diets for basal lineages of both bovids and cervids is congruent with fossil evidence, while the reconstruction of browser ancestors for some impoverished clades—Giraffidae and Tragulidae—is not. Our results offer model-based neontological support to previous palaeontological findings and fossil-based hypothesis highlighting the importance of dietary innovations—especially mixed feeding—in the success of ruminants during the Neogene.

Food item selection of Hanuman Langur (Presbytes entellus) in different season in Char-Koshe jungle of eastern Terai, Nepal

Common langur was found to be a mixed feeder. 33 species of plants were found to be consumed and 16 more species were said to be consumed in that locality. Most of the plants were consumed during fruiting and flowering seasons. Most preferred (frequently used) plants were Terminalia belarica, Geruga pinnata, Spathalobus parviflora, Ficus bengalensis, Schlichera oleosa, Ficus glomerata, Diospyrus tomentosa, Terminalia tomentosa, Emblica officinalis etc. On the basis of time spent to consume, fruit and seed comprised of about 56%, flower, leaf-bud, young leaves 29%, and mature leaves, bark and petiole 15% of annual budget of diet. Amount of different items in different seasons vary according to availability of first item (fruits and flower) and second items (new growths and leaf-bud). Fruits constitute more than 83% of diet during month of monsoon. Insectivory was not observed except during grooming. The langurs were not reported to raid the crops in vicinity. DOI: http://dx.doi.org/10.3126/njbs.v1i0.7476 Nepalese Journal of Biosciences 1: 96-103 (2011)