Mixed Feeders Research Articles

Discovery of the skull ofStephanorhinus kirchbergensis(Jäger, 1839) above the Arctic Circle

AbstractThe skull of the extinct rhinocerosStephanorhinus kirchbergensis(Jäger, 1839) was discovered in the Chondon River valley (Arctic Yakutia, Russia) during the summer of 2014. This is the first find ofStephanorhinusabove the Arctic Circle, expanding significantly the known geographic range of the genus.14C dating and geologic evidence indicate that the skull dates to between 48,000 and 70,000 yr, corresponding to Marine Oxygen Isotope Stage 4/3. It is thus among the latest records of this species. To explore the evolutionary and natural history of this relatively unknown animal, we performed morphological, dietary, and genetic analyses. Phylogenetic inference based on a complete mitochondrial genome sequence confirms the systematic placement ofStephanorhinusas most closely related to the extinct woolly rhinoceros,Coelodonta. Food remains in the fossas of the cheek teeth, identified asLarix,Vaccinium,Betulasp.,Aulacomnium, and dicotyledonous herbs and grasses, suggest a mixed feeder’s diet. Microwear analysis suggests that, during the last months of its life, this individual fed predominantly on leaves and twigs. The habitat ofStephanorhinuscomprised grassland and open woodland that were characterized by moist and cold climate conditions, similar to those in the region today.

From the epipelagic zone to the abyss: Trophic structure at two seamounts in the subtropical and tropical Eastern Atlantic - Part II Benthopelagic fishes

Specific mechanisms, driving trophic interactions between seamount associated fishes and the pelagic community may be highly variable in different seamount systems. This study investigated the trophic structure and the main prey of benthopelagic fishes from the summit and slope regions of Ampère and Senghor, two shallow seamounts in the subtropical and tropical NE Atlantic, and the adjacent deep-sea plains. For the identification of food sources and nutritional links to the pelagic realm a combination of stomach content and stable isotope ratio (δ13C and δ15N) analyses was used. δ13C ranged from −22.2‰ to −15.4‰ and δ15N covered a total range of 8.0–15.9‰. Feeding types of fish species comprised mainly zooplanktivores and mixed feeders, but also benthivores, piscivores, and predator-scavengers. Based on epipelagic particulate organic matter, they occupied trophic positions between the 2nd and 4th trophic level. Differences in stomach contents and stable isotope signatures indicate a resource partitioning among the benthopelagic fish fauna through distinct habitat choice, vertical feeding positions and prey selection. Topographic trapping of vertically migrating zooplankton on the summit seemed to be of minor importance for food supply of the resident near-bottom fishes, rather horizontal current-driven advection of the planktonic prey was assumed as major factor. Vertically migrating micronekton and mesopelagic fishes show up as key players within the food webs at Ampère and Senghor Seamounts and the adjacent deep-sea plains.

Stable isotopes reveal diet shift from pre-extinction to reintroduced Przewalski\u2019s horses

The Przewalski’s horse (Equus ferus przewalskii), the only remaining wild horse within the equid family, is one of only a handful of species worldwide that went extinct in the wild, was saved by captive breeding, and has been successfully returned to the wild. However, concerns remain that after multiple generations in captivity the ecology of the Przewalski’s horse and / or the ecological conditions in its former range have changed in a way compromising the species’ long term survival. We analyzed stable isotope chronologies from tail hair of pre-extinction and reintroduced Przewalski’s horses from the Dzungarian Gobi and detected a clear difference in the isotopic dietary composition. The direction of the dietary shift from being a mixed feeder in winter and a grazer in summer in the past, to a year-round grazer nowadays, is best explained by a release from human hunting pressure. A changed, positive societal attitude towards the species allows reintroduced Przewalski’s horses to utilize the scarce, grass-dominated pastures of the Gobi alongside local people and their livestock whereas their historic conspecifics were forced into less productive habitats dominated by browse.

Dental microwear and Pliocene paleocommunity ecology of bovids, primates, rodents, and suids at Kanapoi

Reconstructions of habitat at sites like Kanapoi are key to understanding the environmental circumstances in which hominins evolved during the early Pliocene. While Australopithecus anamensis shows evidence of terrestrial bipedality traditionally associated with a more open setting, its enamel has low δ13C values consistent with consumption of C3 foods, which predominate in wooded areas of tropical Africa. Habitat proxies, ranging from paleosols and their carbonates to associated herbivore fauna and their carbon isotope ratios, suggest a heterogeneous setting with both grass and woody plant components, though the proportions of each have been difficult to pin down. Here we bring dental microwear texture analysis of herbivorous fauna to bear on the issue. We present texture data for fossil bovids, primates, rodents, and suids (n = 107 individuals in total) from the hominin bearing deposits at Kanapoi, and interpret these in the light of closely related extant mammals with known differences in diet. The Kanapoi bovid results, for example, are similar to those for extant variable grazers or graze-browse intermediate taxa. The Kanapoi suid data vary by taxon, with one similar to the pattern of extant grazers and the other more closely resembling mixed feeders. The Kanapoi primates and rodents are more difficult to associate with a specific environment, though it seems that grass was likely a component in the diets of both. All taxa evince microwear texture patterns consistent with a mosaic of discrete microhabitats or a heterogeneous setting including both tree and grass components.

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.

Influence of cattle on browsing and grazing wildlife varies with rainfall and presence of megaherbivores.

In many savanna ecosystems worldwide, livestock share the landscape and its resources with wildlife. The nature of interactions between livestock and wildlife is a subject of considerable interest and speculation, yet little controlled experimental research has been carried out. Since 1995, we have been manipulating the presence and absence of cattle and large mammalian herbivore wildlife in a Kenyan savanna in order to better understand how different herbivore guilds influence habitat use by specific wildlife species. Using dung counts as a relative assay of herbivore use of the different experimental plots, we found that cattle had a range of effects, mostly negative, on common mesoherbivore species, including both grazers and mixed feeders, but did not have significant effects on megaherbivores. The effect of cattle on most of the mesoherbivore species was contingent on both the presence of megaherbivores and rainfall. In the absence of megaherbivores, wild mesoherbivore dung density was 36% lower in plots that they shared with cattle than in plots they used exclusively, whereas in the presence of megaherbivores, wild mesoherbivore dung density was only 9% lower in plots shared with cattle than plots used exclusively. Cattle appeared to have a positive effect on habitat use by zebra (a grazer) and steinbuck (a browser) during wetter periods of the year but a negative effect during drier periods. Plots to which cattle had access had lower grass and forb cover than plots from which they were excluded, while plots to which megaherbivores had access had more grass cover but less forb cover. Grass cover was positively correlated with zebra and oryx dung density while forb cover was positively correlated with eland dung density. Overall these results suggest that interactions between livestock and wildlife are contingent on rainfall and herbivore assemblage and represent a more richly nuanced set of interactions than the longstanding assertion that cattle simply compete with (grazing) wildlife. Specifically, rainfall and megaherbivores seemed to moderate the negative effects of cattle on some mesoherbivore species. Even if cattle tend to reduce wildlife use of the landscape, managing simultaneously for livestock production (at moderate levels) and biodiversity conservation is possible.

Anatomy of the tongue and microstructure of the lingual papillae in the fallow deer Dama dama (Linnaeus, 1758)

The function of mouth organs in ruminants is connected with the process of rumination. To study morphofunctional relations, microstructures in tongues of 4- to 5-year old adult fallow deer were examined using scanning electron microscopy.When analyzing the tongue of the fallow deer, i.e. a ruminant classified as an intermediate mixed feeder between grass and roughage eaters, two processes were taken into account: (i) foraging and forage selecting, and (ii) chewing the cud during rumination to reduce particle size and improve digestibility.Microstructural results show that the above mentioned processes in fallow deer are important selection factors, which in the anterior part of tongue led to the development of clusters of fungiform papillae connected with preselection of food as well as a specific pattern of filiform papillae promoting increased adhesion of transported food. Massive and flattened conical papillae on the torus are arranged according to sideways jaw movements and are co-localized with flattened fungiform papillae and two rows of vallate papillae. Such an arrangement of papillae on the lingual torus presumably facilities distribution of ruminated food, with simultaneous transferring of taste signals about masticated food particles.

Effects of Feeder Cells on Dopaminergic Differentiation of Human Embryonic Stem Cells.

Mouse embryonic fibroblasts (MEFs) and human foreskin fibroblasts (HFFs) are used for the culture of human embryonic stem cells (hESCs). MEFs and HFFs differed in their capacity to support the proliferation and pluripotency of hESCs and could affect cardiac differentiation potential of hESCs. The aim of this study was to evaluate the effect of MEFs and HFFs feeders on dopaminergic differentiation of hESCs lines. To minimize the impact of culture condition variation, two hESCs lines were cultured on mixed feeder cells (MFCs, MEFs: HFFs = 1:1) and HFFs feeder, respectively, and then were differentiated into dopaminergic (DA) neurons under the identical protocol. Dopaminergic differentiation was evaluated by immunocytochemistry, quantitative fluorescent real-time PCR, transmission and scanning electron microscopy, and patch clamp. Our results demonstrated that these hESCs-derived neurons were genuine and functional DA neurons. However, compared to hESCs line on MFCs feeder, hESCs line on HFFs feeder had a higher proportion of tyrosine hydroxylase (TH) positive cells and expressed higher levels of FOXA2, PITX3, NURR1, and TH genes. In addition, the values of threshold intensity and threshold membrane potential of DA neurons from hESCs line on HFFs feeder were lower than those of DA neurons from hESCs line on the MFCs feeder. In conclusion, HFFs feeder not only facilitated the differentiation of hESCs cells into dopaminergic neurons, but also induced hESCs-derived DA neurons to express higher electrophysiological excitability. Therefore, feeder cells could affect not only dopaminergic differentiation potential of different hESCs lines, but also electrophysiological properties of hESCs-derived DA neurons.

Foraging Behaviour of Damage-causing Birds in Table Grape Vineyards in the Orange River Valley, South Africa

The foraging behaviour of damage-causing birds in table grape vineyards was examined in the Orange River valley, Northern Cape Province, South Africa during the summer harvest season from November 2001 to January 2002. Based on a sample of 300 foraging acts observed, it was found that mixed-feeder species fed more on grapes during the first month of the harvest (November), when only about 13% of the vineyards bore ripe grapes, than during the subsequent two months (December and January). During the latter two months, insects were a more preferred food item, while grape foraging declined significantly despite the increased availability of grapes, suggesting a shift in their dietary preferences during the course of the harvesting season. A daily bimodal feeding pattern was also detected, with birds feeding more regularly on grapes and other food items from early to late morning and in the late afternoon, with a marked decrease during midday. There was also a preference for feeding from the top rather than from the side or bottom of bunches. There were clear differences in foraging strategies among the most commonly recorded species when these were not feeding on grapes. Mixed feeders fed on invertebrates by gleaning vine bark and foliage, hawking, or foraging in ground litter. Granivorous species generally foraged for plant matter, such as seeds, on the ground, but also foraged on grapes during the early stages of the harvest season (November).

Sequential stable isotope analysis reveals differences in multi-year dietary history of three sympatric equid species in SW Mongolia.

Summary Competition among sympatric wild herbivores is reduced by different physiological, morphological and behavioural traits resulting in different dietary niches. Wild equids are a rather uniform group of large herbivores which have dramatically declined in numbers and range. Correlative evidence suggests that pasture competition with livestock is one of the key factors for this decline, and the situation may be aggravated in areas where different equid species overlap.The Dzungarian Gobi is currently the only place where two wild equid species coexist and share the range with the domesticated form of a third equid species. In the winter‐cold Gobi desert pasture productivity is low, highly seasonal, and wild equids additionally face increasing livestock densities.We used stable isotope chronologies of tail hairs to draw inferences about multi‐year diet seasonality, isotopic dietary niches and physiological adaptations in the Asiatic wild ass (khulan), re‐introduced Przewalski's horse, and domestic horse in the Mongolian part of the Dzungarian Gobi.Our results showed that even in the arid Gobi, both horse species are predominantly grazers, whereas khulan are highly seasonal, switching from being grazers in summer to mixed feeders in winter. The isotopic dietary niches of the two horse species were almost identical, did not vary with season as in khulan and were narrower than in the latter. Higher δ15N values point towards higher water use efficiency in khulan, which may be one reason why they can exploit pastures further away from water. Synthesis and applications. The high degree of isotopic dietary niche overlap in the two horse species in the Mongolian Gobi points towards a high potential for pasture competition during the critical nutritional bottleneck in winter and highlights the need to severely restrict grazing of domestic horses on the range of the Przewalski's horses. The evolutionary more distant khulan are less constrained by water and seem more flexible in their choice of diet or less successful in exploiting grass‐dominated habitats in winter due to human presence. Providing additional water sources could increase the competition between khulan and livestock and should, therefore, only be done following careful consideration.

Supplemental nutrients increase the consumption of chemically defended shrubs by free-ranging herbivores

Large herbivores are purported to continue consuming toxin-containing forages as long as their capacity to neutralize, detoxify and excrete dietary toxins is not exceeded. This capacity depends on the availability of liver enzymes, energy and amino acid precursors. While this may explain increased intake of toxin-rich forages by herbivores supplemented with nutrients, a different effect may emerge in rangelands dominated by forages that are rich in condensed tannins which are not as degradable and readily absorbable as toxins. In a field experiment, we investigated the effects of supplementing animals with a high-energy source (yellow maize grain) and a high-protein source (soybean meal) on browse intake, foraging behaviour and diet composition of goats in a semi-arid savanna. In line with our prediction, nutrient supplementation increased the percentage time spent by goats on browsing and subsequently enhanced browse intake. Supplemented goats consumed more condensed tannins than goats that were not supplemented. Goats from supplemented groups tended to compose different diets from goats that received no supplement. Supplementation may have modified animals’ requirements for nutrients in ways that influenced feeding behaviour. We contend that supplements likely replaced the nutrients that are routinely bound and rendered indigestible by condensed tannins and thus increased the intake of tannin-rich forages through delaying a negative post-ingestive feedback (aversion) from dietary tannins. In conclusion, we showed that nutrient supplementation can be used to increase defoliation of tannin-rich shrubs by mixed feeders which suggests a potential for browsers and mixed-feeders to serve as biological bush control agents. Furthermore, these results have serious implication for herbivores and the environment.

The Longevity of the Magnet Effect: Fire-Herbivory Interactions in Central Kenya

The coexistence of grass and trees that typifies savanna ecosystems is maintained in part by top-down forces including herbivory and fire. Understanding fire-herbivore interactions is an integral step in determining the effect of these forces individually and informs decisions about the use of fire as a livestock management technique. The magnet effect, in which grazers are drawn to an area after it is burned, is one such interaction between fire and herbivores. While the process of the magnet effect has been described, neither its longevity nor the manner through which fire intensity affects its strength is understood. In this study, we explored whether the increase in herbivory pressure predicted by the magnet effect is maintained over long periods after a fire, how fire intensity influences the strength of the magnet effect, and which feeder types are most influenced by the magnet effect. We established five field sites at the Mpala Research Centre in Laikipia, Kenya that ranged in fire intensity and elapsed time since last the burn. We found that the magnet effect is transient on a seven-year scale and affects grazers more than browsers or mixed feeders, though herbivory and grass biomass responses to fire intensity were conflicting. This research clarifies the role of the magnet effect in maintaining savanna ecosystems and can aid agriculturalists seeking to use fire as a management technique by indicating how long after a burn increased palatability of grass can be expected. Author’s Note The authors completed this research while studying in Columbia and Princeton’s joint program in Tropical Biology and Sustainability in Kenya. We would like to thank Dr. Carla Staver for her helpful comments on earlier versions of this manuscript. We would also like to thank Josphat Mwangi, Agnes Wachu, and the rest of the staff at the Mpala Research Centre, all of whom were so kind to us during our stay with them.

Spiny plants, mammal browsers, and the origin of African savannas

Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils.

Are cattle surrogate wildlife? Savanna plant community composition explained by total herbivory more than herbivore type.

The widespread replacement of wild ungulate herbivores by domestic livestock in African savannas is composed of two interrelated phenomena: (1) loss or reduction in numbers of individual wildlife species or guilds and (2) addition of livestock to the system. Each can have important implications for plant community dynamics. Yet very few studies have experimentally addressed the individual, combined, and potentially interactive effects of wild vs. domestic herbivore species on herbaceous plant communities within a single system. Additionally, there is little information about whether, and in which contexts, livestock might functionally replace native herbivore wildlife or, alternatively, have fundamentally different effects on plant species composition. The Kenya Long-term Exclosure Experiment, which has been running since 1995, is composed of six treatment combinations of mega-herbivores, meso-herbivore ungulate wildlife, and cattle. We sampled herbaceous vegetation 25 times between 1999 and 2013. We used partial redundancy analysis and linear mixed models to assess effects of herbivore treatments on overall plant community composition and key plant species. Plant communities in the six different herbivore treatments shifted directionally over time and diverged from each other substantially by 2013. Plant community composition was strongly related (R2 =0.92) to residual plant biomass, a measure of herbivore utilization. Addition of any single herbivore type (cattle, wildlife, or mega-herbivores) caused a shift in plant community composition that was proportional to its removal of plant biomass. These results suggest that overall herbivory pressure, rather than herbivore type or complex interactions among different herbivore types, was the main driver of changes in plant community composition. Individual plant species, however, did respond most strongly to either wild ungulates or cattle. Although these results suggest considerable functional similarity between a suite of native wild herbivores (which included grazers, browsers, and mixed feeders) and cattle (mostly grazers) with respect to understory plant community composition, responses of individual plant species demonstrate that at the plant-population-level impacts of a single livestock species are not functionally identical to those of a diverse group of native herbivores.

Dietary flexibility and niche partitioning of large herbivores through the Pleistocene of Britain

Abstract Tooth wear analysis techniques (mesowear and microwear) are employed to analyze dietary traits in proboscideans, perissodactyls and artiodactyls from 33 Pleistocene localities in Britain. The objectives of this study are to examine the variability in each taxon, to track dietary shifts through time, and to investigate resource partitioning among species. The integration of mesowear and microwear results first allowed us to examine dietary variability. We identified differences in variability among species, from more stenotopic species such as Capreolus capreolus to more eurytopic species such as Megaloceros giganteus and Cervus elaphus . Broad dietary shifts at the community level are seen between climatic phases, and are the result of species turnover as well as dietary shifts in the more flexible species. The species present at each locality are generally spread over a large part of the dietary spectrum, and resource partitioning was identified at most of these localities. Mixed feeders always coexist with at least one of the two strict dietary groups, grazers or browsers. Finally, for some species, a discrepancy is observed between meso- and microwear signals and may imply that individuals tended to die at a time of year when their normal food was in short supply.

Paleoecological reconstruction of hominin-bearing middle Pliocene localities at Woranso-Mille, Ethiopia

Woranso-Mille is a paleoanthropological site in Ethiopia sampling an important and under-represented time period in human evolution (3.8–3.6 million years ago). Specimens of cf. Australopithecus anamensis, Australopithecus afarensis, and the recently named Australopithecus deyiremeda have been recovered from this site. Using multiple habitat proxies, this study provides a paleoecological reconstruction of two fossiliferous collection areas from Woranso-Mille, Aralee Issie (ARI) and Mesgid Dora (MSD). Previous reconstructions based on faunal assemblages have pointed, due to the presence of aepycerotins, alcelaphins, and proboscideans, to the existence of open habitats as well as more closed ones, based on the occurrence of cercopithecids, giraffids, and traglephins. Results from community structure analysis (proportions of locomotor and dietary adaptations) at ARI and MSD indicated a predominance of open habitats, such as shrublands. Mesowear analysis revealed that ungulates of all dietary types (grazers, leaf and fruit browsers, and mixed feeders) were present in nearly equal proportions. Ecomorphological analyses using linear measurements of the astragalus and phalanges indicated that bovids utilizing locomotor behaviors associated with all habitat types were present, though the intermediate-cover habitat bovids were best represented in the sample (Heavy cover at ARI and Light cover at MSD). Together, these results suggest that the ARI and MSD localities were heterogeneous habitats (mosaics), likely with densely vegetated areas along a paleo-river and more open regions (woodlands, grasslands) available away from the river.

Preliminary data on the diet and habitat preferences ofCapromeryx mexicana(Mammalia: Antilocapridae) from the late Pleistocene of Cedral, San Luis Potosí, Mexico

Abstract We inferred the diet and habitat preferences of three individuals of the dwarf pronghorn Capromeryx mexicana from Cedral, Mexico, using stable isotope analysis and the mesowear method. Both approaches showed that the individuals were C3/C4 mixed feeders which inhabited open forest. These results differ from previous hypotheses that suggested this species only fed on grasses and lived in grasslands.

Diet of the Four-horned Antelope Tetracerus quadricornis (De Blainville, 1816) in the Churia Hills of Nepal

The food composition of the Four-horned Antelope Tetracerus quadricornis was studied in the Churia Hills of Nepal during summer, monsoon and the winter seasons of 2012–2013. Microhistological technique was used to determine the diet. The Four-horned Antelope was found to be a mixed feeder feeding on trees, shrubs, forbs, grasses and climbers. Trees and shrubs contribute the major percentage of diet in all the three seasons. The Gramineae family is consumed in highest proportion. Mitragyna parvifolia, Bridelia retusa, Bambusa vulgaris, Hymenodictyon sp. and Ziziphus mauritiana are major tree species while Barleria cristata, Pogostemon benghalensis, Achyranthes sp., Clerodendrum viscosum are among shrubs. Ageratum conyzoides and Blumea virens are the main forbs Eulaliopsis binata and Imperata cylindrica are the principal grass species. Climber Trachelospermum lucidum is consumed in a small proportion. Grasses in monsoon were consumed distinctly at a higher percentage than during the other two seasons. The Four-horned Antelopes are concentrated feeders and browsers with a generalized feeding strategy. Similar studies need to be conducted in other landscapes and with sympatric and potential competitor species to understand its niche overlaps and degree of competition.

Incorporating secondary metabolites, tannin-binding proteins, and diet breadth into carrying-capacity models for African elephants

Elephant populations have been historically difficult to manage and have sometimes been subjected to drastic management procedures. One way to monitor elephant populations to estimate a sustainable carrying capacity is through the use of standing-crop carrying-capacity models. Previous carrying-capacity models designed for grazers have posed issues when applied to browsers such as elephants, predicting much higher carrying-capacity estimates than are realized in nature. This might be attributed to the level of plant secondary metabolites, which limit the available nitrogen in browse material that browsers and mixed feeders encounter while foraging. Many browsers and mixed-feeders, including elephants, have a physiological mechanism to tolerate a portion of encountered tannins in the form of salivary tannin-binding proteins. We constructed an optimal-foraging model for carrying capacity for elephants that incorporates the negative effects of plant secondary metabolites and the partial neutralization of these chemicals by the tannin-binding affinity of elephant saliva. In addition, our model includes diet breadth and dietary contribution of browsed species, browse quality, and the available standing crop of browsed species. Ultimately, our model produced more plausible estimates of elephant carrying capacity when compared with estimates that use 100% nitrogen availability and use. Moreover, as the key variables needed for the model can be obtained easily, our model is not site-specific or limited to elephants, but rather can be applied to a wide range of browsing herbivores across a number of reserves of different sizes.

Diet and locomotion, but not body size, differentiate mammal communities in worldwide tropical ecosystems

AimTo test whether tropical habitat groups across the world can be differentiated by using taxon-free mammalian community structures and to discuss the implications of this analysis for palaeoecological community studies. Materials and methodsWe used mammalian community data for 169 localities, which were assigned a priori to hierarchical Olson (1983) vegetation categories. Species over 500g were classified into dietary, locomotion, and body mass groups and the resulting group structures were analysed using community structure analyses (NPMANOVA, CAP, SIMPER). ResultsThe test results show that the mammalian community structures are significantly different between all of Olson's categories. These differences are highest at Olson's major and minor ecosystem levels, and require the least number of variable categories. At the vegetation level, the number of variable categories required to distinguish between them becomes higher. Of the dietary groups, the number of frugivore–granivores, frugivore–omnivores, grazers and mixed feeders contribute most to these differences, while the number of arboreal, arboreal–terrestrial and subterranean–terrestrial species are the key locomotor groups. Body mass was not a good discriminator. Main conclusionsAs general ecosystem categories are broken down into more precisely defined habitats, it requires more detailed knowledge of the species adaptations to distinguish between them. Many of Olson's vegetation groups represent a continuum of cover that are, at least at the worldwide comparison, too detailed to differentiate when broad generalities are sought. We suggest using three worldwide tropical major ecosystems in mammalian community structure analyses: “Humid, closed forests”, “Seasonal or interrupted forests and grasslands”, and “Seasonal, open drylands”. Our results also demonstrate that community structures defined by both dietary and locomotor adaptations are powerful discriminators of tropical ecosystems and habitats across the continents we examined, but body mass should be interpreted with caution when the research question pertains to multiple continents.