Leaf trait?palatability relationships differ between ungulate species: evidence from cafeteria experiments using na?ve tussock grasses

Leaf functional traits have been proposed as general indicators of plant palatability to ungulate herbivores, identifying which species are likely to be most at risk from ungulates, and how ungulate grazing may change ecosystem processes. However, few studies have tested whether leaf trait?palatability relationships are consistent across different ungulate species. The palatability of 44 native New?Zealand grass taxa (from the genera Festuca and Chionochloa) to two ungulate herbivores (sheep Ovis aries and red deer Cervus elaphus scoticus) was assessed in cafeteria experiments. There were significant differences between sheep and deer in the selection or avoidance of grass taxa, in part related to differences in response to variation in leaf functional traits. Deer had a greater tendency than sheep to select grasses with a higher specific leaf area (SLA) and to avoid taxa with a low SLA, suggesting that it is not possible to generalise leaf trait?palatability relationships across different ungulate species. Results suggest different ungulate species are likely to have additive effects on the biodiversity and ecosystem functioning of New?Zealand?s native grasslands. These findings indicate that the impacts of ungulate herbivory on ecosystem processes will depend on which grass species are present.     

Paleoecological and Taphonomic Implications of Insect-Damaged Pleistocene Vertebrate Remains from Rancho La Brea,Southern California

The La Brea Tar Pits, the world’s richest and most important Late Pleistocene fossil locality, offers unsurpassed insights into southern California’s past environments. Recent studies at Rancho La Brea document that insects serve as sensitive and valuable paleoecological and taphonomic indicators. Of the thousands of fossil bird and mammal bones recovered from the Tar Pits, insect trace damage is thus far almost exclusively confined to the foot bones of large herbivores, especially bison, camel, and horse species. Our laboratory experiments with dermestid and tenebrionid beetles establish that the larvae of both consume bone, producing different characteristic feeding traces and providing the first documentation that tenebrionids consume bone. The presence of carcass-exploiting insects in the Rancho La Brea biota provides insight into the taphonomy of the asphaltic bone masses and the environmental conditions under which they accumulated. The succession of dermestids, tenebrionids, and indeterminate traces on many of the foot elements, combined with the climate restrictions and life cycles of these insects, indicate that carcasses could remain unsubmerged for at least 17–20 weeks, thus providing the most reliable estimate to date. Attribution of these traces also suggests that the asphaltic fossils only accumulated during warmer intervals of the Late Pleistocene. Forensic studies need to reevaluate the role of tenebrionids in carcass decomposition and other additional insects that modify bone.     

Traces d’impacts de projectiles sur le gibier : résultats comparés des tirs expérimentaux à l’arc et au propulseur effectués au Cedarc (Treignes, Belgique) en 2003 et 2004

In 2003 and 2004, two series of projectile experiments were organized by P. Cattelain and ourselves at the CEDARC/Musée du Malgré-Tout (Treignes, Belgium). The experiments involved the use of two male ox calves and two female fallow deers as targets for bow and spearthrower shooting. Our main focus was a functional analysis of the antler projectile tips from the Upper Magdalenian layer of the Isturitz cave site (Pyrénées-Atlantiques, France). The study of the impact traces on the bones of the target animals was also included in the project; its results are presented here. The observation of these 127 traces led us to reconsider the nomenclature suggested by P. Morel, and to distinguish between three major traces: notches, punctures and perforations. Correlations appear between the nature of the trace and the shape of the bone (e.g., scapulae strongly associated to perforations), and the bone's mineral content: compared to adult long bones, immature long bones are much more easily perforated by projectile points, which usually remain firmly caught in them. However, our results do not show a clear distinction between the impact traces left by the bow and by the spearthrower.     

Rewilding traditional grazing areas affects scavenger assemblages and carcass consumption patterns

The abandonment of traditional livestock farming systems in Mediterranean countries is triggering a large-scale habitat transformation, which, in general, consists of the replacement of open grazing areas by woodlands through non-managed regeneration. As a consequence, wild ungulates are occupying rapidly the empty niche left by domestic ungulates. Both types of ungulates represent the main trophic resource for large vertebrate scavengers. However, a comparison of how vertebrate scavengers consume ungulate carcasses in different habitats with different ungulate species composition is lacking. This knowledge is essential to forecast the possible consequences of the current farmland abandonment on scavenger species. Here, we compared the scavenging patterns of 24 wild and 24 domestic ungulate carcasses in a mountainous region of southern Spain monitored through camera trapping. Our results show that carcasses of domestic ungulates, which concentrate in large numbers in open pasturelands, were detected and consumed earlier than those of wild ungulate carcasses, which frequently occur in much lower densities at more heterogenous habitats such as shrublands and forest. Richness and abundance of scavengers were also higher at domestic ungulate carcasses in open habitats. Vultures, mainly griffons (Gyps fulvus), consumed most of the carcasses, although mammalian facultative scavengers, mainly wild boar (Sus scrofa) and red fox (Vulpes vulpes), also contributed importantly to the consumption of wild ungulate carcasses in areas with higher vegetation cover. Our findings evidence that the abandonment of traditional grazing may entail consequences for the scavenger community, which should be considered by ecologists and wildlife managers.     

Accumulations osseuses en périphérie de terriers de petits carnivores : les stigmates de prédation et de fréquentation

Faunal remains from spoil heaps of two burrows inhabited by small carnivores (fox and badger) are analysed from a taphonomical point of view. This analysis provides characteristics for bone accumulation produced by small carnivores and will be a powerful tool for deciphering site formation about the occupational alternation of small carnivores and humans. Identified species were grouped by size classes. Faunal spectrum is composed by varied species of microfauna (70%), mesofauna (30%). Macromammal remains are under represented (less than 1%) and come from scavenged carcasses. Predators and consumed species are compared on the basis of the skeletal part representation, age classes and recording of predation marks (gnawed and digested bones). Skeletal part representation shows that all taxons exhibit a low-representation of axial skeleton and autopodial bones. Predators show a high representation of hind limb bones and a low representation of the fore limb bones whereas consumed species exhibit a reverse pattern. Mortality curve analysis provides an attritional profile for carnivores and helps for the establishment of the season of occupation of the burrow. Adults largely dominate consumed species. Moreover, predation marks are found in 1% of the carnivores’ bones and from 15% to more than 40% on prey bones. The large-sized prey bones only wear gnawed marks (20%) and anthropic marks (10–20%) whereas microfaunal remains exhibits more digested marks (40%) than gnawing stigmata (5%). Medium-sized animals bones wear both marks and with the same proportions (10–15%).     

The “Bear” Essentials: Actualistic Research on Ursus arctos arctos in the Spanish Pyrenees and Its Implications for Paleontology and Archaeology

Neotaphonomic studies of large carnivores are used to create models in order to explain the formation of terrestrial vertebrate fossil faunas. The research reported here adds to the growing body of knowledge on the taphonomic consequences of large carnivore behavior in temperate habitats and has important implications for paleontology and archaeology. Using photo- and videotrap data, we were able to describe the consumption of 17 ungulate carcasses by wild brown bears (Ursus arctos arctos) ranging the Spanish Pyrenees. Further, we analyzed the taphonomic impact of these feeding bouts on the bones recovered from those carcasses. The general sequence of consumption that we charted starts with separation of a carcass’s trunk; viscera are generally eaten first, followed by musculature of the humerus and femur. Long limb bones are not broken open for marrow extraction. Bears did not transport carcasses or carcass parts from points of feeding and did not disperse bones appreciably (if at all) from their anatomical positions. The general pattern of damage that resulted from bear feeding includes fracturing, peeling, crenulation, tooth pitting and scoring of axial and girdle elements and furrowing of the upper long limb bones. As predicted from observational data, the taphonomic consequences of bear feeding resemble those of other non-durophagus carnivores, such as felids, and are distinct from those of durophagus carnivores, such as hyenids. Our results have paleontological and archaeological relevance. Specifically, they may prove useful in building analogical models for interpreting the formation of fossil faunas for which bears are suspected bone accumulators and/or modifiers. More generally, our comparative statistical analyses draw precise quantitative distinctions between bone damage patterns imparted respectively by durophagus (modelled here primarily by spotted hyenas [Crocuta crocuta] and wolves [Canis lupus]) and non-durophagus (modelled here by brown bears and lions [Panthera leo]) carnivorans.     

Indirect Short- and Long-Term Effects of Aboveground Invertebrate and Vertebrate Herbivores on Soil Microarthropod Communities

Recognition is growing that besides ungulates, small vertebrate and invertebrate herbivores are important drivers of grassland functioning. Even though soil microarthropods play key roles in several soil processes, effects of herbivores—especially those of smaller body size—on their communities are not well understood. Therefore, we progressively excluded large, medium and small vertebrate and invertebrate herbivores for three growing seasons using size-selective fences in two vegetation types in subalpine grasslands; short-grass and tall-grass vegetation generated by high and low historical levels of ungulate grazing. Herbivore exclusions generally had few effects on microarthropod communities, but exclusion of all herbivore groups resulted in decreased total springtail and Poduromorpha richness compared with exclusion of only ungulates and medium-sized mammals, regardless of vegetation type. The tall-grass vegetation had a higher total springtail richness and mesostigmatid mite abundance than the short-grass vegetation and a different oribatid mite community composition. Although several biotic and abiotic variables differed between the exclusion treatments and vegetation types, effects on soil microarthropods were best explained by differences in nutrient and fibre content of the previous year’s vegetation, a proxy for litter quality, and to a lesser extent soil temperature. After three growing seasons, smaller herbivores had a stronger impact on these functionally important soil microarthropod communities than large herbivores. Over longer time-scales, however, large grazers created two different vegetation types and thereby influenced microarthropod communities bottom-up, e.g. by altering resource quality. Hence, both short- and long-term consequences of herbivory affected the structure of the soil microarthropod community.     

Effects of carrion resources on herbivore spatial distribution are mediated by facultative scavengers

Carcasses of large herbivores are pulsed resources whose impact on animal communities and ecological processes is poorly understood. In temperate forests, long-lasting ungulate carcasses are a prime resource for many species of birds and mammals during winter. Facultative carrion-eaters also consume live prey, thus potentially leading to unexpected secondary effects on populations of species not directly linked to carcass exploitation. By snow-tracking and direct observations we investigated in Bia?owie?a Forest (E. Poland) whether large ungulate carcasses elicit spatial responses in facultative scavengers and their prey. We found that in the vicinity of carcass sites the probability of the presence of common ravens Corvus corax, jays Garrulus glandarius and red foxes Vulpes vulpes increased significantly. Indeed, large groups of the two bird species were exclusively found in those places. Because of these aggregations, the probability of predator–prey encounters (red foxes and brown hares Lepus europaeus) was significantly higher near carcass sites. Accordingly, the abundance of hares and other live prey such as red squirrels Sciurus vulgaris decreased at their vicinities, probably as a consequence of direct killing and/or predator avoidance. This study provides the first evidence of carrion pulses permeating into apparently distant trophic levels, such as herbivores, via facultative scavengers, thus highlighting some unnoticed but relevant effects of carrion resources on community structure.     

Carnivory in the common hippopotamus Hippopotamus amphibius: implications for the ecology and epidemiology of anthrax in African landscapes

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Ungulate Carcasses Perforate Ecological Filters and Create Biogeochemical Hotspots in Forest Herbaceous Layers Allowing Trees a Competitive Advantage

Ecological filters and nutrient heterogeneity are important in the function of ecosystems. Herbaceous layers alter forest ecosystems by filtering tree species during early stages of tree reproduction and influencing nutrient cycling. Important aspects about how tree species successfully establish below and extend above this ecological filter are unanswered in forest ecology. We experimentally tested the effects of large ungulate carcasses on the filtering function of herbaceous layers. Even well-utilized carcasses created unexpected disturbances that reduced herbaceous cover, which effectively perforated the herbaceous layer filter that can differentially influence tree reproduction. Carcasses also created lasting biogeochemical “hotspots” in forest soils that may help maintain plant biodiversity by creating resource heterogeneity and shifting competitive relationships. Because the spatial distribution of carcasses is influenced by predators, these data establish an unrecognized link between large carnivores, prey carcasses, and ecosystem processes. This link supports a novel understanding of disturbance by large herbivores in forest ecosystems by demonstrating an important interaction between predator–prey functional traits and tree seedling dynamics on either side of a major ecological filter.     

Feral horse impacts on threatened plants and animals in sub‐alpine and montane environments in Victoria,Australia

Feral herbivores are a major driver of biodiversity loss globally and can alter the structure, composition and functioning of ecosystems. The direct impacts of feral herbivores on plant communities are well studied, but the direct and indirect effect they have on wildlife is not well understood. In Victoria (south‐eastern Australia), a large feral Horse (Equus caballus) population coincides with highly sensitive and nationally endangered Alpine Sphagnum Bogs and Associated Fens communities, and several threatened animal species. We assessed the impact of feral horses on this ecological community and the Alpine Water Skink (Eulamprus kosciuskoi) and the Broad‐toothed Rat (Mastacomys fuscus) at 20 sites with varying levels of horse disturbance. We used scat counts to determine an index of feral horse abundance and quantified impacts associated with their presence in the landscape. Active searches were used for Alpine Water Skink and scat and runway surveys for Broad‐toothed Rat. We also measured the vegetation structure and the abundance of different vegetation types (life forms). Our results suggest that feral horses are associated with vegetation types and characteristics that negatively influence the presence or abundance of Alpine Water Skink and Broad‐toothed Rat. Sites with high horse activity had more low‐growing forbs, and the abundance of Alpine Water Skink was negatively related to this vegetation type. Grasses, sedges, rushes and shrubs were also less dense and lower in height in high horse activity sites, and Broad‐toothed Rat was less likely to be present in areas with these habitat attributes. We recommend that feral horses are controlled to protect these threatened vertebrate species and their Sphagnum bog habitat.     

Large and small herbivores have strong effects on tundra vegetation in Scandinavia and Alaska

1. Large and small mammalian herbivores are present in most vegetated areas in the Arctic and often have large impacts on plant community composition and ecosystem functioning. The relative importance of different herbivores and especially how their specific impact on the vegetation varies across the Arctic is however poorly understood.
2. Here, we investigate how large and small herbivores influence vegetation density and plant community composition in four arctic vegetation types in Scandinavia and Alaska. We used a unique set of exclosures, excluding only large (reindeer and muskoxen) or all mammalian herbivores (also voles and lemmings) for at least 20 years.
3. We found that mammalian herbivores in general decreased leaf area index, NDVI, and abundance of vascular plants in all four locations, even though the strength of the effect and which herbivore type caused these effects differed across locations. In three locations, herbivore presence caused contrasting plant communities, but not in the location with lowest productivity. Large herbivores had a negative effect on plant height, whereas small mammalian herbivores increased species diversity by decreasing dominance of the initially dominating plant species. Above‐ or belowground disturbances caused by herbivores were found to play an important role in shaping the vegetation in all locations.
4. Synthesis: Based on these results, we conclude that both small and large mammalian herbivores influence vegetation in Scandinavia and Alaska in a similar way, some of which can mitigate effects of climate change. We also see important differences across locations, but these depend rather on local herbivore and plant community composition than large biogeographical differences among continents.

     

Cretaceous small scavengers: feeding traces in tetrapod bones from Patagonia, Argentina

Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem.     

The Seedling Ratio Method for determining ungulate impacts on forest understoreys: Utility in an Australian ecosystem

The Seedling Ratio Method was devised to assess the impacts of introduced ungulates on plant species richness in forest understoreys. The method has successfully assessed ungulate impacts on species richness in forests in New Zealand and Hawaii, which do not have native herbivores. We tested the three critical assumptions that underlie this method to investigate its potential for use in an Australian ecosystem. This study was conducted in the Yarra Ranges National Park (YRNP), Victoria, which had a high‐density population of an introduced deer species, Sambar (Cervus unicolor), in addition to several native herbivore species. One of the three key assumptions of the Seedling Ratio Method was not supported, whereas conventional differential exclosures showed clear and separate impacts by Sambar and native herbivores. We conclude that the Seedling Ratio Method could not provide a clear indication of browsing impact on forest understoreys in YRNP.     

Potential impacts of climate change on patterns of insect herbivory on understorey plant species: A transplant experiment

Species‐specific responses to climate change will lead to changes in species interactions across multiple trophic levels. Interactions between plants and their insect herbivores, in particular, may become increasingly disrupted if mobile herbivores respond more rapidly to climatic change than their associated host plants. We present a multispecies transplant experiment aimed at assessing potential climatic impacts on patterns of leaf herbivory. Four shrubby understorey plant species were transplanted outside their native range into a climate 2.5°C warmer in annual mean temperature. After 12 months, we assessed the types and amount of herbivore leaf damage, compared with plants transplanted to a control site within their native range. The overall amount of foliage loss to herbivores ranged from approximately 3–10% across species and sites, a range consistent with most estimates of leaf loss in other studies. The most common types of leaf damage were sucking and chewing and this pattern was consistent for all four plant species at all sites. There were no significant differences in levels and patterns of herbivory between control and warm sites for three out of four plant species. This suggests that with moderate climate warming, most herbivory will continue to be dominated by chewers and suckers, and that the overall level of foliage loss will be similar to that experienced presently.     

Herbivory and drought interact to enhance spatial patterning and diversity in a savanna understory

The combination of abiotic stress and consumer stress can have complex impacts on plant community structure. Effective conservation and management of semi-arid ecosystems requires an understanding of how different stresses interact to structure plant communities. We explored the separate and combined impacts of episodic drought, livestock grazing, and wild ungulate herbivory on species co-occurrence and diversity patterns in a relatively productive, semi-arid Acacia savanna. Specifically, we analyzed 9 years of biannual plant community data from the Kenya long-term exclosure experiment, a broad-scale manipulative experiment that has excluded different combinations of large mammalian herbivores from 18 4-ha plots since 1995. During droughts, we observed low species diversity and random species co-occurrence patterns. However, when rain followed a major drought, areas exposed to moderate cattle grazing displayed high species diversity and evidence of significant species aggregation. These patterns were not apparent in the absence of cattle, even if other large herbivores were present. To explore possible mechanisms, we examined patterns separately for common and rare species. We found that aggregation patterns were likely driven by rare species responding similarly to the availability of open micro-sites. Our results indicate that in a productive, fire-suppressed savanna, the combination of periodic drought and moderate cattle grazing can enhance plant biodiversity and fine-scale spatial heterogeneity by opening up space for species that are otherwise rare or cryptic. Our findings also emphasize that domestic herbivores can have significantly stronger impacts on plant community dynamics than wild herbivores, even in an ecosystem with a long history of grazing.     

Cutmarked bones from Pliocene archaeological sites at Gona, Afar, Ethiopia: implications for the function of the world's oldest stone tools

Newly recorded archaeological sites at Gona (Afar, Ethiopia) preserve both stone tools and faunal remains. These sites have also yielded the largest sample of cutmarked bones known from the time interval 2.58-2.1 million years ago (Ma). Most of the cutmarks on the Gona fauna possess obvious macroscopic (e.g., deep V-shaped cross-sections) and microscopic (e.g., internal microstriations, Herzian cones, shoulder effects) features that allow us to identify them confidently as instances of stone tool-imparted damage caused by hominid butchery. In addition, preliminary observations of the anatomical placement of cutmarks on several of the recovered bone specimens suggest that Gona hominids may have eviscerated carcasses and defleshed the fully muscled upper and intermediate limb bones of ungulates--activities that further suggest that Late Pliocene hominids may have gained early access to large mammal carcasses. These observations support the hypothesis that the earliest stone artifacts functioned primarily as butchery tools and also imply that hunting and/or aggressive scavenging of large ungulate carcasses may have been part of the behavioral repertoire of hominids by c. 2.5 Ma, although a larger sample of cutmarked bone specimens is necessary to support the latter inference.     

Interactions between herbivory and resource availability on grazing tolerance of Leymus chinensis

Herbivory and resource interact to influence plant regrowth following grazing, but few detailed investigations on grazing tolerance at population levels are available. We conducted two pot experiments along a simulated grazing gradient (0%, 25%, 50% and 75% of shoot removal) at three water or nutrient levels to determine the interaction of resource and herbivory on Leymus chinensis, a perennial, dominant species in the eastern Eurasian steppes. Interactions between water availability and clipping intensity on the relative height growth rate (RHGR) and bud number were significant. Significant interactions between nutrient and clipping on RHGR, total biomass and specific leaf area (SLA) were also found. Total biomass and bud number, showing a unimodal curve along the clipping gradient in resource-rich environments, were highest at light clipping level, suggesting that this species has the plastic compensatory responses from under- to overcompensation. Interactions between herbivory and water or nutrient were opposite to each other. The “cooperative” interactions between water and herbivory magnified the difference in grazing tolerance of L. chinensis between high and low water treatments. The “antagonistic” interactions between nutrient and herbivory, on the other hand, were reflected in the lower tolerance to heavy clipping in the high nutrient than low nutrient treatments. Results partly support the limiting resource model (LRM). A modified and simplified graphic model of the LRM was proposed based on our results. The new LRM clearly demonstrated that “cooperative” interactions between varying water levels and clipping intensities aggravate the detrimental impacts of herbivores on plant growth and reproduction, whereas “antagonistic” interactions between nutrient and grazing alleviate the negative effects of herbivores. Biomass compensation and density compensation were identified as main mechanisms of herbivory tolerance in this clonal species.     

Prairie vegetation and soil nutrient responses to ungulate carcasses

The impact of large ungulate carcasses on grassland dynamics was investigated by monitoring vegetation and soil nutrients in 50-cm circular zones around the center of bison (Bos bison), cattle (B. taurus), and deer (Odocoileus virginianus) carcasses. An ungulate carcass creates an intense localized disturbance that varies with animal size and the season of death. Unlike other natural disturbances, carcasses deposit a concentrated pulse of nutrients into the soil. One year after death, inorganic nitrogen concentrations were significantly higher in the inner 50 cm at both adult and juvenile carcass sites than in surrounding prairie. Areas around a carcass became zones of fertility that favored different components of the vegetation and stimulated biomass production. Species richness and diversity at the center of carcass sites were lowest 1 year after death, but increased significantly in subsequent years. However, warm-season perennial grasses declined near the center of carcass sites and did not recover. Five years after death, ungulate carcass sites remained disturbed patches that harbored vegetation characteristically different in composition and stature from surrounding prairie. By providing a niche for species not normally found in undisturbed prairie, carcasses increased community heterogeneity and may play an important role in adding spatial complexity to grassland ecosytems. Received: 12 April 1999 / Accepted: 7 September 1999     

Effects of plant spinescence on large mammalian herbivores

Summary Plant thorns and spines had these effects on the feeding behaviour of the three species of browsing ungulate that we studied, kudu, impala and domestic goats: (i) bite sizes were restricted, in most cases to single leaves or leaf clusters; (ii) hooked thorns retarded biting rates; (iii) the acceptability of those plant species offering small leaf size in conjunction with prickles was lower, at least for the kudus, than those of other palatable plant species; (iv) the inhibitory effect of prickles on feeding was much less for the smaller impalas and goats than for the larger kudus; (v) from certain hook-thorned species the kudus bit off shoot ends despite their prickles; (vi) for certain straight-thorned species the kudus compensated partially for the slow eating rates obtained by extending their feeding durations per encounter. Most spinescent species were similar in their acceptability to the ungulates to unarmed palatable species, despite higher crude protein contents in their foliage than the latter. Such structural features furthermore reduce the tissue losses incurred by plants per encounter by a large ungulate herbivore, by restricting the eating rates that the animals obtain. In this way prickles function to restrict foliage losses to large herbivores below the levels that might otherwise occur.