scholarly journals The impact of large terrestrial carnivores on Pleistocene ecosystems

2015 ◽  
Vol 113 (4) ◽  
pp. 862-867 ◽  
Author(s):  
Blaire Van Valkenburgh ◽  
Matthew W. Hayward ◽  
William J. Ripple ◽  
Carlo Meloro ◽  
V. Louise Roth
Keyword(s):  
Prey Size ◽  
Habitat Degradation ◽  
Terrestrial Ecosystems ◽  
Growth Data ◽  
Predator Prey ◽  
Body Sizes ◽  
Population Sizes ◽  
Potential Impact ◽  
The Impact ◽  
Ground Sloths

Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are largely immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential impact of Pleistocene large carnivores, we use both historic and modern data on predator–prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater impact on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes.

scholarly journals Influence of fragmentation and disturbance on the potential impact of feral predators on native fauna in Australian forest ecosystems

1996 ◽  
Vol 23 (4) ◽  
pp. 387 ◽  
Author(s):  
S. A. May ◽  
T. W. Norton
Keyword(s):  
Forest Ecosystems ◽  
Prey Species ◽  
Prey Availability ◽  
Current Knowledge ◽  
Native Forest ◽  
Feral Cat ◽  
Predator Prey ◽  
Small Prey ◽  
Potential Impact ◽  
The Impact

The current knowledge is reviewed of the diet and predator–prey relationships of the feral cat (Felis catus), fox (Vulpes vulpes) and dingo (Canis familiaris dingo) (including wild dogs). The effect of forest fragmentation by roads on the use of native forest ecosystems by these species and the significance of this for native fauna is considered. The cat, fox and dingo are significant predators in Australia that interact with native fauna in various ways, including predation, competition for resources, and transmission of disease. On the basis of current knowledge, it is clear that the nature and impact of predation by the cat, fox and dingo on native fauna are primarily determined by prey availability, although there are exceptions to this rule. Generally, dingoes prey upon large to medium-sized prey species (e.g. wallabies, common wombats, and possums), foxes prey upon medium-sized to small prey (e.g. possums and rats) and consume a significant component of scavenged material and vegetation, while cats also prey upon medium-sized to small prey, but may have a greater proportion of reptiles and birds in their diet. The cat is generally considered to be an opportunistic predator and to have contributed to the demise of a number of mammals. The fox is considered more of a threat to small native mammals and it has been asserted that all species of mammals that fall within the critical weight range (CWR) of 120–5000 g are at risk of local extinction when the fox is present. The severity of the impact of the dingo upon the native fauna is considered to be minimal, at least in comparison with the impact that the cat and fox can have on populations. The dingo is not considered a threat to CWR mammals in undisturbed environments. The fox, feral cat and dingo are all considered to have the ability to selectivity prey upon species and, to some extent, individual sexes and age-classes of a number of larger prey species. Although many of Australia's forested areas are relatively heavily fragmented by roads, there are no published studies specifically investigating the use of roads by feral predators. Information on the distribution and abundance of foxes, cats and dingoes in these ecosystems, their ecology and their impact on native fauna is particularly limited. Further, the extent to which roads influence the distribution and abundance of these species and the consequences of these for native fauna are poorly known. One of the most important research needs is to establish the relative impact that exotic predators may have on native fauna under varying degrees of road construction within native forests. For example, are areas with and without roads in forests used differently by exotic predators and what is the significance of this in terms of the potential impact on fauna? The extent to which feral predators forage away from roads needs further investigation, as does the rates of predation within edges, because this may have several consequences for the design, location and size of retained strips and wildlife corridors as well as restoration programmes. Further observations on regional differences influencing predator–prey interactions are required, as is research on the potential impacts on native fauna resulting from prey selection in forests subjected to various degrees of fragmentation and modification.

scholarly journals What’s for dinner? Diet and trophic impact of an invasive anuran Hoplobatrachus tigerinus on the Andaman archipelago

2018 ◽  
Author(s):  
Nitya Prakash Mohanty ◽  
John Measey
Keyword(s):  
Prey Availability ◽  
Foraging Strategy ◽  
Amphibian Species ◽  
Predator Prey ◽  
Future Studies ◽  
Hoplobatrachus Tigerinus ◽  
Body Sizes ◽  
Potential Impact ◽  
Trophic Impact ◽  
Ambush Predators

Amphibian invasions have considerable detrimental impacts on recipient ecosystems; however, reliable risk analysis of invasive amphibians still requires research on more non-native amphibian species. An invasive population of the Indian bullfrog, Hoplobatrachus tigerinus, is currently spreading on the Andaman archipelago and may have significant trophic impacts on native anurans through competition and predation. We assessed the diet of the invasive Hoplobatrachus tigerinus (n = 358), the native Limnonectes spp. (n = 375) and Fejervarya spp. (n = 65) in three sites, across four habitat types and two seasons, on the Andaman archipelago. We found a significant dietary overlap of H. tigerinus with Limnonectes spp., which may lead to competition. Small vertebrates, including several endemic species, constituted a majority of H. tigerinus diet by volume, suggesting potential impact by predation. Diets of the three species were mostly governed by the positive relationship between predator-prey body sizes. Niche breadth analyses did not indicate any significant changes in diet between seasons. Hoplobatrachus tigerinus and Fejervarya spp. chose evasive prey, suggesting that these two species are mostly ambush predators; Limnonectes spp. elected sedentary prey; although a large portion of its diet consisted of other prey types, such electivity indicates ‘active search’ as its major foraging strategy. All three species of anurans mostly consumed terrestrial prey. This intensive study on a new genus of invasive amphibian contributes to the knowledge on impacts of amphibian invasions, and elucidates the feeding ecology of H. tigerinus, and species of the genera Limnonectes and Fejervarya. We stress on the necessity to evaluate prey availability and volume in future studies for meaningful insights into diet of amphibians.

scholarly journals Decomposing the effects of ocean environments on predator–prey body-size relationships in food webs

2018 ◽  
Vol 5 (7) ◽  
pp. 180707 ◽  
Author(s):  
Tomoya Dobashi ◽  
Midori Iida ◽  
Kazuhiro Takemoto
Keyword(s):  
Body Size ◽  
Food Webs ◽  
Oxygen Concentration ◽  
Large Scale ◽  
Small Body ◽  
Large Body ◽  
Predator Prey ◽  
Body Sizes ◽  
And Function ◽  
The Impact

Body-size relationships between predators and their prey are important in ecological studies because they reflect the structure and function of food webs. Inspired by studies on the impact of global warming on food webs, the effects of temperature on body-size relationships have been widely investigated; however, the impact of environmental factors on body-size relationships has not been fully evaluated because climate warming affects various ocean environments. Thus, here, we comprehensively investigated the effects of ocean environments and predator–prey body-size relationships by integrating a large-scale dataset of predator–prey body-size relationships in marine food webs with global oceanographic data. We showed that various oceanographic parameters influence prey size selection. In particular, oxygen concentration, primary production and salinity, in addition to temperature, significantly alter body-size relationships. Furthermore, we demonstrated that variability (seasonality) of ocean environments significantly affects body-size relationships. The effects of ocean environments on body-size relationships were generally remarkable for small body sizes, but were also significant for large body sizes and were relatively weak for intermediate body sizes, in the cases of temperature seasonality, oxygen concentration and salinity variability. These findings break down the complex effects of ocean environments on body-size relationships, advancing our understanding of how ocean environments influence the structure and functioning of food webs.

Predation and prey size choice by the carabid beetlePterostichus melanarius(Coleoptera: Carabidae): the dangers of extrapolating from laboratory to field

2003 ◽  
Vol 93 (3) ◽  
pp. 227-234 ◽  
Author(s):  
A.R. McKemey ◽  
W.O.C. Symondson ◽  
D.M. Glen
Keyword(s):  
Environmental Heterogeneity ◽  
Prey Size ◽  
Laboratory Studies ◽  
Ecological Studies ◽  
Size Frequency Distribution ◽  
Predator Prey ◽  
Laboratory Results ◽  
Prey Interaction ◽  
Pterostichus Melanarius ◽  
The Impact

AbstractThe impact of predation by the generalist carabid beetlePterostichus melanarius(Illiger) on populations of the field slugDeroceras reticulatum(Müller), and the effects of prey size on the predator–prey interaction, were measured under semi-field conditions. It was hypothesized that environmental heterogeneity would lead to very different patterns of comparative mortality than might be deduced from size choice experiments conducted in the laboratory. Results from outdoor mini-plots, emulating conditions in a field of wheat, demonstrated thatP. melanariussignificantly reduced numbers of slugs from all size classes, with no apparent preferences. This was in marked contrast to results from earlier laboratory studies, where this beetle fed preferentially on the smallest slugs. The slugs in the mini-plots ranged in size from 2–100 mg and the numbers in the mini-plot reflected the size frequency distribution in the field. Beetles in mini-plots containing high densities of slugs increased significantly in weight, in contrast to beetles in mini-plots with low slug density or no added slugs, which did not. Enzyme-linked immunosorbent assays (ELISA), using anti-slug monoclonal antibodies, showed that where there was a higher density of slugs there was more slug protein in the guts of the beetles. It was concluded that environmental heterogeneity probably provided a greater number and diversity of refugia for smaller than for larger slugs, counteracting laboratory-measured size preferences measured in arenas without refugia. These results have implications for a range of ecological studies involving inter- and intra-specific prey size choice, and emphasize the dangers of extrapolating from the laboratory to the field.

scholarly journals What’s for dinner? Diet and potential trophic impact of an invasive anuran Hoplobatrachus tigerinus on the Andaman archipelago

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5698 ◽  
Author(s):  
Nitya Prakash Mohanty ◽  
John Measey
Keyword(s):  
Prey Availability ◽  
Foraging Strategies ◽  
Amphibian Species ◽  
Predator Prey ◽  
Hoplobatrachus Tigerinus ◽  
Body Sizes ◽  
Diet Analyses ◽  
Trophic Impact ◽  
The Impact ◽  
Ambush Predators

Amphibian invasions have considerable detrimental impacts on recipient ecosystems. However, reliable risk analysis of invasive amphibians still requires research on more non-native amphibian species. An invasive population of the Indian bullfrog, Hoplobatrachus tigerinus, is currently spreading on the Andaman archipelago and may have significant trophic impacts on native anurans through competition and predation. We carried out diet analyses of the invasive H. tigerinus and native anurans, across four habitat types and two seasons; we hypothesized that (i) small vertebrates constitute a majority of the H. tigerinus diet, particularly by volume and (ii) the diet of H. tigerinus significantly overlaps with the diet of native anurans, thereby, leading to potential competition. We assessed the diet of the invasive H. tigerinus (n = 358), and individuals of the genera Limnonectes (n = 375) and Fejervarya (n = 65) and found a significant dietary overlap of H. tigerinus with only Limnonectes. Small vertebrates, including several endemic species, constituted the majority of H. tigerinus, diet by volume, suggesting potential impact by predation. Prey consumption and electivity of the three anurans indicated a positive relationship between predator-prey body sizes. Individuals of H. tigerinus and Fejervarya chose evasive prey, suggesting that these two taxa are mostly ambush predators; individuals of Limnonectes chose a mixture of sedentary and evasive prey indicating that the species employs a combination of ‘active search’ and ‘sit and wait’ foraging strategies. All three species of anurans mostly consumed terrestrial prey. This intensive study on a genus of newly invasive amphibian contributes to knowledge of the impact of amphibian invasions, and elucidates the feeding ecology of H. tigerinus, and species of the genera Limnonectes and Fejervarya. We also stress the necessity to evaluate prey availability and volume in future studies for meaningful insights into diet of amphibians.

scholarly journals What’s for dinner? Diet and trophic impact of an invasive anuran Hoplobatrachus tigerinus on the Andaman archipelago

2018 ◽  
Author(s):  
Nitya Prakash Mohanty ◽  
John Measey
Keyword(s):  
Prey Availability ◽  
Foraging Strategy ◽  
Amphibian Species ◽  
Predator Prey ◽  
Future Studies ◽  
Hoplobatrachus Tigerinus ◽  
Body Sizes ◽  
Potential Impact ◽  
Trophic Impact ◽  
Ambush Predators

Amphibian invasions have considerable detrimental impacts on recipient ecosystems; however, reliable risk analysis of invasive amphibians still requires research on more non-native amphibian species. An invasive population of the Indian bullfrog, Hoplobatrachus tigerinus, is currently spreading on the Andaman archipelago and may have significant trophic impacts on native anurans through competition and predation. We assessed the diet of the invasive Hoplobatrachus tigerinus (n = 358), the native Limnonectes spp. (n = 375) and Fejervarya spp. (n = 65) in three sites, across four habitat types and two seasons, on the Andaman archipelago. We found a significant dietary overlap of H. tigerinus with Limnonectes spp., which may lead to competition. Small vertebrates, including several endemic species, constituted a majority of H. tigerinus diet by volume, suggesting potential impact by predation. Diets of the three species were mostly governed by the positive relationship between predator-prey body sizes. Niche breadth analyses did not indicate any significant changes in diet between seasons. Hoplobatrachus tigerinus and Fejervarya spp. chose evasive prey, suggesting that these two species are mostly ambush predators; Limnonectes spp. elected sedentary prey; although a large portion of its diet consisted of other prey types, such electivity indicates ‘active search’ as its major foraging strategy. All three species of anurans mostly consumed terrestrial prey. This intensive study on a new genus of invasive amphibian contributes to the knowledge on impacts of amphibian invasions, and elucidates the feeding ecology of H. tigerinus, and species of the genera Limnonectes and Fejervarya. We stress on the necessity to evaluate prey availability and volume in future studies for meaningful insights into diet of amphibians.

scholarly journals Predator–prey body size relationships when predators can consume prey larger than themselves

2013 ◽  
Vol 9 (3) ◽  
pp. 20121193 ◽  
Author(s):  
Takefumi Nakazawa ◽  
Shin-ya Ohba ◽  
Masayuki Ushio
Keyword(s):  
Body Size ◽  
Prey Size ◽  
The Other ◽  
Field Observations ◽  
Species Identity ◽  
Predator Prey ◽  
Size Dependent ◽  
Fish Predators ◽  
Body Sizes ◽  
Prey Mass

As predator–prey interactions are inherently size-dependent, predator and prey body sizes are key to understanding their feeding relationships. To describe predator–prey size relationships (PPSRs) when predators can consume prey larger than themselves, we conducted field observations targeting three aquatic hemipteran bugs, and assessed their body masses and those of their prey for each hunting event. The data revealed that their PPSR varied with predator size and species identity, although the use of the averaged sizes masked these effects. Specifically, two predators had slightly decreased predator–prey mass ratios (PPMRs) during growth, whereas the other predator specialized on particular sizes of prey, thereby showing a clear positive size–PPMR relationship. We discussed how these patterns could be different from fish predators swallowing smaller prey whole.

Characterizing the impact of recovering sea otters on commercially important crabs in California estuaries

2020 ◽  
Vol 655 ◽  
pp. 123-137
Author(s):  
TM Grimes ◽  
MT Tinker ◽  
BB Hughes ◽  
KE Boyer ◽  
L Needles ◽  
...  
Keyword(s):  
Abiotic Factors ◽  
Sea Otter ◽  
Dungeness Crab ◽  
Sea Otters ◽  
Elkhorn Slough ◽  
Enhydra Lutris Nereis ◽  
Crab Abundance ◽  
Population Sizes ◽  
Commercially Important ◽  
The Impact

Protective legislation and management have led to an increase in California’s sea otter Enhydra lutris nereis population. While sea otter recovery has been linked to ecosystem benefits, sea otter predation may negatively affect commercially valuable species. Understanding the potential influence of sea otters is of particular importance as their range expands into estuaries that function as nurseries for commercially valuable species like Dungeness crab Metacarcinus magister. We consider how sea otter predation has affected the abundance and size of juvenile Dungeness crab in Elkhorn Slough, California, USA, and analyzed cancrid crab abundance and size across 4 California estuaries with and without sea otters to understand how biotic and abiotic factors contribute to observed variation in crab size and abundance. We compared trends in southern sea otters relative to Dungeness crab landings in California to assess whether increasing sea otter abundance have negatively impacted landings. In Elkhorn Slough, juvenile Dungeness crab abundance and size have declined since 2012, coinciding with sea otter population growth. However, the impact of sea otters on juvenile Dungeness crab size was habitat-specific and only significant in unvegetated habitat. Across estuaries, we found that cancrid crab abundance and size were negatively associated with sea otter presence. While abiotic factors varied among estuaries, these factors explained little of the observed variation in crab abundance or size. Although we found evidence that sea otters can have localized effects on cancrid crab populations within estuaries, we found no evidence that southern sea otters, at recent population sizes, have negatively impacted Dungeness crab landings in California from 2000-2014.

Climate-forced changes of bio-productivity of Belorussian terrestrial ecosystems

2019 ◽  
pp. 77-88
Author(s):  
S. A. Lysenko
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Vegetation Index ◽  
Precipitation Amount ◽  
Terrestrial Ecosystems ◽  
Vegetation Period ◽  
Climatic Trend ◽  
Vegetation Growth ◽  
Current Century ◽  
The Impact

The spatial and temporal particularities of Normalized Differential Vegetation Index (NDVI) changes over territory of Belarus in the current century and their relationship with climate change were investigated. The rise of NDVI is observed at approximately 84% of the Belarus area. The statistically significant growth of NDVI has exhibited at nearly 35% of the studied area (t-test at 95% confidence interval), which are mainly forests and undeveloped areas. Croplands vegetation index is largely descending. The main factor of croplands bio-productivity interannual variability is precipitation amount in vegetation period. This factor determines more than 60% of the croplands NDVI dispersion. The long-term changes of NDVI could be explained by combination of two factors: photosynthesis intensifying action of carbon dioxide and vegetation growth suppressing action of air warming with almost unchanged precipitation amount. If the observed climatic trend continues the croplands bio-productivity in many Belarus regions could be decreased at more than 20% in comparison with 2000 year. The impact of climate change on the bio-productivity of undeveloped lands is only slightly noticed on the background of its growth in conditions of rising level of carbon dioxide in the atmosphere.

Chasing the phantom: biogeography and conservation of Vipera latastei-monticola in the Maghreb (North Africa)

2018 ◽  
Vol 39 (2) ◽  
pp. 145-161 ◽  
Author(s):  
Inês Freitas ◽  
Soumia Fahd ◽  
Guillermo Velo-Antón ◽  
Fernando Martínez-Freiría
Keyword(s):  
North Africa ◽  
Habitat Degradation ◽  
Conservation Status ◽  
Western Mediterranean ◽  
Niche Modelling ◽  
Habitat Transformation ◽  
Mountain Ranges ◽  
Management Actions ◽  
Suitable Space ◽  
The Impact

Abstract The Maghreb region (North Africa) constitutes a major component of the Mediterranean Basin biodiversity hotspot. During the last centuries, a consistent human population growth has led to an unprecedented rate of habitat transformation and loss in the region and thus, threatening its biodiversity. The Western Mediterranean viper Vipera latastei-monticola inhabits humid and subhumid areas in the main mountain ranges of the Maghreb, facing such threatening factors; however, its elusive character and rarity hindered data collection for distinct biological purposes. Here, we study the biogeographical patterns and conservation status of the Maghrebian V. latastei-monticola resulting from recent sampling campaigns in Morocco and Tunisia. We update species distribution, and integrate phylogeographic and ecological niche modelling analyses at both species and lineage level to identify suitable areas, and to evaluate the impact of anthropogenic transformation and level of protection of their suitable space. We identified four highly divergent mitochondrial lineages, including a new lineage endemic to the Western High Atlas, with allopatric distributions and restricted to mountain ranges, supporting the role of mountains as past climatic refugia. Despite the remoteness of suitable areas, we report widespread habitat degradation and identify the low effectiveness of the current protected areas system in preserving the species and lineages range. Our study shows the urgent need to apply management actions for the long-term conservation of this vulnerable species and suggests a revaluation of the specific status of V. monticola, as these populations likely represent an ecotype of V. latastei.

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