scholarly journals Population modelling insights of extinct environments: the case of the Kem Kem palaeocommunity

2021 ◽  
Author(s):  
Lucas dos Anjos
Keyword(s):  
Functional Group ◽  
Food Sources ◽  
Small Community ◽  
Population Modelling ◽  
Top Predator ◽  
Top Predators ◽  
Large Predators

AbstractThe Kem Kem beds are well-known palaeontological deposits. Among the species that lived there, there are some large theropods, such as Deltadromeus agilis, Carcharodontosaurus saharicus, and Spinosaurus aegyptiacus. It is possible that these large predators were facultative scavengers, and they could compete for carrion. In the present paper, I simulate a small community module of this environment, consisting of Carrion, Fishes, Spinosaurus, and a functional group composed of large terrestrial Theropods. I assume that these top predators feed on carrion, but they also have exclusive food sources. I show that these exclusive food sources could have assured the possibility of coexistence, and in their absence, one top predator could be locally extinct.

scholarly journals Trophic cascades alter eco-evolutionary dynamics and body size evolution

2020 ◽  
Vol 287 (1938) ◽  
pp. 20200526
Author(s):  
Thomas M. Luhring ◽  
John P. DeLong
Keyword(s):  
Body Mass ◽  
Trophic Level ◽  
Evolutionary Dynamics ◽  
Trophic Cascades ◽  
Trophic Levels ◽  
Chain Model ◽  
Top Predator ◽  
Predator Prey ◽  
Top Predators ◽  
Time Changes

Trait evolution in predator–prey systems can feed back to the dynamics of interacting species as well as cascade to impact the dynamics of indirectly linked species (eco-evolutionary trophic cascades; EETCs). A key mediator of trophic cascades is body mass, as it both strongly influences and evolves in response to predator–prey interactions. Here, we use Gillespie eco-evolutionary models to explore EETCs resulting from top predator loss and mediated by body mass evolution. Our four-trophic-level food chain model uses allometric scaling to link body mass to different functions (ecological pleiotropy) and is realistically parameterized from the FORAGE database to mimic the parameter space of a typical freshwater system. To track real-time changes in selective pressures, we also calculated fitness gradients for each trophic level. As predicted, top predator loss generated alternating shifts in abundance across trophic levels, and, depending on the nature and strength in changes to fitness gradients, also altered trajectories of body mass evolution. Although more distantly linked, changes in the abundance of top predators still affected the eco-evolutionary dynamics of the basal producers, in part because of their relatively short generation times. Overall, our results suggest that impacts on top predators can set off transient EETCs with the potential for widespread indirect impacts on food webs.

scholarly journals Subsistence harvesting by a small community does not substantially compromise coral reef fish assemblages

2017 ◽  
Vol 74 (8) ◽  
pp. 2191-2200 ◽  
Author(s):  
Tyson S. H. Martin ◽  
Rod M. Connolly ◽  
Andrew D. Olds ◽  
Daniela M. Ceccarelli ◽  
Douglas E. Fenner ◽  
...  
Keyword(s):  
Reef Fish ◽  
Fish Assemblages ◽  
Fish Communities ◽  
Marshall Islands ◽  
Fish Biomass ◽  
Small Community ◽  
Fish Community Structure ◽  
Small Communities ◽  
Top Predators ◽  
Subsistence Fishing

Abstract Fisheries usually first remove large predators before switching to smaller species, causing lasting changes to fish community structure. Reef fish provide essential protein and income for many people, and the impacts of commercial and high-intensity subsistence fishing on reef fish are well documented. However, how fish communities respond to low levels of subsistence fishing using traditional techniques (fishing for food, few fishers) is less well understood. We use three atolls in the Marshall Islands as a model system to quantify effects of commercial and subsistence fishing on reef fish communities, compared to a near-pristine baseline. Unexpectedly, fish biomass was highest on the commercially-fished atoll where the assemblage was dominated by herbivores (50% higher than other atolls) and contained few top predators (70% lower than other atolls). By contrast, fish biomass and trophic composition did not differ between pristine and subsistence-fished atolls – top predators were abundant on both. We show that in some cases, reefs can support fishing by small communities to provide food but still retain intact fish assemblages. Low-intensity subsistence fishing may not always harm marine food webs, and we suggest that its effects depend on the style and intensity of fishing practised and the type of organisms targeted.

scholarly journals The reintroduction of large carnivores to the Eastern Cape, South Africa: an assessment

Oryx ◽  
2007 ◽  
Vol 41 (2) ◽  
pp. 205-214 ◽  
Author(s):  
Matt W. Hayward ◽  
Graham I. H. Kerley ◽  
John Adendorff ◽  
Lucius C. Moolman ◽  
John O'Brien ◽  
...  
Keyword(s):  
Ecological Integrity ◽  
Large Carnivores ◽  
Eastern Cape ◽  
Founder Population ◽  
Conservation Areas ◽  
Acinonyx Jubatus ◽  
Top Predators ◽  
African Wild Dog ◽  
Wild Dog ◽  
Large Predators

AbstractRecently, conservation estate in South Africa's Eastern Cape Province has increased 10-fold resulting in large predators being increasingly reintroduced to restore ecological integrity and maximize tourism. We describe the reintroductions of large carnivores (>10 kg) that have occurred in the Eastern Cape and use various criteria to assess their success. Lion Panthera leo reintroduction has been highly successful with a population of 56 currently extant in the region and problems of overpopulation arising. The African wild dog Lycaon pictus population has increased to 24 from a founder population of 11. Preliminary results for spotted hyaenas Crocuta crocuta also indicate success. Wild populations of leopards Panthera pardus exist on several reserves and have been supplemented by translocated individuals, although deaths of known individuals have occurred and no estimate of reproduction is available. Cheetah Acinonyx jubatus reintroduction has also been less successful with 36 individuals reintroduced and 23 cubs being born but only 41 individuals surviving in 2005. Criteria for assessing the success of reintroductions of species that naturally occur in low densities, such as top predators, generally have limited value. Carrying capacity for large predators is unknown and continued monitoring and intensive management will be necessary in enclosed, and possibly all, conservation areas in the Eastern Cape to ensure conservation success.

scholarly journals REVIEW AND ANALYSIS OF MERCURY LEVELS IN BLUE MARLIN (Makaira nigricans, Lacepede 1802) AND SWORDFISH (Xiphias gladius, Linnaeus 1758)

2016 ◽  
Author(s):  
Tiago Rodrigues ◽  
Alberto Ferreira Amorim
Keyword(s):  
Hierarchical Cluster ◽  
Mercury Content ◽  
Trophic Chain ◽  
Multivariate Technique ◽  
Blue Marlin ◽  
Makaira Nigricans ◽  
Top Predators ◽  
High Mercury ◽  
High Concentrations ◽  
Large Predators

Mercury in the environment comes from natural processes and industrial activities. The inorganic form associates with the organic matter resulting on methylmercury (MeHg), the most toxic form to man. Mercury occurs in fishes mostly in organic form, the methylmercury. The billfishes appear to have high mercury levels because they are large predators that occupy top levels in the trophic chain. The mercury biomagnificates through the trophic chain and reaches high concentrations in top predators. The present study summarized the information about mercury levels in billfishes available in the literature, with emphasis on swordfish and blue marlin and made an analysis of data from several studies using the multivariate technique Agglomerative Hierarchical Cluster (AHC). The total mercury (THg) ranged from 0.7μg/g to 12.2μg/g in blue marlin and from 0.04μg/g to 5.1μg/g in swordfish, with data from 121 blue marlin specimens and 354 of swordfish. While a large part of the mercury content of the blue marlin was above 0.5μg/g allowed by WHO, the specimens of swordfish summarized on the present study showed generally lower values within or slightly above this limit, but the swordfish is still consumed nowadays, and large amounts consumed oftentimes may represent a risk to human health.

A question of size and fear: competition and predation risk perception among frugivores and predators

2020 ◽  
Vol 101 (3) ◽  
pp. 648-657
Author(s):  
Daiane Cristina Carreira ◽  
Jedediah F Brodie ◽  
Calebe P Mendes ◽  
Katia Maria P M B Ferraz ◽  
Mauro Galetti
Keyword(s):  
Risk Perception ◽  
Predation Risk ◽  
Indirect Effects ◽  
Species Interactions ◽  
Human Impacts ◽  
Activity Patterns ◽  
Fruit Trees ◽  
Visitation Rates ◽  
Top Predators ◽  
Large Predators

Abstract Mammalian spatial and temporal activity patterns can vary depending on foraging behavior or the perception of predation or competition risk among species. These behaviors may in turn be altered by human influences such as defaunation. Herein, we evaluate whether frugivores avoid areas with high visitation rates by potential predators or competitors, and whether this avoidance changes in areas with different degrees of defaunation. We installed 189 cameras under fruit trees in six areas of the Atlantic Forest, Brazil, that differ in the abundance of top predators and large frugivores. Small predators and small frugivores were more frequent at night while large frugivores were more frequent during the day, but small frugivores visited and spent less time at fruiting trees on brighter nights, unlike large predators and large frugivores. Small frugivores also were less frequent in areas with high visitation by large frugivores and more frequent in highly defaunated areas. Our results suggest that the dynamics among mammalian functional groups varied according to diel patterns, potential competitors, and defaunation. We highlight the importance of understanding how species interactions are changing in areas exposed to strong human impacts to mitigate the indirect effects of defaunation.

scholarly journals Extinctions of Late Ice Age Cave Bears as a Result of Climate/Habitat Change and Large Carnivore Lion/Hyena/Wolf Predation Stress in Europe

ISRN Zoology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-25 ◽  
Author(s):  
Cajus G. Diedrich
Keyword(s):  
Ice Age ◽  
Crocuta Crocuta ◽  
Cave Bear ◽  
Large Carnivore ◽  
Wolf Predation ◽  
Top Predators ◽  
Feeding Technique ◽  
Spotted Hyenas ◽  
Inner Organs ◽  
Large Predators

Predation onto cave bears (especially cubs) took place mainly by lion Panthera leo spelaea (Goldfuss), as nocturnal hunters deep in the dark caves in hibernation areas. Several cave bear vertebral columns in Sophie’s Cave have large carnivore bite damages. Different cave bear bones are chewed or punctured. Those lets reconstruct carcass decomposition and feeding technique caused only/mainly by Ice Age spotted hyenas Crocuta crocuta spelaea, which are the only of all three predators that crushed finally the long bones. Both large top predators left large tooth puncture marks on the inner side of cave bear vertebral columns, presumably a result of feeding first on their intestines/inner organs. Cave bear hibernation areas, also demonstrated in the Sophie’s Cave, were far from the cave entrances, carefully chosen for protection against the large predators. The predation stress must have increased on the last and larger cave bear populations of U. ingressus (extinct around 25.500 BP) in the mountains as result of disappearing other seasonally in valleys migrating mammoth steppe fauna due to climate change and maximum glacier extensions around 22.000 BP.

scholarly journals Paleobiogeographic evolution and distribution of Carcharodontosauridae (Dinosauria, Theropoda) during the middle Cretaceous of North Africa

2018 ◽  
Vol 58 ◽  
pp. 29 ◽  
Author(s):  
Carlos Roberto Dos Anjos Candeiro ◽  
Sthepen Louis Brusatte ◽  
Luciano Vidal ◽  
Paulo Victor Luiz Gomes da Costa Pereira
Keyword(s):  
New Species ◽  
North Africa ◽  
Niche Overlap ◽  
Top Predators ◽  
Large Predators

Over the last few decades, the systematics and evolution of carcharodontosaurids, a group of large predatory dinosaurs, from North Africa have been better understood mainly due the discovery of new species. We review this record here and discuss its importance for understanding the evolution and ecology of these dinosaurs. North Africa has one of the best records of carcharodontosaurid species. These species show dietary specializations and paleogeographic distributions similar to other top predatory theropods such as Abelisauridae and Spinosauridae. However, carcharodontosaurids have a wider distribution than other large theropods. The middle Cretaceous of North Africa was characterized by the niche overlap between large predators. This evidence increases our understanding of the evolution of Carcharodontosauridae in a highly competitive region, a conjuncture rarely reported for large top predators.

scholarly journals Protection of large predators in a marine reserve alters size-dependent prey mortality

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161936 ◽  
Author(s):  
Rebecca L. Selden ◽  
Steven D. Gaines ◽  
Scott L. Hamilton ◽  
Robert R. Warner
Keyword(s):  
Size Structure ◽  
Sea Urchins ◽  
Marine Reserves ◽  
Marine Reserve ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Size Dependent ◽  
Predator Size ◽  
Top Predators ◽  
Large Predators

Where predator–prey interactions are size-dependent, reductions in predator size owing to fishing has the potential to disrupt the ecological role of top predators in marine ecosystems. In southern California kelp forests, we investigated the size-dependence of the interaction between herbivorous sea urchins and one of their predators, California sheephead ( Semicossyphus pulcher ). Empirical tests examined how differences in predator size structure between reserve and fished areas affected size-specific urchin mortality. Sites inside marine reserves had greater sheephead size and biomass, while empirical feeding trials indicated that larger sheephead were required to successfully consume urchins of increasing test diameter. Evaluations of the selectivity of sheephead for two urchin species indicated that shorter-spined purple urchins were attacked more frequently and successfully than longer-spined red urchins of the same size class, particularly at the largest test diameters. As a result of these size-specific interactions and the higher biomass of large sheephead inside reserves, urchin mortality rates were three times higher inside the reserve for both species. In addition, urchin mortality rates decreased with urchin size, and very few large urchins were successfully consumed in fished areas. The truncation of sheephead size structure that commonly occurs owing to fishing will probably result in reductions in urchin mortality, which may reduce the resilience of kelp beds to urchin barren formation. By contrast, the recovery of predator size structure in marine reserves may restore this resilience, but may be delayed until fish grow to sizes capable of consuming larger urchins.

Predation of top predators: cane toad consumption of bullet ants in a Panamanian lowland wet forest

2018 ◽  
Vol 34 (6) ◽  
pp. 390-394 ◽  
Author(s):  
Colin R. Morrison
Keyword(s):  
High Rate ◽  
Nest Density ◽  
Ecological Communities ◽  
Top Predator ◽  
Cane Toad ◽  
Predator Species ◽  
Top Predators ◽  
Independent Observations ◽  
Ant Nest ◽  
Lowland Wet Forest

Abstract:Despite a clear consensus about the major roles that predators play in shaping ecological communities, descriptive studies of interactions between ecologically important top predator species are underreported. Native cane toad consumption of predatory bullet ant nests was verified through multiple, independent observations taken on Pipeline Road, Panama. Cane toad predation led to the extirpation of 42% of the nests within a 1.05 km2 area that is characterized as a late-successional wet forest. This predation pressure could be significant given the high rate of predation events and low bullet ant nest density observed here (0.12 nests ha−1). Implications of this interaction for the local bullet ant population, possible top-down effects and trophic cascades resulting from this top predator interaction are discussed.

scholarly journals Co-Existence Ecology of Large Predators in Belize

2018 ◽  
Author(s):  
Brogan Elizabeth Holcombe ◽  
Dr. Marcella J. Kelly
Keyword(s):  
Species Interactions ◽  
Habitat Type ◽  
Pairwise Comparison ◽  
Species Interaction ◽  
Individual Species ◽  
Top Predators ◽  
Presence Data ◽  
Trail Cameras ◽  
Study Sites ◽  
Large Predators

Jaguars, pumas, and ocelots are the main large predators within Belize, Central America that co-exist together and compete for resources. This study focused on determining whether the occurrence and/or detection of smaller predators (ocelots and pumas) is influenced by larger, more dominant predators (jaguars) across the landscape. Additionally, within this study we examined the influence of habitat-type and individual species sex on co-existence ecology utilizing data collected from non-invasive trail cameras in Belize. We formatted raw photo data into “capture histories” for three target species at each camera station across four study sites, and calculated the species interaction factors (SIFs) through co-occurrence modeling in program PRESENCE. Data analysis is currently on-going, but we hypothesize that the top-down control hypothesis, which states top predators will negatively influence space use and/or detection by smaller predators. We expect this will lead to negative SIFs in pairwise comparison indicating avoidance of top predators by smaller ones. Within each species, our preliminary results for the first of four study show that males tend to occur at a camera station shortly after females. Thus we expect this to lead to positive SIF values (indicating attraction) between the sexes of the same species. While analyses are not yet complete, we expect our results to give insight into species co-existence among competitors and also provide a greater understanding to whether sex and/or habitat influences competing species interactions.

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