Predation Research Papers - Academia.edu (original) (raw)

Introduced predators have had, and continue to have, severe impacts on Australian biodiversity. At a recently established conservation reserve, Witchelina, in arid South Australia, we assessed the diet of feral cats (Felis catus) (404... more

Introduced predators have had, and continue to have, severe impacts on Australian biodiversity. At a recently established conservation reserve, Witchelina, in arid South Australia, we assessed the diet of feral cats (Felis catus) (404 samples), red fox (Vulpes vulpes) (51 samples) and dog (Canis familiaris) (11 samples) over a 3-year period. There was marked overlap (98.5%) in dietary composition between cats and foxes. Rabbits (Oryctolagus cuniculus) comprised a major dietary item for all three predators. Invertebrates contributed the largest number of prey items for foxes and cats, but mammals comprised the bulk, by weight, for all three predators. Birds and reptiles had a higher frequency of occurrence in the diet of cats than of foxes or dogs. The size of mammal prey taken was least for cats and greatest for dogs. The diets of cats and foxes showed significant seasonal variation, with reptiles and invertebrates being least common in the diet in winter. The threatened thick-billed grasswren (Amytornis modestus) was found for the first time in the diet of feral cats. Bearded dragons (Pogona vitticeps) occurred in about one-third of cat and fox samples. This study contributes further to the evidence of biodiversity impacts of introduced predators, and the need for their strategic management.

Carrion production is one of the most crucial yet neglected and understudied processes in food webs and ecosystems. In this study, we performed a large-scale estimation of the maximum potential production and spatial distribution of... more

Carrion production is one of the most crucial yet neglected and understudied processes in food webs and ecosystems. In this study, we performed a large-scale estimation of the maximum potential production and spatial distribution of ungulate carrion biomass from five major sources in peninsular Spain, both anthropogenic (livestock, big game hunting, roadkills) and natural (predation, natural mortality). Using standardized ungulate carrion biomass (kg/year/100km2) estimates, we evaluated the relationship between ungulate carrion production and two ecosystem-level factors: global human modification (GHM) and primary productivity (NDVI). We found that anthropogenic carrion sources supplied about 60 times more ungulate carrion biomass than natural sources (mean = 90,172 vs. 1533 kg/year/100km2, respectively). Within anthropogenic carrion sources, livestock was by far the major carrion provider (91.1% of the annual production), followed by big game hunting (7.86%) and roadkills (0.05%). Within natural carrion sources, predation of ungulates provided more carrion (0.81%) than natural mortality (0.13%). Likewise, we found that the spatial distribution of carrion differed among carrion sources, with anthropogenic carrion being more aggregated in space than natural carrion. Our models showed that GHM was positively related to carrion production from livestock and roadkills, and that wild ungulate carrion supplied by natural sources and big game hunting was more frequently generated in more productive areas (higher NDVI). These findings indicate a disconnection between the main ungulate carrion source (livestock) and primary productivity. Ongoing socio-economic changes in developed countries (for example increase of intensive livestock husbandry and rewilding processes) could lead to additional alteration of carrion production processes, with potential negative impacts at the community and ecosystem levels. Overall, we highlight that carrion biomass quantification should be considered a crucial tool in evaluating ecosystem health and delineating efficient ecosystem management guidelines in the Anthropocene.

Near Palmyra, in the Syrian Desert, 5 species of scorpions belonging to 2 families (Buthidae and Scorpionidae) were observed; Buthacus tadmorensis, Androctonus crassicauda, Leiurus quinquestriatus, Orthochirus scrobiculosus, and Scorpio... more

Near Palmyra, in the Syrian Desert, 5 species of scorpions belonging to 2 families (Buthidae and Scorpionidae) were observed; Buthacus tadmorensis, Androctonus crassicauda, Leiurus quinquestriatus, Orthochirus scrobiculosus, and Scorpio maurus palmatus. B. tadmorensis accounted for 80.6% of the total number of recovered or observed scorpions, while O. scrobiculosus was the least common (1.4%). Pitfall traps proved to be more efficient at sampling (304 individuals) than checking under stones (57 individuals). Pitfall trapping results showed that scorpion abundance differed significantly between the 3 survey areas, while their abundance showed no significant difference among the 3 areas when employing the under-stone method. Notes on predation of scorpions (interspecific and intraspecific) and predators of scorpions are also included. Seasonal abundance and emergence of scorpions is described briefly. Biometric data on collected scorpion species indicating their weight are given. Popu...

The leopard Panthera pardus is in range-wide decline, and many populations are highly threatened. Prey depletion is a major cause of global carnivore declines, but the response of leopard survival and density to this threat is unclear: by... more

The leopard Panthera pardus is in range-wide decline, and many populations are highly threatened. Prey depletion is a major cause of global carnivore declines, but the response of leopard survival and density to this threat is unclear: by reducing the density of a dominant competitor (the lion Panthera leo) prey depletion could create both costs and benefits for subordinate competitors. We used capture–recapture models fitted to data from a 7-year camera-trap study in Kafue National Park, Zambia, to obtain baseline estimates of leopard population density and sex-specific apparent survival rates. Kafue is affected by prey depletion, and densities of large herbivores preferred by lions have declined more than the densities of smaller herbivores preferred by leopards. Lion density is consequently low. Estimates of leopard density were comparable to ecosystems with more intensive protection and favourable prey densities. However, our study site is located in an area with good ecological...

Occupied from ca. 7040 B.C. to A.D. 1400, the Eel Point Site (CA-SCLI-43) on San Clemente Island, California represents one of the longest sequences of near-continuous marine resource exploitation on the west coast of North America.... more

Occupied from ca. 7040 B.C. to A.D. 1400, the Eel Point Site (CA-SCLI-43) on San Clemente Island, California represents one of the longest sequences of near-continuous marine resource exploitation on the west coast of North America. Faunal remains suggest transitions from heavy exploitation of fur seals and sea lions during the early Holocene, to increased hunting of cetaceans at mid-Holocene, to a focus on sea otters and fish during the late Holocene. These trends are consistent with patterns of overexploitation and economic intensification on the California and Oregon mainland, but they also suggest watercraft-based hunting earlier on the island than elsewhere. Fur seal and sea lion bones mainly represent females and juveniles, indicating that exploitation of island rookeries was guided more by self-interest than by principles of game conservation. Two intervals of temporary site abandonment, ca. 6150–3970 B.C. and A.D. 1020–1400, were both followed by periods of increased marine mammal exploitation and may reflect intervals during which marine mammal populations rebounded. Broad-scale diachronic trends in the zooarchaeological remains do not correlate with flux in paleo-sea temperatures and are best interpreted as products of overhunting and increased use of watercraft over time.

The mechanical basis of prey capture and behaviour of Phyllorhiza punctata von Lendenfeld, 1884, as with most members of the Order Rhizostomeae, has not been described. Free-swimming medusae were videotaped in order to quantitatively... more

The mechanical basis of prey capture and behaviour of Phyllorhiza punctata von Lendenfeld, 1884, as with most members of the Order Rhizostomeae, has not been described. Free-swimming medusae were videotaped in order to quantitatively describe the feeding process of P. punctata. Kinematic data demonstrated that adult medusae were surrounded by relatively high Re (102–103) flows while swimming. Therefore, momentum dominated these flows and the motions of particles entrained in the fluid surrounding swimming P. punctata. Artemia salina nauplii entrained within these flows contacted two principle capture surfaces: the oral arm cylinder and the underside of the subumbrellar surface. Prey were ingested by small polyp-like mouthlets located on these surfaces. Ingestion followed capture at these sites. P. punctata's body morphology is highly modified to channel flows into these capture surfaces and feeding is dependent upon this pattern. Swimming activity, and hence the creation of flows used for prey capture, is continuous, as is feeding, and plays a central role in this medusa's foraging behaviour.

The diet of the nudibranch mollusc Tritonia odhneri was investigated for the first time based on a detailed anatomical analysis of the gut content of 52 specimens. Digestive tracts of specimens were analysed under stereoscopic microscope... more

The diet of the nudibranch mollusc Tritonia odhneri was investigated for the first time based on a detailed anatomical analysis of the gut content of 52 specimens. Digestive tracts of specimens were analysed under stereoscopic microscope equipped with digital camera. Portions of octocorals containing the calcareous sclerites were removed from the tracts and prepared for scanning electron microscopy (SEM). Sclerite morphology and size were determined at the species and genus level on the basis of a taxonomical revision and compared with fresh octocoral specimens collected from Patagonia (San Jorge Gulf) and with voucher specimens from the collections of Museo Argentino de Ciencias Naturales (MACN-in). Specific predation of T. odhneri on octocoral species present in the southwestern Atlantic Ocean was detected. The nudibranch feeds on the gorgonians Primnoella divaricata, Primnoella scotiae (=P. compressa) and Tripalea clavaria, and the pennatulaceans Renilla octodentata and Stylatula sp. A world checklist of dietary interactions between species of the genus Tritonia and octocorals is presented and discussed.

The discovery in 2008, during an archaeological survey carried out on the Digges Islands (southern shores of Hudson Strait, Nunavut), of a fox den (Vulpes vulpes) with associated bones allow us to better understand the feeding habits of... more

The discovery in 2008, during an archaeological survey carried out on the Digges Islands (southern shores of Hudson Strait, Nunavut), of a fox den (Vulpes vulpes) with associated bones allow us to better understand the feeding habits of the red fox in an arctic periglacial context. The bones, essentially representing diverse bird species, were collected near the entrance and exit points of the still active den. Bird species include the Canada goose (Branta canadensis), the snow goose (Chen caerulescens) and the murres (Uria lomvia). The majority of these birds was caught during the month of July 2008 by the foxes, especially during their summer migration phase. The den being still active, fox cubs were present during our passage. It is planned to make a brief return over the coming years to see if more bones will have accumulated since our
last visit.

We report co-operative group foraging in the African Penguin Spheniscus demersus. Groups of approximately 25 - 165 African Penguins were observed circling schools of pelagic fish, sometimes forcing them to the surface. During this... more

We report co-operative group foraging in the African Penguin Spheniscus demersus. Groups of approximately 25 - 165 African Penguins were observed circling schools of pelagic fish, sometimes forcing them to the surface. During this behaviour 66 - 75% of penguins were underwater at any given time. Smaller numbers of African Penguins also joined foraging groups of Cape Gannets Morus capensis and Cape Cormorants Phalacrocorax capensis, but did not appear to corral fish schools when outnumbered by these species. African Penguins are listed as Endangered due to ongoing rapid population decreases. If group foraging confers an advantage to African Penguins, their dwindling populations may suffer from an Allee effect as colonies become too small to support sufficient densities of birds for foraging groups to form.