Prey Availability Research Papers - Academia.edu (original) (raw)

The viperine snake Natrix maura is a common water snake, which forages on aquatic prey such as fish and frogs in Western Mediterranean water bodies. Female viperine snakes collected from three populations at the Iberian Peninsula during... more

The viperine snake Natrix maura is a common water snake, which forages on aquatic prey such as fish and frogs in Western Mediterranean water bodies. Female viperine snakes collected from three populations at the Iberian Peninsula during the vitellogenesis period were compared. Mean clutch size and range, as well as the slope of the regression between body size and clutch size, did not show differences between populations. In contrast, mean size of enlarged follicles of females collected in May from the Ebro Delta proved significantly smaller than those of females from the Matarranya River (50 km far) and the Granada Depression (500 km far). There were no differences in climatic conditions between areas. However, seasonal variation in food availability was significantly different in the Ebro Delta. In this area, the rice fields are dry in early spring as men control the water flow, and prey are not available. This energetic constraint induced female viperine snakes to adjust reproductive timing according to seasonal availability and to delay vitellogenesis for at least one month. By contrast, other Mediterranean populations exhibited a rather high prey availability from early spring (e.g. Matarranya River), females being in good condition in this season and consequently vitellogenesis starting earlier than in the Ebro Delta. This study illustrates a new case of reproductive plasticity in snakes.

Managing endangered species often involves evaluating the relative impacts of multiple anthropogenic and ecological pressures. This challenge is particularly formidable for cetaceans, which spend the majority of their time underwater.... more

Managing endangered species often involves evaluating the relative impacts of multiple anthropogenic and ecological pressures. This challenge is particularly formidable for cetaceans, which spend the majority of their time underwater. Noninvasive physiological approaches can be especially informative in this regard. We used a combination of fecal thyroid (T3) and glucocorticoid (GC) hormone measures to assess two threats influencing the endangered southern resident killer whales (SRKW; Orcinus orca) that frequent the inland waters of British Columbia, Canada and Washington, U.S.A. Glucocorticoids increase in response to nutritional and psychological stress, whereas thyroid hormone declines in response to nutritional stress but is unaffected by psychological stress. The inadequate prey hypothesis argues that the killer whales have become prey limited due to reductions of their dominant prey, Chinook salmon (Oncorhynchus tshawytscha). The vessel impact hypothesis argues that high numbers of vessels in close proximity to the whales cause disturbance via psychological stress and/or impaired foraging ability. The GC and T3 measures supported the inadequate prey hypothesis. In particular, GC concentrations were negatively correlated with short-term changes in prey availability. Whereas, T3 concentrations varied by date and year in a manner that corresponded with more long-term prey availability. Physiological correlations with prey overshadowed any impacts of vessels since GCs were lowest during the peak in vessel abundance, which also coincided with the peak in salmon availability. Our results suggest that identification and recovery of strategic salmon populations in the SRKW diet are important to effectively promote SRKW recovery.

Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens... more

Stomach contents from tiger sharks, Galeocerdo cuvier, caught on lines off the central coast of Western Australia were analysed to investigate variations in the diet due to sex, size and geographic location. Stomachs from 84 specimens contained food, while 26 had empty stomachs and 66 had regurgitated. Twelve prey groups were identified, the most common being turtles, sea snakes, teleost fishes, dugongs and sea birds. Dietary overlap was high between males and females. An ontogenetic shift was observed in the diet. Smaller prey (e.g. cephalopods, teleosts and sea snakes) were more common in small individuals, while the occurrence of larger prey (e.g. turtles, dugongs and elasmobranchs) increased with increasing shark size. Differences in the diet were observed between four regions along the central Western Australian coast. The ability to catch and consume large prey, prey availability, prey density, and prey profitability were identified as factors influencing the diet. The high level of occurrence of dugongs and turtles in the diet of G. cuvier, relative to their abundance, suggests that shark predation may play an important role in regulating populations of these species.

Habitat utilization of native young-ofthe-year (YOY) muskellunge, Esox masquinongy, was quantified by the type and density of vegetation present, water depth, and fish communities associated with their presence and abundance in nursery... more

Habitat utilization of native young-ofthe-year (YOY) muskellunge, Esox masquinongy, was quantified by the type and density of vegetation present, water depth, and fish communities associated with their presence and abundance in nursery bays of the Upper St. Lawrence River. We completed 441 seine hauls and captured 400 YOY muskellunge in 11 bays that were sampled each July and August over a 3year period (2002)(2003)(2004). We hypothesized a change in habitat utilization related to increasing body size, as YOY muskellunge doubled in total length from July to August. Fine-leafed submerged and emergent macrophytes and prey availability (cyprinids, Notropis sp., banded killifish, Fundulus diaphanous and tessellated darter, Etheostoma olmstedi), were positively related to muskellunge use in July, while in August coverage of broad-leafed submerged macrophytes and increased overall vegetation density were the best habitat descriptor. In both months, muskellunge were associated with moderate (20-60%) vegetation coverage and density, however, captures were in areas of significantly greater vegetation coverage and density than was generally available. A negative relation of muskellunge occurrence with water depth, yellow perch, Perca flavescens, and stonewort, Chara vulgaris, was observed in both months. The negative relationship between muskellunge and depth, plus their strong linkages to nearshore submerged vegetation and forage fish that inhabit the nearshore areas, highlights the importance of protecting the ecological integrity of nearshore habitats. Our findings should assist managers in protecting native stocks, planning restoration and enhancement initiatives, and in regulating riparian and nearshore development.

Pup mortality and the timing of birth of South American sea lions Otaria flavescens were investigated to determine the possible relationship between fluctuations in prey availability in the Peruvian upwelling ecosystem and current and... more

Pup mortality and the timing of birth of South American sea lions Otaria flavescens were investigated to determine the possible relationship between fluctuations in prey availability in the Peruvian upwelling ecosystem and current and future reproductive success of sea lions during six consecutive breeding seasons. Our study from 1997 to 2002 encompassed the strongest El Niño on record and one La Niña event. Pup mortality ranged from 13% before El Niño to 100% during El Niño, and was negatively correlated with prey availability. Abortions were also more frequent when prey availability was low. However, pup mortality remained high following El Niño due to the punctuated short-term effects it had on population dynamics and subsequent maternal behaviour. Births occurred later in the season after years of low food availability and earlier following years of high food availability. The peak of pupping occurred around the peak of mortality in all years, and may have been the product of intensive competition between bulls at the peak of the breeding season. The stronger and more frequent El Niños that appear to be occurring along the Peruvian coast may produce significant stochastic changes in future births and pup mortality, which may place the vulnerable South American sea lion population in Peru at greater risk.

All natural populations fluctuate in abundance and age structure through time; understanding why they do so is a critical step towards their effective management and conservation. However, the long-term data sets needed for such an... more

All natural populations fluctuate in abundance and age structure through time; understanding why they do so is a critical step towards their effective management and conservation. However, the long-term data sets needed for such an understanding are rarely available, especially for tropical organisms. A 17-year capturemark-recapture study yielded detailed information on the demography of water pythons (Liasis fuscus) and their main prey, the dusky rat (Rattus colletti), on the Adelaide River flood plain in tropical Australia. The link between annual rainfall patterns and rat demography was highly non-linear. Rat numbers were low during years with low and high rainfall at the end of the wet season (April). Numbers of both predators and prey fluctuated considerably among years. Annual fluctuations in rat numbers generated a corresponding variation in rates of female python reproduction, python body condition and survival. Although variation in recruitment, survival and prey abundance all had a significant impact on annual fluctuations in python numbers, our analyses suggest that recruitment constituted the main determinant in driving the population dynamics of these large tropical predators. In combination with our other studies on this system, the data show that population dynamics of the water python population is ultimately driven by annual variation in rainfall, mediated via shifts in prey availability. The water pythons and the dusky rats of the Adelaide River flood plain thus demonstrate an unusually clear and direct link between an abiotic factor (rainfall) and predator-prey population dynamics.

In the Kruger National Park, male lions, Panthera leo, acquire most of their food by hunting rather than scavenging. This study, the most intensive to date of male lion ecology, showed that in savanna woodlands, with high buffalo,... more

In the Kruger National Park, male lions, Panthera leo, acquire most of their food by hunting rather than scavenging. This study, the most intensive to date of male lion ecology, showed that in savanna woodlands, with high buffalo, Syncerus caffer, densities, male lions were frequent and successful hunters. The main prey species of all male group types, but particularly nonterritorial males, was buffalo. By contrast, females preyed more frequently on the most abundant medium-sized ungulates, such as wildebeest, Connochaetes taurinus, and zebra, Equus burchelli. Thus intraspecific prey selection separation was based primarily on intersexual and, to a lesser extent, social differences. Furthermore, both nonterritorial males and pride females located their favoured prey, buffalo and medium-sized ungulates, respectively, more often than other prey. We investigated the influence of several ecological variables on the socioecology of male lions, particularly as we had determined that territorial males spent little time with their pride females and tended to hunt by themselves in their respective male coalitions. Further analysis showed that in a range of ecosystems in southern and eastern Africa the proportion of time territorial males spent with, and thus scavenged from, their pride females was strongly influenced by vegetation structure, and therefore probably by the assemblage of available ungulates. In open systems, territorial males were, therefore, likely to be encountered with pride females, whereas in more wooded areas they were likely to be encountered away from their pride females. We suggest that this is because vegetation structure influences food/prey availability and hunting success and influences territory maintenance and/or cub defence.

The Casentinesi Forests, in the northern Apennines, harbour a rich community of wild ungulates, with the wolf representing the largest predator in the area. Between 1993 and 2000, wolf pack distribution in the area was monitored and... more

The Casentinesi Forests, in the northern Apennines, harbour a rich community of wild ungulates, with the wolf representing the largest predator in the area. Between 1993 and 2000, wolf pack distribution in the area was monitored and estimates of pack size were obtained by wolf-howling surveys, snow-tracking, and occasional observations. Three to five packs were detected yearly, with sizes averaging 4.2 AE 0.9 wolves (maximum 7). The overall density in the area was 4.7 wolves per 100 km 2 with an average distance between adjacent packs of 11.1 km. The high wolf density in the Casentinesi Forests is mostly related to abundance and size of wild prey. In this, like in other areas at low latitudes, wolf density depends mainly on the number of packs, as pack size is rather small and recruitment limited by early dispersal and high mortality. Three homesites used in several years by resident packs were discovered. Homesite fidelity and pack reproductive success were higher in fully protected rather than harvested areas. Establishing a network of protected areas with high ungulate diversity and abundance is proposed as the main factor for allowing a full recovery of the wolf population in Italy.

Diet composition of mummichogs, Fundulus heteroclitus, from three marsh habitats (creeks, pools, and marsh surface) within tidally restored and an adjacent unrestricted (reference) region of Sachuest Point salt marsh (Middletown, RI,... more

Diet composition of mummichogs, Fundulus heteroclitus, from three marsh habitats (creeks, pools, and marsh surface) within tidally restored and an adjacent unrestricted (reference) region of Sachuest Point salt marsh (Middletown, RI, U.S.A.) was examined. Major diet components were detritus, copepods, diatoms, insects (larvae and adults), ostracods, and chironomids. Total length, wet weight, and gut fullness of mummichogs were equivalent within habitats between the restoring and unrestricted marshes. Diet composition and percent abundance of diet items were also similar within habitats between the unrestricted and restoring marshes. However, differences in diet patterns were observed among habitats (creeks, pools, and marsh surface) within each marsh. Fish collected from creeks had fuller guts than those sampled from the marsh surface for both the restoring and unrestricted marsh. Diet composition also differed among marsh habitats, but only within the restoring marsh. In the restoring marsh, fish sampled from the creeks consumed primarily detritus, diatoms, and ostracods, whereas fish from the pools consumed mainly detritus, copepods, chironomids, and insects. Differences in diet composition among habitats were most likely a reflection of prey availability. This study provides evidence that tidally restored marshes can provide similar food resources as unrestricted marshes, in terms of consumption patterns of dominant marsh consumers, within the first year after restoration, before major shifts in dominant vegetation (i.e. from Phragmites australis to Spartina spp.) occur.

To investigate the influence of marine macrophyte wrack subsidies on community structure, relationships between community attributes, including species richness, abundance, and biomass of macrofauna and abundance of shorebirds, and a... more

To investigate the influence of marine macrophyte wrack subsidies on community structure, relationships between community attributes, including species richness, abundance, and biomass of macrofauna and abundance of shorebirds, and a variety of factors, including the standing crop of ...

Previous studies have proposed that seagrass habitats, by supporting diverse and abundant fish assemblages, are preferred by foraging dolphins in coastal systems. To test this hypothesis, we (1) examined the fine-scale behavior of... more

Previous studies have proposed that seagrass habitats, by supporting diverse and abundant fish assemblages, are preferred by foraging dolphins in coastal systems. To test this hypothesis, we (1) examined the fine-scale behavior of bottlenose dolphins in relatively pristine and developed inshore sites near Clearwater Harbor, Florida, USA, and (2) used an otter trawl to sample potential fish prey in non-seagrass and seagrass habitats. In the pristine site, dolphins preferred dredged channel and spoil-island habitats, while least preferring shallow seagrass habitats. In the developed site, foraging dolphins preferred the natural channel habitat, but exhibited little further selection. Therefore, the hypothesis that dolphins prefer seagrass habitats while foraging was rejected. Feeding frequency was significantly associated with diel state, with foraging peaking at dawn and decreasing throughout the day. Dolphin group size was negatively correlated and nearest neighbor distance positively correlated with feeding frequency. Analysis of trawl data focused on the pinfish Lagodon rhomboides which dominates the diets of dolphins in west Florida. The relative abundance of pinfish was significantly greater and standard lengths significantly less in seagrass than in non-seagrass habitats. Dolphins therefore forage in non-seagrass habitats where fish prey is both larger and perhaps more available. Although seagrass habitats support greater abundance of smaller fishes, they also provide a structural refuge which obscures fishes both visually and possibly acoustically. Thus, the importance of seagrasses to the health of coastal dolphins is probably indirect, as seagrasses support fish populations on which dolphins rely.

Threadfin shad Dorosoma petenense are commonly introduced into reservoirs to supplement prey available to piscivorous fishes. To determine how early life stages of threadfin shad and their potential competitors and predators interact, we... more

Threadfin shad Dorosoma petenense are commonly introduced into reservoirs to supplement prey available to piscivorous fishes. To determine how early life stages of threadfin shad and their potential competitors and predators interact, we introduced this species into two Ohio lakes-Clark and Stonelick-and evaluated how its young of year influenced young-of-year bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides. After adults were stocked in April, peak abundance of young-of-year threadfin shad occurred in August in both lakes. Bluegills generally spawned earlier than threadfin shad, which apparently reduced competition between young of these species. In Clark Lake, young-of-year threadfin shad did not reduce zooplankton populations, but in Stonelick Lake, peak abundance of young-of-year threadfin shad was followed by a precipitous decline in zooplankton. Data on cladoceran birth rates indicated this decline was due to increased predation by threadfin shad. Survival of bluegills to a size at which they move into the littoral zone also declined in Stonelick Lake, perhaps because of the virtual elimination of zooplankton. Limited survival of bluegills in turn contributed to reduced growth of young-of-year largemouth bass dependent on them as prey. Given that zooplankton declined in one but not the other lake, interactions among young-of-year fishes due to annually introduced threadfin shad will likely vary among systems and years. Nonetheless, introduced threadfin shad could, in some systems in some years, negatively affect growth and recruitment of the very species they were meant to enhance.

The southern sea otter (Enhydra lutris nereis) is listed as ''threatened'' under the Endangered Species Act (ESA) and is a ''keystone species,'' strongly influencing the abundance and diversity of the other species within its kelp forest... more

The southern sea otter (Enhydra lutris nereis) is listed as ''threatened'' under the Endangered Species Act (ESA) and is a ''keystone species,'' strongly influencing the abundance and diversity of the other species within its kelp forest ecosystem. This is accomplished primarily by preying upon urchins that eat the kelp stipe and holdfast, which can reduce a kelp forest to an urchin barren. Sea otters are very susceptible to marine pollutants such as petroleum, which may be directly toxic and/or alter their fur's insulating properties. Sea otters are an excellent sentinel species. They eat approximately 25% of their body weight per day in shellfish and other invertebrates, and can concentrate and integrate chemical contaminants. In addition, they appear to be susceptible to a number of diseases and parasites that may have anthropogenic origins, and shellfish may serve as an intermediary for some of these infections. Many of the shellfish the otters eat are also harvested for human food. In their role as sentinels, sea otter health has implications for human health, economic sustainability of shellfisheries, as well as overall marine ecosystem health. The recent southern sea otter decline has been viewed with some alarm by conservationists and, indeed, recovery seems a long way off. High mortality rather than depressed recruitment appears to underlie the decline. A good deal of debate has centered on the role of infectious diseases and parasites, exposure to contaminants, nutrition and prey availability, net and pot fishery interactions, and other sources of mortality. Current research is being done related to major classes of mortality, various types of pollutants and some specific organisms causing southern sea otter mortality, and their implications for marine ecosystem health and sustainability.

In the Kruger National Park, male lions, Panthera leo, acquire most of their food by hunting rather than scavenging. This study, the most intensive to date of male lion ecology, showed that in savanna woodlands, with high buffalo,... more

In the Kruger National Park, male lions, Panthera leo, acquire most of their food by hunting rather than scavenging. This study, the most intensive to date of male lion ecology, showed that in savanna woodlands, with high buffalo, Syncerus caffer, densities, male lions were frequent and successful hunters. The main prey species of all male group types, but particularly nonterritorial males, was buffalo. By contrast, females preyed more frequently on the most abundant medium-sized ungulates, such as wildebeest, Connochaetes taurinus, and zebra, Equus burchelli. Thus intraspecific prey selection separation was based primarily on intersexual and, to a lesser extent, social differences. Furthermore, both nonterritorial males and pride females located their favoured prey, buffalo and medium-sized ungulates, respectively, more often than other prey. We investigated the influence of several ecological variables on the socioecology of male lions, particularly as we had determined that territorial males spent little time with their pride females and tended to hunt by themselves in their respective male coalitions. Further analysis showed that in a range of ecosystems in southern and eastern Africa the proportion of time territorial males spent with, and thus scavenged from, their pride females was strongly influenced by vegetation structure, and therefore probably by the assemblage of available ungulates. In open systems, territorial males were, therefore, likely to be encountered with pride females, whereas in more wooded areas they were likely to be encountered away from their pride females. We suggest that this is because vegetation structure influences food/prey availability and hunting success and influences territory maintenance and/or cub defence.

While climate change is expected to affect cetaceans primarily via loss of habitat and changes in prey availability, additional consequences may result from climate-driven shifts in human behaviors and economic activities. For example,... more

While climate change is expected to affect cetaceans primarily via loss of habitat and changes in prey availability, additional consequences may result from climate-driven shifts in human behaviors and economic activities. For example, increases in shipping, oil and gas exploration and fishing due to the loss of Arctic sea ice are highly likely to exacerbate acoustic disturbance, ship strikes, bycatch and prey depletion for Arctic cetaceans. In the tropics, climate change may result in increased hunting pressure on near-shore dolphins and whales off Asia, Latin America, Africa, and elsewhere as the availability of other marine resources diminishes. This study explores the range of potential consequences to cetaceans worldwide from predicted climate-driven shifts in human behavior, and evaluates the risks to particular species given their geographic ranges and habitat preferences. While concern about impacts of climate change on cetaceans has largely focused on polar species, the analysis presented here suggests tropical coastal and riverine cetaceans such as the Irawaddy dolphin, Indo-Pacific humpback dolphin, and finless porpoise are particularly vulnerable to those aspects of climate change that are mediated by changes in human behavior. Policy recommendations include the following: (1) information about cetacean populations should be incorporated into national, regional and international climate adaptation decisions wherever possible (for example, via GEF-sponsored adaptation initiatives); and (2) human-mediated impacts of climate change should be included in cetacean conservation and management plans, such as the management procedures of the International Whaling Commission (IWC), where possible. Because human responses to climate change are likely to evolve rapidly over the coming years and decades, it is important that local, regional and international cetacean conservation and management plans include regular reviews to allow them to adapt to new information.

Anecdotal evidence, sighting reports, Inuit traditional knowledge, and photographic identification indicate that killer whale (Orcinus orca) occurrence in Hudson Bay is increasing. Killer whales were not known to be present in the region... more

Anecdotal evidence, sighting reports, Inuit traditional knowledge, and photographic identification indicate that killer whale (Orcinus orca) occurrence in Hudson Bay is increasing. Killer whales were not known to be present in the region prior to the mid-1900s but have since shown an exponential increase in sightings. More sightings from Foxe Basin, Nunavut in the north to Churchill, Manitoba in the south appear to be related to a decrease in summer sea ice in Hudson Strait. Killer whale activity during the open water season has been concentrated in the northwest Hudson Bay region that includes the Repulse Bay and northern Foxe Basin areas.

Conger oceanicus sampled in 1980 to 1983 from the tilefish longline fishery in Mid-Atlantic. and southern New England regions of the USA were supplemented with inshore samples caught by small-meshed trawl. The total lengths (TL) of conger... more

Conger oceanicus sampled in 1980 to 1983 from the tilefish longline fishery in Mid-Atlantic. and southern New England regions of the USA were supplemented with inshore samples caught by small-meshed trawl. The total lengths (TL) of conger eels caught by longline were larger (48 to 123 cm TL) than eels taken by trawl (18 to 67 cm TL). Because males were smaller than all but the smallest females seen in the fishery (< 50 cm TL), the absence of males from the offshore longline catch was attributed to gear selection. Conger eel catch rates in the longline fishery were highest in winter. Otoliths were used to age conger eels and to determine back-calculated length at age. Validation of annulus formation was difficult because a multiple banding pattern occurred and otolith shape was variable. The otolith data indicated that size at a given age was highly variable. Gross morphologies of the gonads were similar to those described for Anguilla spp. Ovaries had "frills" on the distal surface and gonia > 20/~m in diameter in histological sections. Males were distinguished by the presence of gonia in well-defined crypts. Female ovaries were characterized by having either oocytes in a previtellogenic condition, or oocytes undergoing vitellogenesis together with adipose cells. In females > 85 cm TL, the most mature individuals (those having a high gonosomatic index and mean maximum oocyte diameter) occurred during the late spring and early summer. The absence of ripe or spent female conger eels in Mid-Atlantic and southern New England regions suggests that they leave the region to spawn, probably in the Sargasso Sea.

During the 1960s, water management practices resulted in the conversion of the wetlands that fringe northeastern Florida Bay (USA) from freshwater/oligohaline herbaceous marshes to dwarf red mangrove forests. Coincident with this... more

During the 1960s, water management practices resulted in the conversion of the wetlands that fringe northeastern Florida Bay (USA) from freshwater/oligohaline herbaceous marshes to dwarf red mangrove forests. Coincident with this conversion were several ecological changes to Florida Bay's fauna, including reductions in the abundances of top trophic-level consumers: piscivorous fishes, alligators, crocodiles, and wading birds. Because these taxa rely on a common forage base of small demersal fishes, food stress has been implicated as playing a role in their respective declines. In the present study, we monitored the demersal fishes seasonally at six sites over an 8-year time period. During monitoring, extremely high rainfall conditions occurred over a 3.5-year period leading to salinity regimes that can be viewed as ''windows'' to the area's natural past and future restored states. In this paper, we: (1) examine the changes in fish communities over the 8-year study period and relate them to measured changes in salinity; (2) make comparisons among marine, brackish and freshwater demersal fish communities in terms of species composition, density, and biomass; and (3) discuss several implications of our findings in light of the intended and unintended water management changes that are planned or underway as part of Everglades restoration. Results suggest the reduction in freshwater flow to Florida Bay over the last several decades has reduced demersal fish populations, and thus prey availability for apex consumers in the coastal wetlands compared to the pre-drainage inferred standard. Furthermore, greater discharge of freshwater toward Florida Bay may result in the re-establishment of pre-1960s fauna, including a more robust demersal-fish community that should prompt increases in populations of several important predatory species.

We determined the food habits of the endangered Indian wolf Canis lupus pallipes in the Bhal region of Gujarat, western India by analyzing 1246 wolf scats from five packs by estimating prey availability and by monitoring radio-tagged... more

We determined the food habits of the endangered Indian wolf Canis lupus pallipes in the Bhal region of Gujarat, western India by analyzing 1246 wolf scats from five packs by estimating prey availability and by monitoring radio-tagged wolves from three packs for 1994 hour. The frequency of occurrence of blackbuck Antelope cervicapra remains in scats was 55.5%, followed by cattle (25.7%), nilgai Boselaphus tragocamelus (6.3%); and as others ( < 5%). The frequency of food items in scats of different wolf packs reflected their relative availability. For cattle the distinction between scavenging and predation was only possible through continuous monitoring. The average feeding interval obtained from monitoring was 3.6 AE 0.7 (S.E.) days and the average consumption/ wolf/day was 1.8 AE 0.3 (S.E.) Kg. Adult male blackbuck formed most (70%) of the biomass consumed by wolves whereas cattle carcasses and cattle actually killed by wolves contributed 14 and 8%, respectively. Predation on cattle therefore was low and translated in an estimated loss of Rs. 821 (US$ 17) per village per annum. We propose that landscapes such as the Bhal with high wolf densities, high natural prey availability and consequently low human-wolf conflict levels should be prioritized as prime sites for wolf conservation efforts. #

The present study was conducted between January and June 2007 to assess the abundance and density of Ganges River dolphin (Platanista gangetica gangetica) and their prey in a 28-km stretch of the River Ganges between Narora Barrage and... more

The present study was conducted between January and June 2007 to assess the abundance and density of Ganges River dolphin (Platanista gangetica gangetica) and their prey in a 28-km stretch of the River Ganges between Narora Barrage and Anupshahar. Two different sampling methods were used to estimate dolphin densities. Estimated density was 2.58 ± 0.40 individuals/km 2 (mean ± 1 SE) using the direct count method and 4.97 ± 0.60 individuals/km 2 using the boat-based, line-transect distance methods, with an encounter rate of 0.52 ± 0.068 individuals/km and detection probability of 0.647. No significant differences between the upstream and downstream counts (t = 1.29, df = 9, p > 0.05) were detected. The adult male to adult female ratio was 0.66: 1.00, whereas the calf to adult female ratio was 0.42: 1.00. We collected 16 fish species of length class varying from 3.5 to 20 cm (range of preferred size of dolphin prey) with a total density of 176.42 fish/km 2 and a total average biomass of 5.36 kg/km 2 . Dolphin density showed a significant positive relationship (R 2 = 0.587) with density of Reba fish (Cirrhinus reba) (β = 0.31, p = 0.00) and Baam fish (Mastacembelus armatus) (β = 0.50, p = 0.04) and also with water depth (β = 0.17, p = 0.03). Presence of dolphins varied across different water depth categories (χ 2 = 106.38, df = 3, p < 0.01) and different parts of the river (χ 2 = 21.68, df = 2, p = 0.00) with more than 50% of dolphin sightings occurring in confluences, indicating their preference for deep water pools.

We review current knowledge of the diet and predator-prey relationships of the feral cat (Felis catus), fox (Vulpes vulpes) and dingo (Canis familiaris dingo) (including wild dogs), and consider how forest fragmentation by roads may... more

We review current knowledge of the diet and predator-prey relationships of the feral cat (Felis catus), fox (Vulpes vulpes) and dingo (Canis familiaris dingo) (including wild dogs), and consider how forest fragmentation by roads may influence the use of native forest ecosystems by these species and the significance of this for native fauna. 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 than is the cat 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 selectively prey upon species and, to some extent, individual sexes and age-classes of a number of larger prey species.

In order to obtain a reliable method for sexing and ageing Buzzards Buteo buteo breeding in southern Europe, 115 birds from a wildlife rehabilitation centre and 43 trapped birds were measured, sexed and aged over four years... more

In order to obtain a reliable method for sexing and ageing Buzzards Buteo buteo breeding in southern Europe, 115 birds from a wildlife rehabilitation centre and 43 trapped birds were measured, sexed and aged over four years (2000)(2001)(2002)(2003). Dead birds were sexed by examining their gonads, and live birds by the presence of a brood patch. Wing length, minimum tarsus width and body weight were the only variables which differed significantly between the sexes, although there was much overlap for the wing length and weight. Buzzards with less than 7 mm minimum tarsus width were male and those greater than 7.9 mm were female. Birds did not complete moult in one year, moulting less than 60% of the flight feathers in one season. The first and the second moult followed a pattern, but afterwards moult was unpredictable and totally asymmetric. Also, half the females and 33% of males had started to moult within 30 days of their chicks hatching. These results differ from those published for Buzzards from northern Europe. The size and moult pattern depend on factors such as prey availability and migratory status, which in turn vary between areas. We therefore suggest caution when considering the moult strategies, ageing criteria and sexing criteria published for other countries.

Feeding habits of the fishes Lutjanus peru and Lutjanus guttatus (Pisces: Lutjanidae) of Guerrero, México. Diet composition of the Pacific snapper (Lutjanus peru) 130-684 mm fork length (FL) and the spotted snapper (Lutjanus guttatus)... more

Feeding habits of the fishes Lutjanus peru and Lutjanus guttatus (Pisces: Lutjanidae) of Guerrero, México. Diet composition of the Pacific snapper (Lutjanus peru) 130-684 mm fork length (FL) and the spotted snapper (Lutjanus guttatus) 120-550 mm FL, was analyzed. Monthly samples were obtained from commercial landings in three regions off the coast of Guerrero, Mexico. Percentage by number (%N), percentage

During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the whole distributional area of the species. Recovery of the population was slow since 1983 and it has been suggested that large numbers of... more

During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the whole distributional area of the species. Recovery of the population was slow since 1983 and it has been suggested that large numbers of Humboldt penguins die at sea, entangled in nets, or starve to death, even during non-“El Niño” years. We were able to determine for the first time, how Humboldt penguins on Pan de Azúcar Island (26°S; 72°W) utilize their marine habitat and where their feeding areas lie. For this purpose we employed two streamlined Argos satellite transmitters during the 1994/1995 and 1995/1996 breeding seasons, respectively. Mean travelling speed of Humboldt penguins during foraging trips was 0.94 m s−1 and 50% of bird positions were located within 5 km of the island (90% within 35 km). Total area covered by Humboldt penguins foraging from Pan de Azúcar Island was 12 255␣km2. Satellite transmitters also recorded dive duration; penguins spent on average 7.8 to 9 h diving per foraging day but showed no preferences for particular feeding areas. Mean daily dive durations (4-d mean) recorded during the 1994/1995 breeding season were positively correlated between birds. Significant correlation between dive duration and sea surface temperature anomalies and negative correlation between dive duration and fishery landings at nearby Caldera harbour indicate that the 1994/1995 increase in foraging effort was a response to deteriorating prey availability. Sea surface temperatures during the 1995/1996 breeding season were colder than average, and we observed no trends in bird diving activities.

Large-scale spatial surveys of fish species in relation to habitat have tended to focus on depth, sediment type and temperature as descriptors of fish habitats. At a smaller scale, habitat parameters such as the relief of the sea floor,... more

Large-scale spatial surveys of fish species in relation to habitat have tended to focus on depth, sediment type and temperature as descriptors of fish habitats. At a smaller scale, habitat parameters such as the relief of the sea floor, the presence of structuring fauna and prey availability may have a considerable influence on fish distribution, but often are not considered. In the present study we used video survey techniques to study habitat components in areas of the English Channel that were known to support consistently high densities of adult plaice. Habitat features were quantified and related to the density of adult plaice caught within the same study areas. To focus the study on habitat components other than sediment type all sites chosen had sandy substrata. The scale and spatial distribution and heterogeneity of physical and biological structures were quantified for each site and correlated to plaice densities. Plaice densities correlated with the abundance of benthic fauna recorded. In particular the emergent tube-dwelling polychaetes Lanice conchilega and Cheatopterus spp., which are a valuable food source for plaice, dominated some sites. Abiotic habitat features and habitat heterogeneity showed no clear relationships with respect to plaice densities at the scale of our surveys. This indicated that prey availability might be the driving force for habitat selection of adult plaice within sandy habitats and that other habitat descriptors assume less importance at smaller spatial scales.

1. Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km 2 Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo-identification of... more

1. Boat surveys were conducted between 2002 and 2005 to study bottlenose dolphins living in the 400 km 2 Amvrakikos Gulf, western Greece. During 116 survey days, 4705 km of total effort resulted in the individual photo-identification of 106 animals, through long-term natural markings on their dorsal fins. 2. Mark-recapture analyses based on the M th model provided estimates of 82 marked individuals in 2003 (95% CI ¼ 80-91), 92 in 2004 (95% CI ¼ 86-108) and 98 in 2005 (95% CI ¼ 94-110). To include the unmarked portion of the population, the proportion of unmarked individuals was computed based on the number of photographs of marked and unmarked dorsal fins. The mean proportion of unmarked animals in the population was 0.338 (95% CI ¼ 0:288-0.389). By adding this to the estimate for marked animals in 2005, considered as the most robust, a total population estimate of 148 individuals (95% CI ¼ 132-180) was obtained.

Hunting behaviour and use of different habitat types of a breeding Great Grey Shrike family was observed in a recycled landfill near Eilat, Israel. As Great Grey Shrikes were not observed to breed in the Eilat area for more than a decade,... more

Hunting behaviour and use of different habitat types of a breeding Great Grey Shrike family was observed in a recycled landfill near Eilat, Israel. As Great Grey Shrikes were not observed to breed in the Eilat area for more than a decade, detailed observations of hunting site selection were conducted. Additionally, arthropod abundance and impaled prey items were monitored. The breeding pair established its territory on the boundary of the "Bird Sanctuary", a former recycled landfill, where irrigation has facilitated the growth of dense vegetation inside the park boundary, while outside of it the sparse vegetation characteristic of semideserts is found. Huntings were categorised as either inside or outside of the Bird Sanctuary. White-water traps were applied to measure insect availability inside and outside the Bird Sanctuary. We found that the shrikes foraged preferentially within the Bird Sanctuary (Paired t-test, N=150, t-value: 3.63, P< 0.005). Diversity (revealed by Rényi diversity index) and abundance of arthropods were considerably higher inside the Bird Sanctuary (Wilcoxon Matched-pairs Signed-ranks test, z-value > -2.428, P = 0.0152). The monitoring of impaled prey items revealed that besides insects vertebrates were also taken. Interestingly two specimens of the poisonous Black Cone-headed Grasshopper (Poikylocerus bufonicus) were also impaled and consumed.

Adda were negatively correlated to the wasp population size, and the average wasp size increased when the frequency of larger prey increased. We concluded that interactions between extrinsic (prey availability) and intrinsic (wasp size... more

Adda were negatively correlated to the wasp population size, and the average wasp size increased when the frequency of larger prey increased. We concluded that interactions between extrinsic (prey availability) and intrinsic (wasp size distribution) factors may ...

26 Capsule Diet composition and feeding behaviour of Marsh Harriers differed in 27 farmland areas with different degree of agricultural intensification. 28 Aims To analyze diet composition and feeding behaviour of the Marsh Harrier Circus... more

26 Capsule Diet composition and feeding behaviour of Marsh Harriers differed in 27 farmland areas with different degree of agricultural intensification. 28 Aims To analyze diet composition and feeding behaviour of the Marsh Harrier Circus 29 aeruginosus in agricultural landscapes with different degree of agricultural 30 intensification. 31 Methods We assessed diet composition and feeding behaviour of the Marsh Harrier by 32 means of focal observations at nests during breeding seasons 2001-2003 in two 33 agricultural areas within the eastern Ebro Basin (in northern Iberian Peninsula) differing 34 in their degree of agricultural intensification: a traditional non-irrigated and non-35 intensively managed farmland area and an irrigated and intensively managed farmland 36 area. 37 Results Marsh harriers in the intensively managed area took higher percentages of small 38 mammals than harriers in the traditional area managed at low-intensity, where they also 39 had a more diverse diet. Male delivery rates increased throughout the breeding season in 40 the intensively managed area. On the contrary, no significant trend in delivery rates was 41 observed in the traditional area, where harriers turned to larger prey late in the season. 42 Conclusion Marsh harriers took advantage of different prey types in intensively 43 managed and traditional farmland probably according to prey availability. Differences 44 in diet composition seem to be related to different foraging strategies adopted by 45 harriers in traditional and intensively managed farmlands. In the former habitat, harriers 46 respond to increases in the energy requirements of the brood over the course of the 47 breeding season by taking larger prey, whereas in the latter habitat harriers increase 48 feeding rates. 49 50 3

Spring Cave is situated just below the Baboon Point escarpment in Elands Bay and is one of only a handful of central west coast sites with deposits dating to the Medieval Warm Anomaly (MWA, c. 1300-650 cal BP). This was a climatological... more

Spring Cave is situated just below the Baboon Point escarpment in Elands Bay and is one of only a handful of central west coast sites with deposits dating to the Medieval Warm Anomaly (MWA, c. 1300-650 cal BP). This was a climatological period of global significance that brought hot and dry conditions to much of the South African west coast, an ecologically stressed period affecting people, animals and plants alike. Although Spring Cave also dates to before and after the MWA, a large amount of its deposits date to this period. Earlier research on the central west coast has shown that most MWA-dated sites are situated at high elevations and near the coast, and that such placement in the landscape allowed monitoring of the movement of game, predators, and groups of people with or without livestock. High mobility, seeking safety and shelter at higher elevations, and a close watch on the landscape were part of general adaptive strategies, but people at Spring Cave may have added repeated ritual slaughter of small carnivores to the range of coping mechanisms. Doing so, according to ethno-historical records among herding groups, would have brought good luck and well-being. When considering Spring Cave's entire sequence, broad late Holocene regional patterns are also confirmed: i) higher frequencies of exotic lithic raw materials before 3000 cal BP; and ii) greater emphasis on gathering limpets after 2000 BP, while mussels dominate assemblages before then. Moreover, metrical data on limpets, mussels and Cape rock lobster suggest that these species were not processed before their transport back to the cave, an observation at variance with barnacles and fish.

This paper explores the tightness of the linkage between stream-dwelling salmonids and ripar- ian vegetation. Comparison of original distributions of salmonid species with that of vegetation types shows that distribution within a given... more

This paper explores the tightness of the linkage between stream-dwelling salmonids and ripar- ian vegetation. Comparison of original distributions of salmonid species with that of vegetation types shows that distribution within a given salmonid species is not limited to a specific vegetation type, and that differ- ent salmonid species co-occur within a given vegetation type. Examination of reported differences in trout pro- duction among streams appear to be related to differ- ences in riparian setting only indirectly and insofar as these reflect differences in prey availability and, to a lesser extent, differences in habitat features. Variabil- ity in trout production estimates are minimized when comparisons are species-specific and normalized for tem- perature differences among streams. Within a riparian vegetation type, the relationship between trout produc- tion and successional age of the streamside vegetation is often inverse.

The migration of Southern Hemisphere humpback whales Megaptera novaeangliae between their feeding and breeding areas has thus far been considered a highly predictable and seasonal event. However, previous observations on the humpbacks... more

The migration of Southern Hemisphere humpback whales Megaptera novaeangliae between their feeding and breeding areas has thus far been considered a highly predictable and seasonal event. However, previous observations on the humpbacks that pass through the nearshore waters of the west coast of South Africa have revealed deviations from the behaviour and seasonality expected during a typical migration. This 'anomaly' is hypothesised to be associated with prey availability in the region. Shore-based observations between July 2001 and February 2003 from North Head, Saldanha Bay, in the Western Cape province, yielded relative abundances that again did not support a classical migration pattern, with the highest sighting rates from mid-spring through summer. Movement parameters (actual swimming speed, direction and linearity) of humpback groups tracked by theodolite showed mid-spring to be a turning point in their behaviour, after which we observed a significant reduction in actual swimming speed, an increase in 'non-directional' movement, and a distribution farther from shore than in other seasons. Additional data on group composition and sex collected between 1993 and 2008 showed a significantly female-biased sex ratio during mid-spring, the first such recorded for any region. Direct observation of feeding on crustacean prey during spring and summer further supports the notion that humpbacks may have more flexible foraging habits than previously appreciated, and that the southern Benguela upwelling region may function as an important feeding area for these whales.

Increased disturbance hypothesis Intermediate disturbance hypothesis a b s t r a c t

The multicolored Asian lady beetle, Harmonia axyridis (Pallas), native to Asia, has recently been detected in South America after successfully invading North America and Europe. This coccinellid is a voracious predator; therefore, it is... more

The multicolored Asian lady beetle, Harmonia axyridis (Pallas), native to Asia, has recently been detected in South America after successfully invading North America and Europe. This coccinellid is a voracious predator; therefore, it is popular and effective in biological control. Unfortunately, H. axyridis also has associated adverse impacts (i.e., as a household pest, pest of fruit production, and threat to non-target organisms). To predict the potential geographic extent of impacts of H. axyridis in South America we review the history of its invasion in the Western Hemisphere and address various factors critical to the future invasion (i.e., arrival, establishment, and spread) of new areas of South America. The likelihood of continued introductions (i.e., arrival) of H. axyridis to South America seems high, due to its popularity as a biological control agent and through accidental introductions. Establishment also seems likely in broad regions of South America. Climate matching w...

The diet of the short-toed eagle (Circaetus gallicus) was studied during the breeding season by analysing pellets and remains generated by adults and nestlings. The raptor proved to be a specialist feeder, as snake prey comprised almost... more

The diet of the short-toed eagle (Circaetus gallicus) was studied during the breeding season by analysing pellets and remains generated by adults and nestlings. The raptor proved to be a specialist feeder, as snake prey comprised almost 95% of the diet, in both frequency and biomass. We gathered information on prey availability and prey size availability (1499 specimens of nine different species) by searching for snakes in the study area. Regressions of vertebra centrum length and dorsal-scale length on snout±vent length (SVL) of the snakes were used to calculate prey size. The taxonomic diet composition differed depending on the sample analysed ± remains or pellets ± but we failed to ®nd between-year diet differences. Most of the snakes identi®ed (140 out of 141) belonged to only three species, Malpolon monspessulanus, Elaphe scalaris, and Coluber hippocrepis. Other prey included Lacerta lepida, Natrix maura, Bufo bufo, and Alectoris rufa, and many secondary prey (prey from stomach of the prey) were also detected in the pellets. The three main prey species were consumed according to their availability in the study area, but the eagles selected on the basis of prey size. Large snakes within 700±1000 mm SVL were positively selected, whereas snakes under 600 mm SVL were negatively selected. Adult eagles consumed the same prey species as those carried to the nest to feed their single nestling, although prey given to nestlings proved larger in size and biomass, suggesting that adults consumed the smallest prey, reserving the largest for nestlings.

Shorebirds show high variability in parental care strategies among species, populations, and environments. Research on shorebird parental sex roles can help to understand the selective pressures that shape avian breeding strategies.... more

Shorebirds show high variability in parental care strategies among species, populations, and environments. Research on shorebird parental sex roles can help to understand the selective pressures that shape avian breeding strategies. Although several studies have examined parental care strategies in holarctic shorebirds, very little research has been conducted in the tropics. Here we examined parental sex roles during territorial defence, incubation, and chickrearing in Malaysian plovers Charadrius peronii in the Gulf of Thailand. The costs and gains of particular parental behaviour may vary between the sexes and can be affected differently by environmental factors and chick age. Thus we also examined how temperature, prey availability, chick or embryo age, and time of day affected parental sex roles. Males spent more time defending territories and were further away from chicks whereas females spent more time incubating eggs. Both adults contributed to chick defence during disturbances throughout the entire chick-rearing period. Total nest attendance (sum of both sexes) was affected by the modelled temperature of an unincubated egg. Prey availability, embryo age, and time of day had no effect on total nest attendance. Males adjusted incubation effort in response to temperature only at high temperatures (>36°C) whereas females adjusted nest attendance at high and low temperatures. Chick age had no effect on the proportion of time adults spent defending territories or responding to distur-bance. Pairs were more likely to fledge chicks if both the male and female spent more time defending territories. For Malaysian plovers, high cooperation between the sexes during parental care may help to achieve high quality breeding territories, maintain body conditions during hot days, protect offspring from predators and attacking conspecifics, and contribute to high lifetime reproductive success.

The population decline of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) may be linked to a decline in juvenile survivorship. Limitations in prey availability may contribute to the decline, thus it is important to understand... more

The population decline of Steller sea lions ( Eumetopias jubatus (Schreber, 1776)) may be linked to a decline in juvenile survivorship. Limitations in prey availability may contribute to the decline, thus it is important to understand fasting capacities of Steller sea lions. For most mammals, fat catabolism is the preferred energetic pathway to ensure that protein is spared. However, marine mammals also have a conflicting requirement to conserve fat because the main site of fat storage is the blubber layer, which is also their primary thermal barrier when at sea. We developed a dynamic state variable model to demonstrate how protein and fat reserve utilization and maximum fasting duration are influenced by body condition and time spent foraging. This model was parameterized with respect to conditions faced by juvenile and subadult Steller sea lions foraging unsuccessfully during a period of reduced prey availability. The model accurately predicted changes in fat and protein mass of ...

This paper considers a specific kind of hunting strategy, ambush hunting, employed by Ju/'hoansi San who reside in northwestern Botswana and northeastern Namibia. We examine this hunting technique from ethnoarchaeological, archaeological,... more

This paper considers a specific kind of hunting strategy, ambush hunting, employed by Ju/'hoansi San who reside in northwestern Botswana and northeastern Namibia. We examine this hunting technique from ethnoarchaeological, archaeological, historical, and ethnographic perspectives. Data are drawn from an analysis of 14 blinds at ǂGi Pan on the Botswana-Namibia border. These hunting blinds were mapped and two were excavated. Our methods included having Ju/ 'hoansi show us how they constructed blinds. We also conducted interviews of individuals who constructed and utilized the blinds. Based on this information, we assess the structure, distribution, morphology, contents, function, size, timing of use, and reasons for placement of these specialized hunting facilities. Conclusions are drawn concerning the utilization of ambush hunting and its social, economic, environmental, and technological significance in the northern Kalahari. Résumé Cet article examine un type particulier de stratégie de chasse, la chasse à l'embuscade employée par Ju / 'hoansi San qui réside dans le nord-ouest du Botswana et le nord-est de la Namibie. Nous examinons cette technique de chasse du point de vue ethnoarchéologique, archéologique, historique, et ethnographique. Les données sont tirées d'une analyse de 14 stores à ǂGi Pan à la frontière entre le Botswana et la Namibie. Ces stores de chasse ont été cartographiés et deux ont été fouillés. Nos méthodes incluaient que Ju / 'hoansi nous montre comment ils construisaient des stores. Nous avons également mené des entrevues avec des personnes qui ont construit et utilisé les stores. À

Antarctic and sub-Antarctic seabirds, marine mammals, and human ®sheries concentrate their foraging eorts on a single species, Antarctic krill (Euphausia superba). Because these predators may have a signi®cant eect on krill abundance, we... more

Antarctic and sub-Antarctic seabirds, marine mammals, and human ®sheries concentrate their foraging eorts on a single species, Antarctic krill (Euphausia superba). Because these predators may have a signi®cant eect on krill abundance, we estimated the energy and prey requirements of Adelie (Pygoscelis adeliae), chinstrap (Pygoscelis antarctica), and gentoo (Pygoscelis papua) penguins and female Antarctic fur seals (Arctocephalus gazella) breeding on the South Shetland Islands, Antarctica and compared these estimates with catch statistics from the Antarctic krill ®shery. Published data on ®eld metabolic rate, population size, diet, prey energy content, and metabolic eciency were used to estimate prey requirements of these breeding, adult, land-based predators and their dependent ospring. Due to their large population size, chinstrap penguins were the most signi®cant krill predators during the period examined, consuming an estimated 7.8´10 8 kg krill, followed by Adelie penguins (3.1´10 7 kg), gentoo penguins (1.2´10 7 kg), and Antarctic fur seals (3.6´10 6 kg). Total consumption of all land-based predators on the South Shetland Islands was estimated at 8.3´10 8 kg krill. The commercial krill ®shery harvest in the South Shetland Island region (1.0´10 8 kg) was approximately 12% of this. Commercial harvest coincides seasonally and spatially with peak penguin and fur seal prey demands, and may aect prey availability to penguins and fur seals. This diers from the conclusions of Ichii et al. who asserted that the potential for competition between South Shetland predators and the commercial krill ®shery is low.

The small pelagic fish represents the link between nekton and demersal communities, and they are an important food source for some demersal fish species. In the autumns between 1993 and 2002, 74,869 stomach contents of 25 demersal fish... more

The small pelagic fish represents the link between nekton and demersal communities, and they are an important food source for some demersal fish species. In the autumns between 1993 and 2002, 74,869 stomach contents of 25 demersal fish species were analysed during the scientific surveys organized by the Instituto Español de Oceanografía. These species represent the demersal fish community of the southern Bay of Biscay. An important part of their diet (39% by volume) was composed of pelagic fish species (e.g. Engraulis encrasicolus, Gadiculus argenteus, Micromesistius poutassou, Trachurus trachurus, Sardina pilchardus, Scomber scombrus). Among all these prey species, the relevance of M. poutassou and G. argenteus stood out because of their high abundance both in the diets and during the scientific surveys. The relevance of pelagic fish as prey increased with predator size, reaching more than 60% of the diet by volume in the length range 25-29 cm. However, fish predators larger than 50 cm depended less on pelagic fish (33%), since they were also able to feed on other sources such as megafaunal invertebrates, mainly cephalopods. The pelagic fish resource was primarily exploited by 12 demersal fish species, with Merluccius merluccius and Zeus faber being the main ones feeding on small pelagics, which was related to the vertical movement of predators and prey through the water column. Survey abundance indices were used as indicators of prey abundance in the ecosystem, both for biomass and number. There was evidence for density-dependant feeding by predators on E. encrasicolus, G. argenteus and T. trachurus, while the main discrepancies between abundance in the stomachs and in the surveys were due to differential availability of prey length classes in the environment. Small prey species and individuals were exploited by most demersal fish while large prey species were less accessible to predators.

The puma (Felis concolor) has the most extensive range of any terrestrial mammal in the Western Hemisphere, covering over 100 ~ latitude. Food habits of different puma subspecies vary with latitude. Subspecies from temperate habitats... more

The puma (Felis concolor) has the most extensive range of any terrestrial mammal in the Western Hemisphere, covering over 100 ~ latitude. Food habits of different puma subspecies vary with latitude. Subspecies from temperate habitats generally eat larger prey and specialize on a smaller number of prey taxa, whereas, in tropical habitats, they prey on smaller, more varied prey. In North America, ungulates (primarily deer) represented 68% of the puma's diet by frequency of occurrence. Mean weight of vertebrate prey (MWVP) was positively correlated (r = 0.875) with puma body weight and inversely correlated (r=-0.836) with food niche breadth in all America. In general, MWVP was lower in areas closer to the Equator. Patterns of puma prey selection are probably influenced by prey availability and vulnerability, habitat characteristics, and potential competition from the jaguar (Panthera onca).

This paper presents data from a twelve-year (1986–98) monitoring of waterbird populations at Muni Lagoon, and discusses the ornithological importance of the lagoon and trends in the use of the site by waterbirds. The small brackish lagoon... more

This paper presents data from a twelve-year (1986–98) monitoring of waterbird populations at Muni Lagoon, and discusses the ornithological importance of the lagoon and trends in the use of the site by waterbirds. The small brackish lagoon forms part of the Muni-Pomadze Ramsar site situated on the Ghana coast. A total of 48 species of waterbirds were recorded at the site comprising of 29 species of waders, eight species of terns, two species of gulls, seven species of herons and egrets, one species each of duck and cormorant. The most abundant waterbirds species recorded on the site were the Curlew Sandpiper, Ringed Plover, Greenshank, Black-winged Stilt, Common Tern, Black Tern, Royal Tern and the Sandwich Tern. Three species of waders, Black-winged Stilt, Pratincole and Little Tern were observed to breed at the site. The highest numbers of waterbirds occurred on the site in the period September to March. The site remains an internationally important wetland site by virtue of suppor...