Secondary Prey Research Articles

Feeding resource partitioning among four sympatric carnivores in the Peneda‐Gerês National Park (Portugal)

AbstractThe Iberian Peninsula comprises two distinct biogeographic areas: a temperate Atlantic Eurosiberian (north) and a Mediterranean (centre and south), and they provide very different biotopes, landscapes and prey for carnivores. One example is an abundance of the wild rabbit Orytolagus cuniculus in the Mediterranean zone, which contrasts with the Eurosiberian zone, where the rabbit is scarce. The feeding resource partitioning among four sympatric predators (red fox Vulpes vulpes, wild cat Felis silvestris, genet Genetta genetta and stone marten Martes foina) was analysed in the Peneda‐Gerês National Park (north‐west Portugal), located in the Eurosiberian region. Data on the spatial distribution of three important prey species (Apodemus sylvaticus, Microtus lusitanicus and Talpa occidentalis) were also collected to investigate their possible relationships with the feeding habits of each predator. Rodents are the staple prey for this guild of carnivores. Predators are able to supplement their diets with one or two secondary prey types: rabbits and arthropods by the largest carnivores (the red fox and the wild cat); insectivores by the small predators (the genet and the stone marten). These results contrast with the characteristic Mediterranean predator–prey features, where rabbits are the main support of carnivore communities. The feeding resource partitioning revealed a complex structure characterized by a dynamic niche differentiation and overlap, according to a seasonal pattern. To explain this pattern of resource exploitation two hypotheses are discussed in the light of the body size of predators and their use of space.

Spatial and temporal variation in krill consumption by the Antarctic fish Notothenia coriiceps, in Admiralty Bay, King George Island

An index of integrated food preferences (IFA) of Notothenia coriiceps Richardson at two sites in Admiralty Bay (Ipanema and Smok Point), calculated for two sequential summers, showed that during 1998/99, the most important food item was Euphausia superba (krill) at both Ipanema (IFA = 0.83) and Smok Point (IFA = 0.75), while the sum of all other food items was significantly smaller (IFA respectively 0.21 and 0.26). Macroalgae, gammarid amphipods and gastropods dominated the diet in the summer 1999/00 (IFA respectively 0.32, 0.32 and 0.21), at Ipanema, while macroalgae were dominant at Smok (IFA = 0.67), where krill and amphipods were secondary prey (IFA respectively 0.12 and 0.14) and gastropods were absent. Thus, the diet composition of N. coriiceps can possibly be used as an indicator of the presence of pelagic krill swarms.

Analysis of dietary overlap in Antarctic fish (Notothenioidei) from the South Shetland Islands: no evidence of food competition

A dietary overlap analysis between notothenioid species was carried out among three fish assemblages in the South Shetland Island area. Using Tyler's (1972) method, the re-occurrence of main and secondary prey among fish predators was 33% in summer and 37% over the year at Potter Cove, 25% in summer and 7% in winter at Admiralty Bay, and 20% in autumn/winter around Elephant Island. Likewise, using the "S" index of Linton et al. (1981), the diet similarity between most species pairs is <50%. This relatively low dietary overlap may be explained by the about equally divided occurrence of generalised feeders and specialised feeders, with no evidence of competition among them. The fishes' trophic niches seem to be separated by depth and prey taxa. These findings are compared with other Antarctic fish communities and those in similar non-Antarctic cold marine ecosystems.

Safety in numbers for secondary prey populations: an experimental test using egg predation by small mammals in New Zealand

New Zealand's native avifauna is threatened by introduced mammalian predators. Native species are often not the primary prey of these predators, which depend on introduced mice and rabbits as their primary food source. Theoretical models predict that predation risk for a subsidiary, or “secondary” prey species is inversely proportional to its population size. This prediction was tested by a quasi‐natural experiment in which four different sized prey “colonies” were constructed at four existing sooty shearwater breeding sites. Domestic hens' eggs were placed in shearwater burrows immediately following the shearwater breeding season and egg predation rates monitored at five, ten and fifteen days. Treatments were switched between sites and the experiment run for a second time after a two‐week stand‐down period. The net effect of increasing colony size was to lower individual risk of predation. The larger number of individuals present served to effectively “buffer,” or dilute, per‐capita predation risk from predators whose numbers are fixed by extraneous factors: chiefly the abundance of their primary prey. Although eggs were removed more slowly from smaller colonies than from larger ones, each loss had a greater per‐capita effect on individual mortality risk. The inverse density dependent relationship found between colony size and predation risk implies that predator population dynamics are largely independent of secondary prey numbers. Abundant introduced predators can therefore easily drive a small secondary prey population to extinction. Control of primary prey populations may be an important management tool in these circumstances.

DIETS OF FIN, SEI, AND SPERM WHALES IN BRITISH COLUMBIA: AN ANALYSIS OF COMMERCIAL WHALING RECORDS, 1963–1967

AbstractDiets of fin (Balaenoptera physalus), sei (Balaenoptera borealis), and sperm whales (Physeter macrocephalus) were estimated from the stomach contents of individuals killed along the British Columbia coast from 1963 to 1967. The dominant prey types of fin whales were euphausiids, with minor contributions from copepods and fish. Sei whale stomachs contained primarily copepods in three years, whereas euphausiids or a variety of fish dominated the diet in the other two years. Sperm whales consumed primarily North Pacific giant squid (Moroteuthis robusta), but secondary prey differed between males and females. Female sperm whales frequently consumed ragfish (Icosteus spp.) and other fish, whereas the male diet also contained rockfish (Sebastes spp.). The high abundance of euphausiids along the British Columbia coast likely contributed to the presence of a summer resident population of fin whales. The high abundance of large copepods farther north probably influenced the migration of sei whales through the offshore waters of British Columbia. Sperm whale stomach contents differed by sex reflecting location and possibly breeding behaviors.

Human exploitation of seabirds in coastal southern Chile during the mid-Holocene

We analyzed a collection of 738 bird bones, representing a minimum of 71 individuals, found in a settlement of hunter-gatherers from the mid-Holocene, 5,000 years BP, in the coastal locality of Chan Chan, southern Chile. The camp was inhabited for over ca. 500 years, during which time a steady hunting pressure on the local marine resources was exerted, particularly on seabirds. The most abundant taxon (bones/number of individuals) was the red-legged cormorant Phalacrocorax gaimardi (551/44) which was also the prey which provided the highest edible proportion of body mass. Albatrosses Thalassarche cf. melanophris (103/12) and shearwaters Puffinus cf. griseus (20/5) were secondary prey. Cormorants were presumably hunted at their breeding colonies (which are still present in the area) so it is probable that egging also occurred. Because they are pelagic, albatrosses could have been hunted at sea, but the adequate technology for this (boats, hooks) is not apparent in the archaeological record. The bird assemblage obtained in the sample does not qualitatively differ from that of the present, indicating a reasonable stability in species richness from the considered period until the present. The high diversity of coastal resources in Chan Chan was likely important in leading to the, at least seasonal, occupation of these areas by hunter-gatherers and also may have encouraged the development of the adequate technology for the exploitation of these resources.

A model for the conservation management of a ‘secondary’ prey: sooty shearwater ( Puffinus griseus) colonies on mainland New Zealand as a case study

New Zealand's native birds constitute the supplementary or ‘secondary’ prey of introduced mammalian predators. Predation on secondary prey is inversely density dependent. Small populations will therefore be at greater risk of extinction than large, which escape due to the buffering effect of their size on predation impact. A matrix model of a mainland sooty shearwater ( Puffinus griseus) population predicted a mean growth rate of 1.044 (0.967–1.130) with no predation. Survival of adults attending the colony was the most influential population parameter. With predation effects included, colony growth was sensitive to both management intensity and colony size. Small colonies required the removal of almost all predation risk to survive, although the level of management required for growth decreased with increasing colony size. Management intensity may be relaxed as a colony grows and an ‘escape threshold' colony size is eventually reached at which growth continues without predator management.

Does local feeding specialization exist in Eurasian badgers?

Several local populations of the otherwise trophic-generalist Eurasian badger (Meles meles) have been defined as specializing locally on temporally variable food resources such as earthworms (Lumbricus spp.), olive fruits (Olea europaea), or young rabbits (Oryctolagus cuniculus), owing to a lack of correlation between resource availability and use. However, theoretical models predict that temporal variation in resources reduces the probability of diet specialization. To understand the relationship between temporal resource variability and local feeding specialization, we studied temporal variation in diet composition and diversity (using fecal analysis), the availability of a temporally stable key resource, and the relation between consumption and availability of rabbits (key prey) and invertebrates (secondary prey) for a badger population previously described as specialized on young rabbits. We found strong variations in the use of different resources (including young rabbits) and in diet diversity among seasons and years. The main food resource was young rabbits during winter and spring, fruits in autumn, and reptiles in summer. Diet diversity was inversely related to consumption of young rabbits and directly related to consumption of secondary prey (invertebrates). Consumption of rabbits (both young and adults) was correlated with their abundance in the field, with a type 3 functional response in the consumption of young rabbits, which is typical of a generalist to whom alternative prey are available. There was no relationship between the abundance of invertebrates and their consumption. Our results show that badgers in the study area were not locally specialized, therefore care should be taken when referring to a population as specialized without an adequate test of the predictions.

Short-term ecological effects of rabbit haemorrhagic disease in the short-tussock grasslands of the South Island, New Zealand

Rabbit haemorrhagic disease (RHD) has reduced populations of rabbits (Oryctolagus cuniculus) across most rabbit-prone short-tussock grasslands of New Zealand, at scales rarely seen there before. Flow-on effects to other parts of these ecosystems will be inevitable. We report evidence for increases in pasture biomass, increases in abundance of other exotic herbivores, declines in abundance of rabbit-specialist predators, and short-term increases in predation rates of some native birds by these predators. At one site in Central Otago, RHD reduced an index of rabbit abundance by 88%, and an index of their grazing impacts by 77%. Recovered biomass consisted mostly of fast-growing exotic pasture species of moderate palatability to livestock. Spotlight counts and hunters' returns suggest increases in possum (Trichosurus vulpecula) and hare (Lepus europeaus) abundance, but their grazing pressure is unlikely to replace that originally imposed by rabbits. The apparent increase in possum numbers poses an increased risk from the spread and maintenance of bovine tuberculosis (Tb), although this risk may be offset by declines in the counts of ferrets (Mustela furo), which also carry Tb. Declines in predator numbers (including feral cats, Felis catus) may also, in the longer term, benefit some native fauna that are secondary prey of these predators. There is evidence for increased predation of some native birds' eggs since RHD arrived. It is not possible at this stage to generalise the effects of RHD-induced declines in rabbit abundance on New Zealand ecosystems. Effects are highly variable, and their implications for pastoral production, management of bovine Tb, and conservation of native species are likely to vary locally according to the suite of plant and animal species originally present.

Mass mortality of common eiders (Somateria mollissima) in the Dutch Wadden Sea, winter 1999/2000: starvation in a commercially exploited wetland of international importance

Mass mortality of common eiders (Somateria mollissima) was observed in winter 1999/2000 in the Dutch Wadden Sea. Approximately 21,000 common eiders died. Dissected birds were severely emaciated and 94% were infected with the acanthocephalan parasite Profilicollis botulus. Green shore crabs (Carcinus maenas), intermediate hosts of the parasite, were slightly more ‘available’ than in other years, but parasite infections in the eiders were close to normal. Few eiders were oiled (5%), there were no toxicological, bacteriological, or virological explanations for the observed mortality.In the Wadden Sea, a wetland of international importance, mussel (Mytilus edulis) cultures occur in sublittoral areas, while mechanical cockle (Cerastoderma edule) fisheries are licensed annually after evaluation of available resources. The wintering eiders in 1999/2000 required c. 3.1 million kg ash-free dry mass, while information on mussel and cockle stocks (irrespective of accessibility and profitability) suggested a resource 4.7× the requirement of common eiders only. Food shortage is suggested to have caused the observed mortality, involving both principal (mussels and cockles) and secondary (Spisula) prey.Winter census reports showed shifts in wintering distribution of common eiders in the 1990s, indicating the utilisation of Spisula in the North Sea in poor food years in the Wadden Sea. Following particularly intense fisheries in summer 1999, attempts to feed on Spisula in winter 1999/2000 failed. It is hypothesised that overfishing of mussels and cockles in the Wadden Sea in the early 1990s resulted in structurally reduced food resources, contractions of the foraging area of common eiders, and increased use of secondary prey in the North Sea.

Conserving dryland lizards by reducing predator‐mediated apparent competition and direct competition with introduced rabbits

1 Native skinks Oligosoma spp. in New Zealand’s dry grasslands have declined in range and abundance since the arrival of humans. I hypothesized that introduced rabbits Oryctolagus cuniculus exacerbate this decline by supporting introduced mammalian predators for which they are primary prey; by sudden declines in abundance that cause predators to switch to skinks; by grazing vegetation, thereby reducing skink refuges from predators; and by reducing skink food and shelter from climatic extremes. The first three effects cause enhanced skink predation and represent indirect or apparent competition. The fourth effect represents direct competition. 2 Interactions between two introduced predators (ferrets Mustela furo and cats Felis catus), rabbits and two secondary prey (McCann’s skink O. maccanni and common skink O. nigriplantare polychroma) were studied. By measuring skink consumption, and predator, rabbit and skink numbers, offtake of skinks by predators under varying rabbit and skink densities was calculated. 3 Predation by ferrets and cats was inversely density-dependent because predation accelerated at low skink densities. As skink densities rose, predation became an increasingly less important source of mortality. Therefore, predation could potentially exterminate skink populations if densities fell below some critical range. 4 Predation of skinks increased markedly after sudden declines in rabbit abundance, because predators remained abundant but switched to feeding on skinks. Although a temporary effect, repeated cycles of intense rabbit control and population recovery may have chronic detrimental effects on skink population viability. 5 Optimal rabbit management for maintaining viable skink populations is likely to require avoidance of large swings in rabbit abundance by maintaining populations at low, stable levels. Fewer rabbits mean fewer predators and greater refuge (less apparent competition), and improved food and shelter (less direct competition). If large swings in rabbit abundance cannot be avoided, the effects of prey-switching could be reduced by controlling predators when rabbit numbers decline. 6 Better understanding and management of primary–secondary prey systems, where the primary prey consume the habitat of secondary prey, will require recognition of the extra complexities that underlie these systems.

Feeding ecology of the long-eared owl (Asio otus) in northern Italy: is it a dietary specialist?

The feeding ecology of the long-eared owl (Asio otus) in the Stupinigi Natural Park, northwestern Italy, was investigated for 1 year. Owls fed seasonally on three main prey categories. Mice (Murinae) constituted the bulk of the diet from September to March, with voles (Arvicolinae) and birds as secondary prey. During the breeding season, birds became preeminent, constituting about half of the prey ingested. Dietary overlap between the overwintering period and breeding season was low. Food-niche breadth was low in autumn and winter but increased markedly from May to August. A comparison of our results with those of eight other European studies showed that the long-eared owl in Italy has a more varied diet. The diet in Italy and Spain (southern Europe) is based on at least three prey groups and differs from that described for areas in central and northern Europe, where only species of voles are the main prey. Our results show that the long-eared owl is an adaptable predator that expands its food niche in the presence of diversified prey. This adaptability contrasts with the picture of a specialized predator.

INCIDENTAL NEST PREDATION IN SONGBIRDS: BEHAVIORAL INDICATORS DETECT ECOLOGICAL SCALES AND PROCESSES

Incidental predation occurs when secondary prey items are encountered and subsequently consumed, not through directed search for such prey, but through their consequential encounter by a predator engaged in search for primary prey. We developed a mathematical model that examines the relationships between the abundance of primary prey, patch exploitation (i.e., quitting harvest rates), and the rate of incidental predation on secondary prey items. The model's predictions are dependent upon the spatial scale over which a forager integrates foraging costs and thus determines its quitting harvest rate (QHR). At local (i.e., foraging) spatial scales, we predicted that incidental predation should increase with local food abundance. Also at the foraging scale, local food abundance should not influence QHRs, but local predation risk (from higher trophic levels) should increase QHRs. Therefore, we predicted that incidental predation rates should be negatively correlated with QHRs. Over large (i.e., landscape) spatial scales, greater food abundance and predation risk increase QHRs, and we predicted that predation rates should vary inversely with QHR through two complementary mechanisms: foragers use a greater proportion of space and spend more time foraging as quitting harvest rates decrease. We experimentally tested the qualitative predictions of the theory in the field using artificial Veery (Catharus fuscescens) nests depredated by white-footed mice, Peromyscus leucopus, across three spatial scales. We used the technique of giving-up densities to measure QHRs and to determine the scale at which mice integrate different foraging costs. In accord with our predictions, nest predation was positively influenced by the local abundance of food at the foraging scale, and local predation risk to mice and perhaps interference competition from chipmunks resulted in higher giving-up densities and lower nest predation. At the landscape scale, there was an inverse relationship between giving-up densities and nest predation, which was probably the result of large-scale differences in resource abundance between plots. Our study demonstrates how linking theoretical development to the use of empirical behavioral indicators can help determine the relevant ecological scales and processes necessary for understanding predator–prey interactions.

Incidental Nest Predation in Songbirds: Behavioral Indicators Detect Ecological Scales and Processes

Incidental predation occurs when secondary prey items are encountered and subsequently consumed, not through directed search for such prey, but through their consequential encounter by a predator engaged in search for primary prey. We developed a mathematical model that examines the relationships between the abundance of primary prey, patch exploitation (i.e., quitting harvest rates), and the rate of incidental predation on secondary prey items. The model's predictions are dependent upon the spatial scale over which a forager integrates foraging costs and thus determines its quitting harvest rate (QHR). At local (i.e., foraging) spatial scales, we predicted that incidental predation should increase with local food abundance. Also at the foraging scale, local food abundance should not influence QHRs, but local predation risk (from higher trophic levels) should increase QHRs. Therefore, we predicted that incidental predation rates should be negatively correlated with QHRs. Over large (i.e., landscape) spatial scales, greater food abundance and predation risk increase QHRs, and we predicted that predation rates should vary inversely with QHR through two complementary mechanisms: foragers use a greater proportion of space and spend more time foraging as quitting harvest rates decrease. We experimentally tested the qualitative predictions of the theory in the field using artificial Veery (Catharus fuscescens) nests depredated by white-footed mice, Peromyscus leucopus, across three spatial scales. We used the technique of giving-up densities to measure QHRs and to determine the scale at which mice integrate different foraging costs. In accord with our predictions, nest predation was positively influenced by the local abundance of food at the foraging scale, and local predation risk to mice and perhaps interference competition from chipmunks resulted in higher giving-up densities and lower nest predation. At the landscape scale, there was an inverse relationship between giving-up densities and nest predation, which was probably the result of large-scale differences in resource abundance between plots. Our study demonstrates how linking theoretical development to the use of empirical behavioral indicators can help determine the relevant ecological scales and processes necessary for understanding predator–prey interactions.

Prey and prey‐size selection by the short‐toed eagle (Circaetus gallicus) during the breeding season in Granada (south‐eastern Spain)

AbstractThe 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 find between‐year diet differences. Most of the snakes identified (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.

The Foraging Ecology of Egrets in Rice Fields in Southern New South Wales, Australia

-Numbers of wading birds are declining throughout the Murray-Darling Basin in Australia, and the loss of wetland habitats to agriculture is the most likely cause. This study describes the foraging of egrets in irrigated rice fields that occur extensively in areas of former wetlands. Tadpoles were the main prey of Great and Intermediate Egrets (Ardea alba and A. intermedia), with insects important secondary prey. Insects were the main prey of Cattle Egrets (A. ibis). Prey capture rates for Great and Intermediate Egrets declined by around 40% between November and January as the rice plants grew from seedling to mature stages. Cattle Egret prey capture rates did not decline. The abundance of tadpoles and most aquatic insects in the rice fields declined significantly between November and February. All three egret species laid eggs mainly during December and had young in the nest duringJanuary and February. Thus the declining profitability of rice fields as foraging sites coincided with the maximum demand for food by the birds to rear their young. Rice fields may not be an adequate substitute for natural wetlands for Great and Intermediate Egrets. Received 14 February 2001, accepted 20 March 2001.

RÉGIME ALIMENTAIRE DE LA GRANDE ALOSE ALOSA ALOSA (LINNÉ, 1766) ET DE L’ALOSE FEINTE ALOSA FALLAX (LACÉPÈDE, 1803) DANS LE GOLFE DE GASCOGNE.

L’examen de contenus stomacaux de 193 spécimens d’Alosa alosa (longueur totale Lt 181 à 538 mm / 2 à 4 ans) et de 175 d’Alosa fallax (Lt 204 à 486 mm / 2 à 6 ans) pêchés au niveau du plateau continental océanique français de l’Atlantique Ouest montre que les aloses sont en mer des prédateurs sélectifs d’espèces essentiellement pélagiques. A. alosa est à dominante zooplanctonophage. Les euphausiacés sont la composante alimentaire principale avec les copépodes, dans une moindre part. Les poissons avec l’anchois et le sprat (Engraulis encrasicolus et Sprattus sprattus) restent des proies accidentelles toute l’année. A. fallax est nettement plus piscivore. L’anchois constitue sa proie préférentielle tout au long de l’année. Les euphausiacés, mieux représentés dans le bol alimentaire au moment du printemps, restent des proies secondaires. La saison d’alimentation la moins intense se situe en été chez les deux espèces, période où l’embonpoint des aloses chute. L’activité alimentaire de l’alose feinte montre une augmentation durant les 4 à 8 heures qui suivent le lever du soleil.

Prochlorophytes as secondary prey for heterotrophic nanoflagellates in the deep chlorophyll maximum layer of the (sub)tropical North Atlantic

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 204:53-63 (2000) - doi:10.3354/meps204053 Prochlorophytes as secondary prey for heterotrophic nanoflagellates in the deep chlorophyll maximum layer of the (sub)tropical North Atlantic Bouwe R. Kuipers*, Harry J. Witte Department of Biological Oceanography, Netherlands Institute of Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands *E-mail: bouwe@nioz.nl ABSTRACT: Growth rates in prochlorophytes and their loss rates to grazing were investigated by the dilution technique in the lower euphotic zone of the (sub)tropical North Atlantic. Directly above the Œdeep chlorophyll maximum¹ (DCM), prochlorophyte growth rates were approximately 0.3 d-1 and grazing rates 0.4 d-1; both rates were considerably lower in and directly below the DCM. Grazing was only weakly affected by filtration through 3 µm pore-size filters, indicating heterotrophic nanoflagellates as the main grazers. Discrimination between day and night revealed that the prochlorophytes above the DCM, with doubling times of 3 d or more, divided during the day whereas at greater depth division occurred during the night. In contrast, grazing was always restricted to the daylight period and grazing rate was independent of prochlorophyte abundance, growth rate or time of division. Prochlorophyte grazing rates were, however, correlated with the loss rates in the much more abundant heterotrophic bacteria in the same layers. We conclude therefore that prochlorophytes are consumed as a secondary prey by heterotrophic nanoflagellates grazing on heterotrophic bacteria. KEY WORDS: Prochlorophytes · Heterotrophic bacteria · Grazing · Heterotrophic nanoflagellates · Deep chlorophyll maximum · North Atlantic Ocean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 204. Online publication date: October 05, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.

The diet of the Florida panther in Everglades National Park, Florida

We examined the diet of Florida panthers (Felis concolor coryi) in Everglades National Park from 1984 to 1991 using data from 113 kill sites of 9 radio-collared panthers, and 272 scats found at kill sites and from free-ranging panthers. Nine species were identified at kill sites and 14 species from scats. White-tailed deer (Odocoileus virginianus) was the most important prey species according to kill and scat analyses. Most kills were of adult bucks and does. The mean time spent at kills was 3.86 days. Secondary prey species from scat analysis were marsh rabbits (Sylvilagus palustris) and raccoons (Procyon lotor). The diet of panthers in Everglades National Park (ENP) was compared to that of panthers from southwestern Florida, including Big Cypress National Preserve. The estimated consumed biomass of white-tailed deer in ENP was nearly identical to the combined consumed biomass of deer and feral hogs from southwestern Florida.

Local feeding specialization by badgers (Meles meles) in a mediterranean environment.

A case of local feeding specialization in the European badger (Meles meles), a carnivore species with morphological, physiological and behavioural traits proper to a trophic generalist, is described. For the first time, we report a mammalian species, the European rabbit (Oryctolagus cuniculus), as the preferred prey of badgers. Secondary prey are consumed according to their availability, compensating for temporal fluctuations in the abundance of rabbit kittens. We discuss how both predator (little ability to hunt) and prey (profitability and predictability) features, may favour the observed specialization, as predicted by foraging theory. Badgers show a trend to specialize on different prey in different areas throughout the species range. It is suggested that changes in prey features can reverse the badger feeding strategy at the population level. Such dynamic behavioural responses make difficult to label badgers as generalists or specialists at the species level.