Food niche separation between four sympatric Namib Desert carnivores

The diet of four sympatric carnivore species was established by analyzing scats collected during 1978-1980, a period of increasing drought in the Namib Desert. Termites were especially important in the diet of Aardwolves and Bat-eared foxes and the food spectrum was not broadened in response to increased aridity. Black-backed jackals utilized a wide range of prey items, especially rodents and lagomorphs, while the Cape fox largely depended on murid rodents, but also took lagomorphs and insects. Separation in use of space and times of activity between the four species also occurred.     

Variation in the diet of red foxes on Scottish moorland in relation to prey abundance

The diet of red fox Vulpes vulpes was investigated through analysis of 340 scats collected during 1992-1996 from moorland in south-west Scotland. Rodents, game-birds, lagomorphs, carrion and insectivores were the most frequently occurring food types. Fox diet and prey abundance were compared between heather dominant and grass dominant habitat types within the study area. Rodents were the most frequently occurring food type in each habitat and occurred in 63% of seats overall. Rodents occurred more often in scats from grass dominant sites while gamebirds and lagomorphs were more frequent in scats from heather dominant sites. The occurrence of rodents in winter fox scats increased with rodent abundance. In contrast, the occurrence of gamebirds in winter fox scats was unrelated to gamebird abundance but negatively related to rodent abundance. It appeared that foxes switched to gamebirds in years, or habitats, where rodents were uncommon.     

Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

Molecular scatology as a tool to study diet: analysis of prey DNA in scats from captive Steller sea lions

The DNA of prey present in animal scats may provide a valuable source of information for dietary studies. We conducted a captive feeding trial to test whether prey DNA could be reliably detected in scat samples from Steller sea lions (Eumetopias jubatus). Two sea lions were fed a diet of fish (five species) and squid (one species), and DNA was extracted from the soft component of collected scats. Most of the DNA obtained came from the predator, but prey DNA could be amplified using prey-specific primers. The four prey species fed in consistent daily proportions throughout the trial were detected in more than 90% of the scat DNA extractions. Squid and sockeye salmon, which were fed as a relatively small percentage of the daily diet, were detected as reliably as the more abundant diet items. Prey detection was erratic in scats collected when the daily diet was fed in two meals that differed in prey composition, suggesting that prey DNA is passed in meal specific pulses. Prey items that were removed from the diet following one day of feeding were only detected in scats collected within 48 h of ingestion. Proportions of fish DNA present in eight scat samples (evaluated through the screening of clone libraries) were roughly proportional to the mass of prey items consumed, raising the possibility that DNA quantification methods could provide semi-quantitative diet composition data. This study should be of broad interest to researchers studying diet since it highlights an approach that can accurately identify prey species and is not dependent on prey hard parts surviving digestion.     

The diet of the subantarctic fur seal Arctocephalus tropicalis at Marion Island

Scats of subantarctic fur seals Arctocephalus tropicalis at Marion Island were collected from 1996 to 2,000, to examine temporal variability in the diet, factors affecting the variability and how the diet differed from that of the Antarctic fur seal A. gazella in the same period. For A. tropicalis, 19 prey species, of which 18 were fish and one a cephalopod, were identified in 213 scats. Fish were the main prey, occurring in 98.1 % of scats, whereas the cephalopod was present in only 1.4 % of scats. Amongst fish species, Myctophidae were most abundant, with Gymnoscopelus piabilis, G. fraseri and Electrona carlsbergi being the commonest prey items. Other fish families present in the diet in small numbers were Channichthyidae, Paralepididae, Nototheniidae, Microstomatidae and Notosudidae. Fish eaten ranged in size from Protomyctophum bolini and Krefftichthys anderssoni of standard length (SL) 25 mm to a single Dissostichus eleginoides of SL 249 mm. Differences in the diet existed between summer and winter. However, prey type accounted for most variability in the diet. In previous studies based on scats, a dominance of fish in the diet of A. tropicalis was also found at Possession Island (Iles Crozet), Amsterdam Island and Macquarie Island, but the dominant prey species differed between the various localities, also suggesting that prey availability is a major determinant of diet. At Marion Island, from 1996 to 2000 the diet of A. gazella comprised similar prey to that of A. tropicalis, but the proportional contribution of prey types differed in instances.     

Large prey for small cubs - on crucial resources of a boreal red fox population

Many studies of red fox Vulpes vulpes diet have indicated a higher frequency of large prey in the diet of cubs at dens in relation to that of adults From time to time this finding has been questioned as an artifact due to the different types of sampling In this paper I suggest that the observations were correct and reflected optimal behaviour of a central place forager I compared the diet of foxes by analyses of 112 cub scats collected at breeding dens and 168 adult scats collected during the same periods The study was performed in a boreal environment, characterised by cyclically fluctuating vole populations According to theory the diets should converge when voles become plentiful During a year of low, but increasing, vole densities, a significantly higher proportion of large prey was found in the sample from cubs than from adults This was not the case during the peak and the decline year, when the presumably easily available voles appeared frequently in the scats of both cubs and adults I argue that the availability of large prey during the first year of increasing vole densities might determine territory sue and hence also average population density of foxes throughout the whole cycle in boreal foxes     

Diet of Montagu's Harrier Circus pygargus in central Spain: analysis of temporal and geographic variation

The diet of Montagu's Harrier Circus pygargus was studied for 4 years near Madrid, Spain, with the use of pellets and prey remains collected during the breeding season. The diet of the study birds included a wide variety of prey categories, the most important one by weight being lagomorphs (mainly Hares Lepus granatensis ). The diet varied seasonally, with Hares predominating early in the breeding season, while birds increased in importance later. The shift was partly a result of variation in availability (with fledgling birds being more abundant late in the season), but statistical analysis suggested that lagomorphs and then birds were actively chosen in the prelaying and nestling periods, respectively. Montagu's Harrier seemed to be an opportunistic species, hunting a wider range of prey types in more southern latitudes, but specialized in each region in the prey species that was most profitable. This was the only study on Montagu's Harriers to date which found lagomorphs to be the most important part of the diet throughout the season.     

Food habits of the ferret (Mustela putorius furo L.) at Pukepuke Lagoon,New Zealand

The food habits of 44 tagged ferrets at a wildlife management reserve in the Manawatu dune country were examined from analysis of 333 scats, collected over a period of 34 months. Of the 203 scats containing prey, mammals occurred in 54.7%, birds and eggs in 33.5%, frogs in 17.2%, and eels in 13.3%. The 21 insects occurring in 10.3 % of the scats may have been taken as prey, but their importance in the diet is probably minimal. There was significant monthly variation in the occurrence of all prey groups, related to changes in availability or vulnerability of the prey populations. Female ferrets apparently ate the smaller prey items more often than males, but the differences were significant only for mice. No assessment of the effects ferrets have as predators on any of the prey populations is possible from this study.     

Foods of feral house cats (Felis catus L.) in forest of the Orongorongo Valley,Wellington

Abstract

The foods of feral house cats in forest in the Orongorongo Valley, Wellington, were studied over 3 years and related to the availability of prey. Some cats were trapped, tagged, and released, and could be identified individually by coat colour and pattern. The number of cats, estimated from live-trapping and sightings, was stable during the study. Examination of 677 scats revealed that mammals (rat, rabbit, opossum, mouse, and stoat, in descending order of importance) formed the bulk of the diet by weight. Remains of birds occurred in 12% of scats, but birds were estimated to form only 4.5% by weight of the diet. Insect fragments were present in many scats; wetas (Orthoptera), cicadas (Hemiptera), and beetles (Colcoptera) were important seasonally. Although eaten in large numbers, they contributed very little by weight to the diet. Populations of rats, rabbits, and opossums were fairly stable during the study; mice were abundant for most of the first 18 months, but were scarce in the last year. The literature on the food habits of feral house cats is reviewed; it emphasises that cats are primarily predators of small mammals (rodents and lagomorphs). Predation by feral cats can be important in holding rat and rabbit populations at low densities and in reducing seasonal fluctuations in their numbers. Cats can also exert heavy predation pressure on low-density mouse populations. Although the cats now eat few birds, they may have been responsible for reducing the numbers of some forest birds in the past.     

Shifts in fisher (Pekania pennanti) diet in response to climate-induced tree mortality in California assessed with DNA metabarcoding

A recent climate-induced tree mortality event in California, USA has led to dramatic landscape-level changes in the southern Sierra Nevada. Wide-spread conifer mortality was documented in habitat occupied by fisher (Pekania pennanti), a mature-forest associated species of conservation concern in this region. We analyzed fisher scats collected on the Sierra National Forest from the pre-tree-mortality period (PreTM, 2011 – 2013) and post-tree-mortality period (PostTM, 2017 – 2018). We used DNA metabarcoding to successfully identify taxa and summarized diet composition for 109 PreTM and 102 PostTM fisher scats. We observed 48 different diet items (33 assigned to species and 15 to genus). Mammals, birds, and plants of the Ribes genus (gooseberries and currents) comprised the highest proportions of diet items, although scats also contained DNA from reptiles, insects, arachnids, snails, and fungi. The frequency of occurrence of mammalian prey items was lower in PostTM (49.0%) versus PreTM scats (81.7%) with a reduction in the occurrence of two tree squirrels (Douglas squirrel and Humboldt’s flying squirrel). A higher proportion of scats collected PostTM (46.1%) contained DNA from Ribes spp. versus scats collected PreTM (19.3%). Our data reveal potential cascading effects of climate-induced tree mortality on fisher diet in the southern Sierra Nevada. Flexibility in fisher diet, however, may allow resilience to ecological change though future studies should consider the behavioral, energetic, demographic or fitness consequences from a shift away from medium-sized mammalian prey to plants.     

INVESTIGATING THE BIASES IN THE USE OF HARD PREY REMAINS TO IDENTIFY DIET COMPOSITION USING ANTARCTIC FUR SEALS (ARCTOCEPHALUS GAZELLA) IN CAPTIVE FEEDING TRIALS

The analysis of pinniped scats has been used to quantify their diet, using prey remains to identify species and to estimate the numbers and sizes of prey consumed. There are, however, potential biases involved with scat analysis and, for this method to be used successfully, these biases need to be quantified. Thirty-six Antarctic fur seals ( Arctocephalus gazella ) were fed meals of exclusively either fish, squid, or krill and their scats were collected and analyzed. The major sources of error in the analysis of prey remains from scats were the differential erosion and passage rate of items in relation to their size. However, using simple correction functions, such as those which model otolith erosion, it is possible to reduce these errors. Using plastic beads as dietary markers showed recovery rates were negatively related to their size. Larger squid beaks had lower recovery rates than smaller beaks, but there was no size-related bias in the recovery rates of krill carapaces. Only 33% of the squid beaks and 27% of the otoliths originally fed were recovered from the scats. Recovery rates were greater for squid (77%) and fish (50%) eye lenses and these structures gave a better estimate of numbers eaten. Differences found between experimentally derived and published regression equations (used to calculate prey sizes eaten from prey remains) highlights the need for regression equations based on local prey characteristics, if these are to be used with any success to describe the prey eaten.     

Food niches of sympatric Marsh Harriers Circus aeruginosas and Hen Harriers C. cyaneus on the Dutch coast in winter

Analysis of pellets collected from adjacent communal winter roosts of Marsh Harriers Circus aeruginosus and Hen Harriers C. cyaneus on an extensive saltmarsh in the southwest Netherlands showed highly significant differences between the diets of the two species. Marsh Harrier diet showed no change throughout January, February and March. They specialized on ducks, which were about half of their prey numerically and more important by weight. Although Marsh Harriers sampled other prey, this remained at a low level and showed no seasonal response to the availability of young lagomorphs. Hen Harriers occupied the niche of a generalist predator, having a broader diet and responding to the presumed changes in availability of prey with diet shifts. In November, about half of their prey items were passerines but these declined in importance in December, and small mammals rose. The proportions of both small mammals and birds fell in February and March, due to increasing dependence on young lagomorphs. Diet overlap between the two species was greatest in January and declined in February and March.     

Macroscopic prey remains in the winter diet of foxes Vulpes vulpes in rural Britain

• 1 The winter diet of foxes Vulpes vulpes was quantified in seven landscape types in Britain, using faecal samples from 87 sites.
• 2 Medium‐sized mammals (0.1–5.0 kg) were consistently the most important prey group in arable and pastural landscapes, occurring in 44–72% of scats and comprising 50–75% of the mass of prey ingested. Birds and small mammals (< 0.1 kg) were important secondary prey groups.
• 3 Small mammals were the most frequently recorded prey group in marginal upland (42% of scats) and upland landscapes (75%), followed by large mammals (33% and 23%, respectively). In terms of mass ingested, small mammals (38%) and large mammals (52%) were the most important prey groups in these landscapes.
• 4 In all landscapes, field voles Microtus agrestis, lagomorphs, sheep/deer and passerines/galliforms dominated their respective prey groupings.

     

Competition and coexistence in sympatric bobcats and pumas

Space use and diets of sympatric bobcats Lynx rufus and pumas Puma concolor were compared using sign surveys and scat analysis during 1997–2002 in south-eastern Arizona, USA. Bobcats appeared to use grassland, scrub, riparian and woodland habitats equally, but pumas had higher activity in riparian and woodland habitats. There was little evidence that bobcats avoided pumas in space use. Bobcats ate primarily rodents (33% of items in scats), lagomorphs (32%) and ungulates (16%), whereas pumas ate primarily ungulates (69%) and carnivores (21%). Pumas had a narrower dietary niche breadth than bobcats, and puma diet overlapped bobcat diet by 56%, suggesting that pumas may be more vulnerable to changes in prey density than bobcats. Pumas also killed and consumed bobcats, indicating that interference competition may be manifesting through intraguild predation.     

Food Habits and Livestock Depredation of Sympatric Jaguars and Pumas in the Iguaçu National Park Area, South Brazil

Understanding coexistence between sympatric felines with similar body sizes, such as jaguars Panthera onca and pumas Puma concolor , requires knowledge of the way these predators consume and partition food resources. Yet the importance of livestock predation on jaguar and puma coexistence is poorly known. I investigated food habits and patterns of livestock depredation of jaguar and pumas in the Iguaçu National Park (INP) in southern Brazil. From 1997 to 2001, I collected scats opportunistically on trails and roads in INP and visited ranches on the border of INP. I found that jaguars relied mostly on large and medium-sized wild prey species, while pumas concentrated on medium-sized prey species. Livestock was the fifth most frequent prey found in jaguar scats but the most important one in terms of biomass consumed. Jaguar and puma diets differed significantly when all prey items were compared and also when livestock was excluded from the jaguar diet. Jaguar predation on livestock was considerably higher than predation by pumas. However, predation was not substantial relative to availability of livestock, and cattle likely constitute an alternative source of prey for jaguars. Degree of diet overlap between jaguar and puma in INP suggests that coexistence was likely driven by exploitative competition through some degree of food partitioning. My results highlight the importance of more actions toward increasing numbers of large ungulates to preserve the population of jaguars in INP.     

Amplification of DNA markers from scat samples of the least weasel<Emphasis Type="Italic">Mustela nivalis nivalis</Emphasis>

To test the feasibility of using field-collected scats as a source of DNA in the study of the least weaselMustela nivalis nivalis Linnaeus, 1766, DNA was extracted from scat samples collected from captive weasels using a modified extraction protocol. Using universal primers, the control region of the mitochondrial genome was successfully amplified from scat-extracted DNA. This amplification resulted in two products; one equivalent in size and sequence to the product obtained from tissue-extracted weasel DNA, and the other slightly larger and equivalent in size and sequence to the domestic house mouseMus musculus, the food source of the captive weasels. This demonstrates the reliability of DNA extraction from scats, as well as the possibility, under favourable circumstances, of identifying the prey species from the same samples. In addition, we attempted to amplify microsatellite loci from both tissue and scat-extracted DNA using six primer pairs designed for other mustelids, the American minkMustela vison and the wolverineGulo gulo. While three loci, Mvi57 (American mink), Ggu216 and Ggu234 (wolverine), were found to be polymorphic in the least weasel, amplification of these loci from the scat extracted DNA was only successful for approximately half of the samples. Although further work is needed, the present results suggest that it is possible to use scats as a source of DNA in field studies of the least weasel.     

Diet estimation based on an integrated mixed prey feeding experiment using Arctocephalus seals

Food web models depend on identifying which taxa are eaten and in what proportion they are consumed. Arctocephalus seals are generalist foragers and are an ongoing focus of Southern Hemisphere marine ecosystem research. This is the first feeding experiment to use Arctocephalus spp. to assess the utility of hard part scat analysis for diet estimation, based on mixed prey diets integrated over several days. Recovery rates of otoliths were extremely low for all taxa (0-9%). Although we could not collect scats produced during a 90 min period each day, during which the seals had access to a large pool, this result could not be attributed to otolith robustness, pinniped species or class, activity level, meal size or frequency, or fat content of the diet. We conclude that the unusually low recovery rates in this study may be due to unaccounted scats produced during 90 min of each day, if they contained otolith numbers an order of magnitude greater than all otoliths retrieved from scats produced during the other 22.5 h of each day, and/or may be related to the digestive processing of a mixed prey diet. Our study demonstrates the inadequacy of using otoliths in field collected scats for diet estimation due to the high level of unexplained variability of otolith occurrence in scats. We also identify two new potential sources of this variability. These are variability in numbers of otoliths per scat depending on activity level when a scat is excreted, and variability in recovery rates of otoliths as a function of the complexity of the diet.     

Multiple species‐specific molecular markers using nanofluidic array as a tool to detect prey DNA from carnivore scats

Large carnivore feeding ecology plays a crucial role for management and conservation for predators and their prey. One of the keys to this kind of research is to identify the species composition in the predator diet, for example, prey determination from scat content. DNA‐based methods applied to detect prey in predators’ scats are viable alternatives to traditional macroscopic approaches, showing an increased reliability and higher prey detection rate. Here, we developed a molecular method for prey species identification in wolf (Canis lupus) scats using multiple species‐specific marker loci on the cytochrome b gene for 18 target species. The final panel consisted of 80 assays, with a minimum of four markers per target species, and that amplified specifically when using a high‐throughput Nanofluidic array technology (Fluidigm Inc.). As a practical example, we applied the method to identify target prey species DNA in 80 wolf scats collected in Sweden. Depending on the number of amplifying markers required to obtain a positive species call in a scat, the success in determining at least one prey species from the scats ranged from 44% to 92%. Although we highlight the need to evaluate the optimal number of markers for sensitive target species detection, the developed method is a fast and cost‐efficient tool for prey identification in wolf scats and it also has the potential to be further developed and applied to other areas and large carnivores as well.     

The feeding ecology of mink (Mustela vison) in coastal habitat

The diet of a coast-living population of mink was investigated from the scats collected over a three-year period, and compared with information on the availability of principal prey species. Lagomorphs were the single most important prey, and predation upon them matched the abundance of rabbits as determined by monthly counts. Aquatic foraging was particularly important, with rockpool-inhabiting fish accounting for 29–1% occurrence of food items. Fish predation was more pronounced during winter months when lagomorph prey was less available. Crustacean prey, particularly the shore crab, Carcinus maenas , occurred frequently in the diet. Seabirds figured regularly in the diet; these were either taken as carrion from the strand-line or through predation on breeding colonies during the summer months.     

Food habits of stoatsMustela erminea and weaselsMustela nivalis in Denmark

StoatsMustela erminea Linnaeus, 1758 and weaselsMustela nivalis Linnaeus, 1766 exploit the same array of prey species at different frequencies according to body size. The rabbitOryctolagus cuniculus, which typically is the dominant prey for stoats in temperate parts of Europe, is absent in Denmark. The present study based on gastrointestinal tract contents examines the food habits of sympatric stoats (n=112) and weasels (n=132) from Denmark. Rodents were the most important prey group for both stoats and weasels, constituting 77% and 84% of their diet respectively, expressed as frequency of occurrence. No differences were detected in the proportions of major prey groups between sexes within species, but between species the diets differed. Stoats ate birds and birds’ eggs more often than weasels did, while weasels ate more insectivores. Stoats ate more oftenMicrotus voles and water voleArvicola terrestris than weasels did, while weasels ate more bank voleClethrionomys glareolus and moleTalpa europaea. There was a larger dietary overlap between sympatric stoats and weasels in Denmark than in other dietary studies in areas where rabbits were available.