The feeding ecology of the dingo

Summary Changes in the diet of dingoes (Canis familiaris dingo) in response to measured fluctuations of prey populations were followed over 7 years. The study began after great rains had broken a long drought. Eruptions of rodents and rabbits followed, but some prey were always either relatively abundant (live cattle) or scarce (red kangaroo, lizards, birds). Cattle carcasses were increasingly available during a subsequent drought. Small and medium-sized prey, rodents (26%), lizards (12%) and rabbits (56%) were preferred, probably because they were easily caught. Only rabbits were caten consistently regardless of density. By contrast, large prey were eaten in relatively large amounts only during drought, with initial emphasis on red kangaroos (15% overall) and then cattle (17%) mostly as carcasses. The diet was functionally related to the respective abundances of all major prey species, but the relationship shifted during drought when predation on low populations was most severe. There was evidence that growth of resurging prey populations were suppressed by predation. Diets of dingoes did not differ significantly with age or sex. An hypothesis of alternation of predation is presented: dingoes feed sequentially on prey of increasing size (rodents, rabbits, red kangaroos, cattle) in response to rainy periods and subsequent droughts, meanwhile always concentrating on the staple prey (rabbits). The fluctuating abundances of small and medium-sized prey determined not only their own relative availabilities but also that of large prey, and hence determined the diet of the dingo at any time. Prey availability (catchability, accessability) appeared to be more important than prey abundance (numbers, biomass), and the dingo's flexible social organisation allowed versatility in hunting strategies and defence of resources. We conclude that dingoes do not always forage most efficiently as optimal foraging models predict because of the constraints imposed by the capricious environment in arid Australis, where prey availability fluctuates greatly and becomes limited and clumped in drought, so that dingoes may be faced with outright starvation. Instead we conclude that dingoes utilise a conservative feeding strategy and adopt any behaviour which provides at least a threshold quantity of energy or nutrient as part of a trade-off with other competing ecological requirements.     

The feeding ecology and activity budget of proboscis monkeys

A group of proboscis monkeys (Nasalis larvatus) consisting of an alpha‐male, six adult females, and several immatures was observed from May 2005–2006. We collected over 1,968 hr of focal data on the adult male and 1,539 hr of focal data on the six females in a forest along the Menanggul River, Sabah, Malaysia. Availability and seasonal changes in plant species consumed by the focal monkeys were determined by vegetation surveys carried out across an area of 2.15 ha along 200–500 m trails in riverine forest. A total of 188 plant species were consumed by the focal monkeys. The activity budget of members of our study group was 76.5% resting, 19.5% feeding, and 3.5% moving. Young leaves (65.9%) and fruits (25.9%) accounted for the majority of feeding time. Over 90% of fruit feeding involved the consumption of unripe fruits and in the majority of case both the fruit flesh and seeds were eaten. Although fruit eating was rare in some months, during other times of the year time fruit feeding exceeded the time devoted to young leaves. We found that monthly fruit availability was positively related to monthly fruit eating and feeding activity, and seasonal fluctuations in dietary diversity were significantly affected by fruit eating. These results suggest that fruit availability and fruit‐eating behaviors are key factors that influence the activity budget of proboscis monkeys. Earlier assumptions that colobine monkeys are obligate folivores do not apply well to proboscis monkeys and certain other colobines. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of Asian colobines. Am. J. Primatol. 71:478–492, 2009. © 2009 Wiley‐Liss, Inc.     

Feeding ecology of the armored shrew, from the north-eastern Democratic Republic of Congo

The diet of Scutisorex somereni (Soricomorpha: Soricidae) from forests in the Democratic Republic of Congo was investigated to elucidate its feeding ecology in the context of its unique spinal modifications. It ate a wide range of small and large invertebrates, including representatives of Coleoptera, Formicidae, Lepidoptera and Diptera larvae, Chilopoda, Diplopoda and Araneae, but the principal prey was Oligochaeta. All diet samples contained Oligochaeta and these contributed 38–45% of prey volume. While 64% of prey occurrences were <10 mm in length, 56% of prey volume comprised invertebrates >26 mm, mostly large Oligochaeta (some of >50 mm). Soil-dwelling prey comprised 46% by composition (59% by volume) of the diet. Besides its peculiar skeletal modifications, it has an exceptionally long intestine relative to its body size. It was concluded that S. somereni is primarily an earthworm-eating shrew and partially subterranean rather than truly fossorial in foraging mode. Its diet and foraging mode cannot explain the unique vertebral modifications of this zoological curiosity.     

Composition and function of haemolymphatic tissues in the European common shrew

Background

Studies of wild animals responding to their native parasites are essential if we are to understand how the immune system functions in the natural environment. While immune defence may bring increased survival, this may come at a resource cost to other physiological traits, including reproduction. Here, we tested the hypothesis that wild common shrews (Sorex araneus), which produce large numbers of offspring during the one breeding season of their short life span, forgo investment in immunity and immune system maintenance, as increased longevity is unlikely to bring further opportunities for mating. In particular, we predicted that adult shrews, with shorter expected lifespans, would not respond as effectively as young animals to infection.

Methodology/Principal Findings

We examined haemolymphatic tissues from wild-caught common shrews using light and transmission electron microscopy, applied in conjunction with immunohistology. We compared composition and function of these tissues in shrews of different ages, and the extent and type of inflammatory reactions observed in response to natural parasitic infections. All ages seemed able to mount systemic, specific immune responses, but adult shrews showed some signs of lymphatic tissue exhaustion: lymphatic follicles in adults (n = 21) were both smaller than those in sub-adults (n = 18; Wald = 11.1, p<0.05) and exhibited greater levels of depletion (Wald = 13.3, p<0.05).

Conclusions/Significance

Contrary to our expectations, shrews respond effectively to their natural parasites, and show little indication of immunosenescence as adults. The pancreas of Aselli, a unique lymphoid organ, may aid in providing efficient immune responses through the storage of large numbers of plasma cells. This may allow older animals to react effectively to previously encountered parasites, but infection by novel agents, and eventual depletion of plasma cell reserves, could both still be factors in the near-synchronous mortality of adult shrews observed shortly after breeding.     

Functional ecology of feeding in elasmobranchs

Feeding behavior in the species of captive chondrichthyans is studied to clarify the functional mechanisms responsible for feeding ecology. Kinematics and pressure in the buccal, hyoid and pharyngeal regions were quantified in Squalus acanthias, Chiloscyllium plagiosum and Leucoraja erinacea using sonomicrometry and pressure transducers. Means and coefficients of variation were analyzed by species and by behavior to test for stereotypy and flexibility in the feeding mechanism. Several instances of mechanical stereotypy as well as flexibility were found in the feeding kinematics and pressure of the three chondrichthyan species. In general, Squalus acanthias shows more stereotyped feeding behavior than C. plagiosum and L. erinacea. Different aspects of feeding behavior stand out among the three species. Chiloscyllium plagiosum generates lowest pressures, S. acanthias achieves the greatest area changes, and L. erinacea has longer durations for manipulating prey. Capture events are functionally and behaviorally stereotyped while processing events are functionally and behaviorally flexible with the ability to use suction or compression to process the same food item. Squalus acanthias is a functional specialist and C. plagiosum is functionally a generalist, with both species exhibiting behavioral flexibility. Leucoraja erinacea is a functional and behavioral generalist. Using functional morphology to explain mechanical stereotypy and flexibility in the feeding behavior of three suction feeding chondrichthyan species has allowed a better understanding of specialist and generalist trophic behaviors.     

The evolutionary ecology of detritus feeding in the larvae of freshwater Diptera

Detritus (dead organic matter), largely of terrestrial origin, is superabundant in inland waters but because of its indigestible nature, would appear to be a poor food source for animals. Yet this unpromising material is widely used as food and indeed can be viewed as a defining characteristic of the freshwater environment. We here explore the relationships among animals, detritus and its associated micro-organism decomposers, taking a functional approach. We pose questions about interrelationships and attempt to arrive at new insights by disentangling them from an adaptive point of view. To do this we have been careful in selecting the habitats for detailed consideration. Rain pools on rock surfaces in tropical Africa and pools on peat moorland in the UK were chosen. Both examples have a relatively simple community structure and hence offer the prospect of achieving our aim. As model organisms for study we focus principally on the aquatic stages of selected holometabolous insects; that is, selected genera of the universally common midges, Ceratopogonidae and Chironomidae. We approach these case studies from an evolutionary ecology perspective and see detritus as a simple template upon which a beautiful complex of adaptations can evolve.     

Preface: feeding ecology of elasmobranchs

Elasmobranchs are apical predators in most marine communities where they occur, often playing a substantial role in the food web dynamics of those communities. However, despite their high trophic status they are often poorly studied compared to most commercially important teleosts. Furthermore, despite efforts towards ecosystem-based management, elasmobranchs are still often lumped into generic categories referred to as ??shark?? or ??skate?? unclassified, with limited effort to identify individual species. The role of elasmobranchs in ecosystems has never been more important to our understanding of marine ecology due to high levels of exploitation of many species. Similar to other high trophic level predators, many elasmobranchs have life-history characteristics that make them vulnerable to over-exploitation. Elasmobranch populations are now heavily targeted in many fisheries throughout the world. Increasing exploitation of this group is especially alarming because their feeding ecology is poorly studied and by extension their influence in shaping ecosystems. Given recent increased attention on elasmobranchs in the scientific literature, management and conservation circles, and the general news media, researchers over the past decade have begun to more closely examine the ecological role of this important taxon of fishes. Due to this increasing awareness, and the development of new and innovative methods and analytical techniques, it prompted us to organize an international symposium on the ??Feeding Ecology of Elasmobranchs??. The symposium was held on 10 July 2010, in conjunction with the 27^th annual meeting of the American Elasmobranch Society meetings in Providence, Rhode Island.     

The ecology and feeding habits of the arboreal trap-jawed ant Daceton armigerum

Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hypertrophied trap-jaw mandibles, is characterized by a set of unexpected biological traits including colony size, aggressiveness, trophobiosis and hunting behavior. The size of one colony has been evaluated at ca. 952,000 individuals. Intra- and interspecific aggressiveness were tested and an equiprobable null model used to show how D. armigerum colonies react vis-à-vis other arboreal ant species with large colonies; it happens that D. armigerum can share trees with certain of these species. As they hunt by sight, workers occupy their hunting areas only during the daytime, but stay on chemical trails between nests at night so that the center of their home range is occupied 24 hours a day. Workers tend different Hemiptera taxa (i.e., Coccidae, Pseudococcidae, Membracidae and Aethalionidae). Through group-hunting, short-range recruitment and spread-eagling prey, workers can capture a wide range of prey (up to 94.12 times the mean weight of foraging workers).     

The biology and feeding ecology of Arctic charr in the Kerguelen Islands

Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self-sustaining population that has adapted to the unique conditions of the sub-Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size-dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub-Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub-Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub-Arctic lakes. Although they inhabit a resource-poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large-scale environmental change as represented by climate change.     

Weed macaques: The evolutionary implications of macaque feeding ecology

Patterns of feeding ecology among the living macaques conform poorly with recognized phyletic distinctions within the genus because there is an important ecological division which cross-cuts phyletic groupings. This division, between weed species and non-weed species, is based on the differing abilities of macaques to tolerate and even prosper in close association with human settlements. Based on available information about their ecology in the wild, we tentatively assign macaque species to these two categories. Finally, we consider the implications of our argument for scenarios of the initial spread of the macaques.     

Comparative feeding ecology of invasive Ponto-Caspian gobies

Invasions of Ponto-Caspian gobiid fishes are suspected to cause regime shifts in freshwater ecosystems. This study compared the trophic niche differentiations of Neogobius melanostomus and Ponticola kessleri in the upper Danube River using stable isotope analyses (δ¹³C and δ¹⁵N), gut content analyses and morphometric analyses of the digestive tract. Both species were identified as predacious omnivores with high dietary overlap and a generalistic feeding strategy. Amphipods (especially invasive Dikerogammarus spp.) contributed 2/3 to the index of food importance. δ¹⁵N-signatures of N. melanostomus revealed an ontogenetic diet shift and significantly exceeded those in P. kessleri by ~1.5‰, indicating a niche separation of half a trophic level. P. kessleri had shorter uncoiled intestinal tracts than N. melanostomus, indicating a narrower niche and adaptation to animal food. Trophic niches in both species expanded during the growth period with increasing intraguild predation and cannibalism in P. kessleri and increasing molluscivory in N. melanostomus. P. kessleri showed a higher degree of specialization and more stable feeding patterns across seasons, whereas N. melanostomus adapted its diet according to the natural prey availability. The feeding patterns of both species observed in the upper Danube River strongly differ from those in their native ranges, underlining their great plasticity. Both goby species consumed mainly other non-native species (~92% of gut contents) and seemed to benefit from previous invasions of prey species like Dikerogammarus villosus. The invasive success of gobies and their prey mirror fundamental ecological changes in large European freshwater ecosystems.     

The feeding ecology of the Central American cichlid Cichlasoma urophthalmus (Gunther)

The feeding habits of the cichlid Cichlasoma urophthalmus were studied in a brackish-water lagoon in Yucatan Peninsula, Mexico, from spring 1985 to spring 1986. The strong mandibular, maxillary and pharyngeal teeth, and the short intestine strongly suggest that C. urophthalmus is primarily a carnivore. Subsequent gut contents analysis revealed that this species feeds principally on invertebrates throughout the year and that there were few differences between the five seasons studied. The algal material found in some stomachs may be consumed as a consequence of predation on small invertebrates, but the feeding structures and short intestine makes this species unable to digest vegetable materials efficiently. Differences with other cichlids used in aquaculture are discussed.     

Evolution and ecology of feeding in elasmobranchs

Paleozoic chondrichthyans had a large gape, numerous spike-liketeeth, limited cranial kinesis, and a non-suspensory hyoid,suggesting a feeding mechanism dominated by bite and ram. Modernsharks are characterized by a mobile upper jaw braced by a suspensoryhyoid arch that is highly kinetic. In batoids, the upper jawis dissociated from the cranium permitting extensive protrusionof the jaws. Similar to actinopterygians, the evolution of highlymobile mandibular and hyoid elements has been correlated withextensive radiation of feeding modes in elasmobranchs, particularlythat of suction. Modern elasmobranchs possess a remarkable varietyof feeding modes for a group containing so few species. Biting,suction or filter-feeding may be used in conjunction with ramto capture prey, with most species able to use a combinationof behaviors during a strike. Suction-feeding has repeatedlyarisen within all recent major elasmobranch clades and is associatedwith a suite of morphological and behavioral specializations.Prey capture in a diverse assemblage of purported suction-feedingelasmobranchs is investigated in this study. Drop in water pressuremeasured in the mouth and at the location of the prey showsthat suction inflow drops off rapidly with distance from thepredator's mouth. Elasmobranchs specializing in suction-feedingmay be limited to bottom associated prey and because of theirsmall gape may have a diet restricted to relatively small prey.Behavior can affect performance and overcome constraints imposedby the fluid medium. Suction performance can be enhanced byproximity to a substrate or by decreasing distance from predatorto prey using various morphological and/or behavioral characteristics.Benthic suction-feeders benefit by the increased strike radiusdue to deflection of water flow when feeding close to a substrate,and perhaps require less accuracy when capturing prey. Suctionand ram-suction-feeding elasmobranchs can also use suction inflowto draw prey to them from a short distance, while ram-feedingsharks must accelerate and overtake the prey. The relationshipbetween feeding strategy and ecology may depend in part on ecological,mechanistic or evolutionary specialization. Mechanistic suction-feedingspecialist elasmobranchs are primarily benthic, while most epibenthicand pelagic elasmobranchs are generalists and use ram, suction,and biting to catch a diversity of prey in various habitats.Some shark species are considered to be ecological specialistsin choosing certain kinds of prey over others. Batoids are evolutionaryspecialists in having a flattened morphology and most are generalistfeeders. Filter-feeding elasmobranchs are ecological, mechanistic,and evolutionary specialists.