Feeding Trails Research Articles

WHY ARE SOME FRUITS TOXIC? GLYCOALKALOIDS INSOLANUMAND FRUIT CHOICE BY VERTEBRATES

We examined the influence of secondary metabolites (glycoalkaloids) of Solanum fruits on fruit consumption by seed dispersers and seed predators. Our goal was to determine the degree to which secondary metabolites might explain fruit–frugivore interactions that heretofore have not been explained by other fruit-related variables (e.g., color, nutrient content, seediness, etc.). Using feeding trails with real fruits and artificial fruit pulp media, we tested two sets of hypotheses, one relating to the specificity of secondary metabolites and the other to intra- and interspecific variation in secondary metabolite content. First, the Directed Toxicity Hypothesis was tested against its alternative, the General Toxicity Hypothesis. The Directed Toxicity Hypothesis posits that fruit pulp secondary metabolites are directed primarily toward organisms that destroy seeds following fruit consumption, remaining nontoxic to organisms that disperse seeds. The General Toxicity Hypothesis states that these secondary metabolites are general in their effects. Second, the Removal Rate Hypothesis was tested against its alternative, the Nutrient–Toxin Titration Hypothesis. The Removal Rate Hypothesis posits that profitable fruits, with high natural rates of removal, contain only low levels of secondary metabolites as defenses against seed predators and pathogens. In contrast, the Nutrient–Toxin Titration Hypothesis states that profitable fruits are better able to afford protection by high levels of secondary metabolites because high nutrient levels compensate for deterrent effects of secondary metabolites. We compared Solanum carolinense, with high levels of secondary metabolites (glycoalkaloids) in ripe fruit, and S. americanum, with negligible levels, conducting four sets of feeding trials: (1) Real Fruit trials to determine the preferences of our study animals for real fruit of each plant species; (2) Fruit Mimic trials using artificial fruit pulp media to determine the relative effects of nutrient and glycoalkaloid content on fruit preferences; (3) Interaction trials using artificial fruit pulp media to examine relative and interactive effects of the two main glycoalkaloids in our fruits (α-solasonine and α-solamargine); and (4) Nutrient–Toxin Titration trials using artificial fruit pulp media to determine how much nutrient content might compensate for deterrent effects. Both seed predators and seed dispersers preferred the low-glycoalkaloid S. americanum fruits and were deterred by glycoalkaloid levels typical of ripe S. carolinense fruits. Because of the generality of the deterrent effects, we rejected the Directed Toxicity Hypothesis. Additionally, we found no evidence for differences between the two glycoalkaloids in their deterrent effects, and no evidence of synergism between them. Nutrient effects were generally small; we found no evidence that nutrient variation could compensate for the deterrence produced by levels of glycoalkaloids found in ripe S. carolinense fruits. Ripe fruits of the presumably more profitable, preferred S. americanum contain much lower levels of glycoalkaloid. Taken together, our results support the Removal Rate Hypothesis. Secondary metabolites of ripe fleshy fruits are an important determinant of fruit use by frugivores. We suggest that a primary function of these metabolites is defense against pests and pathogens. Thus, these organisms should be considered an important influence on fruit–seed disperser interactions.

Marine mammal faeces as a source of DNA

[Extract] Remote collection of skin biopsies from free-ranging marine mammals has been to date, the most effective and noninvasive means of tissue collection for DNA studies (Amos & Hoelzel 1990; Brown et al. 1991; Weinrich et al. 1991). Although it has been shown that DNA extraction from faeces is possible (Hoss et al. 1992), there are no records of DNA extraction from the faeces of marine mammals, perhaps because it is expected their faeces have a shorter life span compared with the faeces of (dry) land mammals. We have been able to extract DNA from the faeces of a free-ranging dugong (Dugong dugon). We present a sequence from this DNA, a region of the mitochondrial DNA which we have used for a genetic population structure study of the dugong. Extraction of DNA from faeces of marine mammals provides an attractive alternative to biopsy sampling. It is less invasive and more economical. The dugong faecal sample was collected from Borroloola (15°8'S 136°7'E) as part of a feeding study (A.R. Preen, pers. comm., 1995). Dugong feeding trails are easily recognizable and their faeces float to the surface of the water. Several intact faeces were collected after floating for an undetermined time (a few hours?) and individually contained in plastic bags. It was about 3h before they were frozen and, although they stayed cold, they were defrosted during a 2 day transit, refrozen, then thawed for DNA extraction.

Flamingo and duck‐like bird tracks from the Late Cretaceous and early Tertiary: Evidence and implications

Two new Late Cretaceous ichnospecies are named on the basis of tracks of birds with webbed feet discovered in the Uhangri Formation, Hwangsan Basin of South Korea. The first, Uhangrichnus chuni ichnogen. et ichnosp. nov., is based on a large sample of small tracks, whereas the second, Hwangsanipes choughi ichnogen. et. ichnosp. nov., is based on a single trackway of a larger bird from the same stratigraphie level. The tracks form part of a high density track assemblage in lacustrine shoreface sediments and are the oldest traces of web‐footed birds so far reported. A third, Early Tertiary ichnospecies, Presbyorniformipes feduccii ichnogen. et ichnosp. nov., is named on the basis of trackways and feeding trails of a bird with webbed feet from the Early Eocene Green River Formation of eastern Utah. This previously unnamed track type has already been attributed to the Eocene shorebird Presbyornis and cited as an example of trace‐fossil evidence for feeding behavior in a lakeshore setting. Although this attrib...

Food and growth relations of the marine microzooplankter, Synchaeta cecilia (Rotifera)

The trophic interactions of the marine rotifer Synchaeta cecilia were investigated by determining its feeding and growth rates on a wide variety of marine phytoplankton and by determining its susceptibility to predation by the calanoid copepod, Acartia tonsa. Reproduction of S. cecilia was sustained in four-day feeding trails by 13 of 37 algal species tested. Growth-supporting species included species of Cryptophyceae, Dinophyceae, Chlorophyceae and Haptophyceae in sizes from 4 to 47 μm. Within these taxa, other species in the acceptable size range failed to support growth. No species of Cyanophyceae, Bacillariophyceae, or Chrysophyceae supported growth of the rotifer. S. cecilia can be maintained on unialgal cultures of Cryptophyceae but growth is enhanced by a combination of two or three species; a mixture of Chroomonas salina (Cryptophyceae), Heterocapsa pygmaea (Dinophyceae), and Isochrysis galbana (Haptophyceae) has sustained laboratory stocks of S. cecilia for over four years. The expected response of S. cecilia to food quantity was observed: as food concentration was increased from 58 to 1154 μg C 1−1, the population growth constant increased from 0.17 to 0.60 d−1 at 20°C. This is equivalent to population doubling times of 4.0 and 1.1 days at H. pygmaea densities of 500 and 104 cells ml−1, respectively. The susceptibility of S. cecilia to predation was investigated by determining its rate of capture by the omnivorous marine copepod Acartia tonsa. At prey densities of 5 to 35 μg C 1−1 (0.3 to 1.9 individuals 1−1), A. tonsa readily ingested S. cecilia at rates up to 3 μg C copepod−1 day−1.

Maksymalne tempo asymilacji energii u nornicy rudej

The maximum cold-induced energy assimilation rate in nonreproducing bank voles Cletrhionomys glareolus (Schreber, 1780) was estimated by means of feeding trails. It reached 2.56 kJXg-1Xday, which is only about 3 times the basal metabolic rate, and approaches the level of the average daily energy budget of this species. This is, however, much less than assimilation rate previously reported for lactating bank voles.

The effect of source of nitrogen and level of its supplementation on the performance of growing-fattening bulls

ABSTRACTTwo feeding trails were made and in both all the diets given contained about 11 MJ metabolizable energy (ME) per kg dry matter (DM).In trial 1, diets containing three concentrations of crude protein (CP) were given to a total of 84 Friesian bulls in each of three stages of growth. They were, in stage 1 (150 to 250 kg live weight) 130, 145 and 160 g CP per kg dietary DM; in stage 2 (250 to 350 kg live weight) 110, 130 and 145 g CP per kg dietary DM; in stage 3 (350 kg to slaughter) 95, 110 and 130 g CP per kg dietary DM. In stages 2 and 3, the source of supplementary nitrogen at each CP concentration was either soya-bean meal or non-protein nitrogen (NPN) giving six combinations of concentration and source of dietary CP. Live-weight gains in stage 1 were 1·52, 1·60 and 1·58 kg/day respectively (P > 0·05). In the stages involving both concentrations and source of nitrogen (soya-bean meal in parentheses), the mean daily live-weight gains were (1·40), 1·38, (1·32), 1·34 (1·34) and 1·31 kg for stage 2 (F > 0·05) and (1·14), 1·14, (1.24), 1·16, (1·06) and 1·08 kg for stage 3 (P < 0·05), for the diets of 130, 145 and 160 g CP per kg diet respectively.Trial 2 consisted of six stages of growth, the first five of 45 days duration and the sixth of varying length up to a predicted slaughter weight, and seven dietary treatments. Treatment 1 was a negative control (NC) with a dietary CP concentration of 90 g/kg DM. For the other six treatments two concentrations of dietary CP were given; 120 g/kg and 140 g/kg in stages 1 and 2 and 100 g/kg or 120 g/kg in stages 3 to 6. Dietary CP concentration was increased by the addition of NPN, fish meal or soya-bean meal. A total of 98 Friesian bulls were used with an initial average live weight of 185 kg. Daily gain of the NC group in the six stages of the trial was 0·86, 0·97, 101, 1·13, 1·07 and 1·00 kg for stages 1 to 6 respectively. From the results it was concluded that feeding NPN is not efficient at live weights lower than 250 kg and that there is no advantage to feeding fish meal over soya-bean meal in diets of medium energy concentration at live weights heavier than 250 kg.

Winter foraging by individual porcupines

Winter feeding of individual porcupines (Erethizon dorsatum L.) was studied in the northern Catskill Mountains of New York by following individual feeding trails in the snow. The study population as a whole fed primarily on beech (Fagus grandifolia) and sugar maple (Acer saccharum) and less frequently on eight other tree species. Individual porcupines limited their feeding to one or two species. An individual's primary food choice corresponded to the numerically most abundant tree species in its foraging area; its secondary food choice could not be related to relative density nor to relative basal area.

Reassessment of sediments and trace fossils from old red sandstone (Lower Devonian) of Dunure, Scotland, described by John Smith (1909)

In 1909 John Smith, a Scottish naturalist and geologist, described 23 «genera and 51 «species of trace fossils from small patches of sediment associated with andesite lava flows at Dunure, Ayrshire. He interpreted the traces as evidece of a diverse invertebrate fauna which inhabited small pools and fissures in the lava surface between eruptions. Smith's collection (c 300 specimens) was presented to the British Geological Survey, Edinburg but has remained largely unstudied. Re-examination of the Smith collection shows that it came from 3 separate localities which differ in composition of the ichnofaunas, associated sediments and sedimentary structures. Arthropod trackways dominate the ichnofauna occurring in laminated siltstone frequently with ripple marks and foam marks suggesting formation in shallow lacustrine conditions. Preservational and behavioral analysis of trace fossils reveals about 10 valid ichnogenera of locomotion and swimming trackways, resting traces, feeding trails but few burrows. Presence of early terrestrial arthropods traces is uncertain. Palaeoecological interpretation is of ephemeral lakes in distal braid-plain situation subject to subsurface invasion of andesite lava producing fluidization and deformation of wet sediment. The Dunure ichnocoenosis shows unique diversity of Devonian arthropod trace fossils.

Reassessment of sediments and trace fossils from old red sandstone (Lower devonian) of Dunure, Scotland, described by John Smith (1909)

In 1909 John Smith, a Scottish naturalist and geologist,described 23 «genera and 51 «species of trace fossils from small patches of sediment associated with andesite lava flows at Dunure, Ayrshire. He interpreted the traces as evidence of a diverse invertebrate fauna which inhabited small pools and fissures in the lava surface between eruptions. Smith's collection (c. 300 specimens) was presented to the British Geological Survey, Edinburgh but has remained largely unstudied. Re-examination of the Smith collection shows thatit came from 3 separate localities which differ in composition of the ichnofaunas, associated sediments and sedimentary structures. Arthropod trackways dominate the ichnofauna occurring in laminated siltstone frequently with ripple marks and foam marks suggesting formation in shallow lacustrine conditions. Preservational and behavioural analysis of trace fossils reveals about 10 valid ichnogenera of locomotion and swimming trackways, resting traces, feeding trails but few burrows. Presence of early terrestrial arthropod traces is uncertain. Palaeocological interpretation is of ephemeral lakes in distal braid-plain situation subject to subsurface invasion of andesite lava producing fluidization and deformation of wet sediment. The Dunure ichnocoenosis shows unique diversity of Devonian arthropod trace fossils.

Trace fossils from Lower Palaeozoic ocean-floor sediments of the Southern Uplands of Scotland

ABSTRACTThe Ordovician and Silurian rocks of the Southern Uplands of Scotland have been interpreted as sediments deposited on the northern margin of the Iapetus Ocean. Trace fossils are abundant at many localities in ocean-floor turbidites and mudstones that usually lack all other evidence of life. Twelve ichnogenera are present, and they are mainly meandering locomotion and feeding trails and burrow networks: Dictyodora, Caridolites, Helminthoida, Neonereites, Nereites, Protovirgularia, Gordia, Megagrapton, Paleodictyon, Chondrites, Plano-lites and Skolithos. The trace fossils occur in at least five distinct assemblages and the composition of these was probably controlled by the frequency and nature of the turbidity currents, and possibly by the oxygen content of the mudstones. Where turbidity currents were weak, abundant Dictyodora, together with Caridolites, Neonereites, Nereites, Protovirgularia and Gordia occur in various combinations. Where currents were stronger, traces such as Gordia, Paleodictyon and Megagrapton may be exhumed and cast on turbidite soles, and the sand may contain Skolithos. The ‘deep-sea’ Nereites trace fossil facies is divisible into several assemblages, presumably environmentally controlled.

Lower Cretaceous Shelf Storm Deposits, North Texas: ABSTRACT

Many of the important features of shelf storm deposits are displayed in the Lower Cretaceous Washita Group in Grayson County, Texas. Proximal shelf sands are up to 2 m thick. They show channeled tops and abrupt lateral thickness variation and are stacked vertically or separated by thin, sparsely fossiliferous marine muds. Each sand unit has a scoured base and comprises a structureless lower interval that grades upward into hummocky cross-stratification. These features in turn are overlain by subhorizontal lamination, with an uppermost interval consisting of small-scale wave ripples containing abundant horizontal burrows and feeding trails. Distal shelf sands are thin (10 to 40 cm) compared to the intervening muds, and are comparable to modern storm deposits of the Texas s elf. A basal shelly lag, with a scoured base of upward-convex, disarticulated bivalves or current-aligned high-spired gastropods merges upward into subdued hummocky cross-stratification and subhorizontal lamination. Powerful bottom return currents, that in the modern Gulf of Mexico are generated by wind immediately prior to storm landfall, were probably the dominant mechanism of offshore sand transport. Storm waves operated contemporaneously and probably contributed toward sediment entrainment, as evidenced by hummocky cross-stratification. However, the disposition of fossils suggests that initially, at least, unidirectional currents were the dominant transport mechanism. Relatively shallow-water depths (50 m or less) are indicated by associated regressive deltaic sequences. End_of_Article - Last_Page 723------------

Energy Costs of Activity and Daily Energy Expenditure in the Black Duck

Heart rates of 3 wing-clipped black ducks (Anas rubripes) were successfully monitored for up to 11 days in the field. The energy costs of several activities, such as swimming, feeding, and preening, were calculated using regressions of metabolism on the heart rate previously determined in the laboratory for each duck. Total daily energy expenditure during midsummer using time-activity analyses of nonradioed black ducks was 1.5 to 2 times the resting metabolic rates measured in the laboratory. Preliminary data indicate that the energy costs for laying females may be as high as 3.4 times the resting rates. J. WILDL. MANAGE. 42(4):739-745 Investigations into the energy requirements of wild Anatidae have included feeding trails (Owen 1970, Penney and Bailey 1970, Sugden 1971, 1973, 1974, Sugden and Harris 1972, Miller 1974) and respiration calorimetry (Hartung 1967, Berger et al. 1970, Prange and Schmidt-Nielsen 1970, McEwan and Koelink 1973, Smith and Prince 1973, Wooley and Owen 1977). Recently, Dwyer (1975) estimated the energy requirements of free-living male gadwalls (Anas strepera) by extrapolation from time budget data. However, no direct measurements of metabolism under natural field conditions have been made. Owen (1969) and Wooley and Owen (1977) have discussed the relationship of metabolism to heart rate measured under laboratory conditions in blue-winged teal (Anas discors) and black ducks equipped with radio transmitters. We felt that this method offered promise for use with freeliving waterfowl to estimate the energy requirements for specific activities and to obtain daily energy budgets. The following report discusses the results of research on the energy requirements of semifree-living black ducks and the extrapolation of these data to free-living conditions. We thank C. J. Sniffen for his aid in laboratory work and statistical analysis, A. Fuller for his help in maintaining telemetry equipment, and the Maine Dept. of Inland Fisheries and Wildlife for supplying ducks. Special thanks are due to J. Sease, A. Lovewell, and M. Robson for aiding with field work.

Deltaic sediments, Upper Triassic Torlesse Supergroup, Broken River, North Canterbury

Abstract A small block (8.4 km2) of Upper Triassic Torlesse Supergroup rocks is mapped and described. Three sedimentary facies and one probably volcanogenic facies are recognised. They are interstratified and grade laterally into one another. Very thick-bedded sandstone occurs in wedging units up to 450 m thick. It consists mostly of massive, moderately sorted, medium-fine sandstone with scattered zones of parallel lamination, gently inclined lamination, and ripple cross-lamination. Penecontemporaneous black mudstone clasts occur widely. The facies is unfossiliferous. Thin-bedded siltstone forms units up to 95 m thick. It consists of very thin and thin beds of parallel-laminated, small-scale ripple cross-laminated, and deformed cross-laminated, moderately to well sorted coarse siltstone or silty very fine sandstone, alternating with homogeneous or mottled black mudstone. The worm tubes Titahia and Torlessia and feeding trails are widespread. Black mudstone occurs in units up to 150 m thick. It is characte...