Food-searching behaviour of the common merganser (Mergus merganser) I: Functional responses to prey and predator density

1985 ◽  
Vol 63 (6) ◽  
pp. 1260-1270 ◽  
Author(s):  
C. C. Wood ◽  
C. M. Hand
Keyword(s):  
Coho Salmon ◽  
Flock Size ◽  
Previous Exposure ◽  
Functional Responses ◽  
Experimental Conditions ◽  
Natural Stream ◽  
Daily Food ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

The hunting performance of the common merganser (Mergus merganser) was evaluated in relation to prey density and merganser flock size by stocking three enclosed sections of a natural stream with known densities of juvenile coho salmon (Oncorhynchus kisutch). Two size classes of coho were stocked: smolt averaging 43 g at densities of 0.02–0.65/m2, fry averaging 2 g at 0.08–1.6/m2 and various mixtures of smolt and fry at a combined density of 0.65/m2. The stream enclosures differed in the amount of cover available to fish. Mergansers were less successful at capturing coho smolt or fry in the enclosures wth cover from undercut banks. Smolt exposed to mergansers earlier that day were less vulnerable than smolt with no previous exposure. The feeding success of individual mergansers was not significantly affected by flock size for flocks of 25 birds or less. A smoothly asymptotic functional response (type II) was observed under all experimental conditions. Coho smolt were selected over coho fry. It is concluded that a merganser's average daily food requirement (ca. 400 g) can be satisfied at smolt densities of 0.02–0.30/m2 depending on the availability of cover for smolt and their previous exposure to mergansers.

Food-searching behaviour of the common merganser (Mergus merganser) II: Choice of foraging location

1985 ◽  
Vol 63 (6) ◽  
pp. 1271-1279 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Coho Salmon ◽  
Search Pattern ◽  
Flock Size ◽  
Searching Behaviour ◽  
Natural Stream ◽  
Mergus Merganser ◽  
Visit Duration ◽  
The Common ◽  
Common Merganser ◽  
Time Required

Factors influencing the choice of foraging location by the common merganser (Mergus merganser) were investigated by baiting three adjacent, enclosed sections of a natural stream with various densities of juvenile coho salmon (Oncorhynchus kisutch). Merganser abundance within 1 km of the enclosure site increased from < 3 to > 10 birds within 1 week of stocking the enclosures with 43-g coho smolt. Although abundance declined gradually thereafter (as expected from seasonal trends on other nearby streams), the frequency of visits to the enclosure site continued to increase for 22 d until the enclosures were stocked predominately with smaller (2-g) coho fry. Visits were more frequent when other mergansers were already present at the site. Also, the proportion of mergansers flying overhead that landed near a decoy "flock" increased with decoy flock size. In general, the duration of visits to the site was not affected by the number of birds present. Visit duration increased exponentially with increasing fish density and decreased with searching time required until first capture. Mergansers spent more time searching in the most profitable enclosure. Allocation of searching time among the enclosures was not consistent with a "giving up time" decision rule; however, mergansers appeared to follow an area-restricted search pattern both within and among the enclosures.

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. II: Predation of Stream-Resident Juvenile Salmon by Merganser Broods

1987 ◽  
Vol 44 (5) ◽  
pp. 950-959 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Body Weight ◽  
Census Data ◽  
Coho Salmon ◽  
Pacific Salmon ◽  
Vancouver Island ◽  
Juvenile Salmonids ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of stream-resident juvenile salmonids by broods of the common merganser (Mergus merganser) was investigated in three streams on eastern Vancouver Island from 1980 to 1982. Daily fish consumption by merganser ducklings was estimated to range from 80% of body weight for ducklings at 10 d of age to 40% of body weight for those at 40 d of age. Merganser ducklings were never observed to eat juvenile salmonids on tidal waters, but did eat them on the freshwater reaches of streams studied. Typically, broods inhabited only the freshwater reaches of their natal stream while young, but spent progressively more time foraging on tidal waters as they grew older. The biomass of broods (and hence potential consumption) on fresh water was estimated by reconstructing the history of individual broods from census data. These results suggest that merganser broods consumed on the order of 82 000–131 000 coho salmon (Oncorhynchus kisutch) fry in the Big Qualicum River between June 10 and August 25. This is equivalent to 24–65% of the observed wild smolt production from this system, assuming that these fry would otherwise have survived as well as uneaten fry.

Notes on the Feeding Behavior of the Common Merganser (Mergus merganser)

The Condor ◽  
1974 ◽  
Vol 76 (4) ◽  
pp. 472
Author(s):  
Bertin W. Anderson ◽  
Michael G. Reeder ◽  
Richard L. Timken
Keyword(s):  
Feeding Behavior ◽  
Mergus Merganser ◽  
The Common ◽  
Common Merganser

Predation of Juvenile Pacific Salmon by the Common Merganser (Mergus merganser) on Eastern Vancouver Island. I: Predation during the Seaward Migration

1987 ◽  
Vol 44 (5) ◽  
pp. 941-949 ◽  
Author(s):  
C. C. Wood
Keyword(s):  
Mortality Rate ◽  
Prey Size ◽  
Pacific Salmon ◽  
Size Selection ◽  
Juvenile Salmonids ◽  
Seaward Migration ◽  
Mergus Merganser ◽  
The Common ◽  
Tidal Waters ◽  
Common Merganser

Predation of juvenile salmonids by the common merganser (Mergus merganser) was investigated during the period of seaward migration in two streams where fish populations are enhanced by spawning channels and hatcheries. Observation of foraging behaviour and crop-gullet contents indicated that, during this period, mergansers foraging on freshwater reaches of the streams ate juvenile salmonids almost exclusively whereas those foraging on tidal waters rarely ate salmonids. Maximum rates of salmonid mortality were estimated by assessing merganser abundance and the pattern of foraging activity on fresh versus tidal waters. Maximum mortality rate declined as fish abundance increased (i.e. mortality was depensatory) in all cases where the effects of prey size-selection could be ignored owing to an overwhelming abundance of one prey species. Bounds on maximum mortality rate by species for the entire migration period were computed under different hypotheses about the prey size-selection habits of mergansers; maximum mortality rate did not exceed 10% for any salmonid species over the entire seaward migration.

scholarly journals The life history of Hepatozoon leptodactyli (Lesage, 1908) Pessoa, 1970: a parasite of the common laboratory animal: the frog of the genus Leptodactylus

1973 ◽  
Vol 71 (1-2) ◽  
pp. 1-8 ◽  
Author(s):  
Sylvio Celso Goncalves da Costa ◽  
Samuel B. Pessoa ◽  
Neize de Moura Pereira ◽  
Tania Colombo
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Life History ◽  
Laboratory Animal ◽  
Peripheral Circulation ◽  
Experimental Conditions ◽  
History Of ◽  
The Central Nervous System ◽  
The Common ◽  
Common Laboratory

The main object of the present paper is to furnish a brief account to the knowledgement of Protozoa parasitic in common Brazilian frog of the genus Leptodactylus for general students in Zoology and for investigators that use this frog as a laboratory animal. Hepatozoon leptodactyli (Haemogregarina leptodactyli) was found in two species of frogs - Leptodactylus ocellatus and L. pentadactylus - in which develop schizogony whereas sporogony occurs in the leech Haementeria lutzi as was obtainded in experimental conditions. Intracellular forms have been found in peripheral circulation, chiefly in erythrocytes, but we have found them in leukocytes too. Tissue stages were found in frog, liver, lungs, spleen, gut, brain and heart. The occurence of hemogregarine in the Central Nervous System was recorded by Costa & al,(13) and Ball (2). Some cytochemical methods were employed in attempt to differentiate gametocytes from trophozoites in the peripheral blood and to characterize the cystic membrane as well. The speorogonic cycle was developed in only one specie of leech. A brief description of the parasite is given.

scholarly journals Influence of saprophages (Isopoda, Diplopoda) on leaf litter decomposition under different levels of humidification and chemical loading

2020 ◽  
Vol 28 (4) ◽  
pp. 384-389
Author(s):  
A. P. Pokhylenko ◽  
O. O. Didur ◽  
Y. L. Kulbachko ◽  
L. P. Bandura ◽  
S. A. Chernykh
Keyword(s):  
Leaf Litter ◽  
Litter Decomposition ◽  
Zinc Content ◽  
Leaf Litter Decomposition ◽  
Absolute Difference ◽  
Average Weight ◽  
Chemical Stress ◽  
Experimental Conditions ◽  
The Common ◽  
Different Levels

The paper presents a study about the influence of two saprophage groups (Isopoda, Diplopoda) on leaf litter decomposition under different levels of humidification and chemical stress. Because of their worldwide distribution, we focused on the common pillbug Armadillidium vulgare (Latreille, 1804) (Isopoda, Armadillidiidae), and the common millipede species Rossiulus kessleri (Lohmander, 1927) (Julida, Julidae). The function of environment creation by the given saprophages, as destructors of dead plant matter, supporting such ecosystem services as soil fertility improvement and nutrients’ turnover, is highlighted. To conduct the experiment, the animals were collected manually and using pitfall trapping. In order to bring the experimental conditions closer to the natural, the individuals were not sexed. The maximum consumption of leaf litter by woodlice was recorded in the conditions with adequate moisture (0.5 mL of distilled water per box) and amounted to 2.52 mg/10 individuals per day, which exceeds its consumption with low and increased moisture, respectively, by 1.82 and 1.24 times. As for the effect of interaction, the consumption of maple litter with optimal moisture (4.77 mg/10 individuals per day) was the greatest. The largest absolute difference between broad-leaved tree species in the average weight of leaf litter consumed by woodlice was between maple leaf litter and oak leaf litter, the minimum – between robinia leaf litter and oak leaf litter. According to the results of the obtained data (Diplopoda), it can be stated that there is a statistically significant effect of chemical stress and discrepancy of the average zinc content in the object of study (in Diplopoda and their faecal pellets). We found that the diet provided did not affect the distribution of zinc in Diplopoda under conditions of chemical stress. According to the results of pairwise comparisons, we determined that the zinc content in the Diplopoda clearly differs for control and almost every concentration of zinc sulfate solution – 0.03 and 0.15 g/L, the samples of which do not form a homogeneous group. The species composition, abundance and distribution in space of soil invertebrates are informative indicators which reflect the ecological state of soils, intensity in development of soil horizons as well as intensity of processes occurring in them.

Contralateral coordination and retargeting of limb movements during scratching in the locust

1998 ◽  
Vol 201 (13) ◽  
pp. 2021-2032 ◽  
Author(s):  
T Matheson
Keyword(s):  
Nerve Cord ◽  
Tactile Stimulation ◽  
Schistocerca Gregaria ◽  
Limb Movements ◽  
Single Cycle ◽  
Experimental Conditions ◽  
The Subject ◽  
The Common ◽  
Peripheral Sensory ◽  
Stimulus Site

Locusts, Schistocerca gregaria, in common with many limbed vertebrates, can make directed scratching movements in response to tactile stimulation. For instance, stimulation of different sites on a wing elicits different movements that are accurately targeted so that the hindleg tarsus passes across the stimulus site. I have analysed these limb movements to define the ability of a locust to target stimulus sites correctly under a range of experimental conditions. In particular, I describe aspects of the behaviour that reveal possible neuronal pathways underlying the responses. These neuronal pathways will be the subject of further physiological analyses. Limb targeting during scratching is continuously graded in form; different patterns of movement are not separated by sharp transitions. The computation of limb trajectory takes into account the starting posture of the hindleg, so that different trajectories can be used to reach a common stimulus site from different starting postures. Moreover, the trajectories of the two hindlegs moving simultaneously from different starting postures in response to a single stimulus can be different, so that their tarsi converge onto the common stimulus site. Different trajectories can be used to reach a common stimulus site from the same start posture. Targeting information from a forewing is passed not only down the nerve cord to the ipsilateral hindleg but also across the nerve cord, so that the contralateral hindleg can also make directed movements. This contralateral transmission does not rely on peripheral sensory feedback. When the stimulus site moves during a rhythmical scratch, the targeting of subsequent cycles reflects this change. Both ipsilateral and contralateral hindlegs can retarget their movements. The trajectory of a single cycle of scratching directed towards a particular stimulus site can be modified after it has begun, so that the tarsus is redirected towards a new stimulus site.

scholarly journals The Influence of Food Density, Flock Size, and Disturbance on the Functional Response of Bewick’s Swans (Cygnus columbianus bewickii) in Wintering Habitats

Animals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 946 ◽  
Author(s):  
Chao Yu ◽  
Lizhi Zhou ◽  
Nazia Mahtab ◽  
Shaojun Fan ◽  
Yunwei Song
Keyword(s):  
Feeding Behavior ◽  
Functional Response ◽  
Habitat Management ◽  
Feeding Rate ◽  
Handling Time ◽  
Foraging Strategies ◽  
Food Density ◽  
Flock Size ◽  
Functional Responses ◽  
Cygnus Columbianus

Perceiving how animals adjust their feeding rate under a variety of environmental conditions and understanding the tradeoffs in their foraging strategies are necessary for conservation. The Holling functional response, which describes the relationship of feeding rate and food density to searching rate and handling time, has been applied to a range of waterbirds, especially with regard to Type II functional responses that describe an increasing feeding rate with food density but at a decelerating rate as the curve approaches the asymptote. However, feeding behavior components (feeding rate, searching rate, and handling time) are influenced by factors besides prey density, such as vigilance and flock size. In this study, we aim to elucidate how Bewick’s swans (Cygnus columbianus bewickii) adopt flexible foraging strategies and vary their feeding behavior components in response to disturbance, flock size, and food density. We collected focal sampling data on the foraging behavior of swans that foraged rice grains, foxnut seeds, and tubers in paddy field, foxnut pond, and lake habitats, respectively, in Shengjin and Huangpi lakes during winter from 2016 to 2018. The observed feeding rate was not correlated with food density and displayed a positive relationship with searching rate but negative relationships with handling time, flock size, overall vigilance time, and disturbance time. Handling time was negatively correlated with food density and flock size, yet it increased with disturbance, overall vigilance time, and normal vigilance time. Searching rate was negatively correlated with food density, flock size, and disturbance time. Feeding rate was affected by the combined effects of handling time and searching rate, as well as food density and searching rate. The shape of the observed functional response could not be fitted to Holling’s disc equation. However, the disc equation of the predicted feeding rate of wintering swans was found to be driven by food density. This provides insight into how wintering waterbirds adopt appropriate foraging strategies in response to complicated environmental factors, which has implications for wildlife conservation and habitat management.

scholarly journals A laboratory-calibrated model of coho salmon growth with utility for ecological analyses

2018 ◽  
Vol 75 (5) ◽  
pp. 682-690 ◽  
Author(s):  
Christopher V. Manhard ◽  
Nicholas A. Som ◽  
Russell W. Perry ◽  
John M. Plumb
Keyword(s):  
Food Availability ◽  
Coho Salmon ◽  
Meta Analysis ◽  
Growth Patterns ◽  
Growth Data ◽  
Experimental Conditions ◽  
Wide Range ◽  
Klamath Basin ◽  
Constructed Ponds ◽  
Dependent Growth

We conducted a meta-analysis of laboratory- and hatchery-based growth data to estimate broadly applicable parameters of mass- and temperature-dependent growth of juvenile coho salmon (Oncorhynchus kisutch). Following studies of other salmonid species, we incorporated the Ratkowsky growth model into an allometric model and fit this model to growth observations from eight studies spanning ten different populations. To account for changes in growth patterns with food availability, we reparameterized the Ratkowsky model to scale several of its parameters relative to ration. The resulting model was robust across a wide range of ration allocations and experimental conditions, accounting for 99% of the variation in final body mass. We fit this model to growth data from coho salmon inhabiting tributaries and constructed ponds in the Klamath Basin by estimating habitat-specific indices of food availability. The model produced evidence that constructed ponds provided higher food availability than natural tributaries. Because of their simplicity (only mass and temperature are required as inputs) and robustness, ration-varying Ratkowsky models have utility as an ecological tool for capturing growth in freshwater fish populations.

Leaf green-white variegation is advantageous under N deprivation in Pelargonium×hortorum

2015 ◽  
Vol 42 (6) ◽  
pp. 543 ◽  
Author(s):  
Cyril Abadie ◽  
Marlène Lamothe ◽  
Caroline Mauve ◽  
Françoise Gilard ◽  
Guillaume Tcherkez
Keyword(s):  
Surface Area ◽  
Photosynthetic Activity ◽  
Leaf Biomass ◽  
Common Occurrence ◽  
Plant Leaves ◽  
Experimental Conditions ◽  
Metabolic Analysis ◽  
Leaf Variegation ◽  
Green Areas ◽  
The Common

Variegation (patchy surface area with different colours) is a common trait of plant leaves. In green-white variegated leaves, two tissues with contrasted primary carbon metabolisms (autotrophic in green and heterotrophic in white tissues) are juxtaposed. It is generally believed that variegation is detrimental to growth due to the lower photosynthetic surface area. However, the common occurrence of leaf variegation in nature raises the question of a possible advantage under certain circumstances. Here, we examined growth and metabolism of variegated Pelargonium × hortorum L.H.Bailey using metabolomics techniques under N deprivation. Our results showed that variegated plants tolerate N deficiency much better, i.e. do not stop leaf biomass production after 9 weeks of N deprivation, even though the growth of green plants is eventually arrested and leaf senescence is triggered. Metabolic analysis indicates that white areas are naturally enriched in arginine, which decreases a lot upon N deprivation, probably to feed green areas. This process may compensate for the lower proteolysis enhancement in green areas and thus contribute to maintaining photosynthetic activity. We conclude that under our experimental conditions, leaf variegation was advantageous under prolonged N deprivation.

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