Feeding behaviour and prey choice in Macroperipatus torquatus (Onychophora)

1987 ◽  
Vol 230 (1261) ◽  
pp. 483-506 ◽  
Keyword(s):  
Size Distribution ◽  
Prey Item ◽  
Rain Forest ◽  
Feeding Behaviour ◽  
Metabolic Cost ◽  
Handling Time ◽  
Reserve Capacity ◽  
Prey Choice ◽  
The Cost ◽  
Glue Secretion

Macroperipatus torquatus feeds nocturnally on crickets and a few other invertebrates on the floor of the Trinidadian rain forest. Prey are inspected by gentle application of the antennae and, if suitable, are captured by entangling them in proteinaceous glue squirted from the oral papillae. Entangled prey are bitten through an arthrodial membrane and immobilized by injected saliva, which may also partly digest the flesh. Ingestion of the flesh takes several hours, comprising some 90% of total handling time, and normally only one prey item is eaten per night. The deplected carcass is discarded. Fully charged glue reserves amount to about 11% of body mass and after exhaustion are replenished in about 24 days. The quantity of glue used in an attack increases up to about 80% of reserve capacity for larger prey. Glue adhering to the prey is ingested, but some attached to the substratum is always lost. Squirting glue may therefore be costly for two reasons. Firstly, depleted glue reserves render peripatus less capable of attacking further prey or of defending themselves; secondly, unrecovered glue together with the metabolic cost of glue secretion will detract from the energetic yield of the prey. Small prey will scarcely repay the cost of glue used whereas larger ones are more likely to escape; consequently the energetically optimal prey are relatively large, but somewhat smaller than those potentially available. Accordingly, adult peripatus preferred larger prey and grew better when fed on them in the laboratory, whereas juveniles grew better on smaller prey. The size distribution of prey in the forest was heavily biased towards smaller types and it seemed likely that the productivity of large peripatus would be limited by the availability of profitable prey.

scholarly journals Energy cost and muscular activity required for propulsion during walking

2003 ◽  
Vol 94 (5) ◽  
pp. 1766-1772 ◽  
Author(s):  
Jinger S. Gottschall ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Muscular Activity ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Horizontal Force ◽  
Normal Walking ◽  
The Mean ◽  
The Cost ◽  
Muscle Actions

We reasoned that with an optimal aiding horizontal force, the reduction in metabolic rate would reflect the cost of generating propulsive forces during normal walking. Furthermore, the reductions in ankle extensor electromyographic (EMG) activity would indicate the propulsive muscle actions. We applied horizontal forces at the waist, ranging from 15% body weight aiding to 15% body weight impeding, while subjects walked at 1.25 m/s. With an aiding horizontal force of 10% body weight, 1) the net metabolic cost of walking decreased to a minimum of 53% of normal walking, 2) the mean EMG of the medial gastrocnemius (MG) during the propulsive phase decreased to 59% of the normal walking magnitude, and yet 3) the mean EMG of the soleus (Sol) did not decrease significantly. Our data indicate that generating horizontal propulsive forces constitutes nearly half of the metabolic cost of normal walking. Additionally, it appears that the MG plays an important role in forward propulsion, whereas the Sol does not.

scholarly journals Metabolic cost of generating horizontal forces during human running

1999 ◽  
Vol 86 (5) ◽  
pp. 1657-1662 ◽  
Author(s):  
Young-Hui Chang ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Oxygen Consumption ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Vertical Force ◽  
Order Of Magnitude ◽  
Reaction Forces ◽  
The Cost ◽  
Support Body Weight ◽  
Human Running

Previous studies have suggested that generating vertical force on the ground to support body weight (BWt) is the major determinant of the metabolic cost of running. Because horizontal forces exerted on the ground are often an order of magnitude smaller than vertical forces, some have reasoned that they have negligible cost. Using applied horizontal forces (AHF; negative is impeding, positive is aiding) equal to −6, −3, 0, +3, +6, +9, +12, and +15% of BWt, we estimated the cost of generating horizontal forces while subjects were running at 3.3 m/s. We measured rates of oxygen consumption (V˙o 2) for eight subjects. We then used a force-measuring treadmill to measure ground reaction forces from another eight subjects. With an AHF of −6% BWt,V˙o 2 increased 30% compared with normal running, presumably because of the extra work involved. With an AHF of +15% BWt, the subjects exerted ∼70% less propulsive impulse and exhibited a 33% reduction inV˙o 2. Our data suggest that generating horizontal propulsive forces constitutes more than one-third of the total metabolic cost of normal running.

scholarly journals Disentangling the energetic costs of step time asymmetry and step length asymmetry in human walking

2021 ◽  
Author(s):  
Jan Stenum ◽  
Julia T. Choi
Keyword(s):  
Energy Cost ◽  
Metabolic Cost ◽  
Step Length ◽  
Human Walking ◽  
Metabolic Power ◽  
Healthy Human ◽  
Time Asymmetry ◽  
Double Support ◽  
Post Stroke ◽  
The Cost

The metabolic cost of walking in healthy individuals increases with spatiotemporal gait asymmetries. Pathological gait, such as post-stroke, often has asymmetry in step lengths and step times which may contribute to an increased energy cost. But paradoxically, enforcing step length symmetry does not reduce metabolic cost of post-stroke walking. The isolated and interacting costs of asymmetry in step times and step lengths remain unclear, because previous studies did not simultaneously enforce spatial and temporal gait asymmetries. Here, we delineate isolated costs of asymmetry in step times and step lengths in healthy human walking. We first show that the cost of step length asymmetry is predicted by the cost of taking two non-preferred step lengths (one short and one long), but that step time asymmetry adds an extra cost beyond the cost of non-preferred step times. The metabolic power of step time asymmetry is about 2.5 times greater than the cost of step length asymmetry. Furthermore, the costs are not additive when walking with asymmetric step times and step lengths: metabolic power of concurrent asymmetry in step lengths and step times is driven by the cost of step time asymmetry alone. The metabolic power of asymmetry is explained by positive mechanical power produced during single support phases to compensate for a net loss of center of mass power incurred during double support phases. These data may explain why metabolic cost remains invariant to step length asymmetry in post-stroke walking and suggests how effects of asymmetry on energy cost can be attenuated.

Foraging and avoiding predators

2020 ◽  
pp. 120-139
Author(s):  
Graham Scott
Keyword(s):  
Optimal Foraging ◽  
Feeding Behaviour ◽  
Predator Avoidance ◽  
Prey Choice ◽  
Urban Living ◽  
Cooperative Hunting ◽  
Cooperative Foraging ◽  
The Impact

The chapter considers the generalist and specialist diets of birds, and the behaviours and adaptations used by birds to find food. Special attention is given to the threat to birds from plastics pollution and the impact of plastic ingestion. Cooperative foraging and cooperative hunting are discussed as are the behaviours adopted by birds that do not cooperate or share. Feeding behaviour is considered in light of the theory of optimal foraging, particularly in relation to prey choice and to the balancing of risk. The impact of urban living upon the diets and foraging behaviours of birds is discussed. A broad range of predator avoidance behaviours are described and evaluated.

scholarly journals Metabolic cost of feeding in Atlantic Cod (Gadus morhua) larvae using microcalorimetry

2006 ◽  
Vol 63 (2) ◽  
pp. 335-339 ◽  
Author(s):  
Artie McCollum ◽  
Jessica Geubtner ◽  
Ione Hunt von Herbing
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Metabolic Cost ◽  
Specific Dynamic Action ◽  
Total Heat ◽  
Heat Output ◽  
Larval Life ◽  
First Feeding ◽  
The Cost ◽  
Aerobic And Anaerobic

Abstract A microcalorimeter that measures total heat output (μW) was used to determine total metabolic rate (aerobic and anaerobic) and the cost of feeding (specific dynamic action, SDA) in larval Atlantic cod (Gadus morhua) from hatching to 4 weeks post-hatch at 10°C. Total heat output increased throughout development from 2.14 μW at first-feeding to 23.72 μW at 4 weeks post-hatch. SDA was determined by comparing the total heat output among unfed larvae and fed larvae simultaneously. Total heat output increased in the first 2 h after feeding with rotifers (Brachionus sp.) and Artemia, remained high for up to 10 h, was significantly higher in fed larvae than in unfed larvae, and ranged from 16.56 μW at first-feeding to 47.84 μW at 4 weeks post-hatch. The differences in total heat output between unfed and fed larvae were 14.42 μW and 24.12 μW, representing an increase in metabolic cost of feeding by a factor of 1.67 over the first 4 weeks of larval life. That the metabolic cost of feeding increased with development and remained elevated suggests that cod larvae allocate a large part of their energy budget to growth in order to meet the demands of their fast growth rates.

scholarly journals Brain size is correlated with endangerment status in mammals

2016 ◽  
Vol 283 (1825) ◽  
pp. 20152772 ◽  
Author(s):  
Eric S. Abelson
Keyword(s):  
Brain Size ◽  
Extinction Risk ◽  
Small Body ◽  
Cost Benefit ◽  
Metabolic Cost ◽  
Trade Offs ◽  
Extant Species ◽  
Body Sizes ◽  
The Cost ◽  
The Relationship

Increases in relative encephalization (RE), brain size after controlling for body size, comes at a great metabolic cost and is correlated with a host of cognitive traits, from the ability to count objects to higher rates of innovation. Despite many studies examining the implications and trade-offs accompanying increased RE, the relationship between mammalian extinction risk and RE is unknown. I examine whether mammals with larger levels of RE are more or less likely to be at risk of endangerment than less-encephalized species. I find that extant species with large levels of encephalization are at greater risk of endangerment, with this effect being strongest in species with small body sizes. These results suggest that RE could be a valuable asset in estimating extinction vulnerability. Additionally, these findings suggest that the cost–benefit trade-off of RE is different in large-bodied species when compared with small-bodied species.

scholarly journals The rising cost of warming waters: effects of temperature on the cost of swimming in fishes

2011 ◽  
Vol 8 (2) ◽  
pp. 266-269 ◽  
Author(s):  
Andrew M. Hein ◽  
Katrina J. Keirsted
Keyword(s):  
Water Temperature ◽  
Fish Species ◽  
Global Climate ◽  
Swimming Performance ◽  
Metabolic Cost ◽  
Quantitative Model ◽  
The Body ◽  
Energetic Cost ◽  
Cost Of Transport ◽  
The Cost

Understanding the effects of water temperature on the swimming performance of fishes is central in understanding how fish species will respond to global climate change. Metabolic cost of transport (COT)—a measure of the energy required to swim a given distance—is a key performance parameter linked to many aspects of fish life history. We develop a quantitative model to predict the effect of water temperature on COT. The model facilitates comparisons among species that differ in body size by incorporating the body mass-dependence of COT. Data from 22 fish species support the temperature and mass dependencies of COT predicted by our model, and demonstrate that modest differences in water temperature can result in substantial differences in the energetic cost of swimming.

scholarly journals Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments

2003 ◽  
Vol 95 (1) ◽  
pp. 172-183 ◽  
Author(s):  
Timothy M. Griffin ◽  
Thomas J. Roberts ◽  
Rodger Kram
Keyword(s):  
Metabolic Rate ◽  
Stance Phase ◽  
Metabolic Cost ◽  
Direct Proportion ◽  
Muscular Force ◽  
Active Muscle ◽  
Cost Coefficient ◽  
Load Carrying ◽  
Leg Muscle ◽  
The Cost

We sought to understand how leg muscle function determines the metabolic cost of walking. We first indirectly assessed the metabolic cost of swinging the legs and then examined the cost of generating muscular force during the stance phase. Four men and four women walked at 0.5, 1.0, 1.5, and 2.0 m/s carrying loads equal to 0, 10, 20, and 30% body mass positioned symmetrically about the waist. The net metabolic rate increased in nearly direct proportion to the external mechanical power during moderate-speed (0.5–1.5 m/s) load carrying, suggesting that the cost of swinging the legs is relatively small. The active muscle volume required to generate force on the ground and the rate of generating this force accounted for >85% of the increase in net metabolic rate across moderate speeds and most loading conditions. Although these factors explained less of the increase in metabolic rate between 1.5 and 2.0 m/s (∼50%), the cost of generating force per unit volume of active muscle [i.e., the cost coefficient ( k)] was similar across all conditions [ k = 0.11 ± 0.03 (SD) J/cm3]. These data indicate that, regardless of the work muscles do, the metabolic cost of walking can be largely explained by the cost of generating muscular force during the stance phase.

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