scholarly journals Context Matters: Hawaiian Monk Seals Switch Between Feeding Strategies Depending on Ecological Context

2020 ◽  
Vol 60 (2) ◽  
pp. 425-439 ◽  
Author(s):  
Sarah S Kienle ◽  
Jezebel Powers ◽  
Traci Kendall ◽  
Beau Richter ◽  
Leann Castle ◽  
...  
Keyword(s):  
Prey Size ◽  
Head Length ◽  
Feeding Strategies ◽  
Large Prey ◽  
Ecological Context ◽  
Behavioral Repertoire ◽  
Suction Feeding ◽  
Hawaiian Monk Seal ◽  
Trade Offs ◽  
Monk Seals

Synopsis The ability to expand the behavioral repertoire past seemingly rigid morphological features enables animals to succeed in a variety of ecological contexts. The integration of morphology, performance, and behavior produces diverse animal feeding strategies. These different strategies reflect trade-offs between specialization, prey choice, and energetic expenditure, which have important consequences for understanding individual and population-level flexibility in response to environmental change. Here we examined the feeding strategies used by the Hawaiian monk seal (Neomonachus schauinslandi), an endangered marine predator. We tested how Hawaiian monk seal feeding strategies change in response to ecological context, specifically prey size and prey location at different depths. Seven captive Hawaiian monk seals were fed five prey types across a continuum of sizes, and prey were presented at three depths to represent surface, pelagic, and benthic feeding. Hawaiian monk seals used suction feeding and biting strategies, and these strategies were associated with significant differences in behavior and kinematic performance. Hawaiian monk seals used suction feeding most frequently when targeting small to medium prey (0–79% of the seal’s head length) but switched to biting when consuming large prey (>80% of the seal’s head length). These results demonstrate that prey size drives the transition between suction feeding and biting strategies. Seals also switched strategies based on prey position in the water column, primarily using suction feeding when prey were benthic and pelagic, and biting when prey were at the water’s surface. Overall, suction feeding was three to five times faster than biting, required a smaller gape, and used fewer jaw movements, allowing seals to quickly consume numerous small to medium sized prey. In contrast, biting was slower but resulted in the ability to target larger, potentially more energy rich prey. Our results show that Hawaiian monk seals exhibit flexibility in their use of different feeding strategies, which likely facilitates increased foraging success when feeding in spatially and temporally dynamic marine environments.

scholarly journals Fish face a trade-off between ‘eating big’ for growth efficiency and ‘eating small’ to retain aerobic capacity

2017 ◽  
Vol 13 (9) ◽  
pp. 20170298 ◽  
Author(s):  
Tommy Norin ◽  
Timothy D. Clark
Keyword(s):  
Prey Size ◽  
Growth Efficiency ◽  
Specific Dynamic Action ◽  
Meal Size ◽  
Large Prey ◽  
Lates Calcarifer ◽  
Trade Off ◽  
Trade Offs ◽  
Size Growth ◽  
Growth And Reproduction

Feeding provides the necessary energy to fuel all fitness-related processes including activity, growth and reproduction. Nevertheless, prey consumption and digestive processes can have physical and physiological trade-offs with other critical functions, many of which are not clearly understood. Using an ambush predator, barramundi ( Lates calcarifer ), fed meals ranging 0.6–3.4% of body mass, we examined interrelations between meal size, growth efficiency and surplus aerobic metabolic capacity (aerobic scope, AS). Large meals required a greater absolute investment of energy to process (a larger so-called specific dynamic action, SDA), but the percentage of digestible meal energy required in the SDA response (SDA coefficient) decreased with increasing meal size. Combined with the findings that growth rate and growth efficiency also increased with food intake, our results demonstrate that it is energetically advantageous for fish to select large prey. However, following a large meal, SDA processes occupied up to 77% of the available AS, indicating that other oxygen-demanding activities like swimming may be compromised while large meals are processed. This trade-off between meal size and AS suggests that fishes like barramundi would benefit from regulating prey size based on imminent requirements and threats.

scholarly journals Prey Size Decline as a Unifying Ecological Selecting Agent in Pleistocene Human Evolution

Quaternary ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 7
Author(s):  
Miki Ben-Dor ◽  
Ran Barkai
Keyword(s):  
Prey Size ◽  
Prey Availability ◽  
Stone Tool ◽  
Foraging Efficiency ◽  
Energetic Cost ◽  
Large Prey ◽  
Biomass Density ◽  
Cultural Changes ◽  
Progressive Decline ◽  
Brain Expansion

We hypothesize that megafauna extinctions throughout the Pleistocene, that led to a progressive decline in large prey availability, were a primary selecting agent in key evolutionary and cultural changes in human prehistory. The Pleistocene human past is characterized by a series of transformations that include the evolution of new physiological traits and the adoption, assimilation, and replacement of cultural and behavioral patterns. Some changes, such as brain expansion, use of fire, developments in stone-tool technologies, or the scale of resource intensification, were uncharacteristically progressive. We previously hypothesized that humans specialized in acquiring large prey because of their higher foraging efficiency, high biomass density, higher fat content, and the use of less complex tools for their acquisition. Here, we argue that the need to mitigate the additional energetic cost of acquiring progressively smaller prey may have been an ecological selecting agent in fundamental adaptive modes demonstrated in the Paleolithic archaeological record. We describe several potential associations between prey size decline and specific evolutionary and cultural changes that might have been driven by the need to adapt to increased energetic demands while hunting and processing smaller and smaller game.

CHANGES IN PREY SIZE PREFERENCES DURING SUCCESSIVE STAGES OF FORAGING IN THE MEDITERRANEAN WATER SHREW NEOMYS ANOMALUS

Behaviour ◽  
1999 ◽  
Vol 136 (3) ◽  
pp. 345-365 ◽  
Author(s):  
Leszek Rychlik
Keyword(s):  
Predation Risk ◽  
Prey Size ◽  
Large Prey ◽  
Habitat Conditions ◽  
Food Hoarding ◽  
Food Quantity ◽  
Competition For Food ◽  
Mediterranean Water ◽  
Selection Of ◽  
Food Portions

AbstractPrey size preferences in successive stages of foraging of Mediterranean water shrews Neomys anomalus Cabrera, 1907 were investigated in a terrarium. Seven shrews were tested individually in five experimental variants (simulating different habitat conditions) totally for 504 hours. Water shrews displayed partial preferences for prey size but they were selective from the very beginning of the foraging period. When searching for food, N. anomalus preferred big food portions, abandoning significantly more small than big portions. This tendency was especially strong when few food portions were available on land and there were no natural structures in the terrarium. Selection of big portions was intensified probably by their easier detection. Shrews hoarded proportionally more big than small portions in the scattered hiding-places. This tendency was intensified by the presence of natural structures, dispersion of food and reduction of food quantity placed on land. Later, however, more small than big food portions were eaten, apparently because small portions were easier to manipulate. Scattered food hoarding and preference of large prey are proposed to be the strategy of N. anomalus to maximise the energy net gain and minimise the predation risk and competition for food.

scholarly journals Divergence and ontogenetic coupling of larval behaviour and thermal reaction norms in three closely related butterflies

2010 ◽  
Vol 278 (1703) ◽  
pp. 313-320 ◽  
Author(s):  
David Berger ◽  
Magne Friberg ◽  
Karl Gotthard
Keyword(s):  
Developmental Plasticity ◽  
Larval Growth ◽  
State Dependence ◽  
Reaction Norm ◽  
Thermal Reaction ◽  
Reaction Norms ◽  
Feeding Strategies ◽  
Species Differentiation ◽  
Larval Behaviour ◽  
Trade Offs

Genetic trade-offs such as between generalist–specialist strategies can be masked by changes in compensatory processes involving energy allocation and acquisition which regulation depends on the state of the individual and its ecological surroundings. Failure to account for such state dependence may thus lead to misconceptions about the trade-off structure and nature of constraints governing reaction norm evolution. Using three closely related butterflies, we first show that foraging behaviours differ between species and change remarkably throughout ontogeny causing corresponding differences in the thermal niches experienced by the foraging larvae. We further predicted that thermal reaction norms for larval growth rate would show state-dependent variation throughout development as a result of selection for optimizing feeding strategies in the respective foraging niches of young and old larvae. We found substantial developmental plasticity in reaction norms that was species-specific and reflected the different ontogenetic niche shifts. Any conclusions regarding constraints on performance curves or species-differentiation in thermal physiology depend on when reaction norms were measured. This demonstrates that standardized estimates at single points in development, or in general, allow variation in only one ecological dimension, may sometimes provide incomplete information on reaction norm constraints.

The Inactivity of Animals: Influence of Stochasticity and Prey Size

Behaviour ◽  
1985 ◽  
Vol 92 (1-2) ◽  
pp. 1-8 ◽  
Author(s):  
Dorian Moss ◽  
William J. Sutherland
Keyword(s):  
Food Supply ◽  
Prey Capture ◽  
Prey Size ◽  
Large Prey ◽  
Small Prey ◽  
Sufficient Food

As a consequence of prey capture being partly dependent upon chance, each individual may usually spend much of the day inactive even if the population is limited by its food supply. This applies particularly to species that eat large prey and thus experience considerable day-to-day variation in intake which restricts them to relatively rich habitats. Food will be found easily on most days and little time need be spent hunting although, occasionally, they will be unlucky and, despite searching all day, risk starvation. Predators of small prey can survive in environments that provide barely sufficient food as they experience little variation in intake: but they need to search all day to sustain themselves.

scholarly journals Influence of prey size on reproduction among populations of Diamond-backed Watersnakes (Nerodia rhombifer)

2017 ◽  
Vol 95 (12) ◽  
pp. 929-935 ◽  
Author(s):  
J.D. Chamberlain ◽  
I.T. Clifton ◽  
M.E. Gifford
Keyword(s):  
Litter Size ◽  
Prey Size ◽  
Relative Proportion ◽  
Reproductive Allocation ◽  
Offspring Size ◽  
Absolute Amount ◽  
Large Prey ◽  
Additional Energy ◽  
Litter Mass ◽  
Clutch Mass

Mean prey size often varies across landscapes, resulting in predator populations having differing access to energetic resources. Shifts in resource quality are likely to cause differences in energy allocation of reproduction. Thus, additional energy intake may lead to (i) increased offspring size, (ii) increased numbers of offspring, (iii) increased relative proportion of energy allocated to reproduction, (iv) increased absolute amount of energy allocated to reproduction or (v) increased energy allocated to growth of some other nonreproductive function, or (vi) some combination of the above outcomes. To test this hypothesis, we evaluated the reproductive allocation patterns of four populations of Diamond-backed Watersnakes (Nerodia rhombifer (Hallowell, 1852)) that differ in their mean prey size. Snakes at large prey sites produced longer, heavier babies compared with snakes from small prey sites. Statistical interactions among sites confounded our ability to compare differences in litter size, litter mass, and relative clutch mass. We suggest that increased prey size results in populations shifting reproductive allocation to increase offspring size. Effects of prey size on litter size, litter mass, and relative clutch mass remain unclear.

Prey size and availability limits maximum size of rainbow trout in a large tailwater: insights from a drift-foraging bioenergetics model

2016 ◽  
Vol 73 (5) ◽  
pp. 759-772 ◽  
Author(s):  
Michael J. Dodrill ◽  
Charles B. Yackulic ◽  
Theodore A. Kennedy ◽  
John W. Hayes
Keyword(s):  
Rainbow Trout ◽  
Prey Size ◽  
Prey Availability ◽  
Maximum Size ◽  
Large Prey ◽  
Bioenergetics Model ◽  
Prey Biomass ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Temperature Regimes ◽  
Prey Resources

The cold and clear water conditions present below many large dams create ideal conditions for the development of economically important salmonid fisheries. Many of these tailwater fisheries have experienced declines in the abundance and condition of large trout species, yet the causes of these declines remain uncertain. Here, we develop, assess, and apply a drift-foraging bioenergetics model to identify the factors limiting rainbow trout (Oncorhynchus mykiss) growth in a large tailwater. We explored the relative importance of temperature, prey quantity, and prey size by constructing scenarios where these variables, both singly and in combination, were altered. Predicted growth matched empirical mass-at-age estimates, particularly for younger ages, demonstrating that the model accurately describes how current temperature and prey conditions interact to determine rainbow trout growth. Modeling scenarios that artificially inflated prey size and abundance demonstrate that rainbow trout growth is limited by the scarcity of large prey items and overall prey availability. For example, shifting 10% of the prey biomass to the 13 mm (large) length class, without increasing overall prey biomass, increased lifetime maximum mass of rainbow trout by 88%. Additionally, warmer temperatures resulted in lower predicted growth at current and lower levels of prey availability; however, growth was similar across all temperatures at higher levels of prey availability. Climate change will likely alter flow and temperature regimes in large rivers with corresponding changes to invertebrate prey resources used by fish. Broader application of drift-foraging bioenergetics models to build a mechanistic understanding of how changes to habitat conditions and prey resources affect growth of salmonids will benefit management of tailwater fisheries.

Changing Perspectives in Hawaiian Monk Seal Research Using Animal-Borne Imaging

2007 ◽  
Vol 41 (4) ◽  
pp. 30-34 ◽  
Author(s):  
Frank A. Parrish ◽  
Charles L. Littnan
Keyword(s):  
Population Recovery ◽  
Ecological Community ◽  
Foraging Habitat ◽  
Hawaiian Monk Seal ◽  
High Resolution Data ◽  
Management Plans ◽  
Substantial Progress ◽  
Monk Seals ◽  
Conservation And Management ◽  
Resolution Data

The use of animal-borne imaging devices on the endangered Hawaiian monk seal has greatly helped understand where and how they forage. Those devices provide high-resolution data on the behavior, foraging habitat, and prey of seals, and the ecological community where they live. They have indicated that some monk seals regularly forage in mesophotic (100-300 m) and subphotic (>300 m) habitats rather than just in shallow reef habitats. The collected imagery is also helping to guide the development of further research, conservation, and management plans. Use of animal-borne imaging has resulted in substantial progress in understanding the foraging landscape of monk seals. Any refinements in this technology will certainly inform further population recovery efforts.

Size-related shift in feeding strategy and prey-size selection in young grayling (Thymallus thymallus)

1996 ◽  
Vol 74 (9) ◽  
pp. 1597-1603 ◽  
Author(s):  
Philippe Sempeski ◽  
Philippe Gaudin
Keyword(s):  
Body Length ◽  
Feeding Behaviour ◽  
Prey Size ◽  
Feeding Strategy ◽  
River Channel ◽  
Large Prey ◽  
Thymallus Thymallus ◽  
Chironomid Larvae ◽  
Size Selection ◽  
The Mean

Observations of feeding behaviour and analysis of prey-size selection by young grayling revealed a shift in feeding strategy coinciding with a shift in habitat occurring between larval (observed in lateral habitats) and juvenile (observed in the river channel) stages of grayling. The mean number of foraging attempts per minute decreased four times between both stages, while in the same time the mean distance travelled during each foraging attempt decreased from 1.5 body lengths to 1 body length. Gape-limited postemergent larvae fed mainly on small chironomid larvae (<0.5 mm3) but larger larvae and pupae (0.5 – 1 mm3) were consumed with increasing size. The diet spectrum of juveniles >40 mm was characterized by the appearance of very large prey (> 10 mm3), such as simuliid and ephemeropteran larvae, but also by a new increase of the contribution of small chironomid larvae. Changes in the feeding strategy of young grayling are discussed in relation to internal (e.g., morphological limitations) and external (e.g., physical characteristics of habitat) constraints.

Are solitary progressive-provisioning wasps optimal foragers? A study with the digger wasp Bembix merceti (Hymenoptera: Crabronidae)

Behaviour ◽  
2011 ◽  
Vol 148 (2) ◽  
pp. 191-214 ◽  
Author(s):  
◽  
S.F. Gayubo ◽  
◽  
◽  
◽  
...  
Keyword(s):  
Positive Selection ◽  
Natural Enemies ◽  
Prey Size ◽  
Central Place ◽  
Large Prey ◽  
Lift Capacity ◽  
Surrounding Environment ◽  
The Mean ◽  
Selection Of ◽  
Central Place Forager

Abstract Bembix merceti, a central-place forager that captures dipterans to feed its larvae, could be considered a suboptimal forager. The females tend to optimize their provisioning flights, capturing prey in proportions different from those present in the surrounding environment. These wasps make a positive selection of families of flies with greater mean weights even though they are less abundant and, within the families whose weight is not too great, capture individuals whose weight is larger than the mean. Selection is based on prey size and not on the type (family) to which the prey belongs. A significant correlation between the weight of each female and the weight of the largest prey captured by the wasp was found, suggesting that the females capture prey in consonance with their lift capacity. Nevertheless, captures were not optimized maximally; the females maintained a margin with respect to the maximum prey weights that they could transport efficiently. This margin could be related to the low availability of large prey in the environment; to the type of progressive provisioning shown by the females of this species; and to other factors, such as the good manoeuvrability of their prey and the pressure from their natural enemies and congeners.

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