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1.
The effect of dominance hierarchy on the use of alternative foraging tactics: a phenotype-limited producing-scrounging game 总被引:2,自引:0,他引:2
Group living is thought to be advantageous for animals, though it also creates opportunities for exploitation. Using food
discovered by others can be described as a producer-scrounger, frequency-dependent game. In the game, scroungers (parasitic
individuals) do better than producers (food finders) when scroungers are rare in the group, but they do worse when scroungers
are common. When the individuals' payoffs do not depend on their phenotype (i.e. a symmetric game), this strong negative frequency
dependence leads to a mixed stable solution where both alternatives obtain equal payoffs. Here, we address the question of
how differences in social status in a dominance hierarchy influence the individuals' decision to play producer or scrounger
in small foraging groups. We model explicitly the food intake rate of each individual in a dominance-structured foraging group,
then calculate the Nash equilibrium for them. Our model predicts that only strong differences in competitive ability will
influence the use of producing or scrounging tactics in small foraging groups; dominants will mainly play scrounger and subordinates
will mostly use producer. Since the differences in competitive ability of different-ranking individuals likely depend on the
economic defendability of food, our model provides a step towards the integration of social foraging and resource defence
theories.
Received: 30 July 1997 / Accepted after revision: 15 November 1997 相似文献
2.
We use a combination of the marginal value theorem (MVT) of Charnov (1976), and a group foraging model featuring information
sharing to address patch residence in an environment where food occurs in discrete patches. We shall show that among equal
competitors the optimal patch time for the individual that finds the food patch is shorter than that for the non-finder among
equal competitors, T
E < T
N. This is the case if the patch-finder commences food harvesting in the patch earlier and manages to monopolise a fraction
of the prey items (finder's advantage) before the other individuals come to take their benefit. When individuals differ in
their food-searching abilities so that some of them (producers) contribute proportionally more to food-searching than others
(scroungers), and differ in ability to compete for the food found, a difference emerges between producer and scrounger individuals
in the optimal patch time. Within a patch we always have the finder's advantage (T
E < T
N) regardless of phenotype. Between patches a suite of optimal patch times for encountering individuals emerges depending on
the performance of producers and scroungers when changing from solitary feeding to feeding in a group. The optimal patch time
for individuals that are affected more severely by competition is shorter than that for individuals of the phenotype with
better competitive ability. When both phenotypes are affected similarly no difference in optimal patch times emerges.
Received: 13 February 1996 / Accepted after revision: 28 September 1996 相似文献
3.
When animals forage in groups, they can search for food themselves (producer tactic), or they can search for opportunities
to exploit the food discoveries of others (scrounger tactic). Both theoretical and empirical work have shown that group-level
use of these alternative tactics is influenced by environmental conditions including group size and food distribution, and
individual tactic use can be influenced by several measures of individual state, including body condition. Because body condition
has been shown to be heritable for various species, social foraging tactics may also be heritable. We looked for evidence
of heritability in social foraging tactic use in the zebra finch (Taeniopygia guttata) by testing whether: (1) natural variation in body condition correlates with tactic use, (2) there are family-related differences
in body condition, and (3) there are family-related differences in observed tactic use. Tactic use in the zebra finch was
significantly related to body condition; individuals with lower body condition scores had a significantly higher use of the
scrounger tactic as predicted from variance-sensitive producer–scrounger models. Body-condition scores differed significantly
between families, suggesting that this aspect of individual state may have a heritable component. Finally, we recorded significant
family-related differences in the use of producer and scrounger alternatives. These results are consistent with heritability
in observed tactic use resulting from an inheritance of individual state, in this case body condition, which itself influences
tactic use. Understanding how and why individuals differ in their use of alternative tactics is fundamental as it may provide
important insights into inter-individual variation in fitness. 相似文献
4.
Isabelle Coolen 《Behavioral ecology and sociobiology》2002,52(3):232-238
Social foragers can benefit from others' success by joining and sharing their food discoveries. In a producer-scrounger (PS) system, foragers can either search for food themselves (play producer) or search for joining opportunities (play scrounger), but not both at the same time. Empirical evidence is accumulating to show that the joining decision of ground-feeding birds like nutmeg mannikins (Lonchura punctulata) can be modeled by a PS game. However some predictions remain to be tested. For instance, foragers are predicted to increase their use of the scrounger tactic as group size increases. Also, one consequence of the incompatibility between producer and scrounger tactics is that the per capita searching efficiency should decrease as the use of scrounger increases. I tested these predictions in an indoor aviary using four flocks of nutmeg mannikins. I manipulated the stable equilibrium frequency (SEF) of the scrounger tactic by varying group size and the finder's share. As predicted by PS games, birds increased their use of scrounger as group size increased. Also, the per capita interval between patch discoveries increased and the per capita finding rate decreased as conditions called for a higher SEF of scrounger. I discuss why the decreased searching efficiency observed likely follows from the incompatibility between producer and scrounger tactics rather than from artifacts of the conditions used or from any form of interference. 相似文献
5.
Guy Beauchamp 《Behavioral ecology and sociobiology》2014,68(9):1473-1479
Animals that forage in groups can produce their own food patches or scrounge the food discoveries of their companions. Mean tactic payoffs are expected to be the same at equilibrium for phenotypically equal foragers. Scrounging is also typically viewed as a risk-averse foraging strategy that provides a more even food intake rate over time. The occurrence of scrounging and the payoffs from different foraging modes have rarely been investigated in the field. Over two field seasons, I examined patch sharing in semipalmated sandpipers (Calidris pusilla) foraging on minute food items at the surface of the substrate. Birds could find patches on their own, a producing event, or join the food patches discovered by others, a scrounging event. I found that the average search time per patch did not differ between producing and scrounging but that the average time spent exploiting a patch was reduced nearly by half when scrounging. As a result, the proportion of time spent exploiting a patch, a measure of foraging payoffs, was significantly lower when scrounging. The variance in payoffs was similar for producing and scrounging. When producing their own patches, individuals that scrounged spent the same proportion of time exploiting a patch as those that only produced. However, within the same individuals, the search time for a scrounged patch was longer than the search time for a produced patch. The results show unequal payoffs for producing and scrounging in this system and suggest that low success in finding patches elicited scrounging. 相似文献
6.
Kleptoparasitism is a tactic used to acquire food opportunistically and has been shown to provide several benefits, including
greater food intake rate and the acquisition of items not normally available during self-foraging. Host individuals may differ
in their ability to defend themselves against kleptoparasitic attacks and therefore identifying those host individuals that
are particularly vulnerable to attack could both provide energetic benefits and increase the efficiency of kleptoparasitism
as a foraging strategy. Here, we show that the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis) specifically targets juveniles when following groups of cooperatively breeding pied babblers (Turdoides bicolor). Drongos give alarm calls upon sighting a predator, thus providing extra predator vigilance to foraging pied babblers. However,
drongos also use alarm calls to steal food items. During kleptoparasitic attacks, drongos give false alarm calls and then
swoop down to steal food items dropped by alarmed babblers. Juvenile pied babblers are particularly vulnerable to attack because
they (a) spend a longer period handling prey items prior to consumption and (b) respond to alarm calls primarily by immediately
moving to cover, in contrast to adults who respond by looking up and visually scanning the surrounding area. Drongos attack
juvenile babblers significantly more often than adults, with attacks on juveniles more likely to result in the successful
procurement of a food item. This patterns of attack suggests that drongos are able to differentiate between individuals of
different age when targeting pied babblers, thus increasing the efficiency of kleptoparasitism as a foraging strategy. 相似文献
7.
Summary By measuring daily intake of food, we compared the cost of incubation for small and large clutches in adult Bengalese finches (Lonchura striata var. domestica). Natural clutches of captive finches were experimentally manipulated to produce two egg or six egg clutches. While incubating large clutches, parents ate significantly more food and took longer to hatch their first egg than did the same birds when provided with small clutches. This supports the hypothesis that the cost of incubation increases with clutch size. This cost should influence other energy allocation decisions in birds such as determination of clutch size and parental investment decisions. 相似文献
8.
Shallow-water octopuses have been reported as major predators of motile species in benthonic marine communities, capturing
their prey by different foraging techniques. This study assessed for the first time the feeding ecology, foraging behavior,
and defensive strategy during foraging, including the use of body patterns, to construct a general octopus foraging strategy
in a shallow water-reef system. Octopus insularis was studied in situ using visual observations and video recordings. The diet included at least 55 species of crustaceans
(70%), bivalves (17.5%), and gastropods (12.5%); however, only four species accounted for half of the occurrences: the small
crabs Pitho sp. (26.8%) and Mithrax forceps (23.9%), the bivalve Lima lima (5.3%), and the gastropod Pisania pusio (4.9%). Poke and crawl were most frequent foraging behaviors observed in the video recordings. The foraging behaviors were
associated with environmental variables and octopus body size. The sequences of foraging behavior showed characteristics of
a tactile saltatory searching predator, as well as a visual opportunist. Body patterns showed a relationship with foraging
behavior, habitat variables, and octopus body size. Mottle was the most frequent pattern, especially during poke and crawl,
in shallower depths. Dorsal light–ventral blue green was more frequent during swimming at mid-water, and Blotch was the normal
pattern during web-over by large animals. The large proportion of two species of small crabs in den remains, the intense search
for food during short hunting trips, and the intense use of cryptic body patterns during foraging trips, suggest that this
species is a ‘time-minimizing’ forager instead of a ‘rate-maximizer’. 相似文献
9.
The effect of reproductive condition on the foraging behavior of female hoary bats,Lasiurus cinereus
R. M. R. Barclay 《Behavioral ecology and sociobiology》1989,24(1):31-37
Summary Female mammals experience larg changes in time and energy budgets associated with reproduction and these may influence the foraging strategies of individuals. I studied the changes in foraging behavior associated with reproduction in female hoary bats, Lasiurus cinereus. As lactation progressed, individuals departed to forage earlier in the evening and spent more time foraging per night and less time roosting with their young. Foraging time increased by at least 73% between early lactation and fledging and then declined as the young became independent. Females with two young foraged for longer than did those with one and females with pre- and postfledging young foraged in different habitats. The changes in foraging time suggest that foraging activity of female L. cinereus is constrained and individuals act as time minimizers, adjusting their foraging behavior to meet current energy demand. Predation risk is unlikely to constrain the behavior of these bats. However, maximizing energy intake throughout lactation may not be the optimal strategy because storing excess energy increases flight cost and may reduce foraging efficiency. The need to keep newborn young warm may also influence foraging time. Such constraints, causing changes in foraging activity, may alter the availability of habitats and prey and must be considered when modelling foraging strategies. In addition, changes in flight time may significantly alter the energy budgets of bats in different stages of reproduction. 相似文献
10.
Urbanization decreases species diversity, but it increases the abundance of certain species with high tolerance to human activities.
The safe-habitat hypothesis explains this pattern through a decrease in the abundance of native predators, which reduces predation
risk in urban habitats. However, this hypothesis does not consider the potential negative effects of human-associated disturbance
(e.g., pedestrians, dogs, cats). Our goal was to assess the degree of perceived predation risk in house finches (Carpodacus mexicanus) through field studies and semi-natural experiments in areas with different levels of urbanization using multiple indicators
of risk (flock size, flight initiation distance, vigilance, and foraging behavior). Field studies showed that house finches
in more urbanized habitats had a greater tendency to flock with an increase in population density and flushed at larger distances
than in less urbanized habitats. In the semi-natural experiment, we found that individuals spent a greater proportion of time
in the refuge patch and increased the instantaneous pecking rate in the more urbanized habitat with pedestrians probably to
compensate for the lower amount of foraging time. Vigilance parameters were influenced in different ways depending on habitat
type and distance to flock mates. Our results suggest that house finches may perceive highly urbanized habitats as more dangerous,
despite the lower number of native predators. This could be due to the presence of human activities, which could increase
risk or modify the ability to detect predators. House finches seem to adapt to the urban environment through different behavioral
strategies that minimize risk. 相似文献
11.
Juan Carlos Alonso Luis M. Bautista Javier A. Alonso 《Behavioral ecology and sociobiology》1997,40(6):401-408
We studied the behavior of 13 radiotagged cranes dispersing from a communal roost over days when they changed their main
daily foraging area between consecutive days during two winter seasons. Individuals went to a new foraging zone when on the
previous day their morning food intake had fallen below their mean morning food intake measured over the whole winter. Food
intake on the day before a change in foraging area was positively correlated with dominance rank. Dominant cranes changed
to new zones with higher numbers of birds and food density, while subordinate cranes went to new zones with lower numbers
of birds. As a result, all birds increased their food intake over that of the previous day. Dominant cranes remained more
faithful to their most preferred foraging zone, where they spent 69% of the mornings, while subordinate birds were more mobile,
switching among zones frequently. Dominant birds left the roost later than subordinate birds on the days they changed to a
new zone, which could be used to track the main departing flows. The results suggest that the dynamics that led to a truncated
phenotype-limited distribution were determined by social dominance and food abundance, with dominant cranes shifting to a
new zone to maintain their high intake levels and subordinates changing more frequently whenever their daily intake did not
reach the minimum metabolic requirements.
Received: 16 December 1996 / Accepted after revision: 22 February 1997 相似文献
12.
Adjustment of parental effort to manipulated foraging ability in a pelagic seabird,the thin-billed prion Pachyptila belcheri 总被引:6,自引:0,他引:6
Henri Weimerskirch Olivier Chastel Luc Ackermann 《Behavioral ecology and sociobiology》1995,36(1):11-16
An experiment was designed to examine in a long-lived seabird, the thin-billed prion (Pachyptila belcheri), how adults adjust their food provisioning strategy when their foraging abilities are reduced and when the chick's needs are increased. To reduce the foraging abilities of adults we impaired their flying ability by removing some flight feathers (handicapped), and to increase the food needs of the chick one parent was retained (single). Birds made either short foraging trips lasting 1–3 days, or long trips lasting 5–9 days. Control birds alternated long and short trips whereas single birds or handicapped birds made several successive short trips and thereafter a long trip. In each treatment, food loads tended to be heavier after long trips than after short trips, and single birds tended to bring heavier loads than control or handicapped birds. Birds in the three treatments lost similar amounts of mass after short trips and gained similar amounts of mass after long trips. However, the mass of handicapped birds declined through the experiment, while that of control and single birds remained stable. Although the proportion of chicks that died during the experiment was similar among the three treatments, the chicks fledged by a single bird were lighter than those in control nests. The results of the experiment suggest that thin-billed prions adjust their breeding effort differently to decreased flying ability or increased food demand by the chick. Single birds increase foraging effort without allowing their condition to deteriorate. Conversely, handicapped birds are unable to maintain their body condition while sustaining the chick at the same rate as control birds. It is suggested that in this long-lived seabird, adults probably adjust their breeding effort so that they do not incur the risk of an increased mortality, this risk being monitored by the body condition. 相似文献
13.
Carolyn L. Nersesian Peter B. Banks Clare McArthur 《Behavioral ecology and sociobiology》2012,66(1):47-55
Cues for detecting and responding to perceived predation risk may be indirect, i.e., correlated with the probability of encountering
a predator, or direct, i.e., produced by or related to the actual presence of a predator. Research shows, independently, both
types of cues can influence anti-predator and foraging behaviours in prey species. However, since animals naturally encounter
indirect and direct cues simultaneously, we were interested in quantifying their cumulative effect. Our aim was to evaluate
food intake and behaviours (patch use, feeding (rate and time), vigilance) of a nocturnal mammalian herbivore to indirect
(open vs. covered microhabitats; illumination) and direct (fox/owl odours) predator cues. We ran a preference trial with four
paired treatments using a covered Safe food patch and an open Risk food patch, with one of four combinations of indirect and direct predator cues. Predation risk had a significant effect on
both intake and behaviour (including feeding time, rate, and vigilance), but these effects differed depending on cues. No
two combinations of cues produced exactly the same effects, illustrating the complexity of interactions that occur between
cues. Covered patches were always perceived as less risky than open patches, but unexpectedly, open patches were perceived
as riskier when dark rather than light. The strongest suite of (negative) responses to risk was associated with combined indirect
and direct cues. These results highlight the importance of considering jointly, intake from a patch, intake rate, and behaviours,
such as the proportion of time spent vigilant, when quantifying predation risk, rather than intake alone. 相似文献
14.
Gentoo penguins Pygoscelis papua show considerable plasticity in their diet, diving, and foraging behaviors among colonies; we expected that they might exhibit
similar variability over time, at a single site, since flexible foraging habits would provide a buffer against changes in
prey availability. We examined interannual changes in the foraging strategies and diet of gentoo penguins in the South Shetland
Islands, Antarctica, over 5 years with variable prey abundance. Antarctic krill Euphausia superba was the primary diet item, and fish the secondary, though the importance of these items varied among years. Diving behavior
also varied over time: different dive depth distributions were observed among years. Nonetheless, chick-rearing success remained
relatively constant, indicating that gentoo penguins were able to maintain chick provisioning by altering their foraging strategy
among years. Variable abundance of krill in the region did not have observable impacts on the diet, foraging behaviors or
chick-rearing success of gentoo penguins. We suggest that foraging plasticity may be one reason that gentoo penguin populations
have remained stable in the region, while their congeners (P. antarctica and P. adeliae) with less flexible foraging strategies have declined. 相似文献
15.
There is a large literature dealing with daily foraging routines of wild birds during the non-breeding season. While different
laboratory studies have showed that some bird activity patterns are a persistent property of the circadian system, most of
field studies preclude the potential role of an endogenous circadian rhythm in controlling bird’s foraging routines. In this
study we compared the patterns of diurnal foraging activity and intake rates of migrating black-tailed godwits, Limosa limosa (radio-tagged and non-tagged individuals) at two stopover sites (habitats) with different environmental characteristics,
aiming at identifying proximate factors of bird activity routines. To gain insights into the role of food availability in
control of such foraging routines, we also estimated foraging activity patterns in captive godwits subjected to constant food
availability. Captive and wild black-tailed godwits showed a persistent bimodal activity pattern through daylight period.
Food availability had a significant effect on the intake rates, but had a subtler effect on foraging and intake rate rhythms.
Temperature and wind speed (combined in a weather index) showed non-significant effects on both rhythms. Although we could
not discard a role for natural diurnal changes in light intensity, an important timing cue, our findings support the idea
that an endogenous circadian rhythm could be an important proximate factor regulating foraging activity and food items taken
per unit time of wild black-tailed godwits during migration. 相似文献
16.
Rodrigo A. Vásquez 《Behavioral ecology and sociobiology》1994,34(5):375-381
It is well known that the risk of predation affects prey decision making. However, few studies have been concerned with the cues used by prey to assess this risk. Prey animals may use indirect environmental cues to assess predation hazard since direct evaluation may be dangerous. I studied the assessment of predation risk, manipulated via environmental illumination level, and the trade-off between foraging and predation hazard avoidance in the nocturnal rodentPhyllotis darwini (Rodentia: Cricetidae). In experimental arenas I simulated dark and full moon nights (which in nature correlate with low and high predation risk, respectively) and measured the immediate responses of animals to flyovers of a raptor model. Second, varying illumination only, I evaluated patch use, food consumption, central place foraging, and nocturnal variation of body weight. During flyover experiments, animals showed significantly more evasive reactions under full moon illumination than in moonless conditions. In the patch use experiments, rodents significantly increased their giving-up density and decreased their total food consumption under moonlight. On dark nights, rodents normally fed in the food patch, but when illumination was high they became central place foragers in large proportion. Moreover, the body weight of individuals decreased proportionately more during bright nights. These results strongly suggest thatP. darwini uses the level of environmental illumination as a cue to the risk of being preyed upon and may sacrifice part of its energy return to avoid risky situations. 相似文献
17.
Many animals share food, that is, to tolerate competitors at a defensible clump. Most accounts of resource sharing invoke
special evolutionary processes or ecological circumstances that reduce their generality. Surprisingly, the Hawk–Dove game
has been unable to address in a simple and general way why so many group foraging animals share food. We modify the Hawk–Dove
game by allowing a finder the opportunity of retaliating if joiners escalate and by considering the consequences of information
asymmetries concerning resource value among players. Introducing the first change, the retaliator strategy was sufficient
to predict widespread sharing in habitats where food clumps are of intermediate richness. When information asymmetry between
finder and joiner is created by allowing the quality of clumps to vary, we show that the conditions for sharing are even more
easily met and apply to a wider range of resource qualities. Our model therefore offers one of the most parsimonious and potentially
general evolutionary accounts of the origin of non-aggressive resource sharing. 相似文献
18.
Summary To place social insect foraging behavior within an evolutionary context, it is necessary to establish relationships between individual foraging decisions and parameters influencing colony fitness. To address this problem, we examined interactions between individual foraging behavior and pollen storage levels in the honey bee, Apis mellifera L. Colonies responded to low pollen storage conditions by increasing pollen intake rates 54% relative to high pollen storage conditions, demonstrating a direct relationship between pollen storage levels and foraging effort. Approximately 80% of the difference in pollen intake rates was accounted for by variation in individual foraging effort, via changes in foraging activity and individual pollen load size. An additional 20% resulted from changes in the proportion of the foraging population collecting pollen. Under both high and low pollen storage treatments, colonies returned pollen storage levels to pre-experimental levels within 16 days, suggesting that honey bees regulate pollen storage levels around a homeostatic set point. We also found a direct relationship between pollen storage levels and colony brood production, demonstrating the potential for cumulative changes in individual foraging decisions to affect colony fitness.
Offprint requests to: J.H. Fewell at the current address 相似文献
19.
Most studies suggest that during times of nutritional stress, an animal faced with two foraging choices should follow a risk-prone
strategy, choosing the option with highest payoff variance. This “scarcity/risk” hypothesis was developed to account for the
foraging patterns of small animals with high metabolic rates susceptible to the threat of starvation. In this paper, we propose
that animals should also be risk-prone when their diet quality is particularly high, far exceeding that which is needed to
survive. Under these circumstances, the costs of experiencing a low or negative payoff can easily be recouped. We suggest
that large-bodied omnivores are most likely to adopt this “abundance/risk” strategy. We investigate this question among wild
chimpanzees (Pan troglodytes) that choose between a risk-averse strategy of feeding on plant material and a risk-prone strategy of hunting red colobus
monkeys. Using 14 years of data on the Kanyawara chimpanzees of Kibale National Park, Uganda, we find strong evidence that
chimpanzees follow the “abundance/risk” strategy. Both hunting rate (hunts/100 observation hours) and the probability of hunting
upon encountering red colobus monkeys were positively correlated with seasonal consumption of ripe drupe fruits, a class of
preferred food associated with elevated reproductive performance by females. Critically, these results remained statistically
significant after controlling for the potentially confounding effects of male chimpanzee party size and the presence of sexually
receptive females. These findings suggest that the relationship between risk-sensitive foraging and diet quality depends upon
the daily probability of starvation, the number of alternative foraging strategies, and the degree to which diet quality satisfies
an animal’s nutritional requirements. 相似文献
20.
Summary Theory suggests that variance in individual food intake is lower during group foraging. Consequently, group foraging can at times reduce starvation risk. In aviary experiments using green-finches we demonstrate how intake variability decreases during group foraging because individuals use feeding by flock mates as a cue to locate food (local enhancement). Flocking preferences of greenfinches responded to variance in energy gain as predicted by theoretical models for foragers attempting to reduce starvation risk. While energy budget was positive the greenfinches were risk averse and foraged socially. Their preference shifted towards more risk prone solitary foraging when kept on a negative energy budget. We conclude that time or energy net gains are not necessary for foraging groups to form, but reductions in starvation risk may be sufficient. 相似文献