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1.
A brief guide to model selection,multimodel inference and model averaging in behavioural ecology using Akaike’s information criterion 总被引:1,自引:0,他引:1
Akaike’s information criterion (AIC) is increasingly being used in analyses in the field of ecology. This measure allows one
to compare and rank multiple competing models and to estimate which of them best approximates the “true” process underlying
the biological phenomenon under study. Behavioural ecologists have been slow to adopt this statistical tool, perhaps because
of unfounded fears regarding the complexity of the technique. Here, we provide, using recent examples from the behavioural
ecology literature, a simple introductory guide to AIC: what it is, how and when to apply it and what it achieves. We discuss
multimodel inference using AIC—a procedure which should be used where no one model is strongly supported. Finally, we highlight
a few of the pitfalls and problems that can be encountered by novice practitioners. 相似文献
2.
Sonja E. Koski 《Behavioral ecology and sociobiology》2011,65(11):2161-2174
Animals of many species show consistency in behaviour across time and contexts that differs from other individuals' behaviour
in the same population. Such ‘personality’ affects fitness and has therefore become an increasingly relevant research topic
in biology. However, consistent variation in social behaviour is understudied. In socially living species, behaviour occurs
in a social environment and social interactions have a significant influence on individual fitness. This study addressed personality
in social behaviour of 75 captive chimpanzees in three zoos by coding observed behaviour. Fifteen behavioural variables were
significantly repeatable (range 0.21–0.93) in at least two of the three zoos. The behaviours showed considerable long-term
stability across 3 years, which did not differ from the short-term repeatability. The repeatable behaviours were then analysed
with factor analyses. They formed five independent factors, three of which consisted of social traits and were labelled ‘sociability’,
‘positive affect’ and ‘equitability’. The two non-social behaviour factors were labelled ‘anxiety’ and ‘activity’. The factor
scores were analysed for sex and population differences. Males had higher factor scores in all traits except ‘sociability’.
The factor scores differed also between the zoos, implying considerable external effects in trait expression. The results
show that chimpanzees show personality in a broad range of social and non-social behaviours. The study highlights the importance
of assessing personality in the social behaviour, especially in cohesive social species, as only then can we understand the
consequences of personality in socially living species. 相似文献
3.
Antonia Köhler Philipp Hildenbrand Elke Schleucher Rüdiger Riesch Lenin Arias-Rodriguez Bruno Streit Martin Plath 《Behavioral ecology and sociobiology》2011,65(8):1513-1523
Sexual harassment by males has the potential to affect almost any aspect of female behavior and life history. Using Atlantic
mollies (Poecilia mexicana) as a model—a species in which males do not court but almost constantly try to forcefully mate with females—we asked whether
and how male harassment influences (a) females’ time budgets and (b) feeding rates (e.g., through frequent flight from male
approaches), and (c) whether metabolic rates are increased as a response to stress. Field observations in a natural P. mexicana population revealed that males (average feeding rate 15%) spent far less time feeding than females (60%), and clearly traded
off frequent pursuit of females with foraging. Most importantly, females’ feeding times were dramatically reduced when being
pursued by a harassing male. Also in standardized lab experiments, females spent significantly less time feeding when accompanied
by a male as compared to being in the presence of another female. This effect was also observed when partner fish (male or
female) were presented only visually, but could not interact physically with the focal female. It seems, therefore, that females
increase vigilance when a harassing male is around, which keeps them from feeding even before males actually approach them.
Based on the latter result, we asked whether a stress-induced increase in metabolic rates would be discernible. We measured
oxygen consumption and gill ventilation frequencies (opercular rates) of females in different social contexts (alone, with
another female, or a male). The predicted, strong body mass dependency of both physiological parameters was uncovered, but
no evidence for an effect of social context was detected. We argue that male harassment represents such a constant (but non-lethal)
stressor for poeciliid females that their metabolic stress responses have adapted to this through habituation. 相似文献
4.
Rita Hargitai Kathryn E. Arnold Márton Herényi József Prechl János Török 《Behavioral ecology and sociobiology》2009,63(6):869-882
Offspring survival can be influenced by resources allocated to eggs, which in turn may be affected by the environmental factors
the mother experiences during egg formation. In this study, we investigated whether experimentally elevated social interactions
and number of neighbouring pairs influence yolk composition of collared flycatchers (Ficedula albicollis). Social challenge was simulated by presentation of a conspecific female. Experimental females spent more time near the cage
and produced eggs with higher androgen concentration, but local breeding density did not affect yolk androgen level. Moreover,
we found that females exposed to more intra-specific interactions and those that bred at higher density produced eggs with
smaller yolk. These females may be more constrained in foraging time due to more frequent social encounters, and there might
be increased competition for food at areas of higher density. In contrast, the present study did not reveal any evidence for
the effect of social environment on yolk antioxidant and immunoglobulin levels. However, we found that yolk lutein and immunoglobulin
concentrations were related to the female’s H/L ratio. Also, yolk lutein and α-tocopherol levels showed a seasonal increase
and were positively related to the female’s plasma carotenoid level. Mothers may incur significant costs by transferring these
compounds into the eggs, thus only females in good physiological condition and those that lay eggs later, when food is probably
more abundant, could allocate higher amounts to the eggs without compromising their defence mechanisms. Our results suggest
that environmental circumstances during egg formation can influence conditions for embryonic development. 相似文献
5.
Animals’ contest performance is influenced by their recent contest experiences. This influence could either be exerted by
individuals re-estimating their own fighting ability (self-assessment) or by their opponents responding to status-related
cues (social-cue mechanism) or both. Individuals of Kryptolebias marmoratus, a hermaphroditic killifish, were given different contest experiences to examine how two opponents’ prior experiences combined
to determine their contest interaction and to test both of these mechanisms as potential causes of the observed experience
effect. Our data showed that losers’ decisions to retreat at different stages of a contest were influenced by their own but
not by the winners’ contest experience—a result consistent with self-assessment but not with the social-cue mechanism. An
association between the fish initiating and winning contests thus probably arose because both were correlated with an individual’s
assessment of its fighting ability, but not because initiating contests made opponents more inclined to retreat. 相似文献
6.
Social insects are prone to attack by parasites as they provide numerous resources of food and brood, homeostatic nest conditions
and a high density of individuals, enhancing the transmission of parasites. The defence of social insects might occur at different
levels, the individual and the group. Individual defence occurs in part via the innate immune system resulting in the expression
of antimicrobial substances. Group level defences, summarised as ‘social immunity’, represent a suite of behavioural and organisational
features. Here, all effects contributing to social immunity except for the social context were removed from bumblebee (Bombus terrestris) workers, kept either in groups or solitarily. The gene expression of six effector molecules of the immune system was monitored
in both groups and in controls from the same source colonies. The social treatment has a highly significant effect on immune
gene expression, with groups exhibiting higher levels of two antimicrobial peptides (AMPs) and two lysozymes. Phenoloxidase
is affected at the regulatory level, with a strong upregulation of its suppressor Spn27A in groups suggesting a trade-off
with antimicrobial activity. AMPs are strongly upregulated in groups, whereas lysozymes are strongly downregulated in solitary
treatments suggesting another trade-off. Clearly, social immunity impacts elements of individual immunity. 相似文献
7.
Model averaging,missing data and multiple imputation: a case study for behavioural ecology 总被引:1,自引:0,他引:1
Model averaging, specifically information theoretic approaches based on Akaike’s information criterion (IT-AIC approaches),
has had a major influence on statistical practices in the field of ecology and evolution. However, a neglected issue is that
in common with most other model fitting approaches, IT-AIC methods are sensitive to the presence of missing observations.
The commonest way of handling missing data is the complete-case analysis (the complete deletion from the dataset of cases
containing any missing values). It is well-known that this results in reduced estimation precision (or reduced statistical
power), biased parameter estimates; however, the implications for model selection have not been explored. Here we employ an
example from behavioural ecology to illustrate how missing data can affect the conclusions drawn from model selection or based
on hypothesis testing. We show how missing observations can be recovered to give accurate estimates for IT-related indices
(e.g. AIC and Akaike weight) as well as parameters (and their standard errors) by utilizing ‘multiple imputation’. We use
this paper to illustrate key concepts from missing data theory and as a basis for discussing available methods for handling
missing data. The example is intended to serve as a practically oriented case study for behavioural ecologists deciding on
how to handle missing data in their own datasets and also as a first attempt to consider the problems of conducting model
selection and averaging in the presence of missing observations. 相似文献
8.
In mammalian polygynous mating systems, male reproductive effort consists mainly of male–male competition and courting of
females, which entail substantial somatic costs. Males are thus expected to adjust their reproductive effort according to
their age and condition. In this study, we examined how activity budgets of male mountain goats (Oreamnos americanus), a polygynous ungulate, varied with age in a marked population over two periods: (1) summers 1995–2006 and (2) ruts 2004–2006.
We then assessed if the proportions of time spent in male–male competition and courtship behaviors were influenced by age-specific
body mass and social rank during the rut. Males spent most of their time foraging and resting during summer, and rested more
and foraged less with increasing age. During the rut, pronounced shifts in activity budgets occurred as juveniles (1–2 years)
increased time spent foraging, whereas adults (≥3 years) increased standing and time spent in social interactions at the expense
of foraging. At old age, reproductive effort either stabilized or decreased slightly, providing weak support for the ‘mating
strategy–effort’ hypothesis, predicting that courtship behaviors should peak in prime-aged males. Age-specific body mass did
not affect time spent in male–male competition, but was positively related with time spent in courtship behaviors, providing
support for the ‘individual quality’ hypothesis, predicting that males with more resources at the start of the rut should
spend more time in mating-related activities. Age-specific social rank did not affect reproductive effort. Surviving to prime
age while increasing mass each year should thus allow male ungulates to gain greater ability to court estrus females. 相似文献
9.
Assuming that a male’s genetic characteristics affect those of his offspring, extra-pair copulation has been hypothesized
to increase heterozygosity of the progeny—the “genetic compatibility” hypothesis—and the genetic diversity within litters—the
“genetic diversity” hypothesis. We tested these two hypotheses in the alpine marmot (Marmota marmota), a socially monogamous mammal showing a high rate of extra-pair paternity (EPP). In a first step, we tested the assumption
that a male’s genetic characteristics (heterozygosity and genetic similarity to the female) affect those of his offspring.
Genetic similarity between parents influenced offspring heterozygosity, offspring genetic similarity to their mother, and
litter genetic diversity. The father’s heterozygosity also influenced litter genetic diversity but did not affect offspring
heterozygosity. Hence, heterozygosity seems not to be heritable in the alpine marmot. In a second step, we compared genetic
characteristics of extra-pair young (EPY) and within-pair young (WPY). EPY were less genetically similar to their mother but
not more heterozygous than WPY. EPY siblings were also less genetically similar than their WPY half siblings. Finally, the
presence of EPY promoted genetic diversity within the litter. Thus, our data support both the “genetic compatibility” and
the “genetic diversity” hypotheses. We discuss further investigations needed to determine the primary causes of EPP in this
species. 相似文献
10.
Juliana Rangel Sean R. Griffin Thomas D. Seeley 《Behavioral ecology and sociobiology》2010,64(6):979-987
Animals that travel in groups must synchronize the timing of their departures to assure cohesion of the group. While most
activities in large colonies of social insects have decentralized control, certain activities (e.g., colony migration) can
have centralized control, with only a special subset of well-informed individuals making a decision that affects the entire
colony. We recently discovered that a small minority of individuals in a honeybee colony—an oligarchy—decides when to trigger
the departure of a swarm from its hive. The departure process begins with some bees producing the worker-piping signal (the
primer for departure) and is followed by these bees producing the buzz-run signal (the releaser for departure). In this study,
we determined the identity of these signalers. We found that a swarm’s nest-site scouts search for potential nest cavities
prior to the departure of the swarm from its hive. Furthermore, we found that the predeparture nest-site scouts are the sole
producers of the worker-piping signal and that they are the first producers of the buzz-run signal. The control of the departure
of a honeybee swarm from its hive shows how a small minority of well-informed individuals in a large social insect colony
can make important decisions about when a colony should take action. 相似文献
11.
Hamed Haddadi Andrew J. King Alison P. Wills Damien Fay John Lowe A. Jennifer Morton Stephen Hailes Alan M. Wilson 《Behavioral ecology and sociobiology》2011,65(8):1659-1668
Social Network Analysis has become an important methodological tool for advancing our understanding of human and animal group
behaviour. However, researchers tend to rely on arbitrary distance and time measures when defining ‘contacts’ or ‘associations’
between individuals based on preliminary observation. Otherwise, criteria are chosen on the basis of the communication range
of sensor devices (e.g. bluetooth communication ranges) or the sampling frequencies of collection devices (e.g. Global Positioning
System devices). Thus, researchers lack an established protocol for determining both relevant association distances and minimum
sampling rates required to accurately represent the network structure under investigation. In this paper, we demonstrate how
researchers can use experimental and statistical methods to establish spatial and temporal association patterns and thus correctly
characterise social networks in both time and space. To do this, we first perform a mixing experiment with Merino sheep (Ovis aries) and use a community detection algorithm that allows us to identify the spatial and temporal distance at which we can best
identify clusters of previously familiar sheep. This turns out to be within 2–3 m of each other for at least 3 min. We then
calculate the network graph entropy rate—a measure of ease of spreading of information (e.g. a disease) in a network—to determine
the minimum sampling rate required to capture the variability observed in our sheep networks during distinct activity phases.
Our results indicate the need for sampling intervals of less than a minute apart. The tools that we employ are versatile and
could be applied to a wide range of species and social network datasets, thus allowing an increase in both the accuracy and
efficiency of data collection when exploring spatial association patterns in gregarious species. 相似文献
12.
Speed-accuracy tradeoffs are a common feature of decision-making processes, both in individual animals and in groups of animals
working together to reach a single collective decision. Individual organisms display consistent differences in their “impulsivity,”
and vary in their tendency to make rapid, impulsive choices as opposed to slower, more accurate decisions. However, we do
not yet know whether groups of animals consistently differ in their tendency to prioritize decision speed over accuracy. We
challenged 17 swarms of honey bees (Apis mellifera) to simultaneously choose a new nest site in each of three locations, and measured their decision speeds in each trial. We
found that swarms displayed consistent personality differences in the number of waggle dances and shaking signals they performed
and in how actively they scouted for new nest sites. However, swarms did not consistently differ in how long they took to
choose a nest site. We suggest that house-hunting A. mellifera swarms may place an especially high emphasis on decision accuracy when choosing a nest site, and that chance events—such
as the time when each swarm discovers a sufficiently high-quality nest site—may consequently play a greater role in determining
a swarm’s decision speed than intrinsic characteristics such as a swarm’s “impulsivity.” 相似文献
13.
This study provides information about differences in composition of ingested zooplankton amongst bivalve species coexisting
in the same area in a period from May 2009 to December 2010. The study was conducted at the Mali Ston Bay (42°51′ N, 17°40′
E)—the most important bivalve aquaculture area in the eastern Adriatic Sea. Stomach content analysis was performed on cultured
species—Ostrea edulis and Mytilus galloprovincialis, and commercially important bivalve species from their natural environment—Modiolus barbatus and Arca noae. Results confirmed carnivory in bivalves, both from natural and cultured populations, but cultured species had higher numbers
of zooplankters than those living on the seabed. The most abundant taxa were bivalve larvae, followed by tintinnids, copepods,
unidentified eggs and gastropod larvae. Recorded numbers of bivalve larvae in M. galloprovincialis stomach were the highest so far reported and show that mussels impact the availability of natural spat. 相似文献
14.
Bivalves demonstrate various morphological and behavioural adaptations to reduce the risk of being attacked by predators.
This paper examines how the presence of the crab Carcinus maenas (L.), a natural predator of the cockle Cerastoderma edule (L.), affects its burrowing depth and clearance or feeding rate. Cockles were placed in experimental tanks and treated with
three levels of predatory disturbance: (1) unfed crab loose inside the tank, (2) unfed crab inside a cage suspended in the
water column and (3) no crab present. Cockles’ burrowing depth was measured in two sediment types: mud and sand. Cockles burrowed
more deeply in treatments with no crabs. Burrowing depth in sand was significantly greater than in mud. Two factors may contribute
to the reduction in burial depth of C. edule in the presence of C. maenas: the change in the vertical orientation of the cockle and the ‘cough response’. No significant difference was found in the
cockles’ clearance rate among the different levels of predator threat. 相似文献
15.
The giant panda (Ailuropoda melanoleuca) is notoriously difficult to study in the wild, but its interesting reproductive ecology makes the effort worthwhile. Perhaps
more than most species, the panda is energy-limited, which alters the cost/benefit analysis of its reproductive ecology. Using
global positioning system/very high frequency radiocollars to locate mating aggregations, we used behavioral observations
and fecal testosterone assays to gain insight into male panda reproductive effort and strategies, and test theories relating
to reproductive competition. Male pandas initially competed fiercely for access to females that were about to be fertile,
but once male competitive status was determined, aggression rates declined. Contact aggression was only observed during the
first 2 days of mating aggregations; thereafter, it was replaced with noncontact aggression and avoidance. Agonistic interactions
were highly asymmetrical, with contest losers (subordinates) showing less aggression and more avoidance than contest winners
(dominants), both before and after contest outcome was established. The competitively superior male displayed mate-guarding
tactics and secured all observed copulations. Contrary to theoretical predictions, testosterone levels did not predict aggression
levels or contest winners and also were not affected by winning or losing a contest. Body size appeared to be the primary
determinant of contest outcome. We discuss our findings in light of theoretical predictions, such as those arising from the
“challenge hypothesis,” in the context of the giant panda’s foraging and nutritional ecology. 相似文献
16.
Retreat and advance of shoreline position occurs naturally, and also as a result of defences which are constructed to prevent
erosion and flooding. Retreat more commonly manifests itself down-drift of defences due to a sediment deficit causing the
coast to become ‘set-back’. Advance normally develops due to sediment accumulation up-drift of a barrier inhibiting longshore
drift, resulting in the coast becoming ‘set-forward’. Many examples of set-backs and set-forwards are recorded, but their
location, number and cause is not known on a national scale. Using the Futurecoast aerial photographs, approximately 200 localities
were identified as set-back or set-forward in England and Wales, with half situated in the Eastern and South East regions
of England. Half of the total set-backs or set-forwards were on cliffed coasts, and half on low-lying coasts. Without local
knowledge it is difficult to distinguish between set-backs and set-forwards. Set-backs often indicate higher retreat rates,
thus threatening cliff-top infrastructure which requires defence upgrade and extensions, as well as raising maintenance costs.
Monitoring set-backs is important for shoreline management, because as retreat continues, set-backs evolve and artificial
headlands form and grow. This is reinforced by the shift from hard defence policies towards softer engineering approaches,
managed realignment and limited intervention. 相似文献
17.
Mate choice games, context-dependent good genes, and genetic cycles in the side-blotched lizard, Uta stansburiana 总被引:4,自引:0,他引:4
According to mate choice models, a female should prefer males with traits that are reliable indicators of genetic quality
which the sire can pass on to their progeny. However, good genes may depend on the social environment, and female choice for
good genes should be context dependent. The side-blotched lizard, Uta stansburiana, exhibits genetically based throat colors (orange, blue, or yellow) that could be used as a sexually selected signal since
they reliably predict the genetic quality of mates. The frequencies of male and female morphs cycle between years, and both
male and female morphs have an advantage when rare; thus genetic quality will depend on morph frequency. A female should choose
a sire that maximizes the reproductive success of both male and female progeny. We examine a game theoretical model that predicts
female mate choice as a function of morph frequency and population density. The model predicts the following flexible mate
choice rule: both female morphs should prefer rare males in ’boom years’ of the female cycle (e.g., ’rarest-of-N rule’), but
prefer orange males in ’crash years’ of the female cycle (’orange-male rule’). Cues from the current social environment should
be used by females to choose a mate that maximizes the future reproductive success of progeny, given the social environment
of the next generation. We predict that the cue is the density of aggressive orange females. In the side-blotched lizard,
cycling mate choice games and context-dependent mate choice are predicted to maintain genetic variation in the presence of
choice for good genes.
Received: 8 March 2000 / Revised: 26 August 2000 / Accepted: 4 September 2000 相似文献
18.
Graphical models provide an important tool for facilitating communication between scientists, decision-makers, and statisticians—many
complicated ecological processes can be described in terms of “box-and-arrow” conceptual diagrams (e.g., Shipley in Cause
and correlation in biology: a user’s guide to path analysis, structural equations and causal inferences, Cambridge Universtiy
Press, Cambridge, 2000; Clark and Gelfand TRENDS in Ecology and Evolution 21:375–380, 2006). In particular, problems in landscape
ecology often involve modeling relationships among multiple physical and/or biological variables that may operate on differing
spatial scales (e.g., Rossi et al. in Ecol Monographs 62:277–314, 1992; Legendre et al. in Ecography 25:601–615, 2002; Overmars
et al. in Ecol Model 164:257–270, 2003; Brown and Spector in J Appl Ecol 45:1639–1648, 2008; Koniak and Noy-Meir in Ecol Model
220:1148–1158, 2008). These problems are inherently multivariate, though researchers commonly rely on univariate methods,
such as spatial regression models, to address them. In this paper, we introduce a multivariate method—graphical spatial models—that
extends path analysis to incorporate spatial autocorrelation in one or more variables in a directed graph. We show how both
exogenous and endogenous ecological processes as defined by Legendre et al. (Ecography 25:601–615, 2002) and Lichstein et al.
(Ecol Monographs 72:445–463, 2002) can be represented in a graph. Most importantly, we show how to translate graphs representing
these ecological processes into statistically estimable models. We motivate our theoretical results using an example of stream
health data from the Willamette Valley, Oregon. For these data we are interested in the spatial pattern within both riparian
land use and an index of stream health, and whether there is an association between land use and stream health, after accounting
for these spatial patterns. We use a graphical spatial model to address these ecological questions simultaneously. We find
that the health of a stream decreases as the percent of developed land within a 120-m riparian buffer increases; interestingly,
there is only evidence of spatial pattern within land use. 相似文献
19.
Leaf-cutter ants with worn mandibles cut half as fast,spend twice the energy,and tend to carry instead of cut 总被引:1,自引:0,他引:1
Robert M. S. Schofield Kristen D. Emmett Jack C. Niedbala Michael H. Nesson 《Behavioral ecology and sociobiology》2011,65(5):969-982
The importance of mechanical wear in the behavioral ecology and energetics of small organisms is an open question. We investigated
wear in leaf-cutter ants, Atta cephalotes, because their cutting technique can be imitated and the leaves are the main energy source for the colony. We found that
a razor-sharp (50-nm radius) “V-blade” that cuts leaves between the first and second mandibular teeth was dulled (∼10-μm radius)
and often nearly worn away on foragers. We found that the force required to cut standard leaves, using mandibles removed from
foragers cutting in the wild, varied by a factor of 2.5 with tooth wear, defined as the difference between pupal and actual
tooth length. We also found that wear significantly reduced the cutting rate. From the distribution of wear among the cutting
foragers, we estimated that the wild colony would have spent 44% less of both energy and time making the observed cuts if
the cutters’ mandibles had all been pristine. Finally, wear correlated with behavioral differences—foragers with the most
worn 10% of mandibles almost exclusively carried rather than cut. This previously unreported form of task partitioning suggests
that eusociality may extend useful lifespans by making it possible to switch tasks as skills decline. We developed a model,
assuming that ants do work at a constant rate proportional to their mass, to predict the cutting rate from head width, tooth
wear, and force to cut leaves with a scalpel (R = 0.62), and we used this estimate to argue that the partitioning of cutting and carrying was sub-optimal but better than
random. Wear’s strong effect on performance may promote wear-avoiding behavior and wear-resistant mandible composition; it
may affect leaf selection and worker lifespan and it raises the possibility that wear is a similarly important constraint
for many other small organisms. 相似文献
20.
Most social primates live in cohesive groups, so travel paths inevitably reflect compromise: decision processes of individuals
are obscured. The fission–fusion social organisation of the chimpanzee, however, allows an individual's movements to be investigated
independently. We followed 15 chimpanzees (eight male and seven female) through the relatively flat forest of Budongo, Uganda,
plotting the path of each individual over periods of 1–3 days. Chimpanzee movement was parsed into phases ending with halts
of more than 20 min, during which individuals fed, rested or engaged in social activities. Males, lactating or pregnant females
and sexually receptive females all travelled similar average distances between halts, at similar speeds and along similarly
direct beeline paths. Compared to lactating or pregnant females, males did travel for a significantly longer time each day
and halted more often, but the most striking sex differences appeared in the organisation of movement phases into a day's
path. After a halt, males tended to continue in the same direction as before. Lactating or pregnant females showed no such
strategy and often retraced the preceding phase, returning to previously visited food patches. We suggest that female chimpanzee
movements approximate an optimal solution to feeding requirements, whereas the paths of males allow integration of foraging
with territorial defence. The ‘continually moving forwards’ strategy of males enables them to monitor their territory boundaries—border
checking—whilst foraging, generally avoiding the explicit boundary patrols observed at other chimpanzee study sites. 相似文献