67 research outputs found
Competition and group size in Thomas's langurs ( Presbytis thomasi): the folivore paradox revisited
Abstract Among primates, group size is highly variable.
The standard ecological model assumes that better
predation avoidance as group size increases favours living
in larger groups, whereas increased travel costs and
reduced net food intake due to within-group competition
for resources set the upper limit. Folivorous primates,
however, tend to defy this generalisation in that some
live in small groups despite low costs of feeding competition.
To resolve this folivore paradox , it has been suggested
that folivore group size is limited by social factors
such as male harassment or infanticide, or that females
can disperse more easily and thus maintain group size
near optimum levels. In this paper, we examine the effects
of group size on home range size, day-journey
length, activity budget and diet in wild Thomas's langurs
(Presbytis thomasi), which live in one-male multi-female
groups with a limited life cycle. We examined only data
from the stable middle tenure phase when factors such as
the strength of the breeding male or the way in which
groups were formed did not influence ranging and activities.
During this phase, group size affected day-journey
length and home range size, and had a minor effect on
diet, but did not influence time spent feeding or resting,
allogrooming or birth rates. Hence the upper limit to
group size during the middle tenure phase in Thomas s
langurs is not set by feeding competition. The folivore
paradox is not due to frequent female dispersal in
Thomas s langurs. The timing of female dispersal is not
as expected if it serves to keep group sizes near the ecological
optimum, and groups seem to be below this optimum.
Instead, female reproductive success is presumpresumably
maximised in small to mid-sized groups because
larger groups show a clear trend to experience higher
risk of take-over, often accompanied by infanticide. Because
females can redistribute themselves among nearby
groups when groups reorganise each time a new male
starts up a new group, females can keep the group small.
Thus, a social factor, risk of infanticide, seems to provide
the selective advantage to small group size in
Thomas s langurs
The evolution of female social relationships in nonhuman primates
Considerable interspecifc variation in female
social relationships occurs in gregarious primates, par-
ticularly with regard to agonism and cooperation be-
tween females and to the quality of female relationships
with males. This variation exists alongside variation in
female philopatry and dispersal. Socioecological theories
have tried to explain variation in female-female social
relationships from an evolutionary perspective focused
on ecological factors, notably predation and food dis-
tribution. According to the current ``ecological model'',
predation risk forces females of most diurnal primate
species to live in groups; the strength of the contest
component of competition for resources within and be-
tween groups then largely determines social relationships
between females. Social relationships among gregarious
females are here characterized as Dispersal-Egalitarian,
Resident-Nepotistic, Resident-Nepotistic-Tolerant, or
Resident-Egalitarian. This ecological model has suc-
cessfully explained differences in the occurrence of for-
mal submission signals, decided dominance relation-
ships, coalitions and female philopatry. Group size and
female rank generally affect female reproduction success
as the model predicts, and studies of closely related
species in different ecological circumstances underscore
the importance of the model. Some cases, however, can
only be explained when we extend the model to incor-
porate the effects of infanticide risk and habitat satura-
tion. We review evidence in support of the ecological
model and test the power of alternative models that in-
voke between-group competition, forced female phi-
lopatry, demographic female recruitment, male inter-
ventions into female aggression, and male harassment.
Not one of these models can replace the ecological
model, which already encompasses the between-group
competition. Currently the best model, which explains
several phenomena that the ecological model does not, is
a ``socioecological model'' based on the combined im-
portance of ecological factors, habitat saturation and
infanticide avoidance. We note some points of similarity
and divergence with other mammalian taxa; these re-
main to be explored in detail
The forgotten adaptive social benefits of social learning in animals.
Theoretical and empirical scholars of cultural evolution have traditionally studied social learning strategies, such as conformity, as adaptive strategies to obtain accurate information about the environment, whereas within social psychology there has been a greater focus upon the social consequences of such strategies. Although these two approaches are often used in concert when studying human social learning, we believe the potential social benefits of conformity, and of social learning more broadly, have been overlooked in studies of non-humans. We review evidence from studies of homophily, imitation, and rapid facial mimicry that suggests that behaving like others affords social benefits to non-human animals and that behaviour matching may be deployed strategically to increase affiliation. Furthermore, we review studies of conformity in dispersers, and suggest that forgoing personal information or preferences in favour of those of the new group during immigration may be a strategy to facilitate social integration. We therefore propose that the informational and social functions of conformity apply to humans and animals alike. We use this perspective to generate several interesting research questions to inspire work in this field. For example, under what conditions do animals use informational or social conformity and what role does uncertainty play in social learning in immigrant individuals
Towards precision dosing of aripiprazole in children and adolescents with autism spectrum disorder:Linking blood levels to weight gain and effectiveness
Aims: Aripiprazole is one of the most commonly prescribed antipsychotic drugs to children and adolescents worldwide, but it is associated with serious side-effects, including weight gain. This study assessed the population pharmacokinetics of aripiprazole and its active metabolite and investigated the relationship between pharmacokinetic parameters and body mass index (BMI) in children and adolescents with autism spectrum disorder (ASD) and behavioural problems. Secondary outcomes were metabolic, endocrine, extrapyramidal and cardiac side-effects and drug effectiveness. Methods: Twenty-four children and adolescents (15 males, 9 females) aged 6–18 years were included in a 24-week prospective observational trial. Drug plasma concentrations, side-effects and drug effectiveness were measured at several time points during follow-up. Relevant pharmacokinetic covariates, including CYP2D6, CYP3A4, CYP3A5 and P-glycoprotein (ABCB1) genotypes, were determined. Nonlinear mixed-effects modelling (NONMEM®) was used for a population pharmacokinetic analysis with 92 aripiprazole and 91 dehydro-aripiprazole concentrations. Subsequently, model-based trough concentrations, maximum concentrations and 24-h area under the curves (AUCs) were analysed to predict outcomes using generalized and linear mixed-effects models. Results: For both aripiprazole and dehydro-aripiprazole, one-compartment models best described the measured concentrations, with albumin and BMI as significant covariates. Of all the pharmacokinetic parameters, higher sum (aripiprazole plus dehydro-aripiprazole) trough concentrations best predicted higher BMI z-scores (P <.001) and higher Hb1Ac levels (P =.03) during follow-up. No significant association was found between sum concentrations and effectiveness. Conclusions: Our results indicate a threshold with regard to safety, which suggests that therapeutic drug monitoring of aripiprazole could potentially increase safety in children and adolescents with ASD and behavioural problems.</p
Phenology, caudex growth and age estimation of Cyathea corcovadensis (Raddi) Domin (Cyatheaceae) in a subtropical forest in southern Brazil
The effect of size and density on nut removal in Syagrus loefgrenii Glassman (Arecaceae) in the Brazilian Cerrado
Seed removal of Dipteryx alata Vog. (Leguminosae: Faboidae) in the edge and interior of Cerrado
Phenological synchrony and seasonality of understory Rubiaceae in the Atlantic Forest, Bahia, Brazil
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