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Background: Perception by workers of their health problems as work-related is possibly associated with sickness absence (SA). The aim of this study was to to study the relationship between perceived work-relatedness of health problems and SA among workers who visit their GP, taking the influence of other potential determinants into account and to study the influence of these determinants on SA. Design and setting prospective cohort study in 32 Dutch GP practices.Methods: A secondary analysis of RCT data among workers, aged 18-63 years, who visited their GP. We measured self-reported SA days in 12 months and high SA (>20 days in 12 months) and compared workers who perceived work-relatedness (WR+) with workers who did not (WR-). With multivariable linear and logistic regression models, we analyzed the influence of age, gender, experienced health, chronic illness, prior SA, number of GP consultations and perceived work ability.Results: We analyzed data of 209 workers, 31% perceived work-relatedness. Geometric mean of SA days was 1.6 (95% CI: 0.9-3.0) for WR+- workers and 1.2 (95% CI: 0.8-1.8) for WR- workers (P = 0.42). Incidence of high SA was 21.5 and 13.3%, respectively (odds ratio 1.79; 95% CI: 0.84-3.84). SA was positively associated with chronic illness, prior SA, low perceived work ability and age over 50.Conclusions: Perceived work-relatedness was not associated with SA. SA was associated with chronic illness, prior SA, low perceived work ability and age over 50. [ABSTRACT FROM AUTHOR]

In this paper, we investigate how the number and context of male loud calls of Thomas's langurs (Presbytis thomasi) change over a male's tenure, in relation to changes in the intensity of male mate competition and relative male strength. We also investigate how the calls' impact on the behavior of receivers varies over tenure phases. Thomas's langurs live in one-male multi-female groups; only males produce loud calls; both males and females disperse from their natal groups; female secondary dispersal is also common, and infanticide occurs. The life-span of a group is, as a rule, restricted to the tenure of its reproductive male (median tenure length is 72 months). Male tenure in bisexual groups was divided into three phases: the early phase (no infants yet), the stable middle phase, and the late phase (last year). Because AMBs remained after all females had left a male, they were treated as a fourth phase. We hypothesised that the tendency to answer another male's calls decreases with distance because a male will invest less when answering becomes less relevant. The tendency to respond to a loud call by an extra-group male indeed decreased with distance, which suggests that males invested less in (costly) calling behavior when the chance of an interaction with that male was low. Extra-group males seemed to recognise males of new groups: they did not discriminate between medium and far distances in answering calls from (relatively unfamiliar) early tenure males. We further hypothesised that an increase in male mate competition would result in more call bouts per day and a higher tendency to answer calls, which was not found. Males with a relatively low strength were expected to keep signalling their presence, but because this low strength includes a higher risk for females and infants, we expected females to avoid loud calling extra-group males. Males with a declining strength continued to signal their presence, as was expected, but they did reduce participation in dawn call bouts, which might be a particularly sensitive measure of their decreased strength. Extra-group males answered calls by males during their late tenure phase more often at medium and far distances, which shows that males recognised calls from late tenure males. Females' avoidance of calling extra-group males remained constant during the early and middle phase but increased during the late tenure phase, as was expected. AMB males clearly avoided males from bisexual groups: they never participated in dawn call bouts, they rarely started or answered calls and they travelled away from calling males. AMB males only answered a call bout in the case of a betweengroup conflict, when their position was already known. Hence, in Thomas's langurs, loud call behavior influenced male mate competition, and it varied in relation to changes in relative male strength. [ABSTRACT FROM AUTHOR]

Between-group conflicts are believed to serve two major functions: mate defence and resource defence. In addition, in species where females can disperse, both female choice and male coercion may play a role in between-group interactions. In this paper, I evaluate the resource vs mate defence hypotheses and investigate male and female strategies in between-group interactions in wild Thomas's langurs (Presbytis thomasi). This species lends itself well to study the intertwining of male and female strategies. Thomas's langurs live in one-male multifemale groups; both males and females disperse from their natal groups; female secondary dispersal is also common, and infanticide occurs. The life-span of a group is, as a rule, restricted to the tenure of its reproductive male (median tenure length is 72 months). Male tenure in bisexual groups was divided into three phases: the early phase (no infants yet), the stable middle phase, and the late phase (last year). Because AMBs remained after all females had left a male, they were treated as a fourth phase. I analysed interactions of group members with individuals outside the group using data from a four year field study (1093 observation days) of 15 bisexual and eight all-male groups of Thomas's langurs at Ketambe, Indonesia. Two types of interactions could be distinguished: (1) group encounters: whole groups meet each other, and (2) male provocations: a male silently approaches a group and suddenly attacks the individuals. This study involves 329 group encounters and 265 male provocations. The results support the mate defence hypothesis, but are ambiguous about the role of resource competition: Group encounters during the middle and late tenure phase took place more often in the context 'food patch', than was expected, and they mostly took place in fruit patches, which were a preferred food item. However, the proportion of group encounters that involved aggression did not depend on feeding context or tenure, and fruit availability did not influence group encounter rates. Male aggression during between-group conflicts reflected mate defence, rather than resource defence, although females had the possibility of obtaining resource defence through a male's mate defence. This study suggests that females use the outcome of group encounters and male provocations to assess the relative strength of males, and thus 'chose' a male who is able to defend future offspring. It also suggests that males can use coercion (infanticide and aggression against females) to show the relative weakness of a female's current male and encourage her to transfer: Aggressive behaviour during group encounters was primarily between males. Females only reacted aggressively to extra-group males when their infant was under attack. Male infanticide only occurred during provocations by males from neighbouring groups or AMBs. The intensity of male competition for mates, as measured by male-male aggression and extra-group male interest in a groups' females, was higher during the early and late phases, than during the middle phase of the tenure. It was also higher during the AMB than during the late phase of male tenure. The relative strength of males, as measured by a male's provoking behaviour and his ability to protect his females from aggression by extra-group males, was lower during the late than during the middle tenure phase. Male strength seemed lowest during the subsequent AMB phase. Females avoided extra-group males least during the early tenure phase, before infants were born. [ABSTRACT FROM AUTHOR]

This study examines vigilance as a behavioural indicator of the importance of infanticide risk by comparing the infanticide avoidance hypothesis with the predation avoidance and mate defence hypotheses for wild Thomas's langurs ( Presbytis thomasi) in Sumatra. We found that all individuals were more vigilant in situations of high predation risk, i.e. lower in the trees and in the absence of neighbours. Females were also more vigilant on the periphery of the group. However, there were variations in vigilance levels that could not be accounted for by the predation avoidance hypothesis. Males without infants showed higher levels of vigilance in areas of home range overlap than in non-overlap areas during the early phase of their tenure, strongly suggesting mate defence. In these areas of home range overlap where Thomas's langur groups can interact, males may attack females and infants, and so the infanticide risk for males and females with infants is likely to be high in these areas. Only females with infants, but not males with infants or females without infants, showed higher vigilance levels in overlap areas than in non-overlap areas; in addition, in overlap areas, females with an infant were more vigilant than females without an infant, while this was not the case in non-overlap areas. Both females and males with infants were more vigilant high in the trees than at medium heights in overlap areas but not elsewhere. These findings can only be explained by the infanticide avoidance hypothesis. In contrast to predator attacks, infanticidal male attacks come from high in the canopy, and only occur in overlap areas. There was a significant sex difference in vigilance, but males were only more vigilant than females without an infant, and not more vigilant than females with an infant. We conclude that vigilance varied mainly in relation to the risk of predation and infanticide. Mate competition only played a role for males during the early phase of their tenure. Predation risk seems to offer the best explanation for vigilance for all individuals in the absence of infants. Both predation risk and infanticide risk played a role for females and males with infants. [ABSTRACT FROM AUTHOR]