Geographic variation in Thomas langur (Presbytis thomasi) loud calls

2008 ◽  
Vol 70 (6) ◽  
pp. 566-574 ◽  
Author(s):  
Serge A Wich ◽  
Anne Marijke Schel ◽  
Han de Vries
Keyword(s):  
Geographic Variation ◽  
Loud Calls ◽  
Presbytis Thomasi

Thomas Langurs (Presbytis thomasi) Discriminate Between Calls of Young Solitary Versus Older Group-living Males: a Factor in Avoiding Infanticide?

Behaviour ◽  
2004 ◽  
Vol 141 (1) ◽  
pp. 41-51 ◽  
Author(s):  
◽  
◽  
Keyword(s):  
Young Adult ◽  
Animal Species ◽  
Group Living ◽  
Panthera Leo ◽  
Adult Males ◽  
Loud Calls ◽  
Young Adult Males ◽  
Presbytis Thomasi ◽  
Older Males

AbstractThe ability to differentiate among calls from different individuals has been shown for a number of animal species and several functions have been suggested. One hypothesis, developed for lions (Panthera leo), is that the ability to distinguish between calls from neighbour versus strange males is linked to the avoidance of infanticidal ( i.e. strange) males. Since infanticide is widespread among primates, we tested the applicability of this hypothesis to Thomas langurs (Presbytis thomasi). Young adult males, that mostly reside in all-male bands or are solitary (called AMB males), were more likely to be infanticidal than adult, usually older, males that reside in mixed-sex groups (called MSG males). We use playbacks to demonstrate that Thomas langurs are able to differentiate between loud calls from AMB male strangers and MSG male strangers. Thomas langur males responded more vigorously to playbacks of calls from AMB (i.e. more likely to be infanticidal) males than to calls from MSG males. Females showed a more cautious response to the calls from AMB males than to the calls from MSG males. Both these reactions are in accordance with the infanticide hypothesis and suggest that Thomas langurs differentiate between loud calls of AMB and MSG stranger males and incorporate this information in their behaviour to avoid infanticide.

Geographic variation in loud calls of sportive lemurs (Lepilemur ssp.) and their implications for conservation

2008 ◽  
Vol 70 (9) ◽  
pp. 828-838 ◽  
Author(s):  
Maria Méndez-Cárdenas ◽  
Blanchard Randrianambinina ◽  
Andriatahiana Rabesandratana ◽  
Solofonirina Rasoloharijaona ◽  
Elke Zimmermann
Keyword(s):  
Geographic Variation ◽  
Loud Calls

TENURE RELATED CHANGES IN WILD THOMAS'S LANGURS II: LOUD CALLS

Behaviour ◽  
1999 ◽  
Vol 136 (5) ◽  
pp. 627-650 ◽  
Author(s):  
Peter Assink ◽  
Serge Wich ◽  
Romy Steenbeek
Keyword(s):  
Late Phase ◽  
Calling Behavior ◽  
Mate Competition ◽  
Middle Phase ◽  
Loud Calls ◽  
Loud Call ◽  
Reproductive Male ◽  
Presbytis Thomasi ◽  
Low Strength ◽  
Male Mate

AbstractIn 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.

Familiarity and threat of opponents determine variation in Thomas langur (Presbytis thomasi) male behaviour during between-group encounters

Behaviour ◽  
2007 ◽  
Vol 144 (12) ◽  
pp. 1583-1598 ◽  
Author(s):  
Serge Wich ◽  
Elisabeth Sterck
Keyword(s):  
Intensity Variation ◽  
Loud Calls ◽  
Threat Level ◽  
Focal Male ◽  
Presbytis Thomasi

AbstractDuring between-group encounters in primates, males often defend mates, food or infants against other males. Males, however, show variation in contests between opponents. In other taxa, such variation has been attributed to variation in familiarity with or threat of opponents. Here we present the results of analyses of between-group encounter intensity variation in Thomas langurs while controlling for threat when evaluating familiarity and vice versa. Encounter intensity was measured by the proportion of encounters with chases and the number of loud calls per minute during the encounter given by the focal male. The results indicate that both familiarity and threat influence encounter intensity. Less familiar opponents had more intense encounters and opponents that differed in the threat level to each other also had more intense encounters. Thus, Thomas langur males seem to incorporate information on both the level of threat and familiarity of other males to make a decision on how to react during a between-group encounter.

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