ANT 154BN-08 Competition

ANT 154BN-08 Competition - ANT 154B Lecture #8: Competition...

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Unformatted text preview: ANT 154B Lecture #8: Competition 27 January 2011 Thursday, January 27, 2011 1 Ecology of grouping Thursday, January 27, 2011 2 Basic socio-ecology Ecological pressures Female counterstrategies? Female distribution and sociality Male strategies No Group size, Social system Yes Wrangham 1982 Thursday, January 27, 2011 3 Factors thought to affect group size generally GS generally GS contest feeding competition (between groups) scramble feeding competition (within groups) predation infanticide disease parasites Thursday, January 27, 2011 4 Factors affecting group size vs. those affecting population density Population density Population density Gibbons Leaf monkeys Marshall 2010 Thursday, January 27, 2011 5 Feeding competition 1. Types of feeding competition 2. Effects of competitive regimes 3. Overview of infanticide Thursday, January 27, 2011 6 Feeding competition >1. Types of feeding competition 2. Effects of competitive regimes 3. Overview of infanticide Thursday, January 27, 2011 7 What sort of competition? Resource “patchiness” Food-ranges too big to defend Day-journey Annual range Resources defensible? Food-ranges economically defensible o N Ye s Scramble Wildebeest ignore each other Thursday, January 27, 2011 Contest Gibbons defend territories 8 Limited resources -> Competition Contest Resource distribution Resources defensible Fights/threats? Win by... Winners Losers Thursday, January 27, 2011 Scramble Equal No No Efficiency None All 9 Unequal Yes Yes Dominance Territory holders/ dominants Floaters/subordinates Competitive regimes WGS = Within-group scramble WGC = Within-group contest BGC = Between-group contest (BGS = Between-group scramble) Thursday, January 27, 2011 10 Feeding competition 1. Types of feeding competition >2. Effects of competitive regimes 3. Overview of infanticide Thursday, January 27, 2011 11 Effects of food competition Type of competition Within-group scramble Between-group contest Within-group contest Effects costs of grouping benefits of grouping benefits of coalitions Strong effects on grouping and social relationships Thursday, January 27, 2011 12 Within-group scramble costs of group living Thursday, January 27, 2011 13 Logic: individuals in larger groups must travel further to fulfill daily caloric requirements Thursday, January 27, 2011 14 Logic: individuals in larger groups must travel further to fulfill daily caloric requirements Thursday, January 27, 2011 15 Logic: individuals in larger groups must travel further to fulfill daily caloric requirements Thursday, January 27, 2011 16 Logic: individuals in larger groups must travel further to fulfill daily caloric requirements # food patches visited per day group size Thursday, January 27, 2011 17 Scramble competition (a cost of grouping) day range group size Thursday, January 27, 2011 18 Cost-of-grouping varies among species 2000 Day-range Gray-cheeked mangabey 1000 Red colobus 0 0 20 40 60 Group size Mean Group Size Thursday, January 27, 2011 19 RRC: an index of scramble competition Janson and Goldsmith • Predicting group size in primates Bigger groups -> longer day-range 2200 -i Day range (m) y/x = S (slope) S/H = R solitary H = day range ofRC 10 15 20 Group size Group size Figure 1 Calculation of the relative ranging cost (RRC). The slope of the regression re t dai y a engt o p e, s Janson & Goldsmithlahing groluppsitzh l1, fromicgroueasizres4thie dixpdcdedy (1995), data H,hwth mangabeys e vi eet b the path lengt at e h m su foraging effor Thursday, January 27, 2011 t of a solitary individual. Thus, RRC measures the increased ranging cost of an additional group member, scaled reached at smaller group sizes than in those with Until now, nobody has attempted to use within-pop gression parameters of ranging to explain primate g despite some efforts to relate other population-sp logic st to aspects y/xal=coSs (slope) of social structure across pr cies (Isbell, 1991; Mitani and Rodman, 1979; Wr al., 1993). Our goal is to discover how much of th in mean group size between primate populations tributed to variation in this simple within-populatio of die costs of increased ranging (RRC). Of course, many odier factors are likely to affect besides food competition as reflected in increased lengths. First, previous results comparing ranging p fruit- versus leaf-eating primates (Clutton-Brock an 1977; Isbell, 1991) have shown that increases in fora with group biomass are far less evident across leafcies dian across fruit-eating ones. Thus, we though tant examine wheth animalto(intercept)er our measure of food co could predict group size in both diet types. Secon group size is a balance between social net foraging individual predation risk (e.g., Dunbar, 1988; Ter Janson, 1986; van Schaik, 1983), dien group size ma in relation to factors that influence predation lev mates after accounting for the influence of foragin tition. To obtain a more complete understanding terminants of primate group size, we include both *Relative Ranging restria possible correlated of predation risk (terCost lity: C Cardan, 1966; body size: Cheney and Wrangham, 1 with RRC as predictors of primate group siz20in an e analysis. Our results strongly support the importan S = RRC * H Mean group size Folivores Frugivores RRC (Relative Ranging Cost) Janson & Goldsmith (1995) Thursday, January 27, 2011 21 Scramble competition in folivores small group large group Mean day range (m) Food tree density (trees/ha) Red colobus, Gillespie & Chapman 2001 Thursday, January 27, 2011 22 Intake Rate (bites/min) ges in (a) intake in) and (b) ates (m/3 min) of (Piliocolobus ) in Kibale National a. ∗ indicates a significant etween start and end Intake more details) Food for folivores is limited? start 20 15 10 5 0 ll Patches* all Apatches* Young eaves* young Lleaves* end start end rate (bites/min) Mature Leav matureesleaves Movement Rate (m/3 min) 2 1. 5 1 0. 5 0 Movement rate (m/3min) all patches* 0, paired t=−4.01, p<0.0001; mature leaves in=16, start rate x=9.99 end rate x=10.31, paired Red colobus monkeys, Kibale, Uganda p=0.23; mature leaves movement rate: n=14, Thursday, January 27, 2011 =0.30 end rate x=0.19, paired t=0.61, p=0.55; All Patches* young leaves* mature leaves Young Leaves* Mature Leaves costs than smaller groups. These results suggest that red colobus do experience within-group scramble naith & Chapman 2005 S competition, and that this type of competition may be an important fac23 tor determining group size. Further studies are required to Food for folivores is limited? Red leaf monkeys, Gunung Palung, Indonesia Thursday, January 27, 2011 Marshall, Boyko, Feilen, Boyko, & Leighton 2009 AJPA 24 Between-group contest benefits of grouping Thursday, January 27, 2011 25 When food in large clumps, BGC may become important Wrangham 1980 Thursday, January 27, 2011 26 “Intergroup Competition” Model Food distribution Small high quality clumps or uniform distribution Discrete, large high quality clumps Groups as coalitions against other groups No coalitions against other groups larger groups Thursday, January 27, 2011 smaller groups Wrangham 1980 27 Coalitions pay Kin are reliable partners Zero-sum game Kin-bias in alliances Philopatry in sex deriving most benefit from coalitions Thursday, January 27, 2011 28 “Intergroup Competition” Model Food distribution Small high quality clumps or uniform distribution Discrete, large high quality clumps Groups as coalitions against other groups No coalitions against other groups Female kin groups (female philopatry) No kin groups (female transfer) larger groups Thursday, January 27, 2011 smaller groups Wrangham 1980 29 Crofoot et al. 2008 Thursday, January 27, 2011 30 Large groups more successful in inter-group encounters +8 Probability of winning +5 -8 +2 0 -2 -4 Distance from home range center Capuchin monkeys, BCI Thursday, January 27, 2011 Crofoot et al. 2008 31 High ranking groups have higher quality home ranges Core area food quantity and quality index Group rank Black & white colobus, Kibale, Uganda Thursday, January 27, 2011 Harris 2006 32 Within-group contest benefits of coalitions Thursday, January 27, 2011 33 ii Squirrel monkeys (Saimiri spp.) S. oerstedii S. sciureus S. boliviensis Thursday, January 27, 2011 34 Saimiri body size oesrstedii FF BS: < 600 g MM BS: 750 g sciureus FF BS: 635 g MM BS: 740 g sciureus FF BS: 750 g MM BS: 990 g Thursday, January 27, 2011 35 Generalized Saimiri features (A) Feeding Prefer soft fruits Also consume arthropods / small vertebrates (B) Flexible groups Groups coalesce Sexes partly separate (FF-groups; MM-groups) Thursday, January 27, 2011 36 Generalized Saimiri features (C) Susceptibility and adaptation to predation Conspicuous foragers (15-75 / group) ~1 raptor attack / group / week Anti predator behaviors Mothers & young huddle, mob Form frequent poly-specific associations (e.g., with Cebus) Births synchronized within groups Thursday, January 27, 2011 37 Highly variable Saimiri features: female bonding and aggression Bolivian squirrel monkey, Peru Red-backed squirrel monkey, Costa Rica Saimiri boliviensis Aggression/hr (female) FF coalitions 0.29 Saimiri oerstedi 0.004 Common No Philopatry Female Mostly male Thursday, January 27, 2011 38 Bolivian squirrel monkey, Peru Red-backed squirrel monkey, Costa Rica Saimiri boliviensis Saimiri oerstedi Small patches with few fruits Large patches with many fruits Thursday, January 27, 2011 39 Troop-living primates: why females stay with kin Within-group coalitions pay (over food or safety) + Resident – Nepotistic – Dispersal – Egalitarian Bolivian squirrel monkey, Peru Red-backed squirrel monkey, Costa Rica Saimiri boliviensis Large fruit trees Frequent female aggression (70 x S. o.) Thursday, January 27, 2011 Saimiri oerstedi Small trees, tiny fruit crops Rare aggression 40 Saimiri sciureus (common squirrel monkey) in Suriname Saimiri boliviensis Aggression/hr (female) FF coalitions Philopatry 0.29 Saimiri oerstedi 0.004 Saimiri sciureus > 0.33 Common No Rare? Female Mostly male neither? Intense aggression, but no FF coalitions! Thursday, January 27, 2011 41 Bolivian squirrel monkey, Peru Saimiri boliviensis Red-backed squirrel monkey, Costa Rica Common squirrel monkey, Suriname Saimiri oerstedi Saimiri sciureus Small patches with few fruits Large patches with many fruits Small patches with very high density of fruits Intense WGC -> individualistic competition Thursday, January 27, 2011 42 feeding time. The crown diameter distribution of the effective fruit patches harvested by S. sciureus (<5 m, N D 289; 5-10 m, N D 343; 10-15 m, N D 333; 15-20 m, N D 201; 20-25 m, N D 7; >25, N D 0) was relatively homogeneous theRed-backed squirrel ￿ virtually all Bolivian squirrel across(93%)rst 4 categories. However, were in the the effective fruit patch sizes harvested by S. sciureus monkey,ofCosta Rica spent Common squirrel smallest size category monkey, Peru (<5 m). The percentage time each species harvesting fruit in each effective patch size category is depicted in Fig. 2. monkey, Suriname The distribution of effective fruit patch sizes frequented by S. boliviensis is signi￿cantly different from both S. oerstedii (Kolmorgorov-Smirnov D D Small patches with :620, p < 0:001) and 0patches withS. sciureus (D D 0:685, p < 0:001). Saimiri sciureus Large and S. oerstedii are also signi￿cantly different (D D 0:158, p < 0:001). few fruits many fruitsfruit resources for S. sciureus are markedly clumped withinSmall patches with The primary a tree crown. Frequently, a distinct raceme or panicle of fruits ripen at the very high density Saimiri boliviensis Saimiri oerstedi Saimiri sciureus of fruits Fig. 2. The estimates of time allocation by squirrel monkeys across distributions of effective fruit patch sizes at the three study sites. Thursday, January 27, 2011 43 Take home messages 1. Basic socio-ecological model: resources (food) determines female distribution, males map on to females. Other ecological factors (e.g., predation, disease) and male strategies (e.g., infanticide) also probably have important influences on group size and social system. 2. The distribution and defensibility of resources importantly influence competitive regimes (i.e., scramble vs contest). 3. All other things being equal, WGS tends to limit group size, BGC tends to increase GS, and WGC increases the benefits of coalitions. Thursday, January 27, 2011 44 Question to ponder In this and previous lectures, you have learned about relationships among diet, body size, and group size; and about how the nature and distribution of resources can influence competitive regimes and dominance behavior. Based on these general relationships, answer the following question. For the purposes of this question, you may assume that territoriality is solely related to defense of food (e.g., not females). Thursday, January 27, 2011 45 Question to ponder If you have no information other than body size for two species, the Micromono (1 kg) and the Macrosimian (50 kg), make predictions about each of the two species’ diet, group size, degree of territoriality, dispersal regime (which sex is philopatric), and dominance behavior. Be sure to briefly explain the logic behind each prediction. Thursday, January 27, 2011 46 Infanticide 1. Types of feeding competition 2. Effects of competitive regimes >3. Overview of infanticide Thursday, January 27, 2011 47 Beware the naturalistic fallacy! nature ≠ good is ≠ ought Thursday, January 27, 2011 48 Infanticide: the big picture Widespread (mammals: mostly carnivores, rodents, and primates) Can be a strong force Thursday, January 27, 2011 49 Infanticide: the big picture First major blow to concept of primate group solidarity (1970’s, Hrdy) Strongly resisted at first aberrant? birth control? Not “good for the group” Resisted by parents Reduces “group RS” Can lead to group “destruction” Thursday, January 27, 2011 50 Infanticide A. Occurrence Rarely seen directly (quick, rare) Observed: ~60; suspected: 2-300 (~40 spp) B. Typical patterns 100%: infants killed are suckling 91%: by immigrant or non-group males 75%: killer mates mother after infanticide 45-70%: occur in 1-M groups Thursday, January 27, 2011 51 Langurs: the classic case Multi-female 1-M or multi-MM MM emigrate --> AMG or new group Killer: immigrant Killing: deliberate Immigrating M: danger for infant Thursday, January 27, 2011 52 Most infanticide occurs soon after group take-over langurs; Borries & Koenig 2000 Thursday, January 27, 2011 53 Youngest infants most at risk Hanuman langurs red howlers Thursday, January 27, 2011 54 Infanticide distribution Bartlett et al. 1993 Thursday, January 27, 2011 55 Some estimated infanticide rates # attacks % successful % total inf. mortality Red howlers Blue monkey Gorilla 164 50 50 17 71 47 38 37 Thursday, January 27, 2011 56 Infanticide More on infanticide next time... Thursday, January 27, 2011 57 ...
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