Patterns of aggression in spider monkeys at runaway creek nature reserve, Belize

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PATTERNS OF AGGRESSION IN SPIDER MONKEYS AT RUNAWAY CREEK NATURE RESERVE, BELIZE Kayla Hartwell 1 , Hugh Notman 1,2 , & Mary Pavelka 1 1 University of Calgary and 2 Athabasca University, Alberta, Canada

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Patterns of aggression in spider monkeys at runaway creek nature reserve, Belize. Kayla Hartwell 1 , Hugh Notman 1,2 , & Mary Pavelka 1. 1 University of Calgary and 2 Athabasca University, Alberta, Canada. Female-Directed Aggression. - PowerPoint PPT Presentation

Transcript of Patterns of aggression in spider monkeys at runaway creek nature reserve, Belize

Page 1: Patterns of aggression in spider monkeys at runaway creek nature reserve, Belize

PATTERNS OF AGGRESSION IN SPIDER MONKEYS AT RUNAWAY

CREEK NATURE RESERVE, BELIZE

Kayla Hartwell1, Hugh Notman1,2, & Mary Pavelka1

1University of Calgary and 2Athabasca University, Alberta, Canada

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Female-Directed Aggression Described in a number

of studies (Campbell 2003; Link et al. 2009; Slater et al. 2009)

Low intensity intra-group aggression directed from males to females

“Stereotyped displays and chases” (Link et al. 2009)

Photo: Kayley Evans

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Sexual Segregation

Page 4: Patterns of aggression in spider monkeys at runaway creek nature reserve, Belize

Quantifying Sexual Segregation

Sexual Segregation and Aggregation Statistic (SSAS) (Bonenfant et al. 2007)

Association = presence in the same subgroup using 30min subgroup scan data

Distinguishes active segregation and aggregation from random association

Calculates index value ranging from 0 (significant aggregation) to 1 (significant segregation)

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Monthly variation in sexual segregation in spider monkeys in

2009

1

Jan Mar May Jul Sep Nov

0.5

0

SSA

S

Month

(Segregation)

(Aggregation)

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Objectives 1. Compare rates of

aggression by Males to females Males to males Females to males Females to females

2. Compare the contexts in which these aggressive interactions occurred

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Runaway Creek Nature Reserve

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Study Group

34 - 38 group members over course of study 2008-2011

All individuals habituated and individually recognizable

Year Male Females

Adult Subadult Adult Subadult2008 3 2 11 32009 3 2 12 22010 5 2 12 42011 5 3 13 2

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Data Collection Collect scan & focal

data All observations of

fission-fusion events & aggression

For aggression: ID of director(s) & receiver(s) & context

~2000 contact hours over 601 days

193 aggressive interactions

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Contexts of Aggression Food: receiver was feeding when

aggression occurred Fusion: subgroup fusion occurred

within 5min of aggression (food took precedence over fusion)

Sexual: copulation, place sniff, genital inspect occurred immediately following aggression

Other: any other context

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Results

80% M-F (N=154)15% F-F (N=30)3% F-M (N=5)2% M-M (N=4)

80%

2%

3% 16%

Proportion of aggressive interactions

M-FM-MF-MF-F

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Context of Aggression Context of aggression

differed between M-F & F-F (X2= 12 df=3 P=.007)

M-F occurred most often during subgroup fusions (38%) or feeding (31%)

F-F occurred most often during feeding (41%) or other (45%)

Food Fusion Sexual Other0%

10%

20%

30%

40%

50%

Context of Ag-gression

M-F F-F

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FroFalso

Fngus

Fugly

Ficus

Fanta

Frugv

Frckls

FranjFury

FigFlameFlirt

Flora

Flowr

Forgt

Faita

Ferde

Fryjk

Forst

FlipFrog Fidle

0.050.470.89

FroFalso

Fngus

Fugly

Ficus

Fanta

Frugv

Frckls

FranjFury

FigFlameFlirt

Flora

Flowr

Forgt

Faita

Ferde

Fryjk

Forst

FlipFrog Fidle

0.050.470.89

Sociogram of asymmetric matrix of dyadic aggression rates

(arrow points from director to receiver)

Males

Females

Aggression rate/hour

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Conclusions Patterns of female-

directed aggression at Runaway Creek are consistent with that found at other Ateles sites

Results support Link et al. 2009: M-F aggression is a form of social control (indirect sexual coercion)

May encourage sexual segregation as females try to avoid attacks from males

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Acknowledgments Brittany Dean, Kayley

Evans, & Jane Champion

Stevan Reneau, Gilroy Welch, & Birds Without Borders

Dr. Tak Fung Natural Sciences and

Engineering Research Council of Canada, University of Calgary, & National Geographic

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XY = total number of males and females sampledk = total number of subgroups sampledi = selected subgroupNi = subgroup sizeXiYi = number of males and females is a subgroup

𝑆𝑆𝐴𝑆=1− 𝑁𝑋𝑌 ∑

𝑖=1

𝑘 𝑋 𝑖𝑌 𝑖

𝑁 𝑖