Jenn Smith, Ph.D. Candidate in Dept. of Zoology Black-backed jackals Giraffe Naked mole rats Solitary Asocial Obligately gregarious

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1 Social and Ecological Determinants of Fission-fusion Sociality in the Spotted Hyena Jenn Smith, Ph.D. Candidate in Dept. of Zoology studying social behavior of spotted hyenas Jennifer E. Smith, Department of Zoology Program in Ecology, Evolutionary Biology, and Behavior Website: Continuum of sociality Continuum of mammalian sociality Solitary Alone except when breeding Black-backed jackals Giraffe Naked mole rats Pairs (& their extended families) Stable groups, members spend much time alone or in small subgroups Asocial Eusocial Obligately gregarious Individuals in cohesive groups unable to survive on their own Aye Ayes African elephants

2 Most carnivores are solitary 69 out of 27 species of carnivores gregarious 2/37 3/4 4/31 CARNIVORE PHYLOGENY /35 34/36 Beckoff et al Arnason et al. 22 3/65 2/19 /9 8/8 5/5 1/1 7/2 65 (94%) species of gregarious carnivores live in fission-fusion societies Fission-fusion societies Alone except when breeding Pairs (& their extended families) Stable groups, members spend much time alone or in small subgroups Fission-fusion societies in terrestrial carnivores 1) Group members know each other as individuals 2) Group members share a common territory 3) Group members rarely, if ever, occur together concurrently; _ Subgroup sizes and compositions variable 4) Individuals separate regularly, engage in reunion displays Individuals in cohesive groups unable to survive on their own

3 Clans are fission-fusion societies 1) Spotted hyenas live in large, stable social groups called clans Clans contain multiple matrilines (adult females and their offspring) Clans contain multiple matrilines and immigrant males

4 Adult females dominant to immigrant males Loser of fights Clans are fission-fusion societies 2) Each clan defends a common, group territory Winner of fights MRPH SEIN WHO MP NAV BAIL MIG BP BOS MRPH SEIN WHO MP NAV BAIL MIG BP -- 3 BOS -- Talek Clan (62km 2 ) Breeding females Immigrant males Clan members share a communal den where young are socialized Maintain territory boundaries during border patrols

5 Cooperatively defend territory during clan wars against neighboring clans Cooperatively defend food from lions Lion=13-26 kg Hyena=45-86 kg Clans are fission-fusion societies 3) Individuals occur in subgroups of variable size and composition Clans are fission-fusion societies 4) Often alone and engage in displays during subgroup reunions Greeting ceremony Subgroup size = 1 Subgroup size = 2 Subgroup size = 6 Subgroup size = 18

6 Fission-fusion sociality in spotted hyenas 1) Describe fission-fusion sociality in this species 2) Evaluate circumstances promoting subgroups of various sizes to form Behavioral data collection Long-term study (1988-present) Masai Mara Reserve, Kenya 3) Test hypotheses suggesting factors limiting subgroup size Data collection methods: 1) Observation sessions 2) Long-term focal surveys Long-term focal animal surveys for a total of 24 hrs (N =11 females, 9 males) Fission-fusion sociality in spotted hyenas 1) Describe fission-fusion sociality in this species a) Over the course of the day b) Frequency of subgroup sizes c) As a function of life history stage and social rank Focal adult

7 Subgroup size changed many times within a day Measures of fluidity from long-term follows Subgroup size Changes in subgroup size: 26 ± 3/day % of clan met/hour: 5.1 ±.6 Clan size: NIGHT NIGHT Mean values Fission-fusion sociality in spotted hyenas Mara hyenas Subgroup size = 4 Subgroup duration = 56 min % time spent alone=29% Tai chimpanzees* Subgroup size = 6 Subgroup duration = 25 min % time spent alone=18% 1) Describe fission-fusion sociality in this species a) Over the course of the day b) Frequency of subgroup sizes c) As a function of life history stage and social rank (* data obtained or extrapolated from Lehmann et al 24)

8 Members of the Talek clan were seen alone or in subgroups of various sizes % of observations declined with increasing subgroup size Mean subgroup size: 3.7 Clan size: mean = 57 ± 3 (range: 39-74) N = 34,85 sessions Clan size: mean = 57 ± 3 (range: 39-74) N = 34,85 sessions Fission-fusion sociality in spotted hyenas 1) Describe fission-fusion sociality in this species a) Over the course of the day b) Frequency of subgroup sizes c) As a function of life history stage and social rank Life history of the spotted hyena Reproduction (females) Natal den Communal den Weaning (~13-14 mo) Puberty (~24 mo) Join a new clan (males)

9 Tendency to be alone increased as function of life history stage Low-ranking hyenas spent more time alone than did high-ranking ones % of observations alone Females Males A A,B A A,C D D E E E 84 F 74 % of Observations alone Adult females Immigrant males F=1 M= Natal den Communal den Den independent but nursing Weaned but pre-reproductive Reproductively mature Social rank Kruskal-Wallis Test Statistic = 422.5, 8 d.f., P <.1 Females: R s =.77, N=24 ranks, Males: R s =.85, N=18 ranks P <.1 for both Fission-fusion sociality in spotted hyenas Assigned each session to a single context 1) Describe fission-fusion sociality in this species 2) Evaluate circumstances promoting subgroups of various sizes to form Hunting Natal den Mating Mating Communal den Kills Border patrols Communal den Conflicts with lions Clan wars

10 Subgroup size varied by context G F, G 14 F 12 E 1 D 8 6 C 4 B B A Subgroup size % of observations with conspecifics Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Kruskal-Wallis H 8,34847 = , P <.1 Subgroup size varied by context Subgroup size % of observations with conspecifics G F, G F E D C A B B Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Typical kill scene: Predator (6kg) vs. Prey (18kg) Kruskal-Wallis H 8,34847 = , P <.1 Subgroup size varied by context Subgroup size % of observations with conspecifics G F, G F E D C A B B Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Kruskal-Wallis H 8,34847 = , P <.1

11 Subgroup size varied by context G F, G 14 F 12 E 1 D 8 6 C 4 B B A Subgroup size % of observations with conspecifics Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Kruskal-Wallis H 8,34847 = , P <.1 Subgroup size varied by context Subgroup size % of observations with conspecifics G F, G F E D C A B B Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Subgroup size varied by context Kruskal-Wallis H 8,34847 = , P <.1 Subgroup size % of observations with conspecifics G F, G F E D C B B A Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Kruskal-Wallis H 8,34847 = , P <.1 Subgroup size varied by context Subgroup size % of observations with conspecifics G F, G F E D C A B B Hunting Natal den Other (baseline) Courtship/mating Communal den Kills Border patrols Conflicts with lions Clan wars Kruskal-Wallis H 8,34847 = , P <.1

12 Fission-fusion sociality in spotted hyenas Ecological constraints hypothesis (Chapman 199) 1) Describe fission-fusion sociality in this species 2) Evaluate circumstances promoting subgroups of various sizes to form Competition for limited resources constrains gregariousness 3) Test hypotheses suggesting factors limiting subgroup size a) Ecological constraints hypothesis b) Infant safety hypothesis c) Dispersive conflict resolution hypothesis Ecological constraints hypothesis Intense within-group competition over rich food resources that are ephemeral and usurpable Ecological constraints hypothesis If feeding competition limits gregariousness, then: 1) Feeding success should decline with subgroup size and low-ranking animals should suffer most from this decline

13 Energy gain (kj/female/day) Energy gain decreases as the number of hyenas at kills increases 24, 2, 16, 12, 8, 4, Number of adult females (present in subgroup) % of scans a focal female fed Social rank determines feeding success Absolute social rank (in the clan) % of scans a focal female fed Relative social rank (in current subgroup) R s = -.6, N = 24 rank positions, P =.2 R s = -.7, N = 14 relative ranks, P =.6 R s = -.71, P <.1 Ecological constraints hypothesis If feeding competition limits gregariousness, then: 2) Individuals should congregate at food sources in numbers proportional to patch richness Thomson s gazelle Impala (53 kg) Topi (119 kg) Wildebeest (132 kg) Zebra (235 kg) Giraffe (935 kg) Elephant (3,55 kg) (25 kg) Increasing patch richness (Kingdon 1997, Oindo 22)

14 Subgroup size Subgroup Numbers size of increases hyenas at with kill scenes prey size proportional to the prey size 2 18 Elephant 16 Giraffe 14 Zebra 12 Topi 1 Wildebeest Impala 8 Gazelle 6 Scraps Prey mass in kg (log) Ecological constraints hypothesis If feeding competition limits gregariousness, then: 3) Individuals should spend more time with conspecifics when prey are superabundant Annual migration: June-Sept. R s =.98, N = 8 prey types, P <.1 Biweekly prey census Hyenas most gregarious during months of superabundant prey Prey abundance Month % of observations with Counted all prey 1 m of two 4-km transect lines Mann-Whitney U = , P <.1 N = 122 low and 6 high prey months

15 Fission-fusion sociality in spotted hyenas Infant safety hypothesis (Packer et. 199, Otali & Gilchrist, 26) 1) Describe fission-fusion sociality in this species 2) Evaluate circumstances promoting subgroups of various sizes to form Females living in FF societies might avoid group members to reduce the risk of infanticide 3) Test hypotheses suggesting factors limiting subgroup size a) Ecological constraints hypothesis b) Infant safety hypothesis c) Dispersive conflict resolution hypothesis Infant safety hypothesis Infanticide occurs in hyenas Infant safety hypothesis If the risk of infanticide limits gregariousness, then: 1) Females should spend the most time away from conspecifics when she is close to parturition (Kruuk, 1972; East & Hofer, 22; White, 25)

16 % of Observations alone Females close to parturition spend the most time away from conspecifics A B C D A, B Infant safety hypothesis If the risk of infanticide limits gregariousness, then: 2) Mothers should be seen most often with offspring during the most vulnerable life history stages 15 1 Pregnancy 1 Pregnancy 2 Pregnancy 3 Early lactation Late lactation Reproductive state Friedman ANOVA, F 4,38 = 66.4, P <.1 Mothers spend the most time with their offspring when offspring are early in their life history % of observations with mother A 27 B 197 C 136 D 163 E 111 Fission-fusion sociality in spotted hyenas 1) Describe fission-fusion sociality in this species 2) Evaluate circumstances promoting subgroups of various sizes to form 3) Test hypotheses suggesting factors limiting subgroup size a) Ecological constraints hypothesis b) Infant safety hypothesis c) Dispersive conflict resolution hypothesis Natal Den Communal Den Den Independent but nursing Weaned but pre-reproductive Reproductively mature Kruskall-Wallis, H 4,633 = 237.3, 4 d.f., P <.1

17 Dispersive conflict resolution hypothesis (Schino, 2) Might help hyenas avoid the costs associated with aggression Conclusions Fission-fusion societies of spotted hyenas are highly flexible Between group competition: is a cohesive force, promoting large subgroup sizes to form Within group competition: is a disruptive force, promoting the tendency for hyenas to be alone Acknowledgements For cooperation: Kenya Wildlife Service, Office of the President of Kenya, Narok County Council, & the Senior Warden of the Masai Mara National Reserve, Kenya Assistance in the field: L. Smale, N.E. Berry, E.E. Boydston, S.M. Cooper, S.M. Dloniak, M. Durham, A.L. Engh, J. Friedman, P. Garrett, I. Graham, T.H. Harty, C. I. Katona, K. Nelson, G. Ording, M. Szykman, J.B. Tanner, K. Theis, W. Troullioud, H.E. Watts, K. Weibel, S.A. Wahaj, and B. White. Guidance committee: Drs. Laura Smale, Tom Getty, & Andrew McAdam Funding sources: NSF Grants to K.E.H. International P.E.O. Scholar Award and Fellowships from the Zoology Dept., EEBB Program, and Graduate School at Michigan State University to J.E.S. RESEARCH PROGRAM Publications Data analysis Completion of My Dissertation (Spring 29) TEACHING PROGRAM Educating Undergraduates Professional Meetings Community Outreach

18 Number of companions Spotted hyenas often alone Female baboon Female spotted hyena Holekamp et al. 2 But energy gain increases with pack size in wild dogs living in cohesive groups Spotted hyenas hunt by coursing Energy gain (kj/female/day) 12, 11, 1, 9, 8, 7, 6, 5, 4, 3, 2, 1, (Creel 1997) Number of adult females

19 Number of males observed with females increases as females approach estrus Maternal rank inheritance Youngest ascendancy Murphy....1 Athena Seinfeld...3 Whoopie..4 Szykman et al. 21 Maternal rank inheritance Youngest ascendancy Murphy...1 Artemis Athena...3 Seinfeld.. 4 Whoopie.5