Topic 5: Socioecological Models

Clutton-Brock & Janson (2012)

• Many other factors than just food distribution and competition

• Need to include interspecific differences in relationships ebtween females, philopatry, kinship, reproductive strategies, and phylogeny

• Future models should be more holistic

• For individual species, need to collect data ACROSS habitats

Wrangham (1980)

• Hypothesis: females live in kin groups to defend food resources from other groups
• Generally more advantageous to keep same allies as opposed to making opportunistic allyships
• High quality, limited patches of foods => female bonded (FB)
• Low quality, unlimited patches of foods = Non-female bonded (Non FB)
• Presents female bonding as monolithic

van Schaik (1989)

• Hypothesis: females live in groups to avoid predation, while the specific type of relationships within a group depend on food distribution
• Low vulnerability to predators: BGC dominates, females form nepotistic but egailitarian ranking systems with female residence
• High predation risk cohesive groups, WGC dominates through scramble or scramble/contest. If scramble, females have individualistic/egalitarian ranking systems (=varied female bonding), while if scramble and contest, they develop nepotistic and despotic ranking systems (=females do not disperse)
• Scramble competition: seen in folivores and one gregarious insectivore species

Isbell (1991)

• Food abundance predicts intergroup competition, food dispersal predicts intragroup competition
• Food not abundant = more intergroup competition as homeranges expand
• Food clumped = more intragroup competition because food is easier to defend
• Home range will increase with group size if food is limited to access more resources
• Day range will increase with group size if food is clumped because patches depleted faster
• Day range will not get larger with group size if food is dispersed because groups fan out to search for resources and aren't fighting for same clump

Sterck et al. (1997)

• Delineates group types, what causes them, and what behaviors you would expect from these types

• Dispersal egalitarian- F dispersal, limited competition, no linear hierarchy

• Resident egalitarian- F philopatry, intergroup competition, no linear hierarchy

• Resident nepotistic- F philopatry, intragroup competition, linear hierarchy

• Resident nepotistic tolerant- F philopatry, intergroup competition (maybe intragroup too?), linear hierarchy, but tolerant of subordinates

• RNT expected to occur if strong between group competition exists because subordinate females gain little and risk a lot from BGC

• infanticide risk, predation risk, food distribution all contribute to female gregariousness or lack of

• habitat saturation predicts type of competition (intra or inter; scramble or ranked)

• male input - sexual coercion, male policing, male harassment

• talks about carrying capacity - ""social hypercycle"" of non-dispersing females ->input of risks -> nepotism +group size increase causes population to inflate until it is higher than carrying capacity. If it becomes a detriment to kin for a female to stay in a group, they will eventually split (not disperse) along matrilineal lines into two seperate groups.

Isbell & Young (2002)

• Describes models from van Schaik (1989), Wrangham (1980), Isbell (1991), Sterk et al. (1997)
• All main models agree that food distribution/accessibility drives competition (see table)
• Difference in what causes the differences between female philopatry (coalitions with kin for Wrangham and van Schaik, Isbell suggests that female philopatry occurs when dispersal costs outweigh costs of staying
• Coalitions within groups caused by clumped food distribution (Wrangham and van Schaik) or by greater success in usurping food (Isbell)
• Wrangham (1980) splits btwn FB and non-FB, van Schaik splits between types A, B, C, D, Sterck et al. (1997) splits between RN, RNT, DE, and RE, Isbell (1991) splits between contest & scramble between & within groups, contest & scramble between groups only, and no contest & scramble within/between groups

Thierry (2008)

• Sees Wrangham (1980) and van Schaik (1989) as wrong and/or not comprehensive enough
• Is it worthwhile to improve synthetic model by adding more factors? Not all primates react to the same set of ecological conditions.
• No model will work for all primate relationships; there is no ""one size fits all"" model

Koenig & Borries (2009)

• Response to Thierry (2008)
• Argues models should be tested on a clade-by-clade basis instead of throwing out a model entirely to identify phylogenetic constraints
• Ockham's razor warns against complexity, but complexity may increase explanatory power of models