Social behavior/2 ANS 305

My lecture Will discuss two experiments looking at the consequences of social environment on indicators of animal welfare

Social rank Sex ratio Fitness of the offspring Males Females

Costs and benefits of being dominant Dominant males may benefit by siring most (sometimes all) litters or offspring Survival of the offspring of high status individuals is sometimes better than for subordinate offspring Dominant individuals have “privileges” in accessing food (lions; hyenas)

Costs and benefits of being dominant Mate choice is not solely based on dominance Female chimpanzees prefer males who are willing to share food (Tutin, 1979) Large groups may impair the ability of an animal to benefit from their social status Costs of confrontation

Costs and benefits of being dominant Distribution of food (randomly distributed x clumped) may affect the advantage of high social status High ranking females (vervets) were more successful than subordinate females when their food was “clumped” Clumped food is “defensible” Feeder design for domestic (captive) animals

Social rank and sex ratio at birth Pig data conflicting Meikle et al. (1997) Trivers and Willard (1973) Mendl et al. (1997) Local Resource Competition Hypothesis

Offspring reproductive success and social rank Sons of “superior” mothers will, on average, show higher fitness than their daughters Daughters of “inferior” mothers will, on average, show higher fitness than their sons

Our work Mendl, Zanella & Broom, 1992 Broom, Mendl & Zanella, 1996 Zanella et al., 1998 Yuan et al., 1999 Noyes & Zanella (in prep.) Souza & Zanella (in prep.)

Challenges The majority of pregnant sows, in the USA, are kept in gestating crates High levels of unresolved aggressive interactions (Broom, Mendl & Zanella, 1996) Inability to form social groups Piglets are weaned at very young age (2-3 weeks old) Consequences for social behavior ?

Social organization Stall housed sows Group housed sows Divided into three groups: HS= High success in agonistic interactions LS= Low success in agonistic interactions NS= Now success in agonistic interactions

Consequences Stress hormone concentration Productivity Brain size *Higher in the LS sows than HS and NS Productivity *Lowest litter weight in LS sows Brain size **Smallest is NS sows *Mendl, Zanella & Broom, 1992 **Zanella et al., 1996

Housing and agonistic interactions Stalls esf group Escalation of agonistic interactions Broom, Mendl & Zanella, 1996

Housing and agonistic interactions Stalls esf group Intensity of aggressive behavior interactions Broom, Mendl & Zanella, 1996

Housing and agonistic interactions Stalls esf group Outcome of agonistic interactions Broom, Mendl & Zanella, 1996 g

Brain weight and housing

Endogenous “morphine” like substances

Opioids and housing

Opioids and social stress

Challenges.. Maternal deprivation stress, at an early age, may alter social memory in pigs (Yuan et al. 1999)

Agonistic interactions 3 days post-mixing (Yuan et al., 1999) 24 weaned between 9-12 days of age= SEW 23 weaned between 20-23 days of age= CW

Hippocampal function / memory consolidation Glucocorticoid level

Spatial memory in young pigs Piglets (14-20 days of age) were trained to swim in a heated (37oC) pool. We measured mean latency (seconds) taken by individual pigs to reach a submersed platform. Piglets were tested for 12 sessions (6 days) consisting of 5 trials per session (10 minutes of interval between trials). Noyes and Zanella (in prep.)

Spatial memory in young pigs

Silveira de Souza and Zanella (in prep.) Social recognition Piglets were subjected to four sessions (60 seconds) repeated at 10 min of interval. We measured the % of the time that the resident female pig (n=12) spent investigating or interacting with the intruder. Silveira de Souza and Zanella (in prep.)

Social recognition Ten minutes following the fourth exposure a naïve unfamiliar pig was exposed to the resident animal. We measured the % of the time that the resident female pig (n=12) spent investigating or interacting with the unfamiliar intruder.

Social recognition (P<0.01; axb) Silveira de Souza and Zanella (in prep.)