1. Social behavior/2
ANS 305

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

3. Social rank
Sex ratio
Fitness of the offspring
Males
Females

4. 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)

5. 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

6. 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

7. 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

8. 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

9. 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.)

10. 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 ?

11. 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

12. 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

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

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

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

16. Brain weight and housing

17. Endogenous “morphine” like substances

18. Opioids and housing

19. Opioids and social stress

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

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

22. Hippocampal
function /
memory
consolidation
Glucocorticoid level

23. 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.)

24. Spatial memory in young pigs

25. 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.)

26. 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.

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