Social behavior/2

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Social behavior/2

• ANS 305

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My lecture

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

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Social rank

• Sex ratio
• Fitness of the offspring
• Males
• Females

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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)

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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

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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

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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

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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

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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.)

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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 ?

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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

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Consequences

• Stress hormone concentration
• 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
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Housing and agonistic interactions
Stalls esf group

• Escalation of agonistic interactions
• Broom, Mendl Zanella, 1996

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Housing and agonistic interactions
Stalls esf group

• Intensity of aggressive behavior interactions
• Broom, Mendl Zanella, 1996

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Housing and agonistic interactions
Stalls esf group

• Outcome of agonistic interactions
• Broom, Mendl Zanella, 1996

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Brain weight and housing
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Endogenous morphine like substances
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Opioids and housing
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Opioids and social stress
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Challenges..

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

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Agonistic interactions3 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
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(No Transcript)
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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.)

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Spatial memory in young pigs
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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 (n12) spent investigating or
  interacting with the intruder.

• Silveira de Souza and Zanella (in prep.)

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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 (n12) spent investigating or
  interacting with the unfamiliar intruder.

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Social recognition

• (Plt0.01 axb)

Silveira de Souza and Zanella (in prep.)