Snake Mating Systems, Behavior, and Evolution: The Revisionary Implications of Recent Findings Rivas, Jesus A., Burghardt, Gordon M. (2005). Snake Mating Systems, Behavior and Evolution: The Revisionary Implications of Recent Findings. Journal of

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Snake Mating Systems, Behavior, and Evolution
The Revisionary Implications of Recent
FindingsRivas, Jesus A., Burghardt, Gordon M.
(2005). Snake Mating Systems, Behavior and
Evolution The Revisionary Implications of Recent
Findings. Journal of Comparative Psychology.
119(4), 447-454.Laura Cain, Taylor Casillas,
Sarah Fukui and Nick OBrienPsychology of Sex
DifferencesOctober 20, 2010
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Difference between Polyandry and Polygyny?

• Polyandry A mating pattern in which a female
  mates with more than one male in a single
  breeding season.
• Polygyny few males monopolize access to many
  females
• Benefit mate with more females, spread genes
• Ex male elephant seals (dominant one gets to
  mate)
• Previous to this study, it was widely believed
  that the primary form of reproduction in snakes
  is polygyny
• Males have upper hand/advantage (sexual
  selection)
• In mating (male-male competition)
• Attractiveness to females (body size,
  morphological behavior, physiological attributes)

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Framework for understanding diversity of mating
systems

• Relies on
• Degree males can monopolize
• Distribution of resources
• Availability of mates
• Thus sexual selection gt for the sex that
  benefits more from increased number of matings
  (more offspring)
• Polygyny for males
• Four types of polygyny that were believed to
  accompany all snakes
• Female defense (mate guarding)
• Hot-spot
• Prolonged male searching
• Explosive mating assemblage

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Initial research on snake mating systems

• Disproportionate Research
• done on one species
• in a specific climate and location- inaccurate
  findings
• Diverse data for comparative findings unavailable
• Poor database/invalid research due to
• Secretive nature of snakes other difficulties
• Contrary to prejudiced info available, polyandry
  has been found to be the primary, if not
  universal form of mating system in snakes, not
  polygyny
• Snakes are the first species in which polyandry
  best describes their mating system

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Findings on snake mating systems

• Contrary to prejudiced info available, Polyandry
  has been found to be the primary, if not
  universal form of mating system in snakes, not
  polygyny
• Snakes are the first animal in which polyandry
  documented
• Evidence males spend more time courting and
  mating
• Choosier (larger more fertile female)
• Less reproductive investment
• Female multiple mating found in all species
  (anaconda not the rare exception anymore)
• Males are smaller than females (would be opposite
  if polygyny)
• Males rarely if ever feed during reproductive
  period
• Suffer higher mortality rate

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Evidence for polyandry in snakes

• Garter snake
• DNA and molecular studies proved several sires in
  the litters of garter snakes
• Even with molecular methods to assess paternity(
  have found that multiple paternity is the norm
  for snakes), the word polyandry was still avoided
• Although this species still recognized as
  polygynous
• Female Green Anaconda
• One female lays in mud or water
• 13 males come over
• Coil around her and attempt to mate
• This mating can last for up to a month
• Males may stay with female until the end of her
  attractive period
• http//www.youtube.com/watch?v7TF7d4jvays

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Female Snakes

• OSR (operational sex ratio) lt11 for most snake
  species
• OSR is the ratio of available females to
  available males
• Female snakes large reproductive investment
• Cant always mate every year
• Leads to male-biased OSR
• potential for females to mate numerous times

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Conclusion

• Snakes are more likely to exhibit polygynandry
  (group mating) or polyandry than polygyny
• Polgynandry is similar to promiscuity
• When looking at their ancestors and sister taxa,
  evidence for polyandry or serial monogamy
• Explains paradoxical behavioral differences
• Ex lack of territoriality or male-based sexual
  size dimorphism