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Animal Behavior: Sexual Cannibalism

Animal Behavior: Sexual Cannibalism. Mediated by: Joe Heston. Introduction. Very rare phenomenon Laboratory settings Predominately: spiders and scorpions Praying mantis Female  male(some rare exceptions). Big Questions. Why do some species utilize sexual cannibalism?

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Animal Behavior: Sexual Cannibalism

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  1. Animal Behavior: Sexual Cannibalism Mediated by: Joe Heston

  2. Introduction • Very rare phenomenon • Laboratory settings • Predominately: spiders and scorpions • Praying mantis • Female  male(some rare exceptions)

  3. Big Questions • Why do some species utilize sexual cannibalism? • Are there advantages? • If so, why don’t more species utilize sexual cannibalism?

  4. overview • Eating before, during, or after copulation • Anthropoids • Current and former research. Langdon et. al. 2010

  5. Quick review • Principles of Allocation • Males: Reproduction Energy Reproduction Metabolism Growth

  6. Mechanism Intuition: • Direct energy: • Better food available • Low in lipids, high in AA • Competition: • Size dimorphism AustrilianRedback Spider

  7. Evolutionary Significance • AnisogamyPolyandryCost of Meiosis • Quantity > Quality • Males: Semelparity • Live for 3-4 months after maturation. • Females: Iteroparity • 2-3 years after maturation • “Self-sacrifice”

  8. Benefits • Increased Fitness • Larger egg sacs • More fertilized egg sacs • Indirect nutrition • Monopolizing female • C+ * Poly= p=0.047 Welke et. Al. 2012

  9. Benefits (cont.) • Prior advantages directly affected offspring • Average survival was higher in +C • Not significant • Outside experiment? Welke et. Al. 2012 Figure 3: Offspring survival time of all four experimental treatments. Box plots show the median (line), quartiles (box limits), and error bars. Welke et. Al. 2012

  10. Benefits (cont.) • Showed statistical significance between C+ and C- Rabaneda-Bueno et. al. 2008

  11. Drawbacks • Death • No copulation if not first male • “Plugs”

  12. Other examples Scorpions • Males cannibalizing females • “Tricking females” • Similar size • Rids species of inferior genes

  13. Current Research • Focuses on spiders • Some on praying mantis/scorpions. • Rare phenomenon • Little research has been done • Mostly superficial • Fieldwork needed • Original idea C. B. Andrade

  14. Conclusion • Involves one sex cannibalizing the other before, during, or after copulation (predominantly female male) • Benefits males by increasing their fitness with more offspring containing half of their genes (cost of meiosis) and could monopolize females • Females gain better survivability for offspring multiple ways. • Males live short term compared to females, spend most of energy on reproduction (semelparity)

  15. Discussion • Any questions? • What prevents other high level organisms from following sexual cannibalism? • Is it truly advantageous for the male spiders to allocate almost all of its energy after maturation to reproduction? or is it at best just a trade off explaining why it is found only in select species? • What ways might promote sexual cannibalism in a lab more than in the field?

  16. References • Andrade. C.B. (2002). Risky mate search and male self-sacrifice in redback spiders. Oxford Journals: Behavioral Ecology. 14(4): pp. 531-538. • Andrade. C.B. (1998). Female hunger can explain variation in cannibalistic behavior despite male sacrifice in redback spiders. Behavioral Ecology. 9:(1). pp 33-42. • Andrade, M. B. (1996). Sexual selection for male sacrifice in the Australian redback spider. Science, 271(5245), 70-72. • Langdon, Q. Thomas, K. (2010) Sexual cannibalism and mating behaviors in mantids. http://academic.reed.edu/biology/professors/srenn/pages/teaching/web_2010/QLKT_Final/phylogeny.html • Persons, H.P., Uetz, G.W. (2005). Sexual cannibalism and mate choice decisions in wolf spiders: influence of male size and secondary sexual characters. Animal Behavior. 69: 83-94. • Rabaneda-Bueno R, Rodríguez-Gironés MÁ, Aguado-de-la-Paz S, Fernández-Montraveta C, De Mas E, et al. (2008) Sexual Cannibalism: High Incidence in a Natural Population with Benefits to Females. PLoS ONE 3(10): e3484. doi:10.1371/journal.pone.0003484 • Welke, K. W., Schneider, J. M. (2012). Sexual cannibalism benefits offspring survival. Animal Behaviour, 83(1), 201-207.

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