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Behavioral Ecology Vol. 14 No. 4: 531538 Risky mate search and male self-sacrifice in

Summary: Behavioral Ecology Vol. 14 No. 4: 531538
Risky mate search and male self-sacrifice in
redback spiders
Maydianne C. B. Andrade
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
Male redback spiders twist their abdomens onto the fangs of their mates during copulation and, if cannibalized (65% of
matings), increase their paternity relative to males that are not cannibalized. The adaptive male sacrifice hypothesis proposes that
this increased reproductive payoff from a single mating outweighs the residual reproductive value of a cannibalized male,
because high mortality during mate searching restricts alternative mating opportunities. It has been reported that redback male
residual reproductive value is low because males are functionally sterile after one mating--a putative intrinsic constraint that
could arguably favor self-sacrifice in the absence of ecological restrictions on multiple mating. However, sterility and self-sacrifice
may both arise as aspects of a terminal investment strategy if the probability of multiple mating is sufficiently low. Here I report
field data that support the adaptive male sacrifice hypothesis. More than 80% of redback males die without finding a potential
mate in nature. Data from two observational field studies and one release experiment suggest that in the absence of cannibalism,
male redbacks would expect fewer than one mating opportunity in a lifetime. This expectation was not significantly higher for
a large male or one in good condition. A simple quantitative analysis confirms that even if males are assumed to be fertile
throughout life, the measured mortality rate during mate search in combination with previously documented paternity benefits
of cannibalism is sufficient to ensure that self-sacrifice is adaptive for male redback spiders. Key words: constraint, Latrodectus, mate
searching, redback, self-sacrifice, sexual cannibalism, spider. [Behav Ecol 14:531538 (2003)]
Male redback spiders (Latrodectus hasselti) ``somersault''


Source: Andrade, Maydianne C.B. - Department of Biological Sciences, University of Toronto at Scarborough


Collections: Environmental Sciences and Ecology; Biology and Medicine