2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

een conducted to test the function of duets in different species and experimental
evidence suggests that duetting serves a variety of functions. We investigated
duetting in the Crimson-breasted Shrike Laniarius atrococcineus (Malaconotidae).
The focus of our study was on two major functional hypotheses: the joint territorial
defence (Land) and the mate-guarding (Lover) hypothesis. Both hypotheses predict
increased duetting in response to conspecific playback; the critical distinction is in the
relative threat posed by duets and same-sex solo intruders. If duets serve as mateguarding,
signaling of solo same-sex intruders will receive the strongest response,
whereas if territorial defence is the main function, signaling of paired intruders will
receive stronger responses than single intruders. The playback experiments revealed,
that females answered their partner?s song to form duets significantly more often
during female solo playback, suggesting that female duet contributions serve to
guard their males from unpaired females. Males were equally aggressive towards
male solo playback and duet playback, but they produced more solo song during
male solo playback and showed more jamming during duet playback. Solos used in
response to male- solo playback indicate that territorial males may guard their
females from intruding males to prevent them from copulating with their mates.
Males additionally perform territorial defence, mostly through solo song but get
some support from their female who occasionally joins them to perform duets.
Study supported by a grant from the Deutscher Akademischer Austausch Dienst
(DAAD)
�8 Katja Heubel A 704 / 14:15
Bad choosiness? Female competition makes females picky
Author(s): Katja Heubel 1
Affiliation(s): 1 University of Tübingen
Competition among females for access to mating opportunities and its effect on
female mate choice decisions are poorly studied so far. Under natural conditions,
female common gobies (Pomatoschistus microps) often compete for access to mates.
The operational sex ratio is often female-biased and hence availability of nests and
paternal care limited. Female-female competition can be expected to affect female
decisions on mate choice and reproductive effort. With an increasing level of female
competition for access to mates, there is a trade-off between choosing the best male
and missed mating opportunities. I studied the effect of a female-competitive social
environment on female mating decisions for male and nest quality. Female
preferences and mating decisions for male size and nest size were tested either in
presence or absence of competitive females. Surprisingly, females prefer males with
larger nests regardless of the social environment. Preferences for male size, however,
highly depend on the social context.
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