PhD‐theses - Ethologische Gesellschaft

Research Update
THE IMPACT OF SOCIAL RANK AFTER CONFRONTATION WITH CONSPECIFICS ON THE
REPRODUCTIVE COMPETENCE OF MALE DJUNGARIAN HAMSTERS (PHODOPUS SUNGORUS,
PALLAS 1773)
Anna Müller
anna_mueller@gmx.net
Diploma Thesis, Supervisors: Dr. Peter Fritzsche, PD Dr. Dietmar Weinert, Institute of
Biology/Zoology, University of Halle
Dominance is a central feature of agonistic behaviour across a wide range of taxonomic
groups and important in order to occupy new limited territories, resources or to increase the
access to mates within a social group with a hierarchical background. In laboratory analyses,
hamsters seem to be excellent model organisms for studying fundamentally functional and
mechanistic characteristics of aggression processes. Several researchers described high‐
aggressive fights between male Djungarian hamsters (Phodopus sungorus) sometimes
resulting in death of one individual of the encounter pairs. But relatively little is known
about the social behaviour of these animals. Therefore males of Phodopus sungorus were
used in this study to analyse dominance/subordination‐relationships and their possible
impact on fertility and reproductive success. Males were confronted as dyadic encounters in
a neutral arena and in their housing cages to define agonistic and submissive behavioural
patterns as well as to characterize them by means of morphological and physiological
parameters. Furthermore, it was investigated whether females choose males depending on
their social status.
Specific dyadic encounter‐experiments showed that the males were able to form
stable dominance/subordination‐relationships under laboratory conditions and could be
classified into dominant and subordinate individuals by characteristic agonistic and
submissive behavioural patterns. A comparison of dominant, subordinate and singly caged
individuals revealed significant larger and heavier testis and a higher number and density of
sperms in dominant males. Whereas no differences in plasma testosterone could be found,
subordinate males had higher corticosterone levels in their faeces. Finally, females of
P. sungorus in the oestrus phase preferred dominant males compared to the other phases of
the sexual cycle.
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