Examining the role of testosterone in mediating short-term aggressive responses to social stimuli in a lizard
McEvoy, J and While, GM and Jones, SM and Wapstra, E, Examining the role of testosterone in mediating short-term aggressive responses to social stimuli in a lizard, PLoS One, 10, (4) Article e0125015. ISSN 1932-6203 (2015) [Refereed Article]
Hormones have been suggested as a key proximate mechanism that organize and maintain
consistent individual differences in behavioural traits such as aggression. The steroid hormone
testosterone in particular has an important activational role in mediating short-term
aggressive responses to social and environmental stimuli within many vertebrate systems.
We conducted two complementary experiments designed to investigate the activational relationship
between testosterone and aggression in male Egernia whitii, a social lizard species.
First, we investigated whether a conspecific aggressive challenge induced a
testosterone response and second, we artificially manipulated testosterone concentrations
to examine whether this changed aggression levels. We found that at the mean level, plasma
T concentration did not appear to be influenced by an aggression challenge. However,
there was a slight indication that receiving a challenge may influence intra-individual consistency
of plasma T concentrations, with individuals not receiving an aggression challenge
maintaining consistency in their circulating testosterone concentrations, while those individuals
that received a challenge did not. Manipulating circulating testosterone concentrations
had no influence on either mean-level or individual-level aggression. Combined with our
previous work, our study adds increasing evidence that the relationship between testosterone
and aggression is not straightforward, and promotes the investigation of alternative hormonal
pathways and differences in neuro-synthesis and neuroendocrine pathways to
account for species variable testosterone - aggression links.