To identify genes that are differentially expressed during territorial aggression in breeding and non-breeding season, bird hypothalami (with pars tuberalis of pituitary) were collected, RNA extracted and labeled-cDNA samples were hybridized to a custom-made cDNA microarray.
"But since then Doberman breeders in America have cleaned up their act through selectively breeding against aggression," he added.
The inaccessibility of the rookeries due to steep, rocky terrain, the peak breeding season aggression and the sheer density of seals on this most densely populated seal rookery [6], together with the presence of the carcasses in pools of water, precluded tissue sample collection or post-mortem analyses.
Accordingly, in a field-based experiment, we tested the influence of phenotypic similarity on aggression, as directed by breeding territory holders towards heterospecific 'intruders' in cichlids living in Nicaraguan Crater Lake Xiloá.
It featured a segment about a long-running experiment in Siberia breeding hostility out of foxes in one group, and hyper-aggression into another.
During each observation trial we counted i) instances of intraspecific aggression, including both fights and aggressive displays, and ii) breeding attempts and copulations.
Young pups will act aggressively to one another; whilst breeding females may show similar aggression to males.
Non-aggressive dogs were selected for low estimated breeding values for both human- and dog-directed aggression.
In animals that compete for breeding resources, this could lead to increased aggression as individuals age (Kemp 2006).
The zoo community is becoming increasingly interested in this discussion, especially when faced with reproductive failure of breeding pairs due to mate incompatibility or aggression which can lead to injury or death (Wielebnowski et al. 2002).
