Testosterone and competitive ability in male house mice, Mus musculus: laboratory and field studies

Abstract

Abstract. Testosterone enhances aggression and can facilitate dominance in mammals, but most studies have been conducted on laboratory strains of mice and in simple environments. Unlike previous studies, laboratory and field tests were conducted using wild house mice, Mus musculus, to determine whether males with high, but physiological, testosterone levels (High T) would achieve dominance compared with males with low testosterone levels (Low T). All males were castrated and androgen was replaced with a single injection of testosterone enanthate, a long-acting androgen. At 8 days post-treatment the mean testosterone concentration in High T males was 5 . 1 ng/ml, whereas the level in Low T males was 1 . 3 ng/ml. Contests in the laboratory revealed that High T males achieved dominance over Low T males in the presence of females. In the field, equal numbers of High and Low T males, and a corresponding number of females, were released on three highway islands at densities equivalent to the highest density reported on similar sites. Periodic retrapping produced a capture history for males in each group and differences in survival were analysed using the program SURVIV. High T males had a higher probability of survival than Low T males on one island, but on the other two islands the higher capture rates of High T males were not statistically greater than those for Low T males. Of those that survived to the first trapping episode, the High T males had greater subsequent longevity than Low T males. On all three islands High T males were caught more frequently at feeding stations that were established to enhance food competition. There were no differences among the home range sizes of High T males, Low T males and females. However, on two of the islands the ranges of High T males overlapped more of the ranges of resident females than those of Low T males. The findings from this study, using testosterone-treated subjects, suggest that natural variation in basal testosterone also may affect competitive ability in wild house mice.

Sex disparity in colonic adenomagenesis involves promotion by male hormones, not protection by female hormones

“…The congenic mouse strain carrying the Min allele of Apc on the C57BL/6J genetic background is subject to genetic modifiers arising by spontaneous mutation, either in our laboratory or in the production colony at the Jackson Laboratory (12 To supplement ORX mice with male hormones, we administered i.m. injections of testosterone enanthate 0.5 mg per mouse in a 50-μL volume or vehicle every 2 wk, as described by Zielinski and Vandenbergh (13). Hormone supplementation was initiated on the day of surgery.…”

Behavioral effects of testosterone in relation to social rank in the male rabbit

“…Although testosterone has been associated with dominance and with social activity [Farabollini, 1987], it is often unclear if a difference in testosterone causes the dominant pattern or results from it [Zielinski and Vandenberg, 1993]. In mice, although no relationship was found between dominance and testosterone, subordinate individuals had lower testis and seminal vesicle weights [Selmanoff et al, 1977], whereas intermale aggression was correlated with serum testosterone [Maxson et al, 1983].…”

Olfaction, GABAergic neurotransmission in the olfactory bulb, and intermale aggression in mice: Modulation by steroids

“…Adult pTc has been put forward as a possible physiological intermediate between the Y chromosome and intermale aggression (Schuurman, 1980;van Oortmerssen et al, 1987;Albert et al, 1992;Zielinski and Vandenbergh, 1993). Such an hypothesis needs further evidence as stated by Carlier et al (1990).…”