• Female mice housed with castrated males have higher stress levels.
• Female mice housed with castrated males actively avoid their housing partner when provided with a refuge.
• We suggest that females actively avoid males with low levels of testosterone, and that their surrounding social partners can affect their physiology.
To read the full paper for free:
To read the full paper go to sci-hub.tw and paste the full url (the doi one I put above) into the search box. I wont link it directly in case it is against rules.
There should be little reproductive cost with being around infertile males - the females have no risk of getting pregnant and the male rats were not acting sexually towards them. But the females still were stressed out by their presence.
The study looked at 3 groups of rats: fertile, totally castrated, and vasectomised. Despite having no way of knowing (unless pheremones come into play?), the female rats were also stressed out by vasectomised male rats with no visible castration.
- They measure 'cost-of-reproduction' to females as amount of stress hormones they experience. Femaels around alphas had low stress, and females around low-rank males had higher stress. Just by observing stress levels of females around you one might be able to observe your perceived rank. Additionally shit tests could be considered a stress-relief mechanism for the female; if you pass then their stress (cortisol) will go down.
One such measure that is used as an indicator of the costs of reproduction, inter alia, is
glucocorticoid (GC) stress hormones. Male mating behaviour has been demonstrated to
increase female GC levels in primates through sexual coercion and aggression (Muller et al.
2007; Thompson et al. 2010) and changes in male rank (Beehner et al. 2005; Carnegie et al.
2011). Non-preferred mates may also induce stress in females. This has been demonstrated in
a bird, the socially monogamous Gouldian finch (Erythrura gouldiae
, where hens paired
-quality cocks had higher levels of circulating corticosterone (Griffith et al. 2011).
While it is well established that GC stress hormones play crucial adaptive roles in fetal
development (Baxter and Rousseau 1979), prolonged high secretion can also have
suppressive effects on female reproductive physiology and behaviour (Tilbrook et al. 2000;
Wingfield and Sapolsky 2003) and increase susceptibility to disease (Sapolsky et al. 2000). Prenatal maternal stress can additionally have long-term consequences for offspring (Lemaire
et al. 2000; Maccari et al. 2003; Yang et al. 2006; Tamashiro et al. 2009).
h/t to https://twitter.com/DegenRolf/status/1170276714406121472
He has the best twitter feed on science of psychology, sex, behaviour, psychopaths, lies/truth, big 5, etc, so give him a follow.