Table 2.

Influence of mating plug mass on the number of sperm from the plug-producing males that reach the uterus

Factor	Χ12	P
Focal male sperm no. in uterus
Mating role (first or second to mate)	4.10	<0.04*
Focal male mating plug mass (when only plug)	15.96	<0.001***
Cauda sperm count	2.56	0.11
Body mass	2.82	0.09

When subject males mated in either first (in single copulations) or second (in double copulations) mating roles, the number of their sperm recovered from the uterus immediately after ejaculation was predicted by the mass of their mating plug, as well as their mating role (first or second to mate). Body mass and cauda sperm count (measured postmortem as an index of sperm production) are included as covariates with the aim of controlling for variation in the number of sperm ejaculated (see Results and Discussion), which is likely to vary with plug mass. Results are shown for linear mixed models fit by maximum likelihood, for 18 males mating both first (in single copulations) and second (in double copulations) mating roles. Plug mass data exclude four cases for double copulations where proteomic analysis revealed that the plug originated from more than one male. Male identity is included as a random factor in the analysis. Bold text indicates statistical significance (*P < 0.05; ***P < 0.001).