* Generally acquire reproductive behavioural traits such as mounting and erection a long time before they acquire the ability to ejaculate and produce spermatozoa.
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* Generally acquire reproductive behavioural traits such as mounting and [[Reproductive_Behaviour_-_Pre-copulatory_Behaviour_-_Anatomy_%26_Physiology#Erection|erection]] a long time before they acquire the ability to ejaculate and produce spermatozoa.
* Behavioural traits are easy to determine, as mouting behaviour and erection can be easily observed.
* Behavioural traits are easy to determine, as mouting behaviour and erection can be easily observed.