An analysis showed that male guinea pigs of a pet/laboratory strain begin to have some detectable non-motile sperm in their ejaculate when aged on average 11 weeks, but at the earliest 6 weeks and latest 18 weeks. Sperm motility was observed as early as 11 weeks but more commonly occurred between weeks 15 - 19. By 20 weeks of age, the guinea pigs had attained their adult body weights but sperm concentration had not yet reached mature levels. In general, puberty was determined to be at week 18 for the strain but there could be some amount of individual variability.

    Baby boars display sexual behavior from a very young age. It is possible to see rumblestrutting in baby boars as young as 1.5 weeks old. Copulation with young sows in estrus can occur before boars can impregnate them.

    Competitive behavior between young boars for mating rights to a sow in estrus, including fighting that inflicts injuries, can also begin around this size. You might see this if you house a sow of any age that is in estrus in the same pen as young boars around 400g or larger.

    So far, I have not seen a baby boar's competitive behavior prevent an adult boar from covering a sow. I've also not seen an adult boar injure a competitive-behaving baby boar that the adult has been co-habitatating with.

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M. Freund (1962), Initiation and Development of Semen Production in the Guinea Pig. Fertility and Sterility, Volume 13, Issue 2, 190 - 201. March 1962. Retrieved from https://www.sciencedirect.com/science/article/pii/S001502821634448X/pdf?md5=5e349faf386fc74491fd14d0a6231d88&pid=1-s2.0-S001502821634448X-main.pdf February 2024.

This article also include impressions and information directly from the author's experience.


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