rat ~21: guinea pig ~65 days
||Josselyn SA, Frankland PW. Infantile amnesia: a neurogenic hypothesis. Learn Mem. 2012 Aug 16 19(9):423-33. doi: 10.1101/lm.021311.110 p.427 right column top paragraphPubMed ID22904373
||Altman J, Das GD. Postnatal neurogenesis in the guinea-pig. Nature. 1967 Jun 10 214(5093):1098-101 DOI: 10.1038/2141098a0PubMed ID6053066
||P.427 left column bottom paragraph: "Whereas altricial rodents (such as rats) have relatively brief gestation periods (∼21 d), precocial rodents (such as guinea pigs) have much longer gestation periods (∼65 d) (primary source). Unlike rats, guinea pigs are able to walk and see at birth, suggesting that guinea pigs are born with a more developed brain."