Sexual cyclicity in captive lowland gorillas

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Science  05 Sep 1975:
Vol. 189, Issue 4205, pp. 813-814
DOI: 10.1126/science.1162356


Oppositely sexed pairs of gorillas exhibit some behavior indicative of higher cognitive functioning, such as individual partner preferences and varied copulatory positions, but also mate in a cyclic manner closely related to the degree of female genital swelling. The latter finding is contrary to predictions based on their advanced position in phylogeny.