The gene for the vasopressin receptor V$1$a is expressed at higher levels in the forebrain of monogamous vole species than in promiscuous vole species.

$11$

$11$

Can expression of this gene influence monogamy? To test this, Lim et al$.(2004)$ experimentally enhanced V$1$a expression in the forebrain of $11$ males of the meadow vole, a solitary promiscuous species. The percentage of time each male spent huddling with the fem