P2.4 Thursday, Jan. 5 Female release of luteinizing hormone (LH) in response to short- and long-range song in a songbird, the dark-eyed junco (Junco hyemalis) REICHARD, D/G*; HAHN, T/P; KETTERSON, E/D; Indiana Univ., Bloomington; Univ. of California, Davis; Indiana Univ., Bloomington email@example.com
Male courtship signals and displays can have strong stimulatory effects on female reproductive physiology. In songbirds, males use vocal signals, or songs, both to attract and stimulate females into a copulation or lasting pair bond. Previous research has shown that hearing male song can activate the hypothalamic-pituitary-gonadal (HPG) axis leading to the production of sex steroids that drive reproductive development in both sexes. However, studies of the physiological impacts of male song have focused exclusively on high-amplitude, long-range songs (LRS) that project over long distances and overlooked low-amplitude, short-range songs (SRS) that occur during directed courtship. To test the effect of SRS on female physiology, we captured free-living, female dark-eyed juncos (Junco hyemalis), brought them into captivity and played 45 minutes of LRS or SRS, or left them in silence as a control. After an additional 15 minutes of silence, we collected plasma samples that were later assayed for luteinizing hormone (LH), the hormonal link between the pituitary gland and the gonads in the HPG axis. When focusing only on females with LH levels detectable by the assay, females hearing song had significantly higher circulating LH than controls. Also, a higher proportion of females hearing SRS exhibited LH levels above the minimum detection limit of our assay than did females receiving LRS or the silent control. These results suggest that females can rapidly elevate their circulating LH in response to male song and highlight the potential for SRS to elicit a larger release of LH and possibly sex steroid production than LRS. We conclude by arguing that future research on male vocal signals should focus on both LRS and SRS.