Abstract
<title>Abstract</title> <p>Male DBA/2 mice raised in well-resourced (WR) 'enriched' cages are more sexually attractive than conventionally-housed (CH) males. To explore why, we investigated relationships between housing quality, ultrasonic courtship singing (motivations to sing; song phenotypes), and testosterone-related traits (testis weight; anogenital distance, AGD). Singing by 34 males (18 WR, 16 CH, with mixed socio-sexual experience) was induced by oestrus female cues. 24 males sang to just female urine alone, while 10 required live female presence to elicit singing. Housing*time-of-day predicted this singing readiness: within later-tested males, WR males were more likely than CH to sing to just oestrous urine cues, without requiring female presence. WR males' songs also tended to have greater bandwidths. WR males did not have longer AGDs nor heavier testes. Nevertheless, longer AGDs and heavier testes predicted increased readiness to sing to just urine cues and reduced singing latencies. Furthermore, statistically controlling for AGDs revealed clear housing effects on singing motivations: WR males sang with shorter latencies than CH males, and were more likely to sing to just urine. Furthermore, controlling for testis weight revealed a potential housing effect on songs’ peak frequencies, those of WR males tending to be higher-pitched. Both organizational effects of androgens, and being raised in higher quality ‘enriched’ housing, thus independently enhanced males’ motivations to produce courtship songs. Results now need replication, and underlying mechanisms elucidated including whether such effects reflect that ‘enriched’, high welfare housing enhances just male mouse libido (and diverse proceptive behaviours) or instead wider-ranging ‘optimism’ about ambiguous cues of potential reward.</p>