Female fluid collection
We obtained captive Peromyscus maniculatus bairdii, P. polionotus
subgriseus, P. leucopus , P. eremicus , and P. californicus
insignis from the Peromyscus Genetic Stock Center at the University of
South Carolina, and P. gossypinus from Dr. Hopi Hoekstra at
Harvard University. We housed the mice in same-sex cages at 22ÂșC on a
16L:8D cycle in accordance with guidelines established by the
Institutional Animal Care and Use Committee at the University of
Maryland (protocol # R-Jul-18-38). We sought samples from all available
captive Peromyscus species and avoided wild-caught specimens to
control for variation due to age, nutrition, and sexual experience. We
collected fluid from females in estrus (identified by methods in Byers
et al., 2012) to reduce variation associated with the estrous cycle
(Hunter et al. 2011; Simons and Olson 2018). We euthanized all focal
females via isoflurane overdose and cervical dislocation prior to
removing the reproductive tract for fluid extraction.