Effects of maternal social stability on female reproductive success in wild house mice (Mus musculus domesticus)

• Applicant: Dr. Esther H. D. Carlitz
• Subject Area: Animal Physiology and Biochemistry ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 357504347

• Final Report Year: 2023

Final Report Abstract

The Project investigates how the social, stress-related environment of mothers has longlasting influence on a daughter’s reproductive success in wild house mice, while reproductive competition is subject to seasonal variation. The investigations required some preliminary work (chapter 1 and 2). Although we were to focus on females, both studies also included males which provides a great foundation for future work. In chapter one, we biologically validated the steroid hormones measured in hair (corticosterone, progesterone, testosterone) in order to use cortisol in hair as a marker of stress, progesterone as a marker of female reproductive investment, and testosterone as a marker of male reproductive engagement. In chapter two, we studied how reproductive success and reproductive physiology (testosterone, progesterone) was predicted by the stress hormone corticosterone. The latter study revealed that long-term stress hormones, if at all, play a minor role in female reproductive competition. For chapter 3, we consequently shifted our focus from maternal stress to the „masculinization of females“, a phenomenon that is not well understood and that can be influenced by maternal stress. The degree of masculinization is well reflected in the distance between the anus and the genitals (ano-genital distance, AGD), a measure that is available for all pups in our study population. More masculinized females are believed to exhibit bolder behavior, but its environmental causes and implications for reproduction in wild populations remain elusive. We investigate the genetic and environmental causes, the proximate consequences to adult physiology (testosterone, corticosterone), and the ultimate consequences to reproductive success (size of first litter, age at first reproduction, reproductive success yes/no) under varying environmental conditions. Results indicate that – contrary to predictions from the literature – maternal corticosterone and testosterone do not predict the length of AGD (= degree of masculinization), while a large proportion of AGD variation is explained by gene-environment interaction (57% of variance explained by parental ID and litter ID). The season of birth and population density also significantly predict AGD, but effect sizes are much lower (2% of variance explained). Analyses for proximate and ultimate consequences of AGD variation are currently under construction.

Publications

• Steroid hormones in hair reveal sexual maturity and competition in wild house mice (Mus musculus domesticus). Scientific Reports, 9(1).
  Carlitz, Esther H. D.; Runge, Jan-Niklas; König, Barbara; Winkler, Lennart; Kirschbaum, Clemens; Gao, Wei & Lindholm, Anna K.
  
• Immune-Endocrine Links to Gregariousness in Wild House Mice. Frontiers in Behavioral Neuroscience, 14.
  Lopes, Patricia C.; Carlitz, Esther H. D.; Kindel, Morgan & König, Barbara
  
• Steroid hormones in hair and fresh wounds reveal sex specific costs of reproductive engagement and reproductive success in wild house mice (Mus musculus domesticus). Hormones and Behavior, 138, 105102.
  Carlitz, Esther H.D.; Lindholm, Anna K.; Gao, Wei; Kirschbaum, Clemens & König, Barbara