Attentive red squirrel mothers have faster growing pups and higher lifetime reproductive success

Abstract

Parental investment theory predicts that observed levels of parental care afforded to offspring are set by the benefits (to offspring quality and survival) relative to the costs (to parental survival or future reproduction). Although difficult to document in mammals, there is often substantial individual variation in the amount of parental care within species. We measured the impact of individual variation in maternal care (“attentiveness” towards offspring or maternal motivation) on offspring growth and survival in a wild population of North American red squirrels (Tamiasciurus hudsonicus). We used latency to return to pups following a nest intrusion as a measure of maternal attentiveness to pups. We found this behavior to be repeatable within individuals suggesting this behavior is a personality trait or a “maternal style.” In this population, postnatal growth rate is important for pup overwinter survival. Pups from large litters grew faster if they had a highly attentive mother, indicating that maternal care can mitigate the trade-off between litter size and offspring growth and potentially improve survival of pups. Additionally, more attentive mothers had slightly higher lifetime reproductive success than less attentive mothers. These results highlight important fitness effects of having a highly attentive mother and show that maternal care can alter a fundamental life history trade-off between offspring quantity and quality.

Significance statement

It pays to be attentive to your pups as a squirrel mom. In a long-term study of a wild population of North American red squirrels, we tested whether maternal behavior was predictive of growth rate and survival of offspring. To do this, we observed maternal attentiveness towards offspring by recording the time until the mother returned to her pups following a nest intrusion by researchers. We found repeatable individual variation in maternal attentiveness suggesting consistent “maternal styles” among individuals. Mothers who returned faster to pups following a nest intrusion produced faster growing pups and were able to produce larger fast-growing litters. Over their entire lifetime, attentive mothers also had more offspring survive to adulthood.

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Data availability

The datasets generated for the current study are available in a figshare repository after April 13, 2022: https://doi.org/10.6084/m9.figshare.12118704. The datasets analyzed during the current study are available earlier than this date from the corresponding author on reasonable request.

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Acknowledgments

We thank Agnes MacDonald and her family for long-term access to her trapline, and Champagne and Aishihik First Nations for allowing us to conduct our work within their traditional territory. We thank all volunteers, field assistants, and graduate students for their assistance in data collection. We thank two anonymous reviewers for their constructive feedback that improved this manuscript. This is publication #109 of the Kluane Red Squirrel Project.

Funding

This study was funded by American Society of Mammalogists to SEW; University of Michigan to SEW and BD; National Science Foundation (IOS-1749627 to BD, DEB-0515849 to AGM); and Natural Sciences and Engineering Research Council to SB, AGM, and JEL.

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Correspondence to Sarah E Westrick.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. All work was conducted under animal ethics approvals from Michigan State University (AUF#04/08-046-00), University of Guelph (AUP#09R006), and University of Michigan (PRO00005866).

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Westrick, S.E., Taylor, R.W., Boutin, S. et al. Attentive red squirrel mothers have faster growing pups and higher lifetime reproductive success. Behav Ecol Sociobiol 74, 72 (2020). https://doi.org/10.1007/s00265-020-02856-7

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Keywords

  • Fitness
  • Growth rate
  • Maternal behavior
  • Maternal care
  • North American red squirrel
  • Survival