Title

Maternal investment in free-ranging Tibetan macaques (Macaca thibetana)

Presenter Information

Ashley Murphy
Jessa Link

Document Type

Oral Presentation

Location

SURC 201

Start Date

16-5-2013

End Date

16-5-2013

Abstract

The terminal investment hypothesis predicts that in species whose reproductive value decreases with age, primary caregivers should increase energy expended on each successive offspring as a means of enhancing reproductive fitness. We tested this hypothesis on a group of provisioned, habituated Tibetan macaques living in the Valley of the Wild Monkeys, Anhui, China. This species lives in multi-male/multi-female groups. Males disperse at sexual maturity; females remain in the natal group and are the primary caregivers. We conducted our study from August 3 to September 30, 2012 and compared adult females’ investment in offspring born 2009-2012. Females’ ages ranged from 7 to 22 years. We predicted that older mothers would be proximate to their offspring more than were younger mothers, and that older mothers would carry, hold, nurse, and groom their offspring more than did younger mothers. We collected data through randomized, five minute, focal-animal samples during which we recorded mother-offspring proximity (≤ arm’s reach) and maternal behaviors from an ethogram. Mothers did not differ in proximity scores for offspring born in 2009 or 2010, but they did differ for children born in 2011 (Kruskal Wallis One-Way ANOVA, H=27.04, df=3, P<0.0001) and 2012 (H=66.06, df=4, P<0.0001). We found similar results for most maternal behaviors: females significantly differed for children born in 2011 and 2012, but not for older offspring born in 2009 and 2010. Our results cannot be explained by terminal investment and maternal age; rather, they may be related to the child’s age and the total number of dependent offspring the mother has.

Faculty Mentor(s)

Lori Sheeran

Additional Mentoring Department

Anthropology

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May 16th, 3:00 PM May 16th, 3:20 PM

Maternal investment in free-ranging Tibetan macaques (Macaca thibetana)

SURC 201

The terminal investment hypothesis predicts that in species whose reproductive value decreases with age, primary caregivers should increase energy expended on each successive offspring as a means of enhancing reproductive fitness. We tested this hypothesis on a group of provisioned, habituated Tibetan macaques living in the Valley of the Wild Monkeys, Anhui, China. This species lives in multi-male/multi-female groups. Males disperse at sexual maturity; females remain in the natal group and are the primary caregivers. We conducted our study from August 3 to September 30, 2012 and compared adult females’ investment in offspring born 2009-2012. Females’ ages ranged from 7 to 22 years. We predicted that older mothers would be proximate to their offspring more than were younger mothers, and that older mothers would carry, hold, nurse, and groom their offspring more than did younger mothers. We collected data through randomized, five minute, focal-animal samples during which we recorded mother-offspring proximity (≤ arm’s reach) and maternal behaviors from an ethogram. Mothers did not differ in proximity scores for offspring born in 2009 or 2010, but they did differ for children born in 2011 (Kruskal Wallis One-Way ANOVA, H=27.04, df=3, P<0.0001) and 2012 (H=66.06, df=4, P<0.0001). We found similar results for most maternal behaviors: females significantly differed for children born in 2011 and 2012, but not for older offspring born in 2009 and 2010. Our results cannot be explained by terminal investment and maternal age; rather, they may be related to the child’s age and the total number of dependent offspring the mother has.