Date of Graduation

Spring 5-23-2026

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Scott Nunes

Second Advisor

Naupaka Zimmerman

Third Advisor

Tracy Benning

Abstract

Play behavior is ubiquitous among juvenile mammals and can promote motor, social, and cognitive development, providing multiple adaptive benefits to young animals in some cases. The structure of play can be linked to the benefits it confers on individuals. I evaluated the structure of play in juvenile Belding’s ground squirrels (Urocitellus beldingi), a species for which multiple adaptive benefits of play have been identified. I compared juvenile play in U. beldingi to adult sexual and aggressive behavior to determine and classify similarities between juvenile play and adult behavior. I evaluated diversity in the behaviors expressed during play interactions and diversity in the sequences of behavior expressed during play. I further evaluated reciprocity in play interactions, defined as the degree to which partners take turns initiating play bouts within an interaction. I categorized play behaviors as sexual (resembling adult sexual behavior), aggressive (resembling adult aggressive behavior), or indeterminate (not resembling sexual or aggressive behavior or resembling behavior occurring during both adult sexual and aggressive interactions). I further classified play interactions as sexual, aggressive, indeterminate, or mixed (including more than one category of play behavior). Longer play interactions were characterized by a greater number of play bouts. Behavioral diversity increased within play interactions as the number of play bouts in the interaction increased, with the increase in diversity being associated with an increase in the number of behaviors expressed during the interaction rather than an increase in the evenness of representation of different behaviors within the interaction. Sexual play interactions were the most common type of play among juvenile U. beldingi. Mixed play interactions comprised a greater number of behaviors than did other types of interactions, and were more behaviorally diverse, primarily due to including a greater number of behaviors. Thus, although longer play interactions make up a relatively small proportion of all play, they importantly contribute to the diversity of play behavior. Sexual play behaviors in juvenile U. beldingi were most commonly followed by other sexual play behaviors, and aggressive play behaviors were most commonly followed by other aggressive play behaviors. Direct transitions between sexual and aggressive play behaviors were very rare, with indeterminate behaviors frequently occurring in the transition between sexual and aggressive play. These findings support the idea that sexual and aggressive play in U. beldingi are derived from different behavioral systems. Reciprocity increased with the number of play bouts in an interaction, and 98.5% of interactions consisting of more than three play bouts had some degree of reciprocity. By contrast, reciprocity was observed in only 38.8% of play interactions with 2-3 play bouts. As reciprocity increased in play interactions, the behavioral diversity of the interaction also increased. These findings are consistent with the hypothesis that juveniles are more likely to remain in play interactions in which partners take turns initiating new play bouts, and reciprocity and diversity in play contribute to the adaptive benefits young animals gain from play.

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