Final answer:
John Hoogland's study on Gunnison's prairie dogs found that females increased litter size when they mated with multiple males. Later studies reinforce this with findings that resource-depleted males prefer and have greater reproductive success with larger, more fecund females.
Step-by-step explanation:
John Hoogland (1998) studied Gunnison's prairie dogs (Cynomys gunnisoni) and observed that an increase in litter size was observed when females mated with more than one male. This is supported by more recent studies, which have shown that male prairie dogs select mates based on female size, and the selection is more pronounced in resource-depleted males who have already mated and have lower sperm supplies. Specifically, sperm-depleted males who mated with larger, more fecund females were successful in producing offspring, indicating that behaviors leading to choosing larger females were advantageous and thus selected for genetically.
These studies highlight the impact of physiological states, such as sperm availability, on mating behaviors in prairie dogs. They offer evidence that resource-depleted males who mated with larger females maximized their offspring numbers, presenting a clear evolutionary advantage for the traits influencing such mating selections.