December 5, 2013
Polygamy: The Pros And Cons For Prairie Dogs
While polygamy can increase the risk of exposure to diseases and parasites, the likelihood that female prairie dogs will give birth to more offspring often makes mating with more than one male worth the risk, new research claims.
The paper, which was prepared by behavioral ecologist John Hoogland of University of Maryland, reported that the herbivorous rodents that mated with multiple males were likely to rear more offspring than those who copulated with only a single partner. The study appears in the September edition of The Journal of Mammalogy.“Prairie dogs are excellent models for a study of polyandry because they are easy to livetrap, mark, and observe,” Hoogland said.
“Further, each female is sexually receptive for only 5-6 hours of a single day each year, so my students and I can record all the males with whom she mates during that small window of opportunity,” he added. “Finally, females remain in the same territory after mating, so we can determine reproductive success for all the females in our study-colony each year.”
Hoogland has spent the last 35 years studying four different prairie dog species (black-tailed, Gunnison’s, Utah, and white-tailed prairie dogs) living in grassland ecosystems located within wildlife refuges or national parks in the western US. He tracked the number of sexual partners and reproductive success rates for female members of all four species, quantifying the latter based on the number of offspring that survived until the following spring.
He and his research associates documented 2,504 total copulations involving 1,426 females from 1978 through 2012, and found that the frequency of mating with multiple males varied significantly among the four different types of prairie dogs. On the whole, black-tailed and white-tailed prairie dogs tended to mate with just one male, while the other two species were primarily polyandrous.
For three of the four species, the number of yearlings was higher for females with more than one mate, Hoogland and his colleagues discovered. However, Gunnison’s and while-tailed prairie dogs that were polyandrous were themselves less likely than their monandrous counterparts to survive until the following mating season.
“My results underscore the value of long-term comparative research with closely related species. If I had studied only black-tailed prairie dogs, I would have concluded that costs and benefits of polyandry are minimal,’ Hoogland said.
“If I had studied only Gunnison’s prairie dogs, on the other hand, I would have concluded that both costs and benefits of polyandry dramatically affect female survivorship and female reproductive success,” he added. “For most animals, including Utah and white-tailed prairie dogs, the truth about polyandry usually lies somewhere between these two extremes.”