Previous work on other canids such as foxes and wolves – which are all known for their social monogamy – shows genetically that they 'cheat'; between 11 and 50 per cent of young belong to males other than the one bonded with the female.
Professor Stan Gehrt
Recent research in The Journal of Mammalogy
has reported that there is no evidence for polygamy among the urban coyotes of greater Chicago; the third largest metropolitan area in the United States. The scientists involved believe that these findings may go some way to explaining the success of coyotes in North American cities.
Over a period of six years, 236 of the estimated 1000 to 2000 coyotes in the greater Chicago area were genetically tested by taking small samples of blood or tissue. Adults were fitted with radio collars to track their movements and range. Combined with fieldwork observations of behaviour over many years, the genetic sampling led the team to the conclusion that urban coyotes – despite having the opportunity to mate with other individuals – maintained monogamy through long-term pair bonding.
The study was conducted by Cecilia Hennessy – now a doctorate student at Purdue University, Indiana – during her time as a master’s advisee of Professor Stanley Gehrt at Ohio State University
. Professor Gehrt, Extension Wildlife Specialist from the School of Environment and Natural Resources and co-author of the paper, gave ScienceOmega.com
more details about the nature of the coyote research programme he leads, and explained why the results of this particular study were so surprising.
This research is, in fact, a relatively minor component of a much more extensive programme of study on Chicago coyotes with which Professor Gehrt has been involved since 2000.
"The genetic work was initiated for a variety of reasons, and the mating system was a subset of that; so in essence this is a subset of a subset of work," he explained. "We explored the question because I'm interested in how species adjust to urbanisation, and I was curious as to how far they deviated from the traditional monogamous model.
"The bigger questions are to do with how coyotes avoid people, especially in downtown areas; how their demographics change with urbanisation; what diseases are important to them; and what effect they have on other species as they move into cities."
As there are so many coyotes in the urban environment under consideration, territory sizes are extremely small and population density is high. Considering the high number of transients in the population and quite large litter sizes (an average of eight but as many as 12 pups per litter), it came as a surprise to the researchers to find no evidence whatsoever of polygamy.
"Previous work on other canids such as foxes and wolves – which are all known for their social monogamy – shows genetically that they 'cheat'; between 11 and 50 per cent of young belong to males other than the one bonded with the female. The same is true for most bird species, which are also behaviourally monogamous."
While the female is in oestrus and sexually receptive, the male and female become inseparable, and the male protects his partner against the advances of other potential suitors. Professor Gehrt and his colleagues have followed alpha pairs which have stayed together for up to ten years; these partnerships only come to an end when one of the individuals dies.
In a variety of ways, this faithful monogamy could be a contributing factor to the success of these coyotes in an urban environment. The male coyote knows that all the offspring in each litter are his own, and therefore stands to gain by devoting as much time and effort as the female does to raising them succesfully.
"The females can successfully raise large litters because the males help, which affects the population growth rate. Also, the monogamy probably helps maintain a stable pack structure, which benefits the young animals after they are weaned."
asked what further research is planned as part of the ongoing programme at Ohio State.
"One objective that has been at the top of our list since the beginning is to monitor the population for disease," replied Professor Gehrt. "We continue to track coyotes over the years to see if they are beginning to get habituated to people, especially those young animals that have been born and raised in close proximity to people, and we also aim to understand the effects coyotes have on other species as they continue to be successful and start to reach densities much greater than occur in rural areas."