TWEL Ceciia Hennessy Thesis

Mating strategies and pack structure of coyotes in an urban landscape: A genetic investigation
Ceciia A. Hennessy, MS
Advisor: Stan Gehrt
Coyotes (Canis latrans) have come to inhabit many types of ecosystems, including urban and suburban systems, and yet certain aspects of coyote behavioral ecology remain unclear.  Because these predators have found suitable habitat in residential areas, there is a powerful motivation to fully understand coyote behavior and social systems.  As mating strategy form the basis of social systems, the onus is on scientists to determine the basis of this carnivore’s success in the suburban and urban areas of North America.  Mating systems of coyotes have been extensively studied by observation, and the results have lead researchers to conclude that mated pairs are monogamous.  Also, observational studies of coyote packs have led researchers to conclude that packs consist of close family members.  However, recent genetic investigations of wildlife mating systems have revealed that conclusions based on observations can be misleading.  As the coyote is a cryptic, nocturnal species, a genetic investigation may be the most straightforward way to determine the nature of relationships of parents and offspring, mates, and pack members.
Coyotes have been classified as “obligate monogamists”, meaning that a dedicated mate is necessary for reproduction.  This is due in part to the high demands that pups place on their parents.  In addition to monogamy, coyotes reportedly engage in den-sharing, where two females contribute pups to a “double-litter”.  These observations are based on abnormally large litter sizes, den attendance by nursing females, and by size differences among pups.
Coyotes share territories in pack-like groups, which are assumed to comprise family members.  This assumption is based on observed retention of offspring from one year to the next.  The grown offspring often serve as alloparents to their younger siblings.  However, there are also reports of seemingly unrelated coyotes joining established packs, which contradict the theory that packs are family groups.
I investigated 19 coyote litters and 201 offspring and found one double-litter and one instance of polygyny.  The two mated pairs that contributed to the double-litter did not interbreed. The evidence strongly suggests that the majority of coyotes in this population are monogamous.  I investigated the relatedness of coyote packs, and found instances of unrelated members in a pack.  Out of 116 relationships between 62 pack members across 26 pack years, I detected 13 coyotes that were related at levels lower than expected for family members.  I also investigated home range overlap with relatedness and found a weak relationship.  Some animals that share high overlap are unrelated, and some animals that are highly related share small percentages of overlap.
The results of this study verify the findings of previous observation-based studies.  However, as the coyote is a highly adaptable mammal with plastic behaviors, it is unknown whether these same results would be verified by studies of coyotes in more natural areas.