Who’s Your Daddy – Extra Pair Paternity in “Monogamous” Arctic Foxes
Less than 3% of mammals are thought to be socially monogamous. However, with the advent of molecular techniques for establishing paternity, some presumably “monogamous” mammals may exhibit relatively high levels of extra pair paternity (EPP), or “cheating.”
Arctic fox (Vulpes lagopus, Figure 1) are a case in point. The arctic fox forage alone, but the social group usually consists of a breeding pair and their young (and occasionally a non-breeding female). Until just a few years ago Arctic foxes were considered strictly monogamous. However, in 2007 genetic analyses revealed several cases of EPP. It is still not clear how common EPPs are in Arctic fox populations.
Figure 1. Arctic fox (Vulpes lagopus) in the Canadian Arctic. (From Flickr/Angell Williams).
Paternal care (care provided by the father) may help females raise successful litters in harsh Arctic environments. Scientists predict that paternal care may be critical to pup survival when food abundance is low, or when the distribution of food is very patchy. When food is abundant in one area, the density of breeding fox pairs will also be high in that area, leading to increased probability of females seeking extrapair copulations.
Three Canadian scientists (Cameron et al., 2011) recently tested these predictions on Bylot Island in the Arctic (Figure 2). On this island, the presence of a goose colony provided a localized, high-density food source (spatial variation) and cyclic eruptions of lemming populations provided a temporally variable food resource.
Figure 2. Arctic fox study area (gray polygon) and goose colony (dark polygon) on Bylot Island, Nunavut, Canada. Active fox dens are indicated with open triangles and inactive dens by black triangles. Dens are identified by a three digit code followed by the last two digits of the year and an E if EPPs were detected or I if only intrapair paternity was detected. (From Cameron et al., 2011)
The mating systems of Arctic foxes on Bylot Island were monitored over five years using a combination of behavioral observation of family groups and molecular analyses. The results indicate that social monogamy is the rule, but extrapair paternity is relatively common. At least 31% of pups were fathered by a male who was not part of the “family group.” Furthermore, the probability of EPP was correlated with food availability. Incidences of EPP was greatest with in the goose colony (86%) and declined steeply with increasing distance from the goose colony (Figure 3).
Figure 3. Mating system of female arctic foxes as a function of the distance between their den(s) and the center of the goose colony on Bylot Island, Canada. Litters (open circles) were the result of either intrapair (0.0) or extrapair copulations (1.0). (From Cameron, et al., 2011).
The researchers conclude that, “In arctic foxes, behavioral strategies, such as extraterritorial movements and EPP, that increase gene flow are probably important for the genetic structure of populations.”
References
Cameron, C., Berteaux, D., & Dufresne, F. (2011). Spatial variation in food availability predicts extrapair paternity in the arctic fox Behavioral Ecology, 22 (6), 1364-1373 DOI: 10.1093/beheco/arr158
Arctic fox (Vulpes lagopus, Figure 1) are a case in point. The arctic fox forage alone, but the social group usually consists of a breeding pair and their young (and occasionally a non-breeding female). Until just a few years ago Arctic foxes were considered strictly monogamous. However, in 2007 genetic analyses revealed several cases of EPP. It is still not clear how common EPPs are in Arctic fox populations.
Figure 1. Arctic fox (Vulpes lagopus) in the Canadian Arctic. (From Flickr/Angell Williams).
Paternal care (care provided by the father) may help females raise successful litters in harsh Arctic environments. Scientists predict that paternal care may be critical to pup survival when food abundance is low, or when the distribution of food is very patchy. When food is abundant in one area, the density of breeding fox pairs will also be high in that area, leading to increased probability of females seeking extrapair copulations.
Three Canadian scientists (Cameron et al., 2011) recently tested these predictions on Bylot Island in the Arctic (Figure 2). On this island, the presence of a goose colony provided a localized, high-density food source (spatial variation) and cyclic eruptions of lemming populations provided a temporally variable food resource.
Figure 2. Arctic fox study area (gray polygon) and goose colony (dark polygon) on Bylot Island, Nunavut, Canada. Active fox dens are indicated with open triangles and inactive dens by black triangles. Dens are identified by a three digit code followed by the last two digits of the year and an E if EPPs were detected or I if only intrapair paternity was detected. (From Cameron et al., 2011)
The mating systems of Arctic foxes on Bylot Island were monitored over five years using a combination of behavioral observation of family groups and molecular analyses. The results indicate that social monogamy is the rule, but extrapair paternity is relatively common. At least 31% of pups were fathered by a male who was not part of the “family group.” Furthermore, the probability of EPP was correlated with food availability. Incidences of EPP was greatest with in the goose colony (86%) and declined steeply with increasing distance from the goose colony (Figure 3).
Figure 3. Mating system of female arctic foxes as a function of the distance between their den(s) and the center of the goose colony on Bylot Island, Canada. Litters (open circles) were the result of either intrapair (0.0) or extrapair copulations (1.0). (From Cameron, et al., 2011).
The researchers conclude that, “In arctic foxes, behavioral strategies, such as extraterritorial movements and EPP, that increase gene flow are probably important for the genetic structure of populations.”
References
Cameron, C., Berteaux, D., & Dufresne, F. (2011). Spatial variation in food availability predicts extrapair paternity in the arctic fox Behavioral Ecology, 22 (6), 1364-1373 DOI: 10.1093/beheco/arr158