Mating Systems of Game Animals
The Take home Message
- Most popular game species tend to be polygynous (males mate with many females) and sexually dimorphic (the males and females look different).
- Polygyny and sexual dimorphism are the result of millions of years of competition between males and females with different reproductive costs and benefits.
The full story
In many species, males spend reproductive energy on mating while females spend reproductive energy on parental care. Popular game species are often those with the largest disparity in reproductive investment.
Have you ever wondered why some species are more attractive to hunters than others? In large part, it's because of sperm. The reason that monster buck has antlers boils down to sperm. And that gobbler comes to your call because of sperm. A male wood duck’s plumage is so spectacular because of sperm.
Really, I’m not talking about sperm directly, but instead about the strategies males and females use to maximize the number of their genes that are passed on to future generations. For males, which tend to be of more interest to most sport and trophy hunters, achieving such reproductive fitness means doing everything they can to improve the chances it is their sperm fertilizing the egg. Not only do they have to compete against other males to mate with females, but they often have to convince females they are the strongest and healthiest male to be chosen.
The cost of reproduction can be vastly different for males and females, so the reproductive strategies of males and females are often at odds. This disparity has interesting implications in the evolution of mating systems, and mating systems have interesting implications in determining the behavioral and morphological traits that make a species popular for hunting. The first mating system most humans think about is monogamy, which is when a male and female mate exclusively (or almost so) with each other. In monogamous systems, both males and females maximize their reproductive fitness by putting effort into raising offspring. Monogamy is projected on all sorts of non-monogamous species in cartoons and TV shows, so many children grow up thinking monogamy is the norm in the animal world. It's not. Monogamy is relatively rare in birds and mammals, being found in species like waterfowl and songbirds. Among common game species, geese are monogamous. Coyotes and wolves often are as well, although many would probably consider those species pests, not game. Moose can be temporarily monogamous as males and females often form pair bonds during the breeding season, but not usually across seasons.
Really, I’m not talking about sperm directly, but instead about the strategies males and females use to maximize the number of their genes that are passed on to future generations. For males, which tend to be of more interest to most sport and trophy hunters, achieving such reproductive fitness means doing everything they can to improve the chances it is their sperm fertilizing the egg. Not only do they have to compete against other males to mate with females, but they often have to convince females they are the strongest and healthiest male to be chosen.
The cost of reproduction can be vastly different for males and females, so the reproductive strategies of males and females are often at odds. This disparity has interesting implications in the evolution of mating systems, and mating systems have interesting implications in determining the behavioral and morphological traits that make a species popular for hunting. The first mating system most humans think about is monogamy, which is when a male and female mate exclusively (or almost so) with each other. In monogamous systems, both males and females maximize their reproductive fitness by putting effort into raising offspring. Monogamy is projected on all sorts of non-monogamous species in cartoons and TV shows, so many children grow up thinking monogamy is the norm in the animal world. It's not. Monogamy is relatively rare in birds and mammals, being found in species like waterfowl and songbirds. Among common game species, geese are monogamous. Coyotes and wolves often are as well, although many would probably consider those species pests, not game. Moose can be temporarily monogamous as males and females often form pair bonds during the breeding season, but not usually across seasons.
Lions are a good example of a polygynous, sexually dimorphic species, which are traits common among game and trophy species.
Most game species, especially trophy species, are polygynous. In polygynous species, the males try to mate with as many females as possible while the females try to choose a single high-quality male. Why is this mating system so common? Because sperm happens to be cheap to produce, energetically speaking. Combine this with the fact that the male plays no role in rearing the offspring in most species and it makes sense that a male can most successfully pass on their genes by mating with as many females as possible. Females, on the other hand, put far more effort into reproduction and rearing offspring, so the best chance for them to pass on their genes is to mate with high-quality males and produce few, but high-quality offspring.
There are three broad types of polygyny, but the distinction can be quite blurry. In female defense polygyny, the males actively defend females from other males, often forming a harem. Lions and pheasants would be examples of game species that fit in this category. In resource defense polygyny, males defend either a territory or resource the females need. Prairie chickens defend a lek and try to attract females into that lek, for example. Bull elk will sometimes attempt to attract females to them and then fight off other males to defend what is essentially a temporary harem, so they are an example of a species that blurs the distinction between categories. Finally, in some species, the males don’t directly defend resources, but instead attempt to gain access to females through simple dominance over other males. White-tailed deer would best fit here.
It is not coincidence that popular game species tend to be polygynous, because polygynous species tend to have traits that make them attractive to hunters. In polygynous species, the males pursue females until they successfully mate or are outcompeted by another male, then move on. That’s why a gobbler or a white-tailed buck can be enticed by mimicking the calls of a female. In species that form long-term pair bonds, mimicking a female is likely to be less fruitful, so monogamous species are often called with social or prey calls, if at all.
There are three broad types of polygyny, but the distinction can be quite blurry. In female defense polygyny, the males actively defend females from other males, often forming a harem. Lions and pheasants would be examples of game species that fit in this category. In resource defense polygyny, males defend either a territory or resource the females need. Prairie chickens defend a lek and try to attract females into that lek, for example. Bull elk will sometimes attempt to attract females to them and then fight off other males to defend what is essentially a temporary harem, so they are an example of a species that blurs the distinction between categories. Finally, in some species, the males don’t directly defend resources, but instead attempt to gain access to females through simple dominance over other males. White-tailed deer would best fit here.
It is not coincidence that popular game species tend to be polygynous, because polygynous species tend to have traits that make them attractive to hunters. In polygynous species, the males pursue females until they successfully mate or are outcompeted by another male, then move on. That’s why a gobbler or a white-tailed buck can be enticed by mimicking the calls of a female. In species that form long-term pair bonds, mimicking a female is likely to be less fruitful, so monogamous species are often called with social or prey calls, if at all.
Male impala showing off the weaponry they use to battle for mating opportunities.
Polygynous species are often also sexually dimorphic. In sexually dimorphic species, the male and female look noticeably different. Males often have some bright coloration to attract females (like pheasants or some ducks), tend to be much larger than the females (like bears), have some unique anatomical weaponry or ornamentation, or have larger weaponry than the females. In species like deer or impala, the weaponry is used to fight other males. In other cases, ornamentation is to convince females that the male is in such good shape it can afford to maintain a showy ornament and still survive. I don’t know of any game species for which this is the case, but peacocks are a non-game example.
So, ultimately many of the traits that make a bird or mammal attractive as a game species stem from selective pressures on an evolutionary timescale that make males more successful at getting their sperm into as many females as possible. It’s probably not a stretch to imagine that recreational and trophy hunting would be far less popular if all mammals and birds were monogamous and monomorphic.
So, ultimately many of the traits that make a bird or mammal attractive as a game species stem from selective pressures on an evolutionary timescale that make males more successful at getting their sperm into as many females as possible. It’s probably not a stretch to imagine that recreational and trophy hunting would be far less popular if all mammals and birds were monogamous and monomorphic.