10.5 Promiscuity (and Polygynandry)
In promiscuous species, individuals of both sexes will typically mate with multiple individuals of the opposite sex. Unlike polygyny and polyandry, this system typically arises in environments where large sections of territory are less common and less defensible. Instead, individuals may live in social groups or alone, rather than within a mate’s controlled territory. A benefit of this system, for females, is the reduced risk of infanticide; since individuals may have mated with so many others, it can be difficult to know whether or not a young individual is related to them so killing a juvenile is risky. Additionally, it is likely that most members of both sexes will have the opportunity to mate and have some offspring.
This system can sometimes be harder to identify, as there are a wide range of behavioral traits that can be associated with promiscuity. Parental behaviors in particular can vary depending on a species’ needs. In some fish, for example, the offspring will need little support from their parents and will be able to survive on their own from the moment they hatch. For most mammals, however, the offspring can be dependent on the care of their mother for nursing and food during the first months or even years of their lives.
Challenges in Studying Promiscuity
The scientific community is working to better understand and categorize behaviors associated with promiscuity. Biology, unlike physical sciences, has few “laws” or “rules” that dictate exactly what can or will happen. Instead, many aspects of the biological sciences can fall into gray areas, sparking debates about proper categorization. In scientific literature, promiscuity is sometimes referred to as polygynandry, especially for species that live and raise offspring in social groups. For the sake of this class, we will refer to all species in which males and females both mate with multiple individuals as promiscuous, though it is important to know that terminology is sometimes used differently in different contexts.
For the sake of simplicity, you will not need to identify the differences between promiscuity and polygynandry. These systems are highly comparable, both having multi-male multi-female societies with varying amounts of parental care.
Promiscuous Leopards
Leopards tend to be solitary creatures, though during courtship, a male and female will pair for a few days, with the female traveling to a favorable male’s territory. During these few days, the pair will copulate an average of about 250 times, or 4 times per hour. Despite this high frequency of copulations, it will often take a few different courtships before conception is achieved. Within a single mating season, leopards will often experience about 2-3 of these courtships. As a promiscuous species, pair bonding does not occur between the individuals, and they will infrequently cross paths post-courtship. As mammals, there is still a high amount of parental care that the female will invest into the offspring until they are old enough to hunt for themselves. For other promiscuous species, the offspring will often be raised with very little parental care, such as with fish and some other aquatic animals.
Promiscuous Chimps and Bonobos
Living in large social groups, and assisting in the care of others’ offspring, chimpanzees and bonobos are often referred to as polygynandrous, though remember, for the sake of our class, this is the same category of mating system as promiscuity. These groups, while different in some behaviors, are still categorized into the same type of mating system. These similarities come from how mating behaviors are exhibited. During the mating season, individuals of these species will mate to produce offspring, which are then, unlike solitary species, cared for by all members of the group, though often the parents will invest the most energy into the young. In these groups, many males and females will mate with each other, creating uncertainty about paternity and therefore reduced infanticide. When males are unsure whether or not offspring are related to them, they are often less likely to attempt violent acts in order to allow their genes to continue to the next generation.
Check Yourself
- Image "Cheetah family" from Cloudtail the Snow Leopard used with CC-BY-NC-ND 2.0 license. ↵
- Image "Chimpanzees" by Emily Wroblewski shared with CC-BY license. ↵
When an individual, often a male, kills juveniles (typically unrelated to him). When a male kills the offspring of a female, she may become fertile again more quickly and have more energy to mate with him and take care of resulting offspring.
