Sunday, April 4, 2010
Cooperative and Antagonistic Behaviors in Lions
Coyne states on page 119 that "Selection has to explain behaviors, both cooperative and antagonistic". However, these behaviors don't always necessarily appear separately in nature. The lion is a prime example of this. Although living in a highly organized and cooperative social group based on mutual aid in hunting and defense, individualistic tendencies also sometimes take hold in the form of mate competition. In fact, male lions have sometimes been known to kill a lioness' cubs by another mate before reproducing with the lioness. How can such behavior, that may seem very counterproductive in a highly organized social group, exist in the same species that hunts in a cooperative unit? What other examples of organisms can you think of that have a similar structure? Feel free to mention behaviors we have discussed in the ecology unit (ie kin selection, altruism etc).
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The lions' behavior varies between cooperation and antagonism based on what is best for each individual lion at a particular time or in a particular situation. Specifically, Coyne states that "an adaptation must evolve by increasing the reproductive output of its possessor." (120) For lions, both cooperative hunting and killing off a mate's cubs by another father increase the reproductive fitness of the individual male lion.
ReplyDeleteCooperative hunting in lions is mainly practiced by the lionesses, who are more agile than males and not encumbered by a conspicuous, heavy, and hot mane (Wikipedia). The lionesses are not large enough, however, to take down a large animal such as a wildebeest or buffalo alone; therefore, they hunt as a pride and kill their prey by attacking together and strangling it. This group behavior increases the reproductive fitness of the lionesses, as they are able to obtain more food and thus provide more energy to themselves and their cubs.
Meanwhile, the killing of a mate's cubs by other fathers is an example of antagonistic behavior, in which males compete for mates (Campbell 1136). Each male's goal is to pass along as many of his genes to as many offspring as possible. To him, cubs by other lions represent competition with his future offspring. The lioness, whose genes have been passed to the offspring of both males, will care equally for all the cubs to ensure that her genetic fitness is as great as possible. If the male kills off the cubs that are not his, his mate will only have to care for his cubs. This increases the parental care for his offspring and ensures that they will receive the lion's share (pun much?) of the food that the lionesses bring back to the pride. In addition, the male lions of a pride are usually not related to each other, while the females tend to be related (Wikipedia). Therefore, the males would be less likely to practice kin selection than females. Kin selection, when altruistic behavior is practiced to enhance the reproductive success of relatives, could explain why lionesses hunt in packs and feed all of the cubs of the pride (Campbell 1139).
Another species which mixes cooperation and antagonism is the gray wolf. In groups with more than one mating pair, the "alpha" wolf dominates the pack with his offspring (Wikipedia). The other wolves in the pack do not breed as often, but they tend to be related to the alpha wolf, so caring for his offspring increases their genetic fitness via kin selection. However, when it comes to hunting, wolves are well known for their pack mentality in bringing down large prey such as elk and moose. In both cases (breeding and hunting) the behavior increases the fitness of all of the wolves involved, which is the purpose of behavioral adaptations.
The main goal of the male lion is to survive and reproduce so that its genes will be passed on. Therefore, it will take necessary actions to ensure that his genes survive. As Coyne describes on page 121, an invading lion which take the place of the resident males will kill any unweaned cubs. This practice has its advantages and its disadvantages. On one hand, this is detrimental for the species as a whole because it increases the chance of extinction, yet it also decreases the number of lions in the pride that need to be fed. This decreases the competition among the lions and increases the chance that the older lions will survive.
ReplyDeleteIn addition, killing the cubs of another male is beneficial for the individual fitness of the male lion. First of all, by killing the lioness’s cubs from another mate, the lion increases the chance that his genes will be passed on instead of the other male’s. This way his time and energy will be used to protect and feed his offspring rather than another male’s. Second, when the cubs are killed, the females no longer have to nurse the cubs. This allows their estrous cycle to begin again and they are able to ovulate (Wikipedia). This permits the new males to reproduce with the females which increases the chance that their genes will survive.
It is the female’s job to hunt for food. Interestingly, females will eat their food first and then allow the cubs to eat whereas male lions often share their food with the cubs (lion facts). Why is it that the females, who put a lot of time and energy into nursing their cubs, make their cubs wait to get food? They expend large sums of energy hunting and nursing their cubs. Therefore, they are in great need of food to resupply the energy they expended. What is even more interesting is how the male lions share their food with the cubs. This is an example of altruistic behavior because the male lion is sharing his food which make is more likely that he will die, but increases the chances of the cubs survival and the improves his chances of passing on his genes (Campbell 1138).
In class we watched a video on an octopus. An octopus inserted its sperm into the female to be fertilized, and then protects the female octopus. Another octopus challenges him and as is exhibited throughout the animal kingdom, two males fight for the chance to mate with a female. The other octopus wins and exhibits behavior similar to that of the lion. It uses its tentacles to scoop out the sperm of the other octopus before it inserts its own sperm. This ensures that its sperm will be fertilized and no the sperm of the other octopus.
SOURCES
Lion facts:
http://www.lionlamb.us/lion/lionfact.html
Wikipedia:
http://en.wikipedia.org/wiki/Lion#Group_organization
http://en.wikipedia.org/wiki/Estrous_cycle
Campbell
page(s): 1138
The theory of evolution states that organisms with the highest likelihood of survival and reproduction will pass along their genes. Instances of antagonism and cooperation are both necessary to increase these odds.
ReplyDeleteGood competitors are necessary to pass along an individuals genes. Intra-species competition occurs when different members of the same species fight over the same resources to survive and reproduce. This is necessary due to a limited amount of resources that fit similar bodies. Competition can be interference, aggression directly between individuals; or exploitation, indirectly when resources are limited. Lions show exploitation intra-species competition when killing another male's cubs. Trees also exhibit aspects of exploitation intraspecific competition. When two trees of the same species are planted in close proximity, they fight for the light above ground and water and nutrients in the soil. The tree will exert more energy to grow taller and more complicated root systems. Since members of the same species have the same structures to serve the same purpose, individuals must utilize the best version of those structures in order to survive and reproduce. In the instance of the lion, it must be the largest and strongest to defeat other males in mate competition. Thus, in intra-species competition, the relationship between structure and function is largely affected by genetic variation.
Organisms must also be interdependent in order to succeed in evolution. Lions organize into prides consisting of around five related families. Each member of the pride is responsible for protecting one another. Since lions seem to be the most successful hunters in the animal world, it is clear that this interdependence is beneficial. Altruistic behavior is also apparent in meerkats. Some meerkats stand lookout outside the burrow which puts their lives in danger of predation. Some meerkats are also designated to babysit the young. This is another energy investment that may decrease the likelihood of the individual's reproduction, yet increases the survival chances of the group at large. Meerkats are even known to share a burrow with squirrels. Squirrels and meerkats do not compete for resources but benefit off this symbiotic relationship.
It is clear that species do not choose between either competition or cooperation. It is more like a spectrum where each species has a place. Some exhibit more aggressive, competitive sides. Others find success working together with other animals to survive. In addition each organism must decide when what behavior is appropriate. Overall, antagonism and cooperation are intertwined in nature.
Sources:
http://www.biotopics.co.uk/newgcse/Competition.html
http://animals.nationalgeographic.com/animals/mammals/meerkat/
http://www.globalchange.umich.edu/globalchange1/current/lectures/competition/competition.html