A child watches a group of adult birds all cooperating to feed the nestlings and he smiles to himself. Pointing to the birds he tells his mother that like him, they love their family and want to help care for each other. She smiles too and takes him inside for lunch as they discuss the matter of love….

Do animals love though? That is a question that has perplexed many. However, what the little boy was witnessing was actually what we call social behavior. Altruism [1] by definition is a selfless act to benefit the well-being of another individual. Human beings are known to have empathy and act altruistically but do non-human, non-sentient creatures act altruistically? Or is it possible that there are underlying causes that we are overlooking for this behavior in animals?

Social behavior in animals has benefits and costs. These outcomes determine the longevity and fitness of individuals within a population. Cooperation and competition are two key elements of social behaviors. For example, looking at emperor penguins, they tend to form large groups which not only increases genetic variation and offers group protection but also leads to cooperation to find resources. However, with larger numbers, resources become limited leading to competition for food and mates. The group is easily spotted by predators and disease can easily run rampant. These costs and benefits to social groups has lead many to further investigate why animals would indeed act altruistically.

After many observations it has become apparent that altruistic behavior while decreasing direct fitness at that moment, increases indirect fitness and is overall still beneficial for the individual that is offering the assistance. For example in some bird species, there is postponed cooperation where the mating success of one bird is eliminated for a time while it aids another to increase its mating potential. The alpha male is the only one that would mate, but the beta male will participate and forfeit this season so that it may inherit the area in a following season.

Another example of altruistic behavior would be reciprocity as seen in mutual grooming of monkeys. This direct relationship is mutually beneficial for both monkeys involved. Another example of reciprocity is seen in vampire bats who colonize together and blood share. This is beneficial because if one shares with another today, if tomorrow the hunt is unsuccessful, the debt will be repaid. reciprocity is usually only seen in long-term social groups so that assistance will assuredly be repaid.

An interesting social behavior in birds that the little boy had pointed out to his mother was the evolution of helper birds at the nest. This has occurred in about 10% of birds species and is an example of how direct fitness is lost while indirect fitness is gained. Group living is beneficial in that it offers protection and assistance in scavenging efforts. This has arisen due to a long-term shortage of nesting sites due to a low dispersal from origin of birth in these species. These is typically a low adult mortality rate in these populations and therefor nests rarely become available. To test this one could either decrease the bird population and see if nests are taken over, or add more nests and see if helpers take them over.

These birds are also typically monogamous [2] so that siblings are more related to one another. The siblings assist in raising the next season’s babies so that the helper may inherit the nesting location at some point in the future. Since the siblings share genes these helpers are receiving indirect fitness by raising healthy and successful new genetically related siblings. This observation has lead to a hypothesis that genetic relatedness affects behavior in animals…..



Direct Fitness: a measure of personal reproduction.

Fitness: an organisms ability to to produce offspring. It is the number of offspring relative to a population, a comparison. Which individuals genes dominate the next generation?

Indirect Fitness: a measure of the number of relatives that an altruist/helper helps to survive and reproduce.


[1] “Altruism.” Merriam-Webster, Merriam-Webster, 2018, www.merriam-

[2] “Monogamy.” Merriam-Webster, Merriam-Webster, 2018,



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