Monday, October 22, 2012

Foraging Mechanisms and Social Influences

Hello again.
   I have started up my blog post for Psych 118, Comparative Psychology and will be blogging about a variety of topics that differ markedly from my posts in the spring.  I will be writing a comparative analysis on the foraging and eating mechanisms and behaviors between different animals.  I will touch on lineages ranging from the earliest jellyfish when nervous systems were first developing to the more advanced primates and humans.  So far in class we have begun talking about how animals have been evolving and changing over time from the earliest porifera (sponges), to the cnidarians with their primitive nerve nets and on to the mammals - including apes and humans.  The evolutionary trend has been towards developing larger brains that occupy greater volumes relative to body size.  It is this trend that has helped great apes and humans acquire skills to forage for food more effectively.  Some of the topics I will discuss about include using tools to search for food, observing and imitating others, and other social influences that affect the way animals search for food.
    The primary research article I will be discussing today is entitled "Social influences on foraging in vertebrates: causal mechanisms and adaptive functions" by Bennett Galef and Luc-Alain Giraldeau.  It is a summary on 20 years of research on the causes and function of social influences on foraging by animals.  It is interesting to note the different types of behaviors that you find and how they affect foraging behavior in the species.  As animals engage in their daily rituals, which involve searching for food, they provide information for others, which attracts them and guides them.  For example when an agouti gnaws on a nut, the rasping sound it produces attracts other agoutis to find the feeding site as well.  In this way, one member of a pack is benefitting the whole group by alerting the others.  Similarly, rats also engage in social behavior that helps offspring or other members of the group.  When food is found at a source, adult rats deposit certain chemicals on the feeding site and the foods that they have been eating.  This is meant to leave a trail which can also attract other members of the group to find the sites.
   In addition to social cues on finding places to eat, animals can also socially learn what to eat. Visual cues play a very important role in members of the same species.  It has been found in this research that domesticated chicks observing a mechanized-arrow peck at certain colored pinheads will also favor those colored pinheads.  Similarly when red-winged blackbirds or the Burmese fowl watch members of their species eating certain types of foods, they immediately prefer those types of foods as well.  It is much more difficult, however, for species to convey food taste-aversions to other members of the species.  A surprising finding was reported that when a Norway rat saw another member of its species eat a food and become sick, it still showed a preference for that food, rather than an aversion to it.  Comparing to humans, it must be something about the more advanced mind that can decipher what constitutes illness and taste preference, because humans usually avoid a food that they see is making their fellow humans sick.  It is rare, however, to find socially learned taste-aversion in most non-humans, even primates.
    Finally, animals also learn their behaviors of how to eat through social observation.  Black rats that feed on pine seeds from pine cones learn how to break open the cones by observing members of their species.  It is worth noting that multiple lineages and hundreds of different species all learn through similar mechanisms, lending credence to the fact that learning through observation has been around for tens to hundreds of thousands of years.  From early development, infants are unable to forage for themselves, therefore, it would only make sense that they acquire the skills necessary to find food and how to eat them through observation and imitation of the older members of their group.
    The authors of the paper mention that imitation is a "type of learning specialized for exploitation of public information, [which remains] both tentative and largely restricted to apes".  I wonder why this is the case, as they never clarify how what rats and birds do is not imitation, but are simply called observation and social learning.  The example they have given in the text is milk-bottle opening by apes which is a form of learning by imitation. Essentially most types of learning involves some type of observation, internalization and imitation, but this might be about how one defines true "imitation".
    There is no doubt that social behavior plays a large role in learning in a vast array of species.  Ranging from sounds and chemicals alerting others to the location of food, to the types of food and places to find them, animals are constantly interacting with other members of their species.  It is always important to keep things in an evolutionary perspective, as it would be most beneficial to a species for other members to survive as well and pass on their genes.  In a sense it is a type of kin selection, since all members of a species are related in one way or another through a common ancestor, and they are essentially looking out for "one of their own" by providing some of their extra food to others.  There could be the possibility of a reciprocity of the good deed, but in general, favors are doled out for the success of the species as a whole.
   This article was quite lengthy and informative, so I will continue writing about its various topics in the next post.  Stay tuned!


Galef, B. G., Jr, & Giraldeau, L.-A.  (2001).  Social influences on foraging in vertebrates: causal mechanisms and adaptive functions. Animal Behaviour, 61(1), 3-15.

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