Tuesday, March 20, 2012

Helogale parvula and Bucerotidae: Friends ‘til the End!






Introduction:

The dwarf mongoose and hornbill bird share an interesting mutualistic relationship for several reasons. Their spectra of prey and predators are nearly identical (4), making this relationship even more important for both parties involved. In this partnership the hornbill bird eats the leftover insects during the foraging process of the dwarf mongoose (3). In exchange for food, the hornbill warns the dwarf mongoose if a predator is approaching. Both dwarf mongooses and hornbill birds are distributed in much of southeast Africa (2). In regard to their lifecycles, dwarf mongooses reach sexual maturity at one year of age and usually produce an average of five pups per litter (2). Hornbill birds usually form monogamous relationships and usually lay six eggs per birthing cycle (5). Additionally, dwarf mongooses generally sleep in old termite mounds, and hornbill birds can usually be found in the trees above these termite mounds awaiting for the dwarf mongooses to wake up and start foraging for food (4)




Description of the Relationship:

Helogale parvula (dwarf mongoose) and Bucerotidae (hornbill bird) have such a close relationship that they almost seem to seek each other out in their daily lives (4). In the morning, hornbills wait for the mongooses to awaken and when the mongooses start foraging for food the hornbills happily eat the leftover insects (3). Since the mongooses are foraging for food it is up to the hornbills to warn the mongooses of approaching predators like a black eagle. Anne E. Rasa states in her paper that, “This is the closest known mutualistic relationship known between social vertebrates normally living independently (4).” Therefore, in regard to the evolutionary history of the relationship, it can be assumed that this partnership has increased the evolutionary fitness of both parties involved. The relationship is established by the mongoose providing food for the hornbill and the hornbill providing protection for the mongoose (5). Our text explains mutualism as “opposed to parasitic systems, in a mutualistic system each partner takes advantage of the association between the two protagonists (1) (Claude Combes, 553).” It is clear that the mongoose and hornbill fully exemplify this definition of mutualism.




Cost/Benefit Analysis:

When conducting a cost/benefit analysis in mutualism it is important to bear in mind that, in most cases, the benefits outweigh the cost. The cost for the dwarf mongoose in this relationship is decreasing the total amount of food it is able to intake because the hornbill birds are eating from their same food supply (2). The benefit for the mongoose is protection from predators when the hornbills willingly signal a warning call. The cost for the hornbills is using valuable energy to signal a warning call for the mongooses to be warned of approaching predators (3). However, the benefit for the hornbills is the ease of finding excess food, in the form of easily accessible leftovers, when the mongooses are out foraging. The benefit of the hornbills outweighs the cost in that simply finding food is more valuable than the lost energy in providing the mongooses with a warning call. The benefit of the mongoose outweighs the cost in that it is better to have a slightly decreased food supply compared to being killed by a predator. Moreover, a specific strategy employed by the hornbills to ensure participation of the mongooses is living in trees close to termite mounds and waiting for the mongooses to wake up to begin foraging for food (4). Overall, the mutualistic relationship between the dwarf mongoose and the hornbill bird is one that contains a relatively low cost and reaps a relatively high reward. 



References:


(1) Combes, Claude. Parasitism: The Ecology and Evolution of Intimate Interactions; Translated by Isaure De Buron and Vincent A. Connors ; with a New Foreword by Daniel Simberloff. Chicago: University of Chicago, 2001. Print.
(2) "Dwarf Mongoose." African Wildlife Foundation. Web. 17 Mar. 2012. <http://www.awf.org/content/wildlife/detail/dwarfmongoose>.
(3) "Hornbill Family Bucerotidae." Don Roberson Creagrus. Web. 17 Mar. 2012. <http://creagrus.home.montereybay.com/hornbills.html>.
(4) Rasa, Anne E. "Dwarf Mongoose and Hornbill Mutualism in the Taru Desert, Kenya." Behavioral Ecology and Sociobiology 12.3 (1983): 181-90. Print.
(5) "Red-billed Hornbill." World Association of Zoos and Aquariums (WAZA). Web. 17 Mar. 2012. <http://www.waza.org/en/zoo/pick-a-picture/tockus-erythrorhynchus>. 

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