Date of this Version
Gabel, R. 2020. An Analysis of Social Dominance in the Feeding of Ex Situ Humboldt Penguins (Spheniscus humboldti). Undergraduate Honors Thesis. University of Nebraska-Lincoln.
In the field of ecology, complex social structures, including dominance hierarchies, have been demonstrated in a variety of fauna, including bird species. While wild Humboldt Penguins (Spheniscus humboldti) do not exhibit a feeding hierarchy, captive penguins are under very different conditions. Humboldt penguins feed on schooling fish in the wild, but in captivity are hand fed from a zookeeper. I investigated whether there is a nonrandom pattern of dominance in the feeding order of the penguins at the Lincoln Children’s Zoo, in Lincoln, NE, USA. Using a camera and tripod, with assistance from four of the zookeepers, I recorded 32 penguin feedings. I then used an Analysis of Variance (ANOVA single factor function in excel) to look for the variance amongst the mean number of fish eaten. I only ranked the penguins for the first nine fish of each feed, because there are nine penguins, thus if it was truly random they should each have averaged one fish per the first nine. I performed this analysis on all 32 feeds, but also ran it in smaller groupings based on the time of the feed (AM/PM), the weather (sunny/cloudy), and the keeper feeding (of four options), to try and account for potential bias or extra factors. The overall analysis of 32 feeds was statistically significant (F = 13.46, df = 8, 279, P < 0.001), and its results were backed up by the majority of the other nine analyses. Only one was not statistically significant, but was close (P = 0.067), and still supported the results of the overall analysis. Two penguins were found to be more dominant, having eaten on average, much more of the fish of the first nine, and two penguins were found to be more submissive. The dominant ones were a male and a female, the male being the largest penguin in the colony. The two submissive were also a male and a female, both of whom were the smallest in the colony. Neither the dominant nor submissive penguins were pair bonded with each other. This indicates that there is a social structure in captivity, and could have implications for husbandry of Humboldt penguins, perhaps in a manner that decreases fighting during feeds. Future study should look at agonistic behavior, instead of average numbers of fish, to determine if it supports the results of this study.