Analysis of aggregation behavior of Xenopus Laevis tadpoles in relation to sibling rearing condition and presence of a predator cue

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Brane, Kate Elizabeth
Sullivan, Karen Brown

Differential effects on behavior of a focal tadpole subjected either to the absence or presence of a predator cue were examined when the focal animal was in the presence of conspecific tadpoles differing in relatedness and familiarity. Tadpoles of the South African clawed frog (Xenopus laevis) were reared in full-sibling and mixed sibling groups in order to test an individual tadpole’s response to a predator cue while in the social context of a centralized tadpole group that varied in the degree of relatedness and also familiarity. Three different social contexts examined were as follows: 1) focal tadpole both related and familiar (RF) to a centralized tadpole group of 5 individuals from the same clutch and rearing tank; 2) focal tadpole tested with a mixed-related and familiar (MRF) centralized group of tadpoles from four separate clutches but the same rearing tank; and 3) focal animal unrelated and unfamiliar (URUF) with a group of centralized tadpoles from different separate clutches and rearing tanks. BIOBSERVE Viewer2 software allowed a variety of behavioral variables (i.e., velocity, track length, activity, and duration in distinct test arena zones) to be simultaneously filmed and quantitatively recorded for each focal animal. The focal animal was given both visual and olfactory, although not physical, contact with the centralized animals. Focal animal behavior was filmed for 10 minutes, either with or without a conspecific alarm cue present in the test arena. Mean and summary behaviors were calculated for each focal tadpole at 20 s intervals for each minute of the test. The tadpoles in the absence of cue showed greater differences in mean behaviors among test groups toward the end of the ten minute filming period; those in the presence of the cue exhibited a greater number of significant differences in mean values among test groups in the initial part of the films. In the presence of predator cue, test groups responded in a manner that would support the hypothesis of protecting more closely related individuals from the threat of predation and thus increasing inclusive fitness; while in the presence of cue, URUF focal tadpoles tended to expend more time and activity near conspecifics while MRF and RF exhibited behaviors indicating a distancing from center animals. Theoretical expectations for a particular behavior need to be evaluated in the context of the environmental and social conditions. That URUF animals go to the center more in the presence of the cue compared to RF animals suggests that anti-predator strategies are not just a simple response, but may adaptively vary dependent on background conditions. The results of this study support the conclusions that 1) X. laevis tadpoles do respond behaviorally to a conspecific predator cue, 2) the response of the tadpole varies dependent on the potential social interactions available during the predator threat, and 3) these tadpoles behave in manner that can be explained as showing more “altruism” towards related individuals.

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Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Biological Sciences.
Includes bibliographic references (leaves 50-54)