Ecologically relevant cooling early in life does not affect expression of neophobia in zebra finch chicks (Taeniopygia guttatta)

Student: Anna James
Major: Biology
Minor: Spanish
Advisor: Dr. Sharon Lynn
Altricial chicks depend on their parents for warmth during early development. When parents leave the nest, chicks can readily cool to suboptimal temperatures. In response to cooling, altricial chicks exhibit activation of the hypothalamic-pituitary-adrenal axis, resulting in secretion of corticosterone. Repeated exposure to cooling, as a result of females brooding less often, may lead to repeated corticosterone exposure and development of a dampened stress response, both of which affect neophobia (fear of novelty). To study whether cooling affects neophobia, I repeatedly cooled zebra finch (Taeniopygia guttatta) chicks to ecologically relevant temperatures (temperatures they would experience when parents are off the nest) in their first week of life and tested them for neophobia at six weeks of age. My results indicate that Cool and Control chicks did not respond significantly differently to novelty. Thus, variation in nestling temperatures, which is associated with variation in brooding patterns, may not affect offspring neophobia.

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Description

For my senior Independent Study, I investigated if ecologically relevant cooling affects expression of neophobia in zebra finch chicks. Young, altricial chicks (featherless, immobile, and nest-bound) are highly dependent on their parents for warmth. When the parents leave the nest, the chicks are exposed to ambient temperatures and can readily cool to suboptimal temperatures. In response to such cooling, altricial chicks secrete a stress hormone called corticosterone. If the parents repeatedly leave the nest, the chicks are repeatedly cooled and likely repeatedly exposed to corticosterone, which can have dampening effects on the stress response. Furthermore, development of a dampened stress response is linked with reduced expression of neophobia (fear of novelty) later in life. My study focused on the question: Do repeated bouts of cooling, which can lead to the development of a dampened stress response, affect expression of neophobia? I hypothesized that repeated bouts of cooling early in life would promote reduced expression of neophobia. I predicted that chicks that underwent repeated cooling would more quickly approach a novel object on a perch (reduced latency), spend more time close to that novel object, and spend more time on the perch with the object.
To study this question, I bred adult zebra finches and used the resulting chicks in my study. After hatching, I randomly assigned chicks to two treatment groups, Cool and Control. Cool chicks were cooled to temperatures that mimic temperatures they would experience when the mother is off the nest. Control chicks were kept at temperatures that mimic normal brooding temperatures. All chicks underwent four 18-minute temperature treatments between days 1 – 6 post-hatch. At six weeks of age, I tested the birds for expression of neophobia by presenting them with a perch that had a novel object (a green bow) on it. I measured the birds’ latency to approach the bow, time spent close to the bow, and total time spent on the perch.
The results of my study indicate that repeated cooling did not affect expression of neophobia as the Cool chicks did not have reduced latencies to approach the novel object, did not spend more time close to the object, and did not spend more time on the perch overall. Therefore, variation in chick temperature, which is associated with variation in parental brooding behavior (how long and how often parents leave the nest), may not greatly affect the development of neophobia in zebra finch chicks.
Anna will be online to field comments on May 8:
2-4pm EDT (PST 11am-1pm, Africa/Europe: evening)

Posted in I.S. Symposium, Independent Study on May 1, 2020.