Asymmetrical hatching behaviors: The development of postnatal motor laterality in three precocial bird species

Abstract

The effects of asymmetrical hatching behaviors on the development of turning bias and footedness in domestic chicks, bobwhite quail, and Japanese quail chicks were examined. Control tests with incubator reared domestic chicks and bobwhite quail revealed significant individual and population left-side turning bias and right footedness. When late stage hatching behaviors were disrupted, population laterality was not evident and individual laterality was reduced. By contrast, Japanese quail chicks demonstrated no population turning bias or footedness and only weak individual biases. Disruption of hatch behaviors further decreased laterality. Examination of discarded eggshells showed significant differences in the degree of rotation made to cut out of the egg by Japanese quail versus domestic chicks and bobwhite quail. Taken together these findings suggest that the counterclockwise hatching behaviors that are characteristic of many precocial bird species serve to facilitate the development of motor laterality at both the individual and population level.

Comment on “Number-space mapping in the newborn chick resembles humans’ mental number line”

“…As noted previously, there is nevertheless a strong a priori reason to expect motor and perceptual biases under the conditions used in this study [e.g., (4,6,9)]. Evidence of side bias is also detectable in Rugani et al For example, the average absolute deviation from 50/50 responding across all 10 trials for each chick was 12.7% T 1.1%, indicating that most chicks exhibited some degree of bias (t = 11.5, P < 0.00001).…”

“…This Comment will focus on a critical flaw in the study's design and statistical analysis. I argue that Rugani et al failed to measure, model, or control for the significant side biases displayed by precocial birds, including the domestic chicks used in their study (2)(3)(4)(5)(6)(7)(8)(9).…”

“…For example, chicks show significant bias for turning left at the intersection of a T maze (4,6,9,11), in addition to task-dependent preferences for foot and eye use (2,3,5). Such biases are sculpted by normally occurring pre-and perinatal experience, including both differential exposure of the hemispheres to audiovisual stimulation prenatally (4,7,11,12) and the repetitive turning movements necessary for chicks to successfully hatch from the egg (6, 9).…”

“…Such biases are sculpted by normally occurring pre-and perinatal experience, including both differential exposure of the hemispheres to audiovisual stimulation prenatally (4,7,11,12) and the repetitive turning movements necessary for chicks to successfully hatch from the egg (6, 9). As a consequence, as many as 67 to 90% of domestic chicks display significant side biases in tasks requiring a locomotor response (4,6,9).…”

Drift during overground locomotion in newly hatched chicks varies with light exposure during embryogenesis

“…However, investigation into the impact of extended prenatal exposure on postnatal motor development has been limited (Sindhurakar & Bradley, 2010). Studies have examined the effects of light exposure in the final days before hatching, providing evidence that light is a salient stimulus capable of influencing vision-mediated behavior (Casey & Lickliter, 1998; Rogers, 1982; Rogers & Bolden, 1991), hemispheric specialization (Casey & Martino, 2000; Casey, 2005; Rogers, 1982), and social behavior (Rogers, 1982). A few studies in domestic chicks have also shown that extended light exposure during embryogenesis can accelerate development of respiratory control (Bradley and Jahng, 2003), interlimb stepping prior to hatching (Ryu & Bradley, 2009; Sindhurakar & Bradley, 2012), and overground locomotion at hatching (Sindhurakar & Bradley, 2010).…”