Measuring Lateral Biases During Feeding in Semifree-Ranging Black and White Ruffed Lemurs (Varecia variegata variegata) E.L. Nelson 1,2 , F. Ruperti 1,3 and M.A. Novak 2,4 1 Monkeyland Primate Sanctuary, Plettenberg Bay, South Africa, 2 Neuroscience and Behavior Graduate Program, University of Massachusetts Amherst, USA, 3 Primate Conservation Postgraduate Programme, Oxford Brookes University, Oxford, United Kingdom, 4 Psychology Department, University of Massachusetts Amherst, USA Laterality indices were calculated for hand use and head-tilt using the formula [(Right- Left)/(Right + Left)]. Scores ranged from -1 to 1 with negative values indicating a left bias and positive values a right bias. Hand Preference A single-group t-test of hand use revealed a significant group-level left bias, t(10)= -4.038, p<.01, Figure 1. The mean of -0.52 (SD=0.42) was significantly different from 0. Thus the majority of the lemurs preferred the left hand during feeding. This is consistent with previous literature in this species (Forsythe, Milliken, Stafford & Ward, 1988). Head-Tilt Only 9 lemurs had sufficient data for the head-tilt analysis. A single-group t-test did not find a significant trend for head-tilt, t(8)=0.244, p>.05, M=0.02, SD=0.29. Predicting Hand Preference from Head-Tilt Head-tilt was found to significantly predict hand preference (r =0.72, p<.05, Figure 2). There was a positive relationship between the two variables such that the stronger the left hand preference, the greater the degree of left head-tilt. Lemurs were found to be left-preferent for unimanual food processing. These data on hand use replicated previous findings in black and white ruffed lemurs (Forsythe et al., 1988). Although there was no group-level bias for head-tilt, head-tilting behaviour was predictive of hand preference. Concordance between hand use and head turning has also been found in human infants (e.g. Michel, 1981), although the direction of bias differs. Infants show a preference for turning the head towards the right which later corresponds to a preference for reaching with the right hand. In black and white ruffed lemurs, the bias seems to be to the left. Data continue to be collected and analysed as this preliminary report was based on a limited sample. In total there are 22 black and white ruffed lemurs at Monkeyland. With additional study we hope to better understand the role of laterality in brain organisation within and across different primate species. Note : Monkeyland is sustained by responsible eco-tourism. This was the first research study to be conducted at the sanctuary. Science and tourism are mutually beneficial. Monkeyland is currently planning a permanent education and research centre. Providing such a venue for learning is a positive solution to the pressing need to make the public aware of the plight of primates and the environment. Figure 1: Left bias in hand use Figure 2: Predicting hand preference from head-tilt References: Forsythe, C., Milliken, G.W., Stafford, D.K. & Ward, J.P. (1988). Posturally related variations in the hand preferences of the ruffed lemur (Varecia variegata variegata). Journal of Comparative Psychology, 102(3), 248-250. MacNeilage, P.F., Studdert-Kennedy, M.G. & Lindblom, B. (1987). Primate handedness reconsidered. Behavioral and Brain Sciences, 10, 247-303. McGrew, W.C. & Marchant, L.F. (1997). On the other hand: Current issues in and meta-analysis of the behavioral laterality of hand function in non-human primates. Yearbook of Physical Anthropology, 40, 201-232. Michel, G.F. (1981). Right-handedness: A consequence of infant supine head-orientation preference? Science, 212 (4495), 685-687. Papademetriou, E., Sheu, C. & Michel, G.F. (2005). A meta-analysis of primate hand preferences, particularly for reaching. Journal of Comparative Psychology, 119, 33-48. Acknowledgements: The authors wish to thank Tony Blignaut and Lara Mostert of Monkeyland for their support, Neil Berthier for his helpful comments, Inge Vestters for continued data collection, and the black and white ruffed lemurs who were so wonderful to follow day after day. Correspondence to: E.L. Nelson enelson@nsm.umass.edu Laterality, meaning the preference for one side of the body over the other, is often studied in nonhuman primates in the context of feeding. Researchers have primarily been concerned with manual laterality, or asymmetries in the use of the hands (for reviews of hand preference in nonhuman primates, see MacNeilage, Studdert-Kennedy & Lindblom, 1987; McGrew & Marchant, 1997; Papademetriou, Sheu & Michel, 2005). In a species such as the black and white ruffed lemur that has a propensity to feed with the mouth, behavioural asymmetries in feeding may be more subtle. These lemurs have been observed to tilt their heads back while chewing, often at a sharp angle to the left or right side. This study was the first to examine the relationship between head-tilt and hand use during feeding in black and white ruffed lemurs. Data were collected from a semifree-ranging population (n=11) at Monkeyland Primate Sanctuary in Plettenberg Bay, South Africa. Primates were provisioned twice daily at 12 feeding platforms scattered throughout the forest enclosure. Feeding episodes were videotaped between 0730 and 1730 hours. Sampling was based on spontaneous observation and consisted of focal-animal follows until the individual moved out of sight. Behavioral laterality is often studied in nonhuman primates in the context of feeding. Researchers have primarily been concerned with manual laterality, or asymmetries in the use of the hands. In a species such as the black and white ruffed lemur (Varecia variegata variegata) that has a propensity to feed with the mouth, behavioral asymmetries in feeding may be more subtle. Varecia have been observed to tilt their heads back while chewing, often at a sharp angle to the left or right side. This study was the first to examine the relationship between head-tilt and hand use during feeding in Varecia. Data were collected from a semifree-ranging population (n=11) at Monkeyland Primate Sanctuary in South Africa. Primates were provisioned twice daily at 12 feeding platforms scattered throughout the forest enclosure. Varecia were videotaped feeding between 0730 and 1730 hours. Sampling was based on spontaneous observation and consisted of focal-animal follows until the individual moved out of sight. A one-sample t-test of hand use revealed a significant group-level left bias, t(10)=-4.038, p<.01. This is consistent with previous literature in Varecia. There was no group-level bias for head-tilt, although five individuals showed concordance in hand use and head-tilt. This is in contrast to studies of human neonates that have found a rightward bias in head turning which corresponds to a right-hand preference for reaching later in life. Left: Darwin right hand food pick-up; Right: Othello left head-tilt