Grasping the handedness of varecia
Mar 28, 2016
Grasping the handedness
of varecia
Background…
Brain lateralization: the functional specialization of the brain
Evolutionary Significance?
• Avoids costly duplication of
neural circuitry
• Enhances ability to perform two
tasks simultaneously
The cerebral hemispheres of the
brain control different functions
right left
Non-human primates
lateralize too!
Chimpanzees have adapted techniques
for catching and eating termites.
• Evolution of primate
handedness still unclear
• Non-human primates
exhibit “mixed”
handedness
• Handedness in primates
influenced by body
posture, task difficulty, and
experience
Background…
Hypotheses Hypothesis & predictions
bipedalism theory:
• Quadrupedal bipedal
• Required higher balance
• Increased cerebral lateralization
A group of Red Ruffed
lemurs (Varecia rubra) sunning on horizontal limb
P1: Both species of Varecia exhibit
handedness
P2: Handedness consistent among
siblings
Methods 1 Subjects & location
Location: Duke Lemur Center, indoor and outdoor enclosures
NHE 6 NHE 8
• White Ruffed Lemur (Varecia variegata)
• 4 males
• Red Ruffed Lemur (Varecia rubra)
• 2 males, 2 females
triplets twins twins
• Rest
• Manipulate
• Social
• Feed
• Groom
• Locomotion
• Suspension
• Other
Methods
Data collection method: continuous scan sampling
• Manipulating, supporting
• Supported and unsupported Red Ruffed lemur (Varecia rubra) showing leading limb preference
• V. rubra - left limb
preference
– 23.1 ev/hr SE 3.3
• V. variegata – right
limb preference
– 44.0 ev/hr SE 3.5
• Significant
results Varecia species exhibit a manipulating limb preference
0
5
10
15
20
25
30
35
40
45
50
V. rubra V. variegata
Ra
te o
f m
an
ipula
ting
lim
b u
se (
eve
nts
/ho
ur)
Species
Rate of manipulating limb use between
family groups of Varecia
Left limb
Right limb
• V. rubra - right limb
preference
– 10.5 ev/hr SE 1.5
• V. variegata– left
limb preference
– 19.8 ev/hr SE 1.0
results Varecia species exhibit a supporting limb preference
0
5
10
15
20
25
V. rubra V. variegata
Ra
te o
f su
pp
orti
ng
lim
b u
se (
eve
nts
/mo
nth
)
Species
Rate of supporting limb use between family
groups of Varecia
Left limb
Right limb
results Manipulating limb preference is consistent among siblings
0
5
10
15
20
25
30
35
40
45
1 2 3 4
Ra
te o
f m
an
ipula
ting
lim
b u
se (
eve
nts
/ho
ur)
Individual
Rate of manipulating limb use
among V. rubra siblings
Left limb
Right limb
0
10
20
30
40
50
60
1 2 3 4
Ra
te o
f m
an
up
ula
ting
lim
b u
se (
eve
nts
/ho
ur)
Individual
Rate of manipulating limb use
among V. variegata siblings
Left limb
Right limb
conclusions
• V. rubra and V. variegata exhibit handedness
• Vacercia handedness is
consistent among
siblings
Close up of Red Ruffed Lemur (Varecia rubra) hand
Prediction 1
Varecia handedness
Close up of
White Ruffed
Lemur
(Varecia variegata ) using both
hands as
support
• Reflects brain lateralization
– Manipulating limb vs supporting limb
Prediction 2
Species’ consistency among siblings
White Ruffed Lemur (Varecia variegata) triplets
• Possible heritable
component to handedness
– Prior studies
• Mixed preference
• Number and consistency of
study groups
• Relatedness
• Further research