lateral dominance in lemurs- presentation

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