NICHE, MORPHOLOGY AND LOCOMOTION IN LACERTID LIZARDS 
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c d 
Fig. 14 Views of specialised climbing lacertid ascending vertical surface; a, b dorsal; c, d lateral. Crus and foot are not extended far forwards and hind 
digits flex mesially at end of power stroke, the body is kept very close to the surface being climbed. 
Many lacertids climb on open continuous surfaces such as rocks 
and tree boles and branches. These vary in steepness, from gentle 
slopes to vertical and even overhanging surfaces, and lizards may 
run directly up them, or descend, or travel laterally or obliquely. 
Locomotion in specialised lacertid climbers often has many simi- 
larities to that of ground dwellers, but there are marked differences, 
especially when ascending perpendicular and near-vertical faces. 
In this situation, a lizard like Lacerta oxycephala climbs with its 
body very close to the surface and the limbs spread laterally so the 
distal extremity of the femur does not pass dorsal to the crus during 
the power stroke (Fig. 14). As in ground dwellers, the limbs work in 
diagonal pairs. Each hind foot is placed lateral and posterior to the 
ipsilateral forefoot and the hind leg in each diagonal limb pair is 
delayed relative to the foreleg so that, as the recovery phase is brief, 
the proportion of time when two feet are out of contact with the 
substratum is small. In observed sequences of climbing in Lacerta 
oxycephala, the recovery phase took between an eighth and a quarter 
as long as the power phase, the smaller proportion being during slow 
climbing. Counts of the number of frames of cine film in which four, 
three and two feet gripped the rock suggest that four legs may be in 
contact for over half, and three legs for over three-quarters of the total 
time; there is consequently no floating phase. This pattern contrasts 
strongly with fast locomotion in specialised ground dwellers where 
two legs are usually out of contact with the substratum and sometimes 
all four. The distance between the consecutive foot holds is more or 
less equal for both fore and hind limbs, being about half to threequarters 
of the snout-vent distance in the locomotory sequences studied. 
Movements of the hind limb 
The excursion of the hind limbs is relatively restricted and although 
the femur is directed anterolaterally at the beginning of the power 
stroke (right hind limb, Fig. 14a,c), the crus is not brought fully 
forwards at this time and is usually, directed approximately normal 
to the body axis. The metatarsal segment, which is mesially in- 
flected, is then directed anterolaterally and is placed flat on the 
substratum. 
Fig. 15 Flexing in the hind toes of a climbing Lacerta oxycephala at the end of the step. a. oblique lateral view showing flexion in the sagittal plane of the 
toes. b. dorsal view, showing mesial flexion of toes 1-4. 
