The studies on natal dispersal in vertebrates often ignore the family
structure and treat the behaviour of siblings as if they were statisti
cally independent. This might lead to erroneous conclusions since the
non-independence of siblings is supported empirically. We show the pos
sible misinterpretations that may arise from such approaches and propo
se a method allowing to avoid this problem. We illustrate this method
by using data on natal dispersal of the common lizard Lacerta vivipara
.