Lizards cooperatively tunnel to construct a long-term home for family members

Abstract

Constructing a home to protect offspring while they mature is common in many vertebrate groups, but has not previously been reported in lizards. Here we provide the first example of a lizard that constructs a long-term home for family members, and a rare case of lizards behaving cooperatively. The great desert skink, Liopholis kintorei from Central Australia, constructs an elaborate multi-tunnelled burrow that can be continuously occupied for up to 7 years. Multiple generations participate in construction and maintenance of burrows. Parental assignments based on DNA analysis show that immature individuals within the same burrow were mostly full siblings, even when several age cohorts were present. Parents were always captured at burrows containing their offspring, and females were only detected breeding with the same male both within- and across seasons. Consequently, the individual investments made to construct or maintain a burrow system benefit their own offspring, or siblings, over several breeding seasons.

Figure 1. Relatedness composition within burrow systems.

For each of 26 burrow systems two sets of relatedness data (R) are given, the average R±1 s.d between all lizards captured at that burrow and, in the next column to the right, R±1 s.d between the immature lizards. The average relatedness among all 120 genotyped individuals is shown by the lower horizontal line (R = 0.021), the upper horizontal line shows the average within-group relatedness (R = 0.371). Along the x-axis, for each group a series of numbers are given separated by commas. From bottom to top these are; the number of adults, age-cohorts of immature lizards, total group size of sampled individuals and the minimum number of years for which the burrow has been continuously occupied.

Figure 2. The distribution of genotypic similarity (r) with geographic distance (kilometres) for immature lizards.

The solid line tracks relatedness, dashed lines represent the upper (U) and lower (L) 95% confidence interval around random expectations while bars around R show the 95% confidence interval around this estimate determined by bootstrapping. The distance class of 0 kilometres contains the r estimate among individuals sharing the same burrow system.