A geometric analysis of symmetry in the architecture of bifid bat tents and the effects of leaf dimensions on tent construction

Background/Question/Methods

The roosting requirements of bats are largely dependent on the species’ needs as well as the location in which they reside. Appropriate roosting areas are essential for the well-being of bats given their physiological requirements as mammalian heterotherms. In the tropics, a unique group of external foliage-roosting types has developed, and they are characterized by modified leaf structures created by cuts made by bats. While there exists a number of studies on bat roosting ecology and tent architecture, no study has been done on the manner by which the tents are constructed or the factors influencing this. This study investigated the extent of symmetry in bifid tents and the relationship between leaf geometry and cuts made by bats on leaves of Asterogyne spp. and Calyptrogyne spp. in the La Selva Biological Station in Costa Rica. Leaves modified into bifid tents were removed and a number of measurements taken for each half of the leaf to create a holistic geometric representation of the leaf tent. A canonical correlation analysis and regression were used to investigate the extent of symmetrical relationships between two halves of the leaf tents.  

Results/Conclusions

Results of this study provide evidence for symmetry of total tent area and, to a lesser degree, symmetry of the angle of the first cut. Lengths of cuts and angles of the second cut were shown to be asymmetrical. Rather than being consistent in their lengths and angles of cuts across all leaves, the dimensions of cuts changed relative to the leaf dimensions, suggesting that tent-building is an adaptive and plastic behavior in bats. Tenting bats may tend to construct symmetrically sized tents to maintain more stable temperatures, adequate protection, and balanced weight distribution within their roosting sites. Though bats tend to create near-symmetrical tents, leaf geometry does not account for the cuts on both sides equally. It is likely that these differences can be explained by symmetric compensation, wherein the inconsistencies of cuts between the two sides are motivated by the bats’ overall inclination towards tent symmetry. That the left sides of the tents are more consistent than the right leads to the speculation that bats generally begin construction on the left side, followed by corresponding adjustments on the right, providing us further insight on bat tent construction, and neuro-behavioral implications of handedness and cognitive bias in bats.