Structural manipulations of a shelter resource reveal underlying preference functions in a shell-dwelling cichlid fish

Many animals can modify the environments in which they live, thereby
changing the selection pressures they experience. A common example of such
niche-construction is the use, creation, or modification of environmental
resources for use as nests or shelters. Because these resources often have
correlated structural elements, it can be difficult to disentangle the
relative contribution of these elements to resource choice, and the
preference functions underlying niche-construction behaviour remain
hidden. Here, we present an experimental paradigm that uses 3D-scanning,
-modelling, and -printing to create replicas of structures that differ
with respect to key structural attributes. We show that a
niche-constructing, shell-dwelling cichlid fish, Neolamprologus
multifasciatus, has strong open-ended preference functions for exaggerated
shell replicas. Fish preferred shells that were fully intact and either
enlarged, lengthened, or had widened apertures. Shell intactness was the
most important structural attribute, followed by shell length, then
aperture width. We disentangle the relative roles of different shell
attributes, which are tightly correlated in the wild, but nevertheless
differentially influence shelter choice and therefore niche construction
in this species. We highlight the broad utility of our approach when
compared to more traditional methods (e.g. two-choice tasks) for studying
animal decision-making in a range of contexts.