Kepplinger, D. | Search bioRxiv

bioRxiv2025

Egg colour mimicry in the common cuckoo results from coevolutionary alternation, not coevolutionary arms races

The exquisite eggshell mimicry found in many cuckoo-host systems has been the textbook example of a coevolutionary arms race1. In this system, cuckoos lay their eggs in their hosts nests leaving these foster parents to rear their young2. In defence, most of these hosts have evolved the ability to recognize cuckoo eggs. It is long-assumed that these interactions select for ever-improving eggshell mimicry in cuckoo host-races laying distinct eggs that specifically mimic their hosts eggshell, regardless of its particular colour3,4. We challenge this paradigm and demonstrate that coevolutionary arms races and egg colour mimicry are the exception to the rule. Here, using eggshell reflectance spectra from 39 host species and the specific cuckoo eggs found in their nests, we show that eggshell colour mimicry is very uncommon even among frequent hosts. Although cuckoo eggs display considerable variation in eggshell colour, their hosts eggshell colours occupy 6 times their colour volume. As a result, mimicry is only achieved for a small subset of the egg colour gamut. Furthermore, cuckoo host-races rarely lay eggs that match their hosts eggs better than those of other potential hosts or that are distinct from those laid by other cuckoo host-races. These patterns are inconsistent with the long-held assumption of coevolutionary arms races, but consistent with coevolutionary alternation that is defined by a process of continual host-switching. These findings open new avenues for research in a system that has long served as a model for studying coevolutionary processes.

evolutionary biology↗

bioRxiv2022

Recording animal-view videos of the natural world

Plants, animals, and fungi display a rich tapestry of colors. Animals, in particular, use colors in dynamic displays performed in spatially complex environments. In such natural settings, light is reflected or refracted from objects with complex shapes that cast shadows and generate highlights. In addition, the illuminating light changes continuously as viewers and targets move through heterogeneous, continually fluctuating, light conditions. Although traditional spectrophotometric approaches for studying colors are objective and repeatable, they fail to document this complexity. Worse, they miss the temporal variation of color signals entirely. Here, we introduce hardware and software that provide ecologists and filmmakers the ability to accurately record animal-perceived colors in motion. Specifically, our Python codes transform photos or videos into perceivable units (quantum catches) for any animal of known photoreceptor sensitivity. We provide the plans, codes, and validation tests necessary for end-users to capture animal-view videos. This approach will allow ecologists to investigate how animals use colors in dynamic behavioral displays, the ways natural illumination alters perceived colors, and other questions that remained unaddressed until now due to a lack of suitable tools. Finally, our pipeline provides scientists and filmmakers with a new, empirically grounded approach for depicting the perceptual worlds of non-human animals.

animal behavior and cognition↗