Of the two hypotheses proposed to explain lunar activity patterns – the predation risk hypothesis and the visual acuity hypothesis – neither was completely supported by our results. The predation risk hypothesis predicts that, if predation is more successful under bright moonlight, prey species will become lunarphobic by reducing full moon activity. Although 50% of the prey species exhibited the reduction in full moon activity predicted by the predation risk model, the remaining species were either lunarphilic or exhibited no lunar activity pattern.

Lunar activity patterns of coyote, ocelot, and puma were significantly non-random by Rao’s spacing test (coyote: U2136 = 231.0, P < 0.001; ocelot: U505 = 182.0, P < 0.001; puma: U633 = 189.1, P < 0.001), while the Rao’s P-values for the activity patterns of predators with smaller sample sizes were non-significant (tayra: U26 = 129.8, NS; oncilla: U157 = 142.5, NS; margay: U25 = 158.8, NS; jaguar: U46 = 15.0, NS; Table 4, Figure 5).

. One explanation is that brighter moonlight is associated with increased risk of predation (Predation Risk hypothesis), but it has also been proposed that nocturnal activity may be influenced by the sensory ecology of a species, with species that rely on visual detection of food and danger predicted to increase their activity during bright moonlight, while species relying on non-visual senses should decrease activity (Visual Acuity hypothesis).

However, such experiments are not always feasible for all organisms, for a number of reasons, including high mortalities under laboratory conditions, long-lived or endangered species.

However, the confounding processes previously mentioned cannot be ruled out based solely on these experiments and a direct estimation of the genetic determination is needed (de Villemereuil et al., 2016).

The two species of mussels responded differently, to warming and pCO2. The native mussel T. hirsuta grew more under warming (Fig. 1; ANOVA Species × Temperature F1,32 = 6.13, P < 0.05; Supplementary Table 2). In contrast, M. galloprovincialis grew the same at ambient and elevated temperatures (Fig. 1; Supplementary Table 2). There was no effect of elevated pCO2 on growth in either of the mussel species (ANOVA CO2 F1,32 = 0.53, P > 0.05; Supplementary Table 2).