Influence of moon phase on temporal activity & predator-prey overlap
It is recognized that the response of nocturnal mammals to moonlight differs among taxa and may vary according to several determining factors, such as phylogeny, trophic level, sensory systems and human activity (Santos et al., 2019). This camera-trap based assessment has revealed both lunar phobic and lunar philic behaviors of rare and/or shy animals and contributes to building our understanding of the factors shaping activity patterns of multiple sympatric mammals under different lunar phases.
Our results indicated that leopards show no activity pattern throughout the four lunar phases, exhibiting neither a clear lunar phobic nor lunar philic activity pattern, as observed in other felid species too, such as puma (Puma concolor ) and jaguar (Panthera onca ) in Neotropical forests (Harmsen et al., 2011, Prugh and Golden, 2014). Due to the extraordinary reflectance of the feline tapetum cellulosum, assessed to reflect 130 times extra light than the human eye (Huck et al., 2017), we suspect that the leopards’ lack of tendency to be more or less active during the full moon can be at least partly explained by visual acuity. We also suppose that the leopards’ irregular temporal patterns may be influenced by mesopredators in the landscape, such as red fox (Vulpes vulpes ) and leopard cat (Prionailurus bengalensis ), as sympatric carnivores can drive temporal activity fluctuations (Packer et al., 2011, Hua et al., 2020). In terms of human activities, human-leopard conflict has been found to occur often in the summer in TPNR (Hua et al., 2020), and perhaps this can explain irregular activity patterns and the higher relative species abundance in winter. Human activity on foot and in vehicles mostly occurred in the day time in TPNR, so a landscape of fear induced by human activities may adjust leopard behavior, for example our earlier research work conducted by Hua et al., (2020) In TPNR concluded that grazing intensity by free roaming cattle was lower in the winter than summer and may also influence wild animal behavior.
For the herbivore prey species studied, our results are similar with previous research showing that mammals often adapt their nocturnal activity to the level of lunar illumination (e.g (Huck et al., 2017, Pratas‐Santiago et al., 2017). Here, wild boar and Tolai hare were evidently lunar phobic, while roe deer indicated lunar philic activity. Especially in the case of the wild boar and Tolai hare, the results align with the visual acuity hypothesis, as lagomorphs and suids have poor eye sight and avoid the brightness of moon to reduce predation risk (Pratas‐Santiago et al., 2017, Preisser et al., 2005, Tuan, 1979, Zaman et al., 2020a). Lunar phobic behavior has also been observed in Neotropical prey species, such as armadillo (Dasypus novemcinctus ) and paca (Cuniculus paca ) (Harmsen et al., 2011, Prugh and Golden, 2014), while hare have also been observed to dodge the risk of predation by medium-sized felids by adjusting temporal activity (Griffin et al., 2005). Deer species however, including white-tailed deer (Odocoileus virginianus ) and red brocket deer (Masama temama ), have shown both lunar phobic and lunar philic behaviours, and while they have tapetum, prey can shift their night activity because the choroidal tapetum fibrosum (CTC) of carnivores has better light reflectance than the choroidal tapetum fibrosum (CTF) of ungulate herbivores (Botts et al., 2020, Brown et al., 1999).
Although felid activity patterns rarely relate with those of their potential prey (Ramesh et al., 2012) (Krittika and Yadav, 2020), in this study, leopard nocturnal activity had high overlap with that of roe deer and Tolai hare across the full lunar cycle. These results support the prediction that predators should reduce activity at times when major prey species are less active, in accordance with both the visual acuity and optimal foraging model (Pianka, 1973, MacArthur and Pianka, 1966). Conversely, prey can adjust their activity pattern or spatial distribution to avoid predators (i.e., to reduce predation risk), such as bighorn sheep (Ovis canadensis ) spatially eluding pumas (Puma concolor ) (Laundré et al., 2001), and roe deer and wild boar having minimal temporal overlap with tigers (Yang et al., 2019). Hence, while lunar phobia (wild boar and Tolai hare) and lunar philia (roe deer) were observed in the prey species in this study, the activity pattern of leopards observed here, we suspect, is more closely linked with the temporal behaviors of prey species than directly with moon phase per se .
Explicitly during the full moon phase, nocturnal activity of leopards and prey were diversely affected by clear summer nights and moon risk index (MRI). Leopards activity during the full moon showed preference for high lunar luminosity (high MRI) and showed higher activity during clear summer or winter nights. We suppose that clear summer or winter nights or active prey may either force leopards to restrict roaming behavior (and reduce hunting success) or may increase activity as they move towards a safe or warmer refuge (Türk and Arnold, 1988). For prey species, nocturnal activity events during the full moon were more for roe deer in summer or winter (seasonal effect), during clear bright nights for wild boar (clear cover and MRI interaction effect), and during clear nights (especially summer ) for Tolai hare (clear cover and MRI interaction effects). Others have also revealed that cloud cover, which alters moonlight and MRI (Packer et al., 2011, Pratas‐Santiago et al., 2017) and season influence nocturnality and temporal behaviours of carnivores and ungulates (Shamoon et al., 2018), as well as foraging behaviour of wild boar and roe deer (Frauendorf et al., 2016, Yang et al., 2018a).it is reasonable to assume that there is variation in nocturnal activity between seasons.