Effects of temperature and moon phase on the winter activity patterns of a tropical ungulate

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Michaela Peterson and Maria Luisa Jorge, Earth & Environmental Sciences, Vanderbilt University, Nashville, TN

Background/Question/Methods
Animals alter their temporal and spatial activity patterns in response to a variety of environmental cues. Temperatures outside a species preferred range often result in changes in temporal activity, as well as selection for thermally optimal microclimates. Moon phase results in changes in nocturnal activity, due to the effect of light intensity on visual acuity and predation risk. In this study, we examine how the white-lipped peccary (Tayassu pecari), a social ungulate and keystone species found in Neotropical forests, shifts its temporal activity and microclimate selection in response to temperature and moon phase in an Atlantic Forest fragment during the winter. For a period of four weeks in June – July of 2019, we deployed camera traps paired with weather data loggers at 16 sites within Caetetus Ecological Station in São Paulo, Brazil. We used circular kernel density estimation to analyze temporal activity patterns, and calculated coefficients of overlap between the resulting kernel density estimates to examine differences in activity between moon phases, and between cooler and hotter periods. We performed chi-square tests to determine whether peccaries chose sites whose temperatures deviated significantly from the average temperature across the study area.
Results/Conclusions
Throughout the study period, peccaries were more likely to be recorded at camera sites with higher-than-average temperatures for the study area, with the temperature at sites where peccaries were recorded being on average 0.94 °C greater than the average site temperature at the time of the record. On days with a minimum temperature below 6.2 °C (the coldest quarter of days within the study period), peccaries were less active in the morning, more active in the early evening, and showed only a single activity peak as opposed to their more typical bimodal activity pattern. During the full and new moon, peccaries also displayed a unimodal activity pattern, with reduced nocturnal activity. This is the first study to show that peccaries alter their behavior in response to low temperatures or moon phase. Our findings indicate that peccaries alter their spatial and temporal activity patterns in response to ambient temperatures, but that moonlight intensity constrains their nocturnal activity levels.