DOI: 10.5061/dryad.rfj6q57fs
title: Data for: Butterfly foraging is remarkably synchronous in an experimental tropical macrocosm

description: Diel patterns in foraging activity are dictated by a combination of
 abiotic, biotic, and endogenous limits. Understanding these limits is
 important for insects because ectotherm taxa will respond more
 pronouncedly to ongoing climatic change, potentially affecting crucial
 ecosystem services. We leverage an experimental macrocosm, the Montreal
 Insectarium Grand Vivarium, to test the importance of endogenous
 mechanisms in determining temporal patterns in foraging activity of
 butterflies. Specifically, we assessed the degree of temporal niche
 partitioning among 24 butterfly species originating from the Earth’s
 tropics within controlled environmental conditions. We found strong niche
 overlap, with the frequency of foraging events peaking around solar noon
 for 96% of the species assessed. Our models suggest that this result was
 not due to the extent of cloud cover, which affects radiational heating
 and thus limits body temperature in butterflies. Together, these findings
 suggest that an endogenous mechanism evolved to regulate the timing of
 butterfly foraging activity within suitable environmental conditions.
 Understanding similar mechanisms will be crucial to forecast the effects
 of climate change on insects, and thus on the many ecosystem services they
 provide.
description: Design
 overview We sampled four sites in the Montreal
 Insectarium Grand Vivarium (MIGV) between April 6<sup>th</sup>
 and April 19<sup>th</sup>, 2022. Sites were selected initially
 to be similar in conditions but spread across the greenhouse to minimize
 the risk of pseudoreplication. We limited our sample to two weeks because
 we aimed to reduce as much as possible (i) variation in daylight
 conditions throughout the sampling period (Table S1) and (ii) the
 difference in butterfly age between samples. We performed twenty sampling
 cycles within five days, each cycle consisting of a two-minute point count
 per site (<em>n</em> = 80 total point counts). During each
 point count, we recorded foraging events observed at a site within an area
 of 10 m<sup>2</sup> (<em>n</em> = 275 foraging
 events from 24 butterfly species). One observer kept track of butterflies
 within the point count area, with his colleague taking notes. Both
 observers paid attention to avoid double-counting of the same individuals
 during the two-minute point count. Position of the four sampling sites
 inside the MIGV was constant through the sampling period. There were two
 sampling days without visitors in the MIGV and three with visitors; we did
 not observe any effect of visitors on the activity of butterflies.
 Sampling timing
 Preliminary observations
 suggested that most point count samples would sample zero butterflies
 before 7 AM and after 5 PM. Therefore, we spread between three and five
 samples every sampling day, aiming to get at least one sample in the
 morning after 7 AM, one around noon, and one in the afternoon before 5 PM.
 This pattern is consistent
 with butterflies’ characteristic diel activity, which has only a few
 exceptions not represented in our study (e.g., in the Families Hesperiidae
 and Hedylidae [1]). Sampling hours were staggered across days so
 that we could better estimate species-specific flight curves, in no
 particular order (Fig. S1). Sampling nectaring
 behavior A foraging event consisted of a butterfly
 entering the point count area, landing on a flower, and extending its
 proboscis to reach the nectar within that flower. We did not count
 butterflies that were already foraging at the beginning of the point count
 and avoided double-counts. While avoiding double-counts is difficult in
 the field, we found it reasonably easy within the controlled conditions of
 the greenhouse and given the duration of our point counts (two minutes).
 Note that we did not mark
 butterflies to avoid affecting their behavior, and because this was
 not allowed within the
 MIGV. We note that our sample characteristics (always ≤10 individuals per
 point count, typically &lt;5; Fig. S1) in relation to the large
 numbers of butterflies in the greenhouse (i.e., hundreds), suggest limited
 effect of pseudoreplication due to double-sampling of the same butterfly
 in different point counts. However, our results should be interpreted
 cautiously, keeping in mind that some individuals might have been indeed
 sampled more than once. Sampling environmental
 conditions During sampling we recorded time of the day,
 temperature, and cloud cover. Time of the day was recorded to the closest
 30-minute interval (e.g., 7.17 AM was associated to 7.30 AM, 4.01 PM to
 4.00 PM and so on). Cloud cover was visually assessed as proportion
 of the sky covered in clouds. We did not measure light intensity or
 related information (e.g., UV radiation) because these aspects are not
 considered primary determinants of butterfly activity in the literature
 (van Swaay et al. 2015, Riva et al. 2020). 
 Ambient temperature was
 recorded throughout the point counts with a thermometer that was left on
 for the 2-min sampling event duration, at a constant height of 1.5 m. The
 temperature value was recorded once the instrument stabilized on a
 temperature that we deemed representative of the sampling point. Because
 we were within a greenhouse, the temperature value typically was stable,
 so a single value was sufficient to capture changes in the microclimate in
 2 minutes. Substrate temperature was measured each time a
 butterfly landed using an infrared thermometer. Both temperatures were
 recorded with a precision of 0.1°C. Because the ambient temperature
 thermometer did not work on some occasions, we used the substrate
 temperature in our models.