DOI: 10.5061/dryad.zw3r228gb
title: Data from: Does the history of option quality affect nest site choice in the acorn ant?

description: During decision−making, animals consider not only the current but also the
 past quality of options. For example, when humans evaluate performance
 (e.g. sales) of employees, they do not only consider the average
 performance but also the trend of performance　ascending performance is
 often viewed as more favorable than descending performance. In our study,
 we test if non-human animals have a similar bias when they are evaluating
 options using house-hunting by the acorn ant, Temnothorax curvispinosus,
 as our model system. Our data show that when nest-site quality is static
 over time, ant colonies tend to prefer the nest site which was better
 (i.e. darker) between two nest options. However, when the nest quality
 changes—one improves and the other worsens—over time, more colonies choose
 the low-quality, but improving, nest than the high-quality, but worsening,
 nest. These results suggest that a continuous change of option quality may
 influence evaluation. We discuss alternative explanations for our results,
 possible mechanisms and potential ecological benefits for keeping track of
 the nest-site quality.
description: <em>Experimental procedure </em>
 Prior to the experiment, we induced a colony emigration to an
 empty home nest placed in the middle of the experimental arena (19 x 27
 cm) (see Sasaki and Pratt 2018 for the detail of the emigration
 procedure). After 24 hours, we introduced two kinds of potential target
 nests, namely an “improving” nest and a “worsening” nest, one on each side
 (Figure 1a). These target nests were identical to the home nest except the
 interior light level, which was controlled by putting light filters on the
 roof (see Supplementary Information for the detail of the nest design;
 Figure S1). The home nest was always darker than target nests to prevent
 early migration. The improving nest initially had a very bright interior
 light level (approx. 1600 lux) but became darker, and more preferable
 (Franks et al. 2003; Sasaki et al. 2019), over time (Figure 1b). The
 interior light level of the worsening nest, on the other hand, was
 initially very dark (approx. 3 lux) but became brighter, and less
 preferable, over time (Figure 1b). Note that the interior light level of
 the worsening nest was always darker, thus more preferable, than that of
 the improving nest until day 4. <em>Temnothorax</em> ants have
 low sensitivity to light within a bright range, and thus light levels were
 chosen based on the previous finding (Sasaki et al. 2013). Every morning
 until day 5, we adjusted the interior light level by replacing the light
 filters of the secondary roof. To minimize changing the environmental
 cues, we used the same glass slides for the secondary roof throughout the
 experiment. To test whether decisions were influenced by the trend in
 quality, both potential nests had the same interior light level (approx.
 400 lux) on day 5, and, on the following day (day 6), the roof of the home
 nest was removed to induce an emigration. We chose five days as the
 duration of the experiment based on the previous studies, which showed
 that <em>Temnothorax</em> ants retain nest information for at
 least six days (Langridge et al. 2004; Santos et al. 2022). We assayed
 nest-site preference by recording the site occupied by the colony 12 hours
 later. If one site contained more than 90% of colony members including all
 queens and brood items, we designated that as the choice. If no site
 achieved this criterion, we did not record a preference. This occurred
 only once out of a total of 30 tests. Until the roof of
 the home nest was removed on day 5, the interior light level of the home
 nest (approx. 1 lux) was always darker than those of the target nests, so
 the colony stayed at the home nest although some scouts might visit and
 assess these potential nests throughout the experiment. To confirm these
 visits and measure the number of scouts, we recorded the number of ants in
 the target nests at around 9 am each day until the secondary roof was
 replaced for each of the 10 colonies. The food (the agar-based diet
 (Bhatkar and Whitcomb 1970) and spam meat) and water tube were placed next
 to the home nest (Figure 1a) throughout the experiment. The arenas had
 three photography LED lights above them and received 1540-1690 lux light
 intensity. Note that the interior light levels reported above are
 estimations based on the light transmittance (i.e. f-stop) of the light
 filters. In addition to the “trend” condition described
 above, we also conducted two additional conditions as control conditions.
 In both the control conditions, the procedure was identical to the one
 used for the trend condition except that the interior light levels of the
 target nests were constant over time until day 4. In the “average” control
 condition and the “last-point” control condition, the interior light
 levels of the target nests were the average of the light levels for each
 nest type (1024 lux for the improving nest and 88 lux for the worsening
 nest) and the last level for each nest type (565 lux for the improving
 nest and 200 lux for the worsening nest), respectively (Figure 1c). On day
 5, the light level for the target nests became identical (400 lux), and
 the roof of the home nest was removed to induce emigration. Out of the 30
 tests conducted for each of the two control conditions, six tests in the
 average condition and two tests in the last-point condition did not
 achieve the consensus criterion. We used 30 colonies
 (see Supplementary Material for the detail of the subjects), all of which
 were tested for each condition, and the order of the conditions was
 randomized for each colony. The interval between the tests was at least
 two weeks. Before each test, all glass slides were washed using a
 commercial dishwasher, and the experimental arena was cleaned with
 ethanol. Cardboard plates were made fresh for each test and never
 reused. Colonies in the trend condition chose the
 improving nest over the worsening nest more frequently than the ones in
 the average condition did, suggesting that the nest-quality change
 influenced the nest preference (i.e. the nest with improving quality
 became more preferable than the one with worsening quality). However,
 because there was not a significant preference for the poor nest site in
 the trend condition (see Results for details), one possible alternative
 hypothesis was that the nest-quality change impaired the ability to assess
 nest quality (Burns et al. 2016), leading to no nest-site preference. To
 test this hypothesis, we collected additional 29 colonies (see
 Supplementary Material for the detail of the subjects) and ran another
 experiment similar to the trend condition. In this “follow-up trend”
 condition, we also changed the qualities of two nests—one improved and the
 other worsened over time—but, unlike the trend condition, the quality of
 the improving nest was better than that of the worsening nest in later
 days (days 3 and 4; Figure 1d). Note that the means of these over-time
 qualities were the same (approx. 700 lux). All colonies were tested only
 once, and four colonies did not achieve the consensus criterion. In the
 follow-up trend condition, we did not record the number of ants in the
 target nests each day as we did for the trend and control conditions. 
    <em>Analysis</em>
 Preferences in the binary choice were assayed with a
 χ<sup>2</sup> goodness of fit test. The effect of the
 nest-quality change was tested with a χ<sup>2</sup> test of
 independence. We have removed the choices that did not achieve the
 criterion for consensus. We ran a generalized linear mixed-effects model
 (GLMER) and tested colony size (the numbers of workers and brood) and
 order of the test as fixed effects and colony ID as a random effect . The
 statistical software R (v. 4.1.2) was used for all analyses.  The data and
 code can be accessed online (Tyler et al. 2023).
description: # Data from: Does the history of option quality affect nest site choice in
 the acorn ant?
 [https://doi.org/10.5061/dryad.zw3r228gb](https://doi.org/10.5061/dryad.zw3r228gb) In our study, we test if non-human animals have a similar bias when they are evaluating options using house-hunting by the acorn ant, *Temnothorax curvispinosus*, as our model system. Our data show that when nest-site quality is static over time, ant colonies tend to prefer the nest site which was better (i.e. darker) between two nest options. However, when the nest quality changes—one improves and the other worsens—over time, more colonies choose the low-quality, but improving, nest than the high-quality, but worsening, nest. ## Description of the data and file structure There are eight columns (A-H): colony ID, choice based on the majority rule, choice based on the consensus rule, condition, number of workers, number of brood items, and the test order. There were four conditions. In the trend condition, the interior light level of the improving nest became darker, and more preferable, over days, while that of the worsening nest became brighter, and less preferable. On the 5th day, the light levels of these nests became the same. On the following day, nest choice was induced by removing the roof of the home nest. In the two control conditions (average and last-point conditions), the light level of the target nest was constant over time until day 5. In the average condition, the light level of the target nest was the average of the light levels for each nest type. In the last-point condition, the light level was the last level for each nest type. In the follow-up trend condition, while one nest became darker, and better, over time, the other became brighter, and worse, over time. The means of the interior light levels of these nests were same. We used 30 colonies (see Supplementary Material for the detail of the subjects), all of which were tested for each condition, and the order of the conditions was randomized for each colony. The interval between the tests was at least two weeks. In the follow-up trend condition, all colonies were tested only once (and thus all the data for the order column are "NA").  ## Code/Software The statistical software R (v. 4.1.2) was used for all analyses.