DOI: 10.5061/dryad.c866t1g69
title: Great tit predation on colour morphs of the wood tiger moth at different relative frequencies

description: Polymorphic warning signals in aposematic systems are enigmatic because
 predator learning should favor the most common form, creating positive
 frequency-dependent survival. However, many populations exhibit variation
 in warning signals. There are various selective mechanisms which can
 counter positive frequency-dependent selection and lead to temporal or
 spatial warning signal diversification. Examining these mechanisms and
 their effects requires first confirming whether the most common morphs are
 favored at both local and regional scales. Empirical examples of this are
 uncommon and often include potentially confounding factors such as a lack
 of knowledge of predator identity and behavior. We tested how bird
 behavior influences the survival of three coexisting morphs of the
 aposematic wood tiger moth Arctia plantaginis offered to a sympatric
 predator (great tits, Parus major) at different frequencies. We found that
 although positive frequency-dependent selection is present, its strength
 is affected by predator characteristics and varying prey
 profitability.  These results highlight the need to understand
 predator foraging in natural communities with variable prey defences, in
 order to better examine how behavioral interactions shape evolutionary
 outcomes.
description: Freeze-killed
 adult wood tiger (<i>Arctia plantaginis</i>) moths from a
 multi-year laboratory stock, were thawed and spread so that their hindwing
 color was visible. The forewing length of each moth was measured with
 calipers prior to the start of the experiment. Specimens were then laid
 unpinned on their ventral side, with the dorsal side visible on individual
 Petri dishes. Each experiment contained a total of 24 moths laid out in a
 4x6 grid in one of two enclosed indoor aviaries. The floor of each aviary
 was covered in dark green sheeting (tarp) to approximately mimic a natural
 background. Four different frequency treatments were created as follows:
 Control – 8 white males, 8 yellow males, 8 orange/red females (hereby just
 called red); Red biased- 6 white males, 6 yellow males, 12 red females;
 White biased – 12 white males, 6 yellow males, 6 red females; and Yellow
 biased – 6 white males, 12 yellow males, 6 red females. Each bird was
 assigned to a single treatment. Moth position on the grid was
 randomized. Wild Great tits
 (<i>Parus major</i>) were caught from baited traps at
 Konnevesi Research Station (Central Finland), where this experiment took
 place, in October 2015. Once trapped, all birds were measured, aged,
 sexed, housed individually in plywood cages (80x65x50 cm) with a daily
 light period of 11h:13h (light:dark), fed on sunflower seeds, peanuts and
 vitamin-enriched tallow, and provided with fresh water <i>ad
 libitum</i>. After the experiment, all birds were ringed for
 identification purposes before being released at the capture site. Wild
 birds were used with permission from the Central Finland Centre for
 Economic Development, Transport and Environment, licensed from the
 National Animal Experiment Board (ESAVI/9114/04.10.07/2014) and the
 Central Finland Regional Environment Centre (VARELY/294/2015), and used
 according to the ASAB guidelines for the treatment of animals in
 behavioral research and teaching. Birds were
 trained in groups overnight to forage in the experimental room and take
 palatable food (peanuts and sunflower seeds) from the petri dishes laid
 out in the grid, before being returned to their home cages.  Trials were
 run the following day after training. Prior to the start of each trial the
 participating bird was food deprived for one to two hours to ensure they
 were motivated to forage. Twenty-four moths were then laid out on petri
 dishes in a 4x6 experimental grid (Figure 1) and a single bird was
 released. We observed each trial through a one-way mirror and recorded the
 timing, order, and outcome (i.e. eaten or rejected/dropped) of each
 attack, as well as other bird behaviors such as beak wiping or cleaning.
 Trials lasted until each bird had attacked at least twelve moths, or two
 hours had passed, whichever came first. All treatments included 10 trials
 and birds were only used for a single trial, for a total of 40 birds used
 in the entire experiment. Following their use in the experiment, birds
 were given at least six hours to feed in their home cages before being
 released.