DOI: 10.5061/dryad.tmpg4f5bk
title: Data from: High detectability costs select weak warning signals in chemically defended gregarious prey

description: The evolution of costly chemical defenses in cryptic prey is puzzling, as
 conspicuousness should be adaptive for defended prey by enhancing predator
 avoidance learning. Here, we explore three hypotheses that may promote
 weak visual signal strategies: (1) Low prey conspicuousness is favored in
 diverse predator communities; (2) Conspicuousness is less critical if
 color patterns or behavior allow defended prey to be distinguished from
 cryptic prey; and (3) in gregarious prey species, aggregation itself could
 act as a deterrent signal. We used chemically defended and gregarious
 European pine sawfly (Neodiprion sertifer) larvae, exhibiting
 green-black-grey coloration, as our study system. First, we manipulated
 the conspicuousness of the larvae by placing them either solitarily or in
 groups and marking them with either cryptic or conspicuous coloration,
 then testing their survival against predators in the field. Second, we
 analyzed how conspicuous the ventral side (which larvae reveal during a
 defense display) of N. sertifer appears to avian predators and how its
 conspicuousness correlates with the larvae's chemical defenses. Our
 results indicate that increased conspicuousness was costly and decreased
 larvae survival. The ventral side of larvae making the defense display was
 more conspicuous (showed higher luminance) than that of larvae not
 displaying; however, this was not associated with chemical defense traits.
 The signaling function of synchronous displays involving defensive
 secretions in sawflies presents a promising avenue for future studies on
 the mechanisms by which weak visual signals operate in nature.
description: # GENERAL INFORMATION ## 1. Paper Citation Koskenpato K, Mikkonen T,
 Mappes J, Valkonen J & Lindstedt C. 2026. High detectability costs
 select weak warning signals in chemically defended gregarious prey.
 *Behavioral Ecology.* ## 2. Brief abstract Why do some chemically defended
 prey use weak visual signals when conspicuous aposematic coloration seems
 more effective for predator avoidance? Using weakly conspicuous pine
 sawfly larvae as a study system, we found that increased conspicuousness
 under predation risk from natural predator communities reduces their
 survival. Our findings highlight the importance of understanding
 ecological mechanisms behind the evolution of weak visual signal
 strategies. ## 3. Originators Katja Koskenpato ## 4. Contact information
 Katja Koskenpato, Faculty of Agriculture and Forestry, Department of
 Forest Sciences, University of Helsinki, Helsinki, Finland,
 [katja.koskenpato@helsinki.fi](mailto:katja.koskenpato@helsinki.fi) ## 5.
 Year of data collection 2013-2014 ## 6. Geographic location(s) of data
 collection Puumala, Finland (61°31´25´´N, 28°10´40´´E) ## 7. Information
 about funding sources that supported the collection and curation of the
 data Academy of Finland (grant numbers 257581 and 330578) and Emil
 Aaltonen Foundation # DATA FILES AND VARIABLES ## 1. prepaint.csv Data to
 verify that painting do not affect larval mortality * id = ID of larva *
 color: paint treatment (1 = no paint, 2 = green paint, 3 = yellow paint) *
 branch: ID of given food branch * survival: survival of larvae (0 = died
 during the experiment, 1 = survived till the end of experiment) * time:
 survival time of larva in days * event: 1 = larva survived till the end of
 experiment, 2 = larva died during the experiment ## 2. larvalweight.csv
 Data to verify that weights of experimental larvae do not differ *
 transect: experimental transect 1 or 2 * group: treatment group size of
 larvae (1 = solitary, 2 = group of 10 larvae) * box: larval rearing box ID
 * petri_weight: weight of the petri dish without larva(e) (g) *
 petri_larva_weight: weight of the petri dish with larva(e) in it (g) *
 larva_weight: weight of larva(e) (g) * treatment: 1 = yellow marking, 2 =
 green marking, 3 = mesh bag ## 3. norep_predationexperiment.csv Data
 including only the first attacks of predation experiment * area:
 experimental transect 1 or 2 * tree: ID of tree where the experimental
 larvae were put * groupsize: treatment group size of larvae (1 = solitary,
 2 = group of 10 larvae) * colour: treatment color of larva (1 =
 cryptic/green, 2 = conspicuous/yellow) * bag: mesh bag/exposed treatment
 (1 = exposed/no mesh bag, 2 = mesh bag) * treatment: experimental
 treatment (1 = cryptic/green exposed, 2 = conspicuous/yellow exposed, 3 =
 cryptic/green in mesh bag, 4 = conspicuous/yellow in mesh bag) * fate:
 survival of larvae during the experiment (0 = survived, 1 = died) *
 survival: survival of larvae during the experiment (1 = survived, 0 =
 died) * time: survival time of larva in days * family: larval family ID *
 event: survival of larvae during the experiment (1 = survived, 2 = died) *
 NA / empty cells: data not available ## 4. predationexperiment.csv Data
 including all attacks (first and repeated) of predation experiment * area:
 experimental transect 1 or 2 * tree: ID of tree where the experimental
 larvae were put * groupsize: treatment group size of larvae (1 = solitary,
 2 = group of 10 larvae) * colour: treatment color of larva (1 =
 cryptic/green, 2 = conspicuous/yellow) * bag: mesh bag/exposed treatment
 (1 = exposed/no mesh bag, 2 = mesh bag) * treatment: experimental
 treatment (1 = cryptic/green exposed, 2 = conspicuous/yellow exposed, 3 =
 cryptic/green in mesh bag, 4 = conspicuous/yellow in mesh bag) * fate:
 survival of larvae during the experiment (0 = survived, 1 = died) *
 survival: survival of larvae during the experiment (1 = survived, 0 =
 died) * time: survival time of larva in days * family: larval family ID *
 event: survival of larvae during the experiment (1 = survived, 2 = died) *
 NA / empty cells: data not available ## 5. phenotypicdata.csv Data on
 larval phenotypic traits * family: larval family ID * lenght: lenght of
 larva (mm) * defending: production of defensive fluid (1 = produced fluid,
 0 = did not produce fluid) * volume: volume of produced defensive fluid
 (mm in capillary tube) * col_dor_jnd: jnd (just noticeable difference)
 value of color contrast on dorsal side of larva * col_ven_jnd: jnd (just
 noticeable difference) value of color contrast on ventral side of larva *
 lum_dor_jnd: jnd (just noticeable difference) value of luminance contrast
 on dorsal side of larva * lum_ven_jnd: jnd (just noticeable difference)
 value of luminance contrast on ventral side of larva * movement: U-posture
 of larva (1 = larva took U-posture, 2 = larva did not take U-posture) *
 pupamass: pupa mass (mg) * sex: sex of larva/individual (1 = male, 0 =
 female) * NA / empty cells: data not available