DOI: 10.5061/dryad.tht76hf7c
title: Data from: Grasshoppers do not flee from their alarmed predators but from non-alarmed ones

description: Alarm calls produced by basal prey have well-known informative value. In
 multipredator communities, mesopredators, when faced with top predators,
 may emit alarm calls that could inform basal prey about their lowered
 predation risk. To test this unexplored possibility, we conducted one
 field and one mesocosm experiment in which we simulated alarm and
 non-alarm calls from little owls (Athene noctua) as mesopredators and
 measured their effects on grasshoppers as prey of little owls but not of
 top predators. In the field experiment, we found that grasshopper species
 were significantly more abundant in patches where we simulated either the
 presence of scared little owls (alarm treatment) or no owls (control
 treatment) compared to patches where the presence of non-scared little
 owls (non-alarm treatment) was simulated. In the mesocosm experiment,
 locusts’ (Locusta migratoria) moved significantly more to exposed areas
 when we simulated the presence of scared little owls (alarm treatment) or
 of a granivorous bird (control treatment), while they moved to sheltered
 areas when we simulated the presence of non-scared owls (non-alarm
 treatment). These results show that prey could cue on predators’ calls to
 assess their predation risk and make decisions, revealing unprecedented
 potential ecological consequences of alarm calls in invertebrate
 communities.
description: Firstly, in a field experiment we sampled the abundance of
 several grasshopper species in patches after broadcasting repeatedly for
 several days either little owls’ alarm calls (alarm treatment, simulating
 scared owls) or non-alarm/contact calls (non-alarm treatment, simulating
 non-scared owls), or just visiting the patches (control treatment,
 simulating no owls). In addition, in a mesocosm experiment, we recorded
 the distribution of migratory locusts (<em>Locusta
 migratoria</em>) in exposed and sheltered areas before and after
 broadcasting little owls´ alarm calls (alarm treatment), non-alarm/contact
 calls (non-alarm treatment) or vocalizations of a woodpigeon
 (<em>Columba palumbus</em>) as a granivorous, non-predator
 bird for grasshoppers (control treatment). The
 abundance of grasshoppers in the field experiment were sampled in all
 patches by counting all detected individuals, either inactive or during
 their flights/jumps, while walking at constant speed (about 2 km per hour)
 along longitudinal transects 50 m long and with a 5-m band. The number of
 grasshoppers was used as the response variable to the call treatment
 because it is a proxy of insect abundance as prey of little
 owls. In the mesocosm experiment, locusts behavior was
 recorded with video cameras and we counted the proportion of individuals
 in exposed areas at the end of pre-treatment and treatment conditions (day
 1<sup>st</sup> and 2<sup>nd </sup>of the trials)
 and calculated the difference as a measure of preference to be exposed
 <em>versus</em> hidden in response to the call
 treatments.
description: # Grasshoppers do not flee from their alarmed predators but from
 non-alarmed ones
 [https://doi.org/10.5061/dryad.tht76hf7c](https://doi.org/10.5061/dryad.tht76hf7c) We provide data obtained in a large-scale field experiment (**first sheet**) and in a mesocosm experiment (**second sheet**) to study the response of grasshoppers to different calls of their predators. #### **Description of the data and file structure** In the first sheet, we provide the data extracted from the Field experiment. Variables used were: **Transect_ID** = Identification of the transect **Patch**= Experimental patch **Treatmen**t =Call treatment as Alarm, Non-alarm or Control **Julian_date** = date expressed as the number of days since the first of January **Juliandate_class** = classification of the transects as early or late according to whether they were carried out before or after the median date value **Grasshoppers_abundance** = Number of counted grasshoppers per transect **Size**(m2) = Patch size in m2.  Only one value per patch is provided, so that patch size can be compared among treatments avoiding pseudoreplication. Missing data code: n/a In the second sheet, we provide the data extracted from the Mesocosm experiment. Variables used were: **Mesocosm_ID** = Identification of the mesocosm **Julian_date1** = Date of the first day of each experiment expressed as the number of days since the first of January **Tmax_1** = Maximum temperature in degrees Celsius during the recording of locust behavior during the first day of each experiment **Tmax_2** = Maximum temperature in degrees Celsius during the recording of locust behavior during the second day of each experiment **dif_tmax** =Difference of maximum temperature in degrees Celsius between the two experimental days in each experiment **%locusts_moved_to_exposed_hab** = Difference of percentage of locusts in the exposed habitat from the first to the second day of the experiment **Treatment** =Call treatment as Alarm, Non-alarm or Control