DOI: 10.5061/dryad.q2bvq83rr
title: Data from: Constraints and demands interact to affect prey dietary reaction to predation

description: Prey alter their foraging when threatened by predators. Two mutually
 inclusive hypotheses explain this response. The first entails that defense
 behaviors to minimize exposure to predators prevent prey from achieving
 their preferred diet, while the second postulates that prey deliberately
 change their diet to fulfill new stress-induced nutritional demands. We
 combined field observations and laboratory experiments to determine which
 hypothesis dictates snail dietary responses to risk of beetle predation.
 Snails exposed to predation-risk reduced activity, increased climbing,
 increased respiration, ate distinctively to achieve a certain nutrient
 target, and preferred eating on the cage floor at the costs of nutritional
 imbalance and elevated risk. When only carbohydrates-rich food was on the
 floor, stressed snails reduced activity and foraged less, but when only
 protein-rich food was on the floor snails increased activity and consumed
 more carbohydrates than their no-risk conspecifics. This outcome suggests
 that nutrient accessibility may determine which hypothesis governs the
 prey dietary reaction to predation risk.
description: Snails' density- counting live snails in 1 square meter, in
 each microhabitat Snails' activity and vertical
 location- observations Snails' physiological
 stress- CO<sub>2</sub> respiration rates
 Snails' macronutrient consumption- weighing artificial food
 consumption  
description: # Data from: Constraints and demands interact to affect prey dietary
 reaction to predation
 [https://doi.org/10.5061/dryad.q2bvq83rr](https://doi.org/10.5061/dryad.q2bvq83rr) Tha manuscript includes three experimental parts: 1. **Measuring snail density and behavior in the field** To quantify the snail’s habitat use and activity, we randomly located 34 one square meter plots within the Loess Park Nature Reserve. In each plot, we recorded the number of snails in each patch type ( i.e., biological soil crust, perennial shrubs, or plant litter)  and noted whether snails were active or not. We also noted whether the snails were above or below a threshold height of 2 cm, since beetles pose much lesser risk above this height. In all plots, the relative area of each patch type was evaluated. The overall coverage could exceed 100% since shrubs canopy overlapped with other patch types. Based on these estimations we calculated the snail density in each patch type. During the observations we monitored the ambient temperature and relative humidity using HOBO Pro v2 data loggers.  ***Data : "field_merge_data_covertype.csv", script:"1st. field survey.R"*** 2. **Snails’ defense responses to risk of free-ranging predatory grubs** To test what inducible defenses snails use, we reared snails with and without free-ranging beetle grub and measured their behavioral and physiological responses. We tested the snail physiological stress responses to risk of grub predation by measuring CO<sub>2</sub> respiration rates, using *flow through* system connected to a designated self- manufactured multiplexer and *Picarro G2201-i* Cavity Ring-Down [Spectrometer](https://www.sciencedirect.com/topics/earth-and-planetary-sciences/spectrometer) (Picarro, CA, USA) CO<sub>2</sub> analyzer (for detailed information about the metabolic measurements see supplementary material 2). To assess the behavioral responses to predation, we measured the location and activity of all snails 24h after food replacement. Snails were defined as active when their "foot" protrudes from the shell, and their location was categorized as being below or above 5cm from the mesocosm floor. ***Data CO***<sub>2</sub> respiration rates- "respiration_data_bind.csv", behavioral data: "exp.2 behav data.csv", script: "2nd exp. resp, behav, graphs .R" 3. **What mechanisms govern the predator induced diet change?** This experiment aimed to explore whether snails can regulate their nutritional intake target and disentangle the roles of the FST hypothesis and the CND hypothesis in determining the prey dietary responses to predation. The food treatments ("setups") were a) both carbohydrates and protein-rich foods on both the risky floor and safer upper shelf ("all options"); b) carbohydrate-rich foods on the floor and protein-rich foods on the upper shelf ("COH bottom"); c) protein-rich foods on the floor and carbohydrate-rich foods on the upper shelf ("protein bottom"). Comparing the snail intake target between the treatments enables to determine whether prey avoidance or preference for certain nutrients govern the snail dietary responses to risk of grub predation. We marked each snail individually using a permanent marker and weighed them at the beginning and end of the experiment to assess behavior and the consequences to snails’ growth and survival. ***Nutritional data: "food_5weeks_location.csv"- data on food accumulated consumption after 5 weeks, including the vertical location of the nutrients "food_5weeks_nolocation.csv"- data on food accumulated consumption after 5 weeks from 3rd experiment, not including the vertical location of the nutrients and they were summed together from both vertical locations, script:"3rd experiment nutrition.R".*** ***Behaviorl data: "behav_weeks15_count.csv", mass gain data: "snail_wieght_delta.csv", script: "3rd exp. behavior & mass gain.R".*** ***script: "3rd exp. graphs.R"- uses the above data and "accumulate table C_P over 5 weeks.csv" to generate the graphs for this part of the manuscript.*** ## Description of the data and file structure ***"field_merge_data_covertype.csv"*** * **plot**- one of 34 1 square meters plots that were surveyed (categorial 1-34) * **subplot**- each plot was split into 4 subplots to facilitate the calculating of cover and counted snails * **plot_subp**- the merged plot & subplot number * **cover_type**: one of three optional cover types: "crust", "litter", "shrub" * **area_cover_sqm:** the area cover in cubic centimeter, in the field in each subplot the % cover (1-100%) was estimated and then transformed to cubic centimeter by multiplying in 0.25 (each subplot was a quarter of 1 square meter). * **live_snails**- number of live snails * **act_snails**- number of active snails * **up_snails**- number of snails located above 2 cm * **Average_temp_c**- the average temperature in Celcius during the plot survey * **Average_rh-** average relative humidity during the plot survey. ***"exp.2 behav data.csv"*** * **change**- the number of food changes during the experiment (continuous) * **day date**- date of observation date dd/mm/yyyy * **hour**- AM or PM * **box num**- mesocosm number (categorial) * **treatment**- predator (free-ranging grab) or predator-free (categorial) * **snail num-** individual snail number (categorial) * **sp_location**- categorial specific snail's location in the mesocosm. First letter represent the vertical location (u- "up", m- "middle", d- "down"), second represent location depth (f- "foword", b= "back"), third letter reprecnt horizontal location (l- "left", r-"right"). * **g_location**- general vertical location of snails (u- "up", m- "middle", d- "down") * **active**- is snail active or not (1/0) * **distance**- the snail's distance from the mesocosm floor in cm * **snail_dead_live**- is the individual snail is "live" or "dead". ***"respiration_data_bind.csv"*** * **Date-** date dd/mm/yyyy, * **row_num-** shelf number where mesocosm located on (categorial row1/row2) * **cycle**- the cycle number (categorial 1-6) air was taken from mesocosm, * **location**- tube connection to Piccaro (categorial 1-16) * **co2_dry**- measurement of CO2 (ppm) by the Piccaro * **flow**- air flow observed on the flow meter (L/minute) * **snail_w-** snails weight in the mesocosm (g) * **live_snails-** number of live snails in the mesocosm * **cont_co2**- CO2 measurement by the Piccaro in snail free mesocosm (ppm) * **treatment-** categorial- predator (free-ranging grab) or predator-free * **CO2ppm_l_min_g**- calculation of Piccaro measurement flow /snails weight (ppm/l/m/g) * **CO2ppm_l_min_snails**- calculation of Piccaro measurement flow/number of snails (ppm/l/m/live snails) * **row_cycle**- merged columns of row number and cycle (categorial). ***"food_5weeks_location.csv"*** * **box.num-** mesocosm number * **food_location-** vertical location of food (top/bottom) * **delta_mg-** consumption of food in mg * **c_mg**- consumption in mg of COH * **p_mg**- consumption in mg of protein * **P_C_reatio**- ratio of proteins to COH consumed (p_mg/c_mg) * **block-** the block the mesocosm located on (categorial 1-5) * **setups**- vertical food location treatment ("all options"/ "COH bottom"/ "protein bottom") * **predation-** predation risk treatment ("predator"/"control"). ***"food_5weeks_nolocation.csv"*** * **box.num-** mesocosm number * **delta_mg-** consumption of food in mg * **c_mg**- consumption in mg of COH * **p_mg**-consumption in mg of protein * **P_C_reatio**- ratio of proteins to COH consumed (p_mg/c_mg) * **block**- the block number the mesocosm located on * **setups-** vertical food location treatment ("all options"/ "COH bottom"/ "protein bottom") * **predation-** predation risk treatment ("predator"/"control") ***"behav_weeks15_count.csv"*** * **box_num-** mesocosm number * **week-** week number from the beginning of the experiment (continuous 1-5) * **day_date-** date dd/mm/yyyy * **act_s-** number of active snails * **up_s-** number of snails located at the top * **n**- number of snails in the mesocosm * **box_week**- merge of mesocosm number and week (categorial) * **setup-** vertical food location treatment ("all options"/ "COH bottom"/ "protein bottom") * **predation-** predation risk treatment ("predator"/"control") * **prop_act-** the proportion of active snails (act_s/n) * **prop_up-** the proportion of snails up (up_s/n) * **c.week-** mean centered transformation of "week" * **block-** the block the mesocosm located on. ***"snail_wieght_delta.csv"*** * **box num-** mesocosm number * **snail num-** individual snail number * **weight (g)-** the snail's mass at the beginning of the experiment * **weight end(g)**- the snail's mass at the end of the experiment * **delta-** the delta between the snail's mass at the beginning and end of the experiment * **block-** the block the mesocosm located on * **setup-** vertical food location treatment ("all options"/ "c bottom"/ "p bottom") * **predator-** predation risk treatment ("predator"/"control") * **setups-** vertical food location treatment ("all options"/ "COH bottom"/ "protein bottom") ***"accumulate table C_P over 5 weeks.csv"*** * **setup-** vertical food location treatment ("all options"/ "COH bottom"/ "protein bottom") * **predation-** predation risk treatment ("predator"/"control") * **sum_weeks-** the accumulated food consumed over how many weeks * **CH_total_mean**- the average accumulated consumption of COH * **CH_total_SE**- standard error of accumulated COH * **P_total_mean**- the average accumulated consumption of protein * **P_total_SE-** standard error of accumulated protein ## Code/Software Statistical analyses were based on Zuur et al. 2009. For all analyses, we used the software R version 4.2.2 and the "lme4" package for Linear Mixed Effects Model (LMM) and Generalized linear mixed models (GLMM) analysis. When fixed effects were found significant, we performed Tukey’s p-value adjustment post-hoc analysis using the package "emmeans".  In all relevant analyses, we assessed the significance of the fixed effects using LRTs that compared our model to LMMs or GLMMs that do not contain the fixed factors. To organize the data we used the package "dplyr". For graphs, we used the packages: "ggplot2", "car", "plotrix" & "ggpubr".