DOI: 10.5061/dryad.cfxpnvxkn
title: Drought-driven lipid deficits in overwintering monarch butterflies revealed by δ²H and fatty acid analysis

description: Eastern populations of monarch butterflies (Danaus plexippus) overwinter
 in the central trans-volcanic belt of Mexico, relying primarily on lipids
 accumulated during migration to sustain this several-month-long
 overwintering period. This study examined how drought conditions in
 north-central Mexico influenced lipid dynamics in monarchs overwintering
 in Sierra Chincua (Michoacán, Mexico) across two consecutive seasons.
 Butterflies were collected in 2022-2023 (n = 150), following mildly dry
 conditions, and in 2023-2024 (n = 180), after an extreme drought affecting
 the entire Mexican migratory corridor. We measured abdominal mass, lipid
 mass fraction, lipid mass, fatty acid composition, and the δ2H values of
 non-essential palmitic and oleic acids as source indicators of dietary
 energy. In both years, non-essential fatty acids served as metabolic fuel,
 but all lipid metrics were significantly reduced in the drought year.
 Correlations between fatty acid δ2H values and content (palmitic = 0.35;
 oleic = 0.28; p &lt; 0.05) suggested altered nectaring behavior and
 limited lipid accumulation at high-altitude sites near the overwintering
 colonies during extreme drought. Fatty acid δ2H values became increasingly
 negative while lipid levels converged between years by the end of
 overwintering, possibly due to in situ lipid synthesis or selective
 mortality. These results highlight the vital role of nectar resources
 along the Mexican migratory corridor and near overwintering sites in
 supporting lipid reserves crucial for the survival of overwintering
 monarchs. While our findings strongly indicate a connection between
 drought and reduced monarch lipid reserves, we recognize that additional
 efforts are needed to evaluate nectar quality and floral abundances more
 effectively to establish causality.
description: # Drought-driven lipid deficits in overwintering monarch butterflies
 revealed by δ²H and fatty acid analysis Dataset DOI:
 [10.5061/dryad.cfxpnvxkn](10.5061/dryad.cfxpnvxkn) ## Description of the
 data and file structure Lipid and hydrogen isotopic data for
 **Drought-driven lipid deficits in overwintering monarch butterflies
 revealed by** ***δ*****²H and fatty acid analysis.**  Isotopic (δ2H) and
 Lipid content metrics of monarch abdominal lipids in 5 csv files:
 S1._Monarch_Wing_H, which contains the δ2H values of male and female
 monarch wings. These monarchs were collected in two different years at
 three time points within each overwintering period. \  
 S2._Monarch_Abdomen_Mass__Lipid_Mass_Fraction_and_Lipid_Mass which
 contains the abdominal mass, abdominal lipid mass fraction and lipid mass
 of male and female monarch abdomens. These monarchs were collected in two
 different years at three time points within each overwintering period. \  
 S3._Monarch_Abdomen_FA_proportions which contains the fatty acid
 proportional composition of lipid in male and female monarch abdomens.
 These monarchs were collected in two different years at three time points
 within each overwintering period.   S4._Monarch_Abdomen_H which contains
 the δ2H values of palmitic and oleic fatty acids in male and female
 monarch abdomens. These monarchs were collected in two different years at
 three time points within each overwintering period.  
 S5._Monarch_Correlation_Analysis_with_Mass_Fraction which contains the δ2H
 values of palmitic and oleic fatty acids in relation to the mass fraction
 of respective fatty acid content in male and female monarch abdomens.
 These monarchs were collected in two different years at three time points
 within each overwintering period. ### Files and variables #### File:
 S5._Monarch_Correlation_Analysis_with_Mass_Fraction.csv **Description:** 
 ##### Variables * Year: The year from which overwintering monarchs were
 collected. Year 1 is 2022/2023 and Year 2 is 2023/2024. * Collection time:
 The time point within an overwintering period that monarchs were
 collected. All monarchs were collected either early, midway or at the end
 of the overwintering period.  * Sex: Monarchs were either male (M) or
 female (F). * ID: Within each year ID designates which sampled monarch the
 data corresponds to.  * PA 2H: The deuterium value of monarch abdominal
 palmitic acid.  * OL 2H: The deuterium value of monarch abdominal oleic
 acid. * PA (ug/mg): The mass fraction (ug/mg of freeze-dried abdominal
 tissue) of monarch abdominal palmitic acid. * OL (ug/mg): The mass
 fraction (ug/mg of freeze-dried abdominal tissue) of monarch abdominal
 oleic acid. #### File: S4._Monarch_Abdomen_H.csv **Description:**  #####
 Variables * Year: The year from which overwintering monarchs were
 collected. Year 1 is 2022/2023 and Year 2 is 2023/2024. * Collection time:
 The time point within an overwintering period that monarchs were
 collected. All monarchs were collected either early, midway or at the end
 of the overwintering period.  * Sex: Monarchs were either male (M) or
 female (F). * ID: Within each year ID designates which sampled monarch the
 data corresponds to.  * PA 2H: The deuterium value of monarch abdominal
 palmitic acid.  * OL 2H: The deuterium value of monarch abdominal oleic
 acid. #### File: S3._Monarch_Abdomen_FA_proportions.csv **Description:** 
 ##### Variables * Year: The year from which overwintering monarchs were
 collected. Year 1 is 2022/2023 and Year 2 is 2023/2024. * Collection time:
 The time point within an overwintering period that monarchs were
 collected. All monarchs were collected either early, midway or at the end
 of the overwintering period.  * Sex: Monarchs were either male (M) or
 female (F). * ID: Within each year ID designates which sampled monarch the
 data corresponds to.  * PA proportion: The proportion of palmitic acid
 comprising lipids of monarch abdomens.  * ST proportion: The proportion of
 stearic acid comprising lipids of monarch abdomens.  * OL
 proportion: The proportion of oleic acid comprising lipids of monarch
 abdomens. * LA proportion: The proportion of linoleic acid comprising
 lipids of monarch abdomens. * ALA proportion: The proportion of
 alpha-linolenic acid comprising lipids of monarch abdomens. * EPA
 proportion: The proportion of eicosapentaenoic acid comprising lipids of
 monarch abdomens. #### File:
 S2._Monarch_Abdomen_Mass__Lipid_Mass_Fraction_and_Lipid_Mass.csv
 **Description:**  ##### Variables * Year: The year from
 which overwintering monarchs were collected. Year 1 is 2022/2023 and Year
 2 is 2023/2024. * Collection time: The time point within an overwintering
 period that monarchs were collected. All monarchs were collected either
 early, midway or at the end of the overwintering period.  * Sex: Monarchs
 were either male (M) or female (F). * ID: Within each year ID designates
 which sampled monarch the data corresponds to.  * Ab Lipid Mass fraction
 (ug/mg):he mass fraction (ug/mg of freeze-dried abdominal tissue) of
 monarch abdominal lipid. * Ab Mass (mg): Mass of freeze dried monarch
 abdomens. * Ab Lipid Mass (mg): Mass of lipid present in monarchs
 abdomens. #### File: S1._Monarch_Wing_H.csv **Description:**  #####
 Variables * Year: The year from which overwintering monarchs were
 collected. Year 1 is 2022/2023 and Year 2 is 2023/2024. * Collection time:
 The time point within an overwintering period that monarchs were
 collected. All monarchs were collected either early, midway or at the end
 of the overwintering period.  * Sex: Monarchs were either male (M) or
 female (F). * ID: Within each year ID designates which sampled monarch the
 data corresponds to.  * wing 2H: The deuterium value of monarch wing
 sample.