An analysis of monarch butterfly flight performance and navigational orientation Open Access

Abstract

Successful, efficient long-distance flight is integral to the fitness of migratory monarch butterfly (Danaus plexippus) populations. The behavior allows the insect to accomplish its world-renowned migratory journey that encompasses up to a 4,500-kilometer distance from areas in the United States and Canada into overwintering sites in Central Mexico. Despite how well-regarded monarch migration is among the public, there continues to be a lack of understanding of the factors that affect successful flight performance. Monarch overwintering populations in Mexico have declined over the last few decades, while the incidence of non-migratory, sedentary populations has increased. Despite this, it remains unknown how sedentary populations drive migration loss in terms of flight behavior and efficiency. 

To address these two areas, in two sequential studies, we investigated the impact of monarch larval diet on the mechanisms of flight and comparatively analyzed the flight performance displayed by a migratory and non-migratory population of monarchs. The first study displayed that the milkweed source that monarchs are reared on has important implications for flight performance, while the second study showed that migratory monarchs did not display differential flight performance when compared alongside non-migratory monarchs. Thus, overall, these two studies displayed the significant role that environment plays in the successful flight function of the monarch butterfly. 

Additionally, while the genetic, physiological, and environmental components of monarch migratory navigation have been thoroughly investigated in prior studies, the ability of the monarch to display such precise navigational ability amid their long journey remains elusive. Thus, in a third study, we investigated the efficacy of two methodologies meant to understand the navigational orientation of the monarch. In this study, we studied eastern North American monarchs in the migratory stop-over site in St. Marks, Florida, from 2019 to 2022. Overall, the purpose of these sequential studies was to confer an increased understanding of the mechanisms that allow the monarch butterfly to orient, fly, and, as a result, thrive in its environment. 

Table of Contents

Table of Contents 

1. Chapter 1: Larval diet impacts flight performance in monarch butterflies from two populations.

1.1 Introduction……………………………………………………………………………1

1.2 Materials and Methods…………………………………………………………….......3

1.2.1 Monarch Rearing……………………………………………………………3

1.2.2 Flight Trials and Metrics.……………………………………………………5

1.2.3 Statistical Analyses.………………………………………………..………..6

1.3 Results…………………………………………………………………………………7

1.4 Discussion……………………………………………………………………………..8

1.5 Table 1………………………………………………………………………………..11

1.6 Figure 1………………………………………………………………………………13

1.7 Supporting Information………………………………………………………………14

1.7.1 Methods……………………………………………………………….……14

1.7.1.2 Lineages…………………………………………………….……14

1.7.1.3 Wire Attachment…………………………………………………14

1.7.1.4 Flight Trials………………………………………………………15

1.7.1.5 Flight Metrics…………………………………………………….17

1.7.1.6 Oxygen Consumption Rate………………………………………17

1.7.1.7 Wing Morphometrics……………………………………….……18

1.7.2 Results……………………………………………………………………...19

1.7.2.1 Table S1…………………………………………………….……19

1.7.2.2 Table S2…………………………………………………….……20

1.7.2.3 Table S3…………………………………………………….……21

1.7.2.4 Table S4…………………………………………………….……22

1.7.2.5 Table S5…………………………………………………….……23

2. Chapter 2: Monarch butterflies from two populations display similar flight performance.

2.1 Introduction……………………………………………………………………..……25

2.2 Materials and Methods………………………………………………………….……27

2.2.1 Monarch Sourcing……………………………………………….…………27

2.2.2 Flight Trials and Metrics……………………………………...……………28

2.2.3 Statistical Analyses…………………………………………………...……29

2.3 Results………………………………………………………………….…………….29

2.3.1 Figure 1………………………………………………………….…………30

2.3.2 Figure 2………………………………………………………….…………31

2.4 Discussion……………………………………………………………………………32

3. Chapter 3: Gone with the Wind: Testing the efficacy of two experimental orientation procedures in the eastern North American monarch butterfly.

3.1 Introduction……………………………………………………………………….….34

3.2 Materials and Methods……………………………………………………………….37

3.2.1 Experimental Location…………………………………………………..…37

3.2.1.1 Figure 1…………………………………………………………..37

3.2.2 Mesh Cage Orientation Procedure…………………………………………38

3.2.2.1 Figure 2…………………………………………………………..38

3.2.2.2 Table 1……………………………………………………………39

3.2.3 Vanishing Bearings Procedure…………………………..…………………39

3.2.4 Image Compilation and Statistical Analyses………………………………40

3.3 Results………………………………………………………………………….…….41

3.3.1 Figure 3…………………………………………………………………….41

3.3.2 Figure 4…………………………………………………………………….43

3.3.3 Table 2……………………………………………………………………...43

3.4 Discussion………………………………………………………………………...….44

3.5 Supporting Information………………………………………………………………48

3.5.1 Figure S1…………………………………………………………………...48

3.5.2 Figure S2…………………………………………………………………...49

3.5.3 Figure S3…………………………………………………………………...50

4. References

List of Figures

1. Chapter 1: Larval diet impacts flight performance in monarch butterflies from two populations.

Figure 1……………………………………………………………………………..……13

2. Chapter 2: Monarch butterflies from two populations display similar flight performance.

Figure 1………………………………………………………………………..…………30

Figure 2………………………………………………………….……………….………31

3. Chapter 3: Gone with the Wind: Testing the efficacy of two experimental orientation procedures in the eastern North American monarch butterfly.

Figure 1………………………………………………………………………..…………37

Figure 2………………………………………………………………………..…………38

Figure 3………………………………………………………………………..…………41

Figure 4………………………………………………………………………..…………43

Figure S1………………………………………………………………………....………48

Figure S2………………………………………………………………………..……..…49

Figure S3………………………………………………………………………..……..…50

List of Tables

1. Chapter 1: Larval diet impacts flight performance in monarch butterflies from two populations.

Table 1…………………………………………………………………………………....11

Table S1…………………………..………………………………………………...……19

Table S2……………………………..…………………………………………..….……20

Table S3…………………………………………………………………………….……21

Table S4…………………………………………………………………………….……22

Table S5…………………………………………………………………………….……23

Table S6…………………………………………………………………………….……24

3. Chapter 3: Gone with the Wind: Testing the efficacy of two experimental orientation procedures in the eastern North American monarch butterfly.

Table 1………………………………………………………………………..…………..39

Table 2………………………………………………………………………..………..…43

About this Honors Thesis

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School	Emory College
Department	Biology
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, General Biology, Evolution and Development Biology, Ecology
Keyword	flight performance Savannah migration milkweed directionality flight orientation Danaus plexippus Lepidoptera metabolism Puerto Rico
Committee Chair / Thesis Advisor	de Roode, Jacobus, Emory University
Committee Members	Zarrabi, Ali, Emory University Morran, Levi, Emory University

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