Size of the Canadian Breeding Population of Monarch Butterflies Is Driven by Factors Acting During Spring Migration and Recolonization

Crewe, Tara L.; Mitchell, Greg W.; Larrivée, Maxim

doi:10.3389/fevo.2019.00308

Cited by 14 publications

(21 citation statements)

References 36 publications

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“…Surveys made during that period therefore underestimated the actual size of the monarch population. Survey data from after that period do show a correlation with overwintering population size (Crewe et al, 2019;Saunders et al, 2019) as does egg production for the last two decades that incorporates information on milkweed abundance (Pleasants and Oberhauser, 2013;Pleasants et al, 2017). Because migrating butterflies come from all habitats, including corn and soybean fields, the sampling bias seen in butterfly counts in the late 1990s and early 2000s is not an issue.…”

Section: Comparison Of Number Tagged and Overwintering Population Sizementioning

confidence: 99%

“…factors affecting monarch breeding population development from March through October, rather than migration success, primarily determine overwintering population size. While physical factors, such as weather and spring and summer temperatures are important determinants of population growth each year (Saunders et al, 2016(Saunders et al, , 2018(Saunders et al, , 2019Crewe et al, 2019), there is also strong evidence for the role of milkweed availability (Pleasants and Oberhauser, 2013;Flockhart et al, 2015;Pleasants, 2017;Pleasants et al, 2017). Tagging data arguably can provide a better picture of the size of the migrating population than counts made at peninsula points where monarchs stop over during migration.…”

Section: Comparison Of Number Tagged and Overwintering Population Sizementioning

confidence: 99%

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Evaluating the Migration Mortality Hypothesis Using Monarch Tagging Data

et al. 2020

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The decline in the eastern North American population of the monarch butterfly population since the late 1990s has been attributed to the loss of milkweed during the summer breeding season and the consequent reduction in the size of the summer population that migrates to central Mexico to overwinter (milkweed limitation hypothesis). However, in some studies the size of the summer population was not found to decline and was not correlated with the size of the overwintering population. The authors of these studies concluded that milkweed limitation could not explain the overwintering population decline. They hypothesized that increased mortality during fall migration was responsible (migration mortality hypothesis). We used data from the long-term monarch tagging program, managed by Monarch Watch, to examine three predictions of the migration mortality hypothesis: (1) that the summer population size is not correlated with the overwintering population size, (2) that migration success is the main determinant of overwintering population size, and (3) that migration success has declined over the last two decades. As an index of the summer population size, we used the number of wildcaught migrating individuals tagged in the U.S. Midwest from 1998 to 2015. As an index of migration success we used the recovery rate of Midwest tagged individuals in Mexico. With regard to the three predictions: (1) the number of tagged individuals in the Midwest, explained 74% of the variation in the size of the overwintering population. Other measures of summer population size were also correlated with overwintering population size. Thus, there is no disconnection between late summer and winter population sizes. (2) Migration success was not significantly correlated with overwintering population size, and (3) migration success did not decrease during this period. Migration success was correlated with the level of greenness of the area in the southern U.S. used for nectar by migrating butterflies. Thus, the main determinant of yearly variation in overwintering population size is summer population size with migration success being a minor determinant. Consequently, increasing milkweed habitat, which has the potential of increasing the summer monarch population, is the conservation measure that will have the greatest impact.

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Section: Comparison Of Number Tagged and Overwintering Population Sizementioning

confidence: 99%

Section: Comparison Of Number Tagged and Overwintering Population Sizementioning

confidence: 99%

Evaluating the Migration Mortality Hypothesis Using Monarch Tagging Data

et al. 2020

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“…barnacle goose, Branta leucopsis, climate disruption, Cormack-Jolly-Seber (CJS) model, productivity, survival Crewe, Mitchell, & Larrivée, 2019;Saalfeld et al, 2019;Wismer, Tebbett, Streit, & Bellwood, 2019). Indeed, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (Díaz et al, 2019;IPBES, 2019) identified anthropogenic climate disruption as one of the main drivers of the global state of nature.…”

Section: Introductionmentioning

confidence: 99%

“…Much of the recent literature concerns the negative impacts of climate shifts on animal population trends across a variety of taxonomic classes (e.g. Albouy et al., 2020; Crewe, Mitchell, & Larrivée, 2019; Saalfeld et al., 2019; Wismer, Tebbett, Streit, & Bellwood, 2019). Indeed, the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services (Díaz et al., 2019; IPBES, 2019) identified anthropogenic climate disruption as one of the main drivers of the global state of nature.…”

Section: Introductionmentioning

confidence: 99%

Temperature and precipitation at migratory grounds influence demographic trends of an Arctic‐breeding bird

Doyle

Cabot

Walsh³

et al. 2020

Global Change Biology

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Anthropogenic climate disruption, including temperature and precipitation regime shifts, has been linked to animal population declines since the mid‐20th century. However, some species, such as Arctic‐breeding geese, have thrived during this period. An increased understanding of how climate disruption might link to demographic rates in thriving species is an important perspective in quantifying the impact of anthropogenic climate disruption on the global state of nature. The Greenland barnacle goose (Branta leucopsis) population has increased tenfold in abundance since the mid‐20th century. A concurrent weather regime shift towards warmer, wetter conditions occurred throughout its range in Greenland (breeding), Ireland and Scotland (wintering) and Iceland (spring and autumn staging). The aim of this study was to determine the relationship between weather and demographic rates of Greenland barnacle geese to discern the role of climate shifts in the population trend. We quantified the relationship between temperature and precipitation and Greenland barnacle goose survival and productivity over a 50 year period from 1968 to 2018. We detected significant positive relationships between warmer, wetter conditions on the Icelandic spring staging grounds and survival. We also detected contrasting relationships between warmer, wetter conditions during autumn staging and survival and productivity, with warm, dry conditions being the most favourable for productivity. Survival increased in the latter part of the study period, supporting the possibility that spring weather regime shifts contributed to the increasing population trend. This may be related to improved forage resources, as warming air temperatures have been shown to improve survival rates in several other Arctic and northern terrestrial herbivorous species through indirect bottom‐up effects on forage availability.

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“…In this paper, we examine two current assumptions considered in the design of Monarch conservation strategies. First, following classic exponential growth, we hypothesize that first-generation breeding success across the southern part of the range may be more critical to the demographics of subsequent generations leading to the final pre-overwintering population, compared with the mid-section of the breeding range as it is commonly assumed (Crewe et al, 2019). Mortality and lack of reproductive activity while overwintering (L. P. Brower and Missrie, 1999) translate into the lowest Monarch abundance during the early spring, i.e., when Monarchs arrive at the southern edge of their breeding range from the overwintering grounds.…”

Section: Introductionmentioning

confidence: 99%

A Landscape-Level Assessment of Restoration Resource Allocation for the Eastern Monarch Butterfly

Solis-Sosa

Mooers

Larrivée

et al. 2021

Front. Environ. Sci.

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The Monarch butterfly eastern population (Danaus plexippus) is in decline primarily due to habitat loss. Current habitat restoration programs focus on re-establishing milkweed, the primary food resource for Monarch caterpillars, in the central United States of America. However, individual components of the Monarch life cycle function as part of an integrated whole. Here we develop the MOBU-SDyM, a migration-wide systems dynamics model of the Monarch butterfly migratory cycle to explore alternative management strategies’ impacts. Our model offers several advances over previous efforts, considering complex variables such as dynamic temperature-dependent developmental times, dynamic habitat availability, and weather-related mortality across the entire range. We first explored whether the predominant focus of milkweed restoration in the mid-range of the Monarch’s migration could be overestimating the Monarch’s actual habitat requirements. Second, we examined the robustness of using the recommended 1.2–1.6 billion milkweed stems as a policy objective when accounting for factors such as droughts, changes in temperature, and the stems’ effective usability by the Monarchs. Third, we used the model to estimate the number and distribution of stems across the northern, central, and southern regions of the breeding range needed to reach a self-sustainable long-term Monarch population of six overwintering hectares. Our analysis revealed that concentrating milkweed growth in the central region increases the size of the overwintering colonies more so than equivalent growth in the south region, with growth in the northern region having a negligible effect. However, even though simulating an increase in milkweed stems in the south did not play a key role in increasing the size of the overwintering colonies, it plays a paramount role in keeping the population above a critically small size. Abiotic factors considerably influenced the actual number of stems needed, but, in general, our estimates of required stems were 43–91% larger than the number of stems currently set as a restoration target: our optimal allocation efforts were 7.35, 92, and 0.15% to the south, central, and northern regions, respectively. Systems dynamics’ analytical and computational strengths provided us with new avenues to investigate the Monarch’s migration as a complex biological system and to contribute to more robust restoration policies for this unique species.

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Size of the Canadian Breeding Population of Monarch Butterflies Is Driven by Factors Acting During Spring Migration and Recolonization

Cited by 14 publications

References 36 publications

Evaluating the Migration Mortality Hypothesis Using Monarch Tagging Data

Evaluating the Migration Mortality Hypothesis Using Monarch Tagging Data

Temperature and precipitation at migratory grounds influence demographic trends of an Arctic‐breeding bird

A Landscape-Level Assessment of Restoration Resource Allocation for the Eastern Monarch Butterfly

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