Findings
We are constantly analyzing the numbers of monarchs found by
MLMP volunteers every year, looking for changes and trends in population
numbers. We’ve also shared a lot of MLMP data with
the scientific community in several publications. Here are summaries of a few of
these publications; you can link to the full publication of most papers.
Publications
Prysby, M. and K. Oberhauser. 1999. Large scale monitoring of monarch populations.
Proceedings of the 1997 North American conference on the Monarch Butterfly,
pp. 379-384. Hoth, J, I. Pisanty, K. Oberhauser, L. Merino and S. Price, editors.
Commission for Environmental Cooperation: Montreal, QC. Our first paper on the MLMP
provided an overall summary of the distribution and abundance of larval monarch
populations during the breeding season in North America. Among other things, we
showed that the abundance of monarchs did not increase uniformly throughout the
season, but showed two or more peaks in abundance. Mortality appeared to be high
in the egg and early instar stages at all sites, based on the densities and proportions
of individuals in each stage in consecutive week.
Rea, B., K. Oberhauser, M. Quinn. 2002. A field guide to invertebrates on milkweed.
(96 pp.) Bas Relief Publishing Group, Pennsylvania. Milkweed, Monarchs, and More is a book that shows the
diverse natural community you may experience while monitoring. It helps show the
exciting world of monarchs and milkweed with tons of pictures and information.
Oberhauser, K.S., Prysby, M.D., Mattila, H.R., Stanley-Horn, D.E., Sears, M.K.,
Dively, G., Olson, E., Pleasants, J.M., Lam. W.F. & Hellmich, R. 2001.
Temporal and spatial overlap between monarch larvae and corn pollen. Proc.
Nat. Acad. Sci. 98 (21): 11913-11918. This study observed the milkweed and monarch
densities in cornfields to determine the likelihood that the monarchs would be exposed
to Bacillus thuringiensis (Bt) pollen. In order to collect their data, they
used MLMP monitoring protocols. The findings showed that many monarchs used milkweed
in cornfields, indicating that changes in the agricultural practices of these areas
could have large impacts on both milkweed and monarchs.
Prysby, M. and K. Oberhauser. 2004.
Temporal and geographic variation in monarch densities: Citizen scientists document
monarch population patterns. Pp. 9-20 in: Oberhauser, K.S. and M.J. Solensky,
eds. The Monarch Butterfly: Biology and Conservation. Cornell University Press.
This paper, part of a collection of 27 studies on monarchs, used MLMP data to look
at immature monarch survival rates, and patterns within and between years. Only
about 10-20% of monarchs survive from the egg to 5th instar, and there is a great
deal of variation in monarch densities from one year to the next. Densities tend
to be higher in the central part of the US than the Northeastern. Prysby and Oberhauser
also compared findings from this project to other monarch monitoring projects.
Prysby, M. 2004. Natural enemies and survival
of monarch eggs and larvae. Pp. 27-38 in: Oberhauser, K.S. and M.J. Solensky,
eds. The Monarch Butterfly: Biology and Conservation. Cornell University Press.
Michelle Prysby investigated the effects of natural enemies on the survival of monarch
eggs and larvae in three field studies. In an exclosure experiment, monarch survival
was significantly higher with terrestrial predators excluded. In a second study,
she investigated effects of an aphid-tending ant species on monarch survival. Survival
was seven times higher for monarchs on milkweed from which ants had been excluded.
Finally, she used both her own data and MLMP to demonstrate that tachinid flies
represent an important source of mortality; of the fourth and fifth instars collected,
15% were parasitized by tachinids in 1999 and 23% in 2000.
Oberhauser, K. S., I. Gebhard, C. Cameron, S. Oberhauser. 2007.
Parasitism of monarch butterflies (Danaus plexippus) by Lespesia archippivora
(Diptera: Tachinidae). Amer. Midl. Nat. 157:312-328. This study analyzes the
parasitism rates of wild monarch by the tachinid fly, using data collected over
7 years by 77 volunteers in the Monarch Larva Monitoring Project. In a sample of
2903 larvae from 1999–2005, 80.4% resulted in healthy adult monarchs, 7.4% died
of other causes, and 13% contained tachinid flies. Monarchs that were collected
in later stages of life were more likely to be parasitized, and there were no consistent
patterns in the parasitism rates from year to year.
Batalden, R., K.S. Oberhauser, A.T. Peterson. 2007.
Ecological niches in breeding generations of Eastern North American monarch butterflies.
Ecol. Entomol. 36:1365-1373. This study uses eastern North American MLMP data to
show a series of shifts in monarchs’ breeding season habitat. We used ecological
niche modeling to identify the ecological conditions that monarchs use for breeding
in successive summer months, and then see how climate might affect the habitats
in which monarch breed. In the early months of the breeding season (March-June),
monarchs will actually be able to use more habitat than they can now, but in June-August
the ideal conditions move farther north. Whether monarchs will be able to adapt
to these changes isn’t known.
Oberhauser, K. S. and M. D. Prysby. 2008.
Citizen science: creating a research army for conservation. American Entomologist
54:97-99. There are many conservation outcomes of engagement in a citizen science
project like the MLMP. Volunteers often work to preserve habitat, share their findings
with others, and collect information that allow us to assess overall population
trends.
Kountoupes, D., and K. S. Oberhauser. 2008.
Citizen science and youth audiences: Educational outcomes of the Monarch Larva Monitoring
Project. Journal of Community Engagement and Scholarship. 1:10-20. Many adult
MLMP volunteers engage students in the project. This study summarizes the educational
and scientific value for these students, many of whom have gone on to do their own
independent research projects because of monitoring.
Lindsey, E., M. Mudresh, V. Dhulipala, K. Oberhauser, S. Altizer. 2009.
Crowding and disease: effects of host density on response to infection in a butterfly-parasite
interaction. Ecological Entomology 34:551–561. This study shows how the changes
in the density of monarch affect their susceptibility to the parasite Ophryocystis
elektroscirrha (O.E.). MLMP data were used to show the degree to which monarch
butterfly larval densities vary over time and space in eastern North America. The
study showed that the probability of infection increased with the increase in population
density.