Monarch Health Annual Results

 

Every year, we compile all of the data from our citizen scientists and analyze it to determine what trends are emerging. Starting in 2011, we began our annual newsletter, which we send out to all participating volunteers. These newsletters highlight the trends from the year, as well as provide an update on the Monarch Health team. Click on the year below to see a recap of the results, plus a link to that year's newsletter.

2018 Results

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In 2018, citizen scientists collected a record number of samples for Project Monarch Health, and monarchs numbers reached at 12-year high in Mexico! 207 volunteers from 32 US states and 2 Canadian provinces submitted 10,497 samples to Project Monarch Health. The average number of samples per volunteer was 50.71. Infection prevalence by the protozoan OE was 24.6% across all samples, with highest infection prevalence occurring in the southern US, in regions with resident, non-migratory monarch populations. Just under 60% of these samples were heavily infected, down from the previous year. The prevalence in eastern migratory populations was up from last year at around 20%.

2017 Results

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In 2017, 225 volunteers tested 7,356 monarch butterflies for the protozoan parasite Ophryocystis elektroscirrha (OE). Our citizen scientists sampled across 29 states in the US and 2 provinces in Canada. Both the southeastern US and California populations exhibited very high infection prevalences, both at 67%. In contrast, only 5% of the eastern migrants were heavily infected with OE.

2017 Results

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In 2016, 152 Monarch Health volunteers sampled 5,832 monarchs for OE. This season we saw a rise in OE prevalence in all migratory regions except the Midwest. Notably, the West rose from 20% in 2015 to 37% in 2016 while the South and Northeast appear to be returning to the average prevalence of 10% previously maintained by these populations from 2005-2013. The non-migratory populations in South Florida, and along the Pacific and Gulf Coasts are still maintaining high OE infection levels, however the Pacific did drop significantly from 68% in 2015 to 43% in 2016.

 

Overall, we see higher OE prevalence in these monarchs because they are not migrating. This means that they cannot escape infected milkweed and sick individuals are not weeded out by the strenuous long-distance migration. Disease builds up in these populations, particularly when tropical milkweed (A. curassavica) is present to facilitate year-round breeding.

Results 2006-2015

2014 Results


Click Here to View the 2014 Newsletter Monarch Health volunteers tested 5,725 monarchs for Ophryocystis elektroscirrha (OE) infection in 2014. This year's data show that only 2% of monarchs in the Midwest and northeast had OE infections in 2014, which is lower than the average for 2002-2012. Moreover, program data show a decline in OE prevalence over the past 5 years among summer-breeding monarchs in the northern U.S. and southern Canada. Lower parasitism rates might occur if lower monarch population sizes in eastern North America support less parasite transmission. At the same time, prevalence of OE in non-migratory monarchs in coastal areas in the southern US and Pacific Coast remained high, with prevalence ranging from 60 to 100% in areas with year-round milkweed. Many monarchs in these areas breed during the winter on non-native tropical milkweeds. Past research based on Monarch Health data showed that monarchs are healthiest when they use seasonal (rather than year-round) milkweed and when they engage in migration, which helps to weed out sick butterflies and provides an escape from habitats contaminated with parasites.




2013 Results


Click Here to View the 2013 Newsletter In 2013, results from 1,549 samples collected by 88 citizen scientists across 19 states and 2 Canadian provinces indicated that 7.5% of the eastern migratory monarchs, excluding sites where monarchs breed year-round, were infected with OE across the entire sampling period (May through October). This is lower than in 2012 when 16.6% of monarchs were infected. Overall, the proportion of infected butterflies decreased throughout the breeding season (from mid-season to late in the breeding season). In contrast, data from past years showed an increase in infected monarchs later in the breeding season, likely due to the building of OE in the environment. The monarch migration in 2013 was also unusual, with monarchs arriving in Mexico later than expected and at historically low numbers. The winter of 2013 had the lowest number of overwintering monarchs ever recorded. The low number of monarchs may have stopped the buildup of OE in the environment. Volunteers in the southern coastal areas also sampled 396 monarchs at sites where year-round breeding may occur. Monarchs in these areas show a higher OE prevalence than in migratory monarchs. When combining all Monarch Health data for 2013, including the southern coastal areas, prevalence was 26.3%.




2012 Results


Click Here to View the 2012 Newsletter In 2012, results from 1,936 samples collected by 56 observers showed that 16.6% of eastern North America monarchs sampled in the breeding season (April-October) were heavily infected with OE. This is a slightly higher percentage than in 2011, which showed a prevalence of 11.2% in eastern monarchs. The results indicate that OE prevalence increased from April through October, as seen in previous years. This patterns shows that monarchs experience a higher risk of OE infection later in the breeding season, as OE might build up in the environment.




2011 Results


Click Here to View the 2011 Newsletter In 2011, a total of 78 citizen scientists from 21 states tested over 2,000 wild monarchs for the protozoan parasite Ophryocystis elektroscirrha (OE). In the eastern United States, 11% of monarchs sampled in 2011 were heavily infected with OE. This is lower than in 2010, when 22% of eastern monarchs were heavily infected. In the western U.S. in 2011, only 6% were heavily infected with OE. From April through October, the prevalence of OE in the eastern region increased as the breeding season progressed: Eastern monarchs sampled earlier in the year had an infection rate of 8.2%, and monarchs sampled later in the year had an infection rate of 11.7%. This build-up of OE in the eastern U.S. monarchs before fall migration and the decline of OE after migration have been observed in previous years and highlight how migration may enhance monarch population health.




2010 Results


Results from 4,320 samples showed that across the entire sampling period (from May through October), 29.5% of all eastern migratory monarchs were infected with OE. The proportion of infected butterflies increased over time throughout the breeding season. Prevalence late in the summer was high similarly across all regions. In the Gulf coast population, total prevalence was 48% (from 120 samples) and in the western migratory population, 13.5% were infected (from 59 samples). After 5 years of collecting data, we observed similar trends in infections levels of O. elektroscirrha in eastern migratory monarchs, with the highest levels of infection in the later part of the breeding season.




2009 Results


Results from 2388 samples showed that across the entire sampling period (from May through October), 10% of all eastern migratory monarchs were infected with O. elektroscirrha. The proportion of infected butterflies increased over time throughout the breeding season. Prevalence late in the summer was highest in the Northeast. In the Gulf coast population, prevalence was 57.3%.




2008 Results


Results from 1,056 samples showed that across the entire sampling period (from May through October), 13.1% of all eastern migratory monarchs were infected with O. elektroscirrha. The proportion of infected butterflies increased over time throughout the breeding season. Prevalence late in the summer was highest in the Northeast. In the Gulf coast population, prevalence was 60%.




2007 Results


Results from 1553 samples showed that across the entire sampling period (from May through October), 24.0% of all eastern migratory monarchs were infected with O. elektroscirrha. The proportion of infected butterflies increased over time throughout the breeding season. Prevalence late in the summer was highest in the Southeast. In the western population, prevalence was 44.4%, whereas in the Gulf coast population, prevalence was 64.7%.




2006 Results


Results from 449 samples showed that across the entire sampling period (from April through October), 10.5% of all eastern migratory monarchs were infected with O. elektroscirrha. The proportion of infected butterflies increased over time throughout the breeding season. Prevalence throughout the summer was highest in the Midwest (below). In the Western population, prevalence was 77.8%.




2015 Results


Click Here to View the 2015 Newsletter Monarch Health volunteers tested 6,739 monarchs for Ophryocystis elektroscirrha (OE) infection in 2015! This enormous effort involved 185 citizen scientists. This breaks yet another record, making 2015 the most productive year in the history of the program. Since 2006, volunteers have sampled a total of 27,000 butterflies in the U.S. and Canada. Our data show that only 5% of monarchs in the Midwest and 3% in the Northeast in 2015 (yellow bars in graph) were heavily infected with OE, which is slightly higher than rates in 2014 (3% and 1%, respectively.) This remains below the higher percentages observed during 2005-2013, when 10% or more of monarchs were heavily infected with OE from across the eastern N. American breeding range and at wintering sites in Mexico. Lower monarch population sizes in eastern North America in recent years might explain this trend, as fewer hosts could lower the likelihood that parasites get transmitted between adult and larval monarchs. At the same time, non-migratory monarchs in coastal areas in the southern U.S. and Pacific Coast (orange bars in graph) remained highly infected in 2015, with prevalence averaging 68% at sites with year-round milkweed. The previous year (2014) showed similar infection levels (73%) at year-round breeding sites.





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