A Research and Education Project of New Jersey Audubon’s Cape May Bird Observatory

The Monarch Monitoring Project (MMP), established in 1990, is a research and education program focusing on the fall migration of monarch butterflies along the Atlantic coast. For over three decades, the MMP has gathered data on monarchs moving through Cape May during September, October, and now November. MMP staff and volunteers also conduct informational programs on monarch biology, conservation, and tagging.

Imagine an insect weighing less than a paper clip beginning a journey in Scarborough, Maine in late August. If successful, they arrive at the overwintering grounds high in the Transverse Neo-Volcanic Mountain Range in Michoacan, Mexico in October, completing a journey of over 2500 miles. This amazing migration of the monarch butterfly is still mysterious to us, and there are many questions left to explore.

The Monarch Monitoring Project’s (MMP) overall goal is to increase our understanding of the fall migration of monarchs along the Atlantic coast, through both research and education. Ultimately, it is our hope that these efforts will improve the knowledge and awareness of these remarkable butterflies so that populations of migrant monarchs will enjoy a secure future.

Monarch butterflies are the only butterfly species that completes a multigenerational two-way migration, traveling from Mexico to as far north as Canada. Imagine a delicate butterfly setting out on this amazing and mysterious journey of over 2,500 miles, where danger lurks throughout!

Loss of habitat, extreme weather, predators, toxic pesticides, and climate change have all taken a toll on fragile populations. Today, the future of monarchs is at risk. You can make a difference and save this migrational phenomenon for future generations.

When you Adopt a Monarch, you support New Jersey Audubon’s efforts to protect this iconic species. Your tax-deductible gift will fund our Monarch Monitoring Project, tagging and monitoring these butterflies for more than three decades, while teaching people how to protect them.


The Cape May Point Road Census is conducted three times per day from September 1st through October 14th and then two times a day from October 15th through November 7th. Rather than trying to count all the monarchs moving through Cape May, our methodology uses sampling criteria which result in data reflecting relative annual numbers. We also count Cloudless Sulphurs (Phoebis sennae) in addition to Monarchs because, as a southern species, they are an indicator species for climate change. Meaning, that changes in their movement can tell us how our changing climate may be impacting our butterfly populations and ecosystems. Counts are made by a single observer driving a car approximately 20-25 miles per hour along a 5.5-mile route. Migrating butterflies are observed and tallied but no stops are allowed to count specific concentrations. The route passes through a variety of habitats including southern hardwood forests, agricultural fields, brackish wetland meadows, suburban neighborhoods, and coastal dunes along the Atlantic Ocean and Delaware Bay. Annual summaries include yearly data for the Road Census.

The giant magnet for the back of the censusing vehicle


Educational outreach has always been an important part of the MMP. Our most popular programs are the informational sessions we offer at Cape May Point State Park, where locals and tourists of diverse backgrounds are fascinated by the monarch migration. MMP staff and volunteers talk to thousands of these visitors each year, sharing the basics of monarch biology, conservation, our project, and its history, and (everyone’s favorite) how to tag monarch butterflies.

In addition to public tagging demonstrations, MMP staff also works with educating school groups across Cape May County, both in the classroom and in the field. MMP has worked with The Nature Center of Cape May, Monarch Fest, Cape May Fall Fest, and other summer programs.

A critical aspect of MMP educational efforts is data sharing with other projects, such as Monarch Watch and Journey North. Tags are distributed to us by Monarch Watch, and we report back with our tagging data. Notable migration days and large roosts are reported to Journey North.

Publications are also an important piece of our educational work. MMP staff have written popular articles for American Butterflies and CMBO’s Peregrine Observer. Our project has also been the focus of articles in Journal of the Lepidopterists’ Society, Annals of the Entomological Society of America, and Journal of the Kansas Entomological Society. In 2006 we produced the DVD Cape May – Fall Flight.

Blog Roll


Upcoming Monarch Events



Before 1975, Western science had not discovered where North American monarchs spent the winters. This great natural history mystery was finally solved by Ken and Cathy Brugger, working in collaboration with Fred and Norah Urquhart. On January 9th, 1975, they discovered the overwintering site for monarch butterflies high in the mountains of central Mexico.

Over the following two decades, researchers, including Dr. Lincoln Brower, contributed greatly to our knowledge of the monarch migration puzzle. Although the overwintering site was discovered in central Mexico, it was still unclear whether the Atlantic coast monarchs could make it that far. Urquhart suggested this group might be “aberrant,” moving south along the Florida peninsula, ultimately over-wintering in the Yucatan or some other unknown location to the south. When the MMP began fieldwork in 1991, it was widely assumed that the Atlantic coast migrants overwintered in Mexico, so an early goal of the MMP was to settle this debate.

Although MMP workers initially tagged less than 1000 monarchs per season, a 1994 MMP tagged monarch recovered in Temple, Texas pointed toward the Mexican hypothesis. In 1995, Gayle Steffy, our research intern and veteran monarch worker, set new benchmarks for our efforts by tagging over 5000 monarchs. That same year, the first monarch from Cape May was recovered at the monarch overwintering grounds of Mexico. This recovery changed our understanding of monarch migration and proved that these little insects were making this 2,500+ mile journey.

Following Gayle’s lead, we redoubled our tagging efforts in subsequent years. The payoff came in 1998 when 7 of our tagged monarchs were recovered at the El Rosario site in Mexico. Details of MMP recaptures both along the migratory route as well as in Mexico can be found in the annual summaries.

Butterfly nets are used to capture monarchs. In order to ensure the tags stick to the wing of the butterfly, a few scales are scrapped off the hindwing (figures 2 & 3), ensuring that the tag sticks to the wing itself. The tag is an adhesive sticker that can be placed right in the spot prepared on the hindwing (figures 4 & 5). Data points are then collected including: wing condition (figure 6), sex (figure 6), fat content (figure 7), and length of the forewing (figure 8). Once the tag is placed and the data is recorded, the butterfly is released to continue its migratory journey.
Photo by Mark Garland of monarch butterflies roosting in an oyamel fir tree in the mountains of central Mexico.

MMP Tag Recoveries

Monarch Conservation

The amazing migration spectacle of the monarch butterfly is under threat. One of the main problems these butterflies face is habitat loss. Illegal logging and climate change in their overwintering grounds in Mexico have led to significant decreases in the area of forest occupied by monarchs each winter. Climate change not only causes a smaller area at higher elevation to be suitable for the oyamel fir trees, it also leads to more erratic freezing temperatures. Historically, the mountains of central Mexico have provided monarchs with the perfect weather that is cool enough that the butterflies go into a low metabolic state but not too cold that the butterflies freeze. Today, fewer acres of suitable land for monarchs to occupy in the winter has posed a threat to their populations.

One way to support the protection of these overwintering grounds in the mountains of central Mexico is through ecotourism. Tourist dollars encourage the Mexican government to prioritize the protection and conservation of these lands. On top of that, witnessing the sheer numbers of monarch butterflies and sharing your experiences with others helps inspire others to care for these amazing creatures.

Monarchs face a huge hurdle as they head back north from the overwintering grounds in Mexico. As the next few generations fly north in the spring, they disperse over the Midwest. What was historically shortgrass, mixed grass, and tallgrass prairie has been converted to agricultural land. The Midwest used to be a perfect place for monarchs, full of milkweed to lay eggs on and flowers to nectar from. Now, corn and soybean stretch for miles. Growing monoculture crops year after year deplete the soil of its essential nutrients. The more depleted the soil is, the more farmers are incentivized to use pesticides and fertilizers to increase their yields. Glyphosate is the compound found in most pesticides and it is known commercially as RoundUp. This chemical is toxic to pollinators and lowers their immune systems. Glyphosate can spread through the air and soil when it is sprayed, affecting plants that were not intended to be sprayed. Many farmers also purchase seeds that are coated in neonictinoids that contaminate the entire plant.  Neonictinoids are also toxic to insects, affecting their central nervous system and causing paralysis.

To help butterflies and other pollinators, consider buying organic produce. Supporting local organic farmers not only helps the environment, but it hopefully will also encourage other farmers to change their practices.

Another great way to help monarch butterflies and the ecosystem is to plant native plants. Lepidoptera (moth and butterfly) species rely on their host plants to breed and reproduce. Monarchs rely on milkweed as their host plant and other native nectar sources to build their fat stores. Not only do native plants support these lepidoptera species, these lepidoptera species contribute to the food web. Sixteen of the twenty songbird families use caterpillars as the primary food source for their young. Compared to non-native plants, native plants significantly contribute to higher levels of species abundance and diversity. Native plants also have higher levels of carbon sequestration to aid in the fight against climate change. The more native plants in gardens and lawns, the healthier our ecosystems become.

The average number of acres that monarchs occupy in their overwintering grounds in Mexico from 1993 to 2022.


Counting Monarchs in Cape May for Over A Quarter Century


Each yearly column shows the average number of monarchs seen per hour for each of the nine* census weeks. The final cell in the yearly column is the average number of monarchs seen per hour for that year over the entire season.

Road Census Data


Brower, L., Taylor, O.,Wiliams, E., Slayback, D., Zubietas, R., Ramirez. 2011. Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? The Royal Entomological Society, Insect Conservation and Diversity.
Davis, A. 2011. Are migratory monarchs really declining in eastern North America? Examining evidence from two fall census programs. The Royal Entomological Society, Insect Conservation and Diversity.
Brindza, L., Brower, L.P., Davis, A.K. & Van Hook, T. 2008 Comparative success of monarch butterfly migration to overwintering sites in Mexico from inland and coastal sites in Virginia. Journal of the Lepidopterists’ Society, 62, 189–200.
Gibbs,D., Walton, R., Brower, L., and Davis, A. Monarch Butterfly (Lepidoptera: Nymphalidae) Migration Monitoring at Chincoteague, Virginia and Cape May, New Jersey: A Comparison of Long-term Trends. 2006. Journal Of The Kansas Entomological Society 79(2), 2006, pp. 156–164.
Walton, R., L. P. Brower, and A. K. Davis. 2005. Long-term monitoring and fall migration patterns of the monarch butterfly (Nymphalidae: Danainae) in Cape May, NJ. Annals of the Entomological Society of America 98:682–689.
Walton, R. and L. Brower. 1996. Monitoring the fall migration of the monarch butterfly Danaus plexippus L. (Nymphalidae: Danainae) in eastern North America: 1991–1994. Journal of the Lepidopterists’ Society 50:1–20.
Brower, L. 1995. Understanding and misunderstanding the migration of the monarch butterfly (Nymphalidae) in North America: 1857–1995. Journal of the Lepidopterist’s Society 49:304–385.

Staff & Personnel

Adehl Schwaderer and Tom Reed
Project Supervisors

Jack McDonough
Field Coordinator

Maya Clark
Monarch Field Naturalist 

Anna Haggenjos
Monarch Field Naturalist 

Richard K. Walton
Founder and Director Emeritus

Lincoln P. Brower
Founding Scientific Advisor

Contact Us