Peninsula Point Monitoring Project

Coordinated by: Gina Badgett

The Peninsula Point recreation area, administered by the USDA/Forest Service, is a 48.5 ha area of land that juts into the northern shore of Lake Michigan (circled in red in map to right). Most of the peninsula is wooded with cedar, aspen, or paper birch. At the southern end of the peninsula the forest is cleared around a lighthouse tower. An interpretive 4 km long nature trail passes through the southern clearing and the wooded area. A monarch monitoring program was initiated in 1996 to census monarchs as they stopover at this site. The census entails an early morning roost count in the lighthouse area followed by 2 walking censuses daily along the nature trail around the peninsula from 1 Sept-30 Oct.

Census coordinator Gina Badgett

Volunteer Therese Fix

Peninsula Point lighthouse

Now in its 15th year, the data from this program represents one of the longest-running and most valuable sources of information regarding the integrity of the monarch migration and the status of the monarch population in this area (see graph below).

 

Key findings thus far:

The first 7 years of Peninsula Point migration census data was examined in a study by CJ Meitner (the original project coordinator), Lincoln Brower and Andy Davis. The study looked at the effect of environmental variables on the abundance of migrating monarchs at the site. The study found that the timing of the peak migration period was not consistent from year to year - in some years the migration was early, in others it was later in the fall. However, the authors concluded that the large numbers of monarchs that pass through this site make it an important stopover location for monarch migration.

For the weather variables, the study showed that the number of monarchs seen was directly related to the wind direction, with north winds resulting in the most monarchs. Certain other variables were also important.

Reference:
Meitner, C.J., L.P. Brower and A.K. Davis. 2004. Migration patterns and environmental effects on stopover of monarch butterflies (Lepidoptera, Nymphalidae) at Peninsula Point, MI. Environmental Entomology 33(2): 249-257.

Long-term trends:

To the right is a graph showing the long-term trend in monarch numbers recorded on the Peninsula Point migration census, since the project began in 1996.

The bars represent the average number of monarchs seen per census per year.

Each census is approximately the same - same distance, same time observing, etc.