Inventory & Monitoring Network

Map showing the nine sites of the Great Lakes Inventory and Monitoring Network, Voyageurs, Isle Royale, Grand Portage, Apostle Islands, Saint Croix, Pictured Rocks, Sleeping Bear Dunes, and Indiana Dunes, Mississippi River
The 9 Great Lakes Inventory and Monitoring Network sites


Biologists with the National Park Service’s Inventory and Monitoring Division help to improve park management through greater reliance on scientific knowledge by conducting long-term monitoring of park “vital signs”–– physical, chemical, and biological elements and processes that represent the overall health or condition of the parks’ natural resources. The Great Lakes Inventory and Monitoring Network is comprised of nine parks whose major resource is water. Network biologists work with park managers and others to conduct long-term monitoring. The network has resource briefs and reports from studies conducted on Isle Royale available on their webpage.

The monitoring we do at Isle Royale looks for trends in the health of inland lakes, forest vegetation, and populations of songbirds, amphibians, and bats. What we learn from these monitoring programs helps park managers to decide if more in-depth research is needed or when some sort of management action may be required to protect the island’s natural systems. Because the data are collected the same way at eight other national parks in the region, we can compare Isle Royale with other parks and estimate the health of wild lands across the region. Monitoring these vital signs today gives us a chance to see warning signs of declining health when they first appear, take action, and reverse the decline before it’s too late.


Current monitoring programs at Isle Royale

Monitoring goals

  • Establish long-term monitoring programs based on park management objectives and information needs.
  • Collect and organize data, put the park into regional context, and provide information to park managers, staff, and the public.
Song Meter on Tree
A song meter (“frog logger”) near an Isle Royale wetland.



There are 10 amphibian species on Isle Royale: six frogs, three salamanders, and one toad. Amphibians have two life stages, a larval stage that is lived in the water and an adult stage that is lived on land but returns to water for breeding.

Amphibians are considered a “vital sign” because they are sensitive to environmental changes and can serve as indicators of both aquatic and terrestrial habitat quality.

There are 10 recorders (“frog loggers”) placed at different wetlands around the island each summer that record singing frogs and toads for five minutes every hour between 3:00 pm and 3:00 am every day for 14 weeks (98 sampling days). Salamanders are surveyed by searching for and identifying egg masses in the same wetlands.
A northern long-eared bat clutches to the trunk of a pine tree
Northern long-eared bat

NPS / Paul Brown


As white-nose syndrome (WNS) expands and causes declines in bat populations, the NPS has determined that monitoring bat populations can help inform appropriate management of bats within the parks.

Seven bat species are believed to inhabit Isle Royale, including the northern long-eared bat (Myotis septentrionalis), which was listed as Threatened under the Endangered Species Act in 2015.

Similar to amphibian monitoring, but using microphones that detect the ultrasonic calls of bats, there are 10 song meters placed around the park. They record calls between 6:00 pm and 8:00 am over a 7-14 day period between June 1 and August 15 continuously .
An Ecologist wraps a measuring tape around a tree trunk to measure tree diameter.
Ecologists measure tree diameters to help determine the age structure of a forest plot.


Forest Vegetation

How do island forests change over time? To learn and understand such changes, forest ecologists visit 52 sampling plots representing five forest types scattered across the island.
Points are visited every 10 years to identify, count, and measure trees, saplings, shrubs, and ground layer plants, as well as measuring the amount of coarse woody material (down trees).
A shoreline with a spruce forest that is dying
A stand of spruce trees killed by a forest pathogen is the most common form of disturbance on Isle Royale.


Landscape Dynamics

Disturbance (fire, wind storm, flood, insect or disease outbreaks) is an important part of how the boreal ecosystem functions here at the southern edge of its range.

Disturbed areas are identified and classified using a set of satellite imagery and aerial photography spanning a period of six years or more.

Disturbances on Isle Royale are most often caused by forest pathogens, beaver, or wind events.
Biologist wade into Lake Harvey to collect Dragonfly Larva with a net
Searching for larval dragonflies on Lake Harvey.

Sean Bailey

Mercury Contamination

Great Lakes Network parks, including Isle Royale, are part of the national Dragonfly Mercury Project, in partnership with the University of Maine, the NPS Air Resources Division, and parks across the country.

By measuring methylmercury contamination in dragonfly larvae, we can learn about contamination throughout the aquatic food web.

Larval dragonflies are collected annually from four of the island’s inland lakes––Angleworm, Harvey, Richie, and Sargent.

Biologists survey with binoculars for songbirds
A park biologist conducts a songbird survey on Passage Island.



There are 130 survey points on eight trails across the park. A five-minute count is done at each point during the month of June to document all birds heard and seen.

More than 1,400 birds of 89 species have been recorded since 1996.

There are 12 species showing significant population increases on the island, while nine other species are declining. Ravens present a mystery and a concern, as they are declining at a rate of 3% per year despite showing increasing trends throughout the region.
A biologist lowers an instrument in a lake from a canoe to take scientific measurements
A park biologist lowers a multi-probe instrument that will measure dissolved oxygen, pH, and other chemical parameters of lake water.


Water Quality

Water quality of the park’s inland lakes is important not just to the aquatic life that live in them, but also to the visitors who get their water from them and occasionally hope to catch some fish.

Chemical (such as dissolved oxygen, pH, and chlorophyll) and physical (water clarity and water level) data are collected from each of nine lakes once a month during the open-water months.

Temperature data are also collected year-round from one lake, using a set of temperature sensors strung along a line running from the surface of the lake to the bottom. Year-round temperature data combined with the annual sampling give us a bigger picture of lake health.
Map Locations of Isle Royale Weather Stations
Data from six weather stations on Isle Royale are gathered together on the Climate Analyzer website.


Weather and Climate

Weather and climate data collected by six existing stations on Isle Royale are collated onto the Climate Analyzer website.

Users can create tables and graphs of the data, some of which goes back to 1940.

Last updated: April 1, 2019

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800 East Lakeshore Drive
Houghton, MI 49931


(906) 482-0984

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