For some, September means school is starting up again; at the Crane Trust, it means that we’re into small mammal surveys again!
We conduct small mammal surveys for several reasons. For one, they are very sensitive to habitat changes (whether from grazing, haying, or woody encroachment), and they are a great indicator of results of our management practices. For another, they are an important food source for Whooping Cranes and other predator species, such as raptors and snakes. These little guys are also rare to encounter by chance, so this is one of our only ways to see what diversity of small mammals we have here!
Left: meadow jumping mouse (Zapus hudsonius). Right: white-footed mouse (Peromyscus leucopus). Photo credits Elsa Forsberg.
During these surveys, we set out 40 Sherman traps along a 200-meter transect, baited with cracked corn, oats, sunflower seeds, and dried mealworms. These box traps have a hinge door that closes shut behind a small mammal when it enters, so that it is safe from harm. We set these traps in the evening and check early in the morning to make sure no one’s in a box for too long.
I didn’t know very much about small mammals coming into these surveys, so I have learned a lot in just the last few weeks! I’ve seen seven different species so far, including a variety of mice, shrews, and voles. The mice are my favorite to find because of their cute little faces! Many of these species are difficult to tell apart, so we have a helpful guide that helps us identify them based on minute features, such as number of foot pads, grooves on the teeth, and head/body or tail length.
Small mammal trapping does not always go as planned. One week we caught zero small mammals during three nights of trapping – these guys are less active during nights with bright moonlight, and that week was the full moon! They prefer darker nights, because it’s harder for predators to see them. Cattle can also pose an issue, because they run into traps and accidentally trigger them to close. Fortunately, we have had more success the last couple weeks!
Left: Elsa Forsberg, wildlife biologist, measures the tail length of a white-footed mouse (Peromyscus leucopus). Right: prairie vole (Microtus ochrogaster), photo credit Will Hamson.
Small mammal surveys are also a good time to run into other cool wildlife species. Our lead biologist, Bethany Ostrom, found a smooth green snake near the transect a few weeks ago! Our wildlife biologist, Elsa Forsberg, and I saw several species of shorebirds near another transect, including Wilson’s snipes, a white-faced ibis, and multiple species of sandpipers. Earlier this week we also saw over forty cattle egrets all together! We love seeing the variety of birds that are starting to travel during the fall migration!
Many of our surveys have wrapped up for the 2026 field season, including bumble bees, butterflies, and fish seining. (We call these “Fishy Fridays”, as we always survey fish on Fridays!) We also completed our second round of bison fecal sampling, which is a fun opportunity to bust out our microscopes and count parasite eggs!
Left: a flock of cattle egrets (Ardea ibis) forages on Mormon Island, photo credit Elsa Forsberg. Right: a female monarch butterfly (Danaus plexippus) warms her wings after a dewy morning.
Aside from small mammal trapping, we are tagging migrating monarch butterflies for Monarch Watch, and have set up trail cams for a nation-wide mammal monitoring project called Snapshot USA. We’re excited to see what we find on these cameras!
Lastly, I wanted to share two fun plants I found at the Crane Trust this week: Great Plains ladies’ tresses, a type of orchid, and green comet milkweed, one of the less common milkweeds on property. Check them out below!
Left: Great Plains ladies’ tresses (Spiranthes magnicamporum). Right: green comet milkweed (Asclepias viridiflora).
Wherever you are this fall, keep your eyes open to the changing season around you as the birds and butterflies start to migrate again!
~ Clara Freese, Lila O. Wilson Fellow