Photoperiodism

Young leaves blooming on a ginkgo tree in early spring (Photo credit: Margo Taylor)

The seasons come and go every year. The continual shift from spring to summer to fall to winter and then back to the beginning. But as most of us have experienced, we often get a “false spring”. Every year, we get a few days that are warm like springtime when it should feel cold like winter, and then days later we get hit with more winter weather. But during this stretch of warmth, how do plants and animals know that this is only a “false spring” and there is more winter weather to come? Many plants and animals use a mechanism called photoperiodism, which is a response triggered by changes in the length of daylight in a day. This response often comes with the changing of seasons and cues seasonal actions. 

Many plants use photoperiodism to regulate one or several of their functions. These functions include reproduction, flowering, leaf production, and dormancy. Photoperiodism is especially evident with deciduous trees. Deciduous trees lose their leaves in the fall and become dormant before growing leaves again in the spring. But how do they know the right time to start growing? Trees do not want to start growing too early and experience damage due to the cold, but they also do not want to start growing too late and miss out on vital sunlight. To address this issue, trees use photoperiodism. There are special receptors called photochromes in the bark of trees that measure the amount of light it receives during the day. These photochromes help the tree recognize the signs of “false spring” and wait until the arrival of “true spring” to begin growing.

buck with antlers (Photo credit: Wikipedia)

antler shed from a white tailed deer (Photo credit: northamericanwhitetail.com)

Animals can also use photoperiodism! Indiana’s largest resident mammal, the white-tailed deer, is one example. Every spring, male bucks will shed their antlers. Antlers are used to signify breeding status, attract potential mates, and also help the buck defend its territory. Antlers stop growing after a certain amount of time, but shedding antlers allows a buck to grow bigger antlers than before. This process is dependent on photoperiodism because light directly influences the hormones that cause the shedding and regrowth of antlers. 

These are just a few of the many organisms that use photoperiodism to respond to the changing of the seasons. Other environmental factors may influence an organism's activities, but the use of photoperiodism is an important tool for plants and animals so they are not fooled by a “false spring”.

Margo Taylor

1st Year Environmental Educator Fellow

Maple Sugar Time

This time of year is prime time in Northwest Indiana for maple sugaring! The Indiana Dunes National Park is unique for many reasons, including that it is one of the only National Park sites where the park taps trees and boils the sap down into syrup on-site. The park’s Maple Sugar Time festival is definitely worth visiting, but my favorite part about this time of year is getting to teach Dunes Learning Center’s high school forestry program on sugar maples because it’s a great opportunity for the students to get to experience maple sugaring for themselves and explore different ways they could get involved in stewardship or forestry in the future.

indiana dunes maple sugar range

boiling sap into syrup in the sugar shack

So many different conditions have to happen just right for us to be able to make maple syrup. Sugar maples only grow in a limited range across the northeastern U.S. and the southeast region of Canada, and their range continues to shift with the ongoing effects of climate change. Not only that, but the prime season for extracting sap to make syrup requires specific weather conditions: usually, temperatures need to reach up to about 40 degrees during the day and then drop below freezing at night. This temperature swing makes pressure build up underneath the bark so that sap will flow out when someone taps it. These two factors and more make it so remarkable to me that there is such a long history of maple sugar production and that we are able to carry on this tradition in the region.

Indiana dunes sugar shack at chellberg farm

It’s also remarkable that high schoolers and their teachers and chaperones are able to take time out of their busy schedules to attend a day-long field trip at the sugar bush across from Chellberg Farm. Our Climate Change in the Maple Sugar Range program is one of the only opportunities we have to work with high schoolers during the school year, so it’s extra exciting for us as educators.

students measuring trees in the sugar range

My favorite part of our Climate Change in the Maple Sugar Range program is getting to see students grow confidence in their abilities with forestry tools and making observations about the nature around them in the sugar bush. Both years that I’ve helped teach this program, I’ve watched the students gain a closer understanding of the trees around them as we work, and I especially enjoy talking with them about what they wanted to do moving forward past high school. Even if they don’t all see themselves becoming foresters, I hope that getting the chance to do field work in the national park plants seeds in students’ heads about how they can grow into stewards of nature in whatever way works for them.

Hope Rodgers

2nd Year Environmental Educator Fellow

Snowy Owls

One of the most prized species for birders in Indiana to find is the Snowy Owl. This bird is elusive to many in the United States but can be found abundantly in its breeding grounds within the Arctic Circle. The Snowy Owl occasionally migrates far enough south in the winter to be seen in Northern Midwest states- including here in the Indiana Dunes. The Snowy Owl has even been seen as far south as Southern California! These owls capture the interests of people across the country because of their unique features and rare visits.

The Snowy Owl is the only species of owl that has mostly white plumage. This coloration lets the bird blend into its surroundings of white snow in the Arctic. It uses this camouflage to help protect it from predators such as foxes and wolves. If they were a brown color like most other owls, they would stick out to their predators in the arctic snow.

This magnificent bird has multiple adaptations that help it survive the cold arctic winters, where temperatures often reach -4°F (-20°C). Eating lots of food is important to maintaining a high metabolism and keeping their bodies warm. An adult Snowy Owl can weigh up to 4.5 pounds (which is surprisingly heavy for a bird) and can eat over a pound of food each day. Can you imagine a human eating one-quarter of its weight in a single day?? Their diet consists mostly of lemmings during the summer months, but if food is sparse they may also eat ducks, fish, and whatever small animals that they can find. Snowy Owls also have particularly long, thick contour feathers- surface feathers that cover the majority of the tail, wing, and body of birds- to protect them from the wind. 

Snowy Owls are one of the most unique birds that we can find in Northern Indiana. So the next time that you are outside in the winter, make sure to look out for these elusive birds!

Alex Butina

1st Year Environmental Educator

Migration vs Hibernation

Something about winter that has often intrigued me, aside from the winter wonderlands, are the reasons why different animals choose to migrate or hibernate. In nature, migration is the act of traveling from one area to another to escape seasonal changes. Hibernation is the act of “shutting down” and “sleeping” to avoid harsh environmental conditions. Many organisms of the Indiana Dunes have evolved to either use migration, hibernation, or a combination of the two during the winter. But what is it that makes these strategies so desirable? Why do some species waste precious energy traveling hundreds of miles, while others stay confined in a cramped-little den for months-on-end? These are the kinds of questions I’m left with when I wonder to myself, “how are our various Dune’s critters doing these days?” 

What I’ve come to think is that these animals may have had the right idea all along. The reason these techniques are so preferable is because they are especially helpful for avoiding the worst aspects of winter. 

Take hibernators for instance; little creatures like groundhogs, turtles, and snakes don’t have the mobility necessary to travel long distances. A winged-warbler can fly from Northwest Indiana to South Florida with (relative) ease, but a lowly-lizard would have a pretty hard time crawling that far. So if they can’t leave their frigid homes so easily, then their only practical option is to stick around. Times are tough in the winter though, and finding enough food, water (that isn’t frozen solid), and shelter can be hard. It’s a challenge that our cold-blooded friends must overcome in order to survive though. Enter hibernation: a real winning strategy! By “going to sleep” for the winter, animals can cut back on the amount of food and water they need to survive. Other animals that stay awake all winter, like deer, need to forage constantly for food or run the risk of starvation. But all a hibernator needs to survive the winter is a belly full of fat and a good shelter to hide in until spring. Of course, when they do wake up, they’ll be hungry and seriously dehydrated, but that’s a problem they can solve when the snow thaws!

Migrators, on the other hand, avoid the problems that come with winter by leaving all together. They COULD stay and try to weather the cold with the rest of us, BUT as we said earlier, times are tough in the winter and finding enough resources to survive is never a guarantee. For those with the means then, getting away for the season is pretty appealing. “Why bother staying amidst the snow and ice when we could go to the tropics instead?” Birds are probably the most recognizable migrants; every year millions of birds travel back and forth between their summer and winter homes during migration season. Traveling so much takes a long time and a lot of energy (like A LOT of energy), but they can just “recharge their batteries” in their vacation homes. Food sources like fruit or insects, especially, are a lot easier to find in warmer, more southern areas compared to Indiana in the winter season.

It’s truly amazing what adaptations nature can come up with to survive. I believe that we all could learn a thing or two from our Park’s winter critters. Maybe we all can try taking a nap the next time a blizzard blows through, or perhaps we may be happier in Mexico enjoying some “invierno” cuisine! Whatever strategies we choose though, we can rest easy knowing our Dunes critters will still be here when spring arrives again.

Alex “Burdy” Burdsall

2nd Year Environmental Educator Fellow