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Illinois Summer Nights
Who’s awake and who’s asleep?
Many different animals have different times when they are active. Some animals in the same area may never see each other because of when they are awake or asleep. This is called temporal niche differentiation. Some animals shift between times when they are active based on the time of year or where they live.
Illinois Summer Nights poster
southern flying squirrel (Glaucomys volans) – completely nocturnal which is why most people do not see them, the flap of loose skin between the front and hind legs allows them to glide, they do not truly fly
great horned owl (Bubo virginianus) – nocturnal, is the largest of all owls in Illinois, “horns” or “ears” on their heads are tufts of feathers, have great vision at night
white-tailed deer (Odocoileus virginianus) – mainly crepuscular but can be active at night and day, only the males have antler which fall off in the winter and are covered with velvet in the summer
black-crowned night heron (Nycticorax nycticorax) – mostly nocturnal and active at dusk, found in wetlands, once common throughout Illinois, only two nesting sites are found in Illinois
coyote (Canis latrans) - mainly crepuscular, but can be active at other times depending on the environment, they live in family groups , weighing 25 to 40 pounds
raccoon (Procyon lotor) – primarily nocturnal, but can be seen at other times, very adaptable species and can be found in a variety of habitats
crayfish – most are nocturnal, hiding during the day
boreal chorus frog (Pseudacris maculata) – primarily nocturnal outside of their breeding season or overcast days, the male calls sound like a finger rung over a comb
luna moth (Actias luna) – mainly nocturnal, they are not a pollinating species as they lack mouth parts, it is one of the larger species of moths in the state
bats – nocturnal, but can be seen at dusk, we have 13 different species in the state, and all are insectivores (insect eaters)
fireflies – most nocturnal and at dusk, a few species are diurnal and do not have glowing light, there are over 20 species documented in the state and each has its own flash and flight pattern
The Eyes Have It
In some vertebrates, when a light shines on tapetum lucidum layer at night, it creates an eye shine or iridescent reflection. This layer helps to improve night vision in low lights so the animal can see. The glow of the eyes comes in different colors based on species, age, and the type of minerals in the tapetum lucidum crystals.
Diurnal animals do not have this like humans and some squirrels. Some nocturnal animals also do not have this layer like little brown bat, snakes, and armadillo as they use other senses.
Do You Know These Words?
Diurnal – active in the daytime
Why? – forage for food, stay warm, avoid predators like owls
Nocturnal – active at night
Why? – avoid predators like hawks and eagles, extreme heat, hunt for prey, avoid humans
Crepuscular – active at dusk and dawn
Why? – avoid predators, avoid extreme heat, dim light offers hiding
Cathemeral - active sporadically and in irregular intervals both day and night based on food, temperature, time of the year
Why? – adapt to food availability, temperatures, predation
Circadian Rhythms – the internal biological clock that manages when an animal or plant is active
Noctiflorous – a plant or flower that blooms or is open at night
Anthesis –fully opened flowers at night for their pollinators – moths and bats
Bioluminescence – the light given off by fireflies created by combining oxygen and luciferin in the presence of luciferase enzyme
Vespertine – active at dusk
Matutinal – active at dawn
Tapetum Lucidum – reflective layer behind the retina in the eye
It’s All in the Numbers
Mammals Across the World
- 70% of mammals are nocturnal
- 20% are diurnal
- 2.5% are crepuscular
- 8.5% are cathemeral
Mammals in Illinois
- Over 60% are nocturnal
- Mammals in urban areas are more nocturnal than in rural areas to avoid humans
Birds in Illinois
- Of 463 species of birds recorded in Illinois, only eight are nocturnal
- 80% of migrating birds do so at night
- 30% of diurnal bird species vocalize at night
Amphibians
- 90% of amphibians are nocturnal or crepuscular
- Many species in their larval state are diurnal
Reptiles
- 50-60% of reptiles are diurnal
- 20-30% are crepuscular
- 10-20% are nocturnal
