Announcements from the Nov. 2022 Chapter Meeting

Highlights from the November 2022 Chapter Meeting

The Announcements

Please view the full set of November announcements by clicking here. Further activities are listed on the chapter calendar. Opportunities and contacts, websites, and other details are available in the announcements.

Highlights of the Meeting

Officers Elected – Congratulations to our new officers for the 2023-2024 board term.
Vice President – Timothy Skipworth
Co-Treasurer – Judy Cato
Secretary – Nancy Wilson
New Class Director – Anne Edwards
Membership Director – Steve Wilson
State Representative – Lara Guerra
Youth Development Director – Shelby Smith

Your willingness to serve the chapter is much appreciated!

Nature by Night

Many thanks to our excellent panelists for their presentation on nocturnal wildlife, their adaptations, and effects of light and noise pollution. Panel roles were organized by taxa. Rachel Richter, Texas Parks & Wildlife Urban Biologist, addressed mammals; Michael Smith, naturalist and author, amphibians and reptiles; Jake Poinsett, Trinity River Audubon Center Program Manager, birds; and Sam Kieschnick, Texas Parks and Wildlife Urban Biologist, invertebrates.

Rachel began by discussing why mammals are primarily nocturnal (or crepuscular – active at dawn and dusk), a behavior pattern thought to be first driven by the dinosaurs. Advantages of nocturnal activity include being less visible to predators and limiting exposure to the hottest times of the day.

She also showed examples of four key sensory adaptions. The raccoon’s paws are an example of tactile adaptation, where the environment is perceived in detail by a highly developed sense of touch. The bobcat’s eyes are highly adapted for night vision, dominated by rods rather than cones. Like many nocturnal vertebrates, the bobcat eye also has a reflective “tapetum lucidum” behind the retina. Its reflection gives light a second chance at striking photoreceptors, vastly improving night vision, also creating the eyeshine we see.

Enhanced sense of smell also aids nocturnal activity. Rachel pointed out how larger snouts contain many more olfactory receptors, with the whitetail deer having some 60 times more than humans. Moveable ears and ear hairs/tufts are helpful adaptations. Bats are prime examples of nocturnal mammals with superior hearing, with size, shape and folds that aid in echolocation.

Jake discussed nocturnal adaptations in birds, focusing on owls, nightjars and night herons. Owl vision is enhanced by having tube-shaped eyes, which accommodate more rods. Since this structure can’t move like an eyeball, compensation comes in owls’ ability to turn their heads up to 270°. Comb-like feather tips make their flight nearly silent. Their hearing benefits from asymmetric ears that locate sounds more precisely and a facial disc that gathers more sound.

Both nightjars and night-herons are adaptively nocturnal and crepuscular, depending on various factors, such as lunar phases and prey behavior. Nightjars can modify their metabolism, reducing their temperature when less moonlight limits feeding, and some can go into deep torpor for extended periods. This hibernation-like behavior is not known in other birds. Night-herons’ large, red eyes improve their vision. They are more opportunistic, often shifting to diurnal activity.

Michael reviewed nocturnal/crepuscular behavior in herpetofauna. Many shift their activity by the season, becoming more nocturnal during summer heat as the lower nighttime temperatures and increased humidity are less desiccating. He explained how pit vipers can use their heat sensing not only to locate prey but also to identify warmer areas to shelter and avoid freezing. Vertical pupils in snakes aid depth perception, enabling them to better judge the distance to prey.

He also reviewed how snakes are less active during the brightest parts of the lunar cycle. This tracks prey behavior and conserves hunting energy for when prey are more available.

Frogs and toads have excellent night vision, including color. Cooler night temperatures are also a metabolic advantage for amphibians.

Sam contrasted invertebrate adaptations to “sight-heavy” vertebrates, noting that invertebrates use a wider range of tools to sense their environment. He drew on the example of insect antennae, how these structures are packed with chemoreceptors. His moth images showed more filiform and sensitive antennae in males. He also noted keen vision in spiders’ adaptations. Typically having 6-8 eyes (mostly 8), many spiders also have tapetum lucidum layers to sense light better.

Generously lumping plants in with organisms without backbones, Sam pointed out how night-blooming plants often have strong fragrance and light-colored blossoms to better draw nocturnal pollinators. Bull nettle and moonflower show these traits. The moonflower’s deep trumpet shape is also well adapted to its pollinators, the sphinx moths.

The discussion then turned to how noise and light pollution impact nocturnal species. Excessive light can limit prey activity and availability, stressing both prey and predators. If activity is shifted to later at night, there is less time for foraging. Light can also disorient phototaxic animals, a prime example being baby sea turtles getting confused when they try to make their way to the ocean. Noise can reduce effectiveness of predators reliant on their sense of sound, such as bats and owls.

Both light and noise pollution affect amphibians negatively. Urban noise can interfere with frogs’ calls and locating. Light can limit activity and negatively affect breeding patterns. These cumulative effects call for action on our part to limit impacts of artificial light and excessive noise.

Going Deeper:

For Love of Insects by Michael Eisner – book recommended by Sam K.

By panelist Michael Smith –

Gad Perry – Texas Tech researcher referenced

When the recording of this meeting is available, it will be posted here.

Thanks to our guests and members for participating in this month’s meeting. I hope all feel welcome at NTMN.

Take care,
Scott Hudson
President
North Texas Master Naturalist

 

 

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