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Quinta M A Z AT L A N
CRE ATURES OF THE NIGHT
At Quinta Mazatlán By Quinta Mazatlán-Center for Urban Ecology
Nature stays awake at night. It’s less seen than nature during the day, but much more heard. It presents itself as creaks, chirps, buzzes, yowls, and other sounds our undistracted ears tune into. It’s a shadowy form rustling its way into a bush; a quick flash of reflecting eyes; the dark trunk of a tree silhouetted against the night sky. It’s a community shift – nocturnal for the diurnal – with different plants and animals leading the way. Sometimes diurnal and nocturnal counterparts are pretty similar – eating many of the same foods and living in the same area – but being active at different times of the 24-hour day allows them to avoid competing with each other for resources. Ecologists call this temporal niche differentiation. One study on wildcats (including tigers and clouded leopards) in Sumatra found that the more similar the cats were in size and prey items, the less they were seen at camera traps during the same times of day. A potential example closer to home would be hawks and owls – they eat many of the same prey items (rodents, reptiles, amphibians, birds), but hawks are diurnal and most owls are nocturnal.
Bark Scorpion (UV and flashlight)
Whether they forage at night to avoid competition with other species or not (or a host of other reasons), nocturnal animals tend to have certain characteristics. Because they’re active in low light, they tend to have more rod photoreceptors than cones (cones being responsible for color vision). They also tend to have larger eyes with slit pupils – a way to help protect their sensitive eyes from any bright lights they encounter. Look no further than a house cat’s eyes for an example!
Holding a stick insect
Another trait in many nocturnal vertebrates, like mammals and birds, is reflective eyes. The reflection is caused by a part of their eye called tapetum lucidum (meaning “bright tapestry” in Latin). The tapetum lucidum is found in the back of the eye, where it reflects light back through the retina to help the rod photoreceptors get more light. What we see in opossum and pauraque eyes at night is the light that’s passed through their eyes twice – once on the way in, once on the way out – a remarkable way to enhance night vision. Some animals that are mostly diurnal can spend more time active at night. In urban areas, where human-generated noise is common throughout the day, some animals will change their behavior to take advantage of the quieter city nights. For instance, European Robins may sing more at night when they live in an area that’s noisy in the day, which allows them to be heard better by other robins. The Valley’s diversity of plants and animals is amazing enough during the day, full of brightly birds, butterflies, and flowers, but it’s just half the picture. The other half? Cooler nights where sound carries further and nature is just as alive. Join the Center for Urban Ecology every Tuesday this summer for Flashlight Nights, a guided walk through the woods. Flashlight Nights is from 8:30 pm – 10:00 pm every Tuesday at Quinta Mazatlán in McAllen, located at 600 Sunset Drive. Bring a flashlight and a sense of adventure! $5 program fee. Advance registration required at quintamazatlan.ticketleap.com.
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