water retention – Discover-Nature

Heat Effects

The midwestern United States is experiencing a heat dome this week. This is the result of a high pressure system hundreds of miles across and moving very slowly. Air in the upper atmosphere of a heat dome is already warm, but is still cooler than the air below, and cooler sir sinks towards the Earth’s surface. As the air moves downward, it compresses air molecules together releasing heat, making the lower layers even hotter and drying out the area as moisture evaporates. With little or no moisture, no clouds form to relieve the heat and dry conditions.

^{Heat Dome over Eastern US by National Weather Service, Jun 26 2025}

Humans have a variety of ways to cope with high heat including being less active, drinking plenty of fluids, and remaining in shady or air-conditioned areas. Wildlife still has to get food and water every day and may have fewer opportunities available to them to avoid the high heat. Let’s look at how the heat is affecting a few of the backyard species common in the Midwest.

^{Photinus pyralis, Big Dipper firefly by Terry Priest}

Fireflies are cold-blooded, or ectothermic, and prefer warm and humid areas. They come out in the early evening and as their bodies warm, they become more active, flying and flashing more frequently, communicating with other fireflies to find a mate. Eggs are laid soon after mating, but these will perish if they do not remain hydrated. Turning off outdoor lighting for a few hours in the evening and maintaining taller, well-watered vegetation will help fireflies during hot and dry conditions.

^{American Toad by Brad Carlson, Mar 2012; and Bullfrog at Waterfall Place by DonArnold, 2022}

Frogs and toads are also ectothermic and require heat from the environment to live. Species worldwide, including American toads and bullfrogs in our area, find temperatures in the 70s to be ideal. As temperatures move into the mid-80s, these species and others are prone to dehydration and heat stress. In addition, they normally look for shady and humid areas to regulate their body temperatures, but the lack of moisture in a heat dome does not make those niches easy to locate. Maintaining shady, well-watered areas of the garden provides refuge for many amphibian species.

^{Cardinal looking to stay in the shade by Don Arnold, 2023}

Birds are often affected by extreme heat. Most birds have lower body temperatures than the outside air. This allows birds to easily dissipate heat from high energy activities, such as flight. Once the outside air gets above a hundred degrees, birds cannot lose heat to the atmosphere and become severely compromised by heat and dehydration. Rapid open-mouthed breathing, changing eating times to early or late in the day, sitting with wings outstretched, or exhibiting poor balance are all signs of heat stress in birds. Providing shady, undisturbed areas and readily available water sources gives birds the opportunity to move around less and stay hydrated.

Wild animals have to deal with weather extremes just as we do. Come to the Jurica-Suchy Nature Museum or a nature center near you to learn more about providing opportunities for wildlife to survive heat, drought, and other environmental conditions.

Beat The Heat

This week, the weather has been hot for the upper Midwestern U.S. with temperatures topping out above 100°F. Combined with high dew points in the mid-70s, the heat index temperature was upwards of 110°F. Here are some ways that plants and animals keep cool in the extreme heat.

^{Mojave Desert by LezusRocks, Getty Images}

^{Kit fox at entrance to desert den by Stevelenzphoto, Getty Images}

Desert environments, where hot conditions exist daily, are home to numerous animal species that live underground. Heat from the sun penetrates soils and sand layers for several inches, but at 20″ below the surface of the sand in the Mojave Desert, temperatures are fairly constant around 86°F while the surface may be over 110°F. Few large mammals are known to use burrows, although kit foxes and humans are two examples. Basements and lower levels in buildings are often preferred areas on hotter days.

^{Shaded walk in the woods by Felixmizioznikov, Getty Images}

Shade from trees is highly effective in creating cooler areas. Leaves are lighter in color than most soils and paved areas, and leaves reflect much of the sun’s radiation upwards, away from the shady area underneath. Denser foliage and rough leaf textures enhance the cooling effect. Under a shade tree, temperatures may drop up to ten degrees and other surfaces no longer exposed to direct sunlight, including our skin, may be 20 to 40 degrees cooler.

^{African elephant by Petr Polak, Getty Images: Black-tailed jackrabbit by Rancho_Runner, Getty Images; Fennec fox by Nattanan726, Getty Images}

Vasodilation occurs when blood vessels near the skin’s surface expand so more blood flows next to the skin. Many animals living in hotter climates, including fennec foxes, black-tailed jackrabbits, and African elephants, have large ears with broad, flat surfaces devoid of hair, fur, or other insulation. The ear’s large surface area is covered by a thin layer of skin and blood vessels. During hot weather, heat carried in the blood through the ear is readily lost to the outside environment, providing a cooling effect for the rest of the body.

^{Large crowd by Shaunl, Getty Images Signature}

Evaporative cooling is another method through which heat can be dissipated from a body. Trees use this method by losing water vapor through their leaves during photosynthesis, cooling the air under the leaves. Humans employ this method in a process called sweating. We lose warm water through skin pores directly to the air around us. Sweating also moistens our skin’s surface, indirectly providing additional cooling as air moves across the skins surface and wicks away additional heat. An important aspect enhancing the effectiveness of this method is our posture. Being supported by two legs, rather than four, exposes much less surface area to the direct rays of the sun, and much more surface area to air currents.

^{Forest path by Inga Nielsen, Getty Images}

While sweating is good for cooling, it is removing water from the body, which must be replaced for the process to continue. Exposure to today’s temperature extremes may result in a loss of three gallons of water or more from an average-sized human. As you are out enjoying nature during hot days, remember to keep hydrating to stay cool and keep other bodily systems healthy.

Desert Habitat, pt.3

In the past two blogs, we have explored deserts and the plants which inhabit them. Animals native to these habitats have general adaptations for coping with temperature extremes, aridity, and finding water, food, and shelter. Strategies include hunting during cooler hours including at dawn, dusk, or overnight; obtaining water from sources other than standing water; burrowing underground to avoid temperature spikes and solar radiation; ability to conserve water in their body; ability to dissipate body heat; and being well-camouflaged. Look for each of these adaptations in the following species that live in our desert regions.

Greater roadrunner, Geococcyx californianus, by Tony Cyphert, Sep 2018

Ord’s Kangaroo Rat, Dipodomys ordii, by Andy Teucher, Jun 2005

The greater roadrunner, Geococcyx californianus, can only fly for several seconds at a time, but can reach speeds up to 17mph when running. They hunt early in the morning, retiring to shade when temperatures heat up mid-morning. Water requirements are met from foods including grass and prickly pear cactus, plus prey that includes lizards, scorpions, and rattlesnakes. Roadrunners do not urinate, but can excrete salt and save the water. They have an un-feathered area under their chins used to dissipate body heat. Ord’s kangaroo rat, Dipodomys ordii, is another species that gets all of their water requirements from the seed they eat. Individuals live in underground burrows, coming out only at night to feed. They conserve water in their bodies and do not sweat or pant. They have many predators, but with a 9-foot jump and excellent hearing, they are hard to catch. Seeds are collected and stored in their burrows, and they will gain 50% more water from the underground humidity before being eaten.

Horned Toad, Phrynosomasp., by TJFrom AZ, May 2009

Gila monster, Heloderma suspectum , by Karla Kishinami, Apr 2012

Horned toads, Phrynosoma spp., are small, ant-eating lizards with thick scales to conserve water and deter predators. To escape a predator, these animals can squirt a directed stream of blood from their eyes up to five feet away. They are sandy-colored with undefined outlines allowing them to easily hide amid rocky outcrops. Normally active during the day, they can retreat to burrows or under rocks if temperatures become too hot. During winter, horned toads will spend a period of inactivity, called brumation, in underground burrows. The Gila monster, Heloderma suspectum, is another lizard with armor protected skin marked with black and pink coloration that camouflages them well in sandy soils. They shelter from daytime heat under rocks and shrubs, emerging in early morning or evening to hunt small mammals, lizards, insects, and bird eggs. One of only two venomous reptiles in North America, their venom adversely affects their prey’s nervous system. The short, thick tail stores water in fatty tissue for use when needed.

Tarantula, Aphonopelma sp., by Saguaro National Park, Nov 2020

Western coral snake, Micruroides euryxanthus, by Ashley Wahlberg, Apr 2016

The tarantula, Aphonopelma spp., shelters in deep burrows lined with silk to prevent the sand from caving in. They are nocturnal hunters of insects, arthropods, and small lizards with a bite that delivers a small amount of venom to stun their prey. Venom immediately starts to break down tissue to liquify the meat, allowing the spider to use sucking mouth parts to draw in its meal. The Western coral snake, Micruroides euryxanthus, is brightly colored with red-white-black-white banding and venom that is twice as deadly as most rattlesnakes. They are very secretive, living under rocks or buried in the sand. Coming out at night or on some overcast days, they hunt for lizards and other snakes. Venom causes rapid paralysis and respiratory failure, although due to their small size and small amount of venom injected, they are not a threat to humans.

Like many environments, a healthy desert community exists when plants, animals, and habitat are all present and undisturbed. With much of the life in deserts underground, walking off trails and driving off roads can negatively impact what is under the surface. Removing plants and rocks used for water and shelter is equally damaging. I encourage you to get out, observe, and enjoy this unique habitat, or research many of the fun and interesting adaptations at a local natural history museum.

^{Pictures above clockwise: Bark scorpion by Josh More, May 2014; Cactus wren by Mick Thompson, Feb 2019; Jackrabbit, by Mark Gunn, Mar 2014; Javelina, Sonora Desert, by Richard Bonser, Jan 2005; Tarantula hawk wasp by Jim Mulhaupt, May 2010; Sonoran mud turtle by Grigory Heaton, Sep 2022; Round tailed ground squirrel by Wendy Miller, May 2022; Hoary bat by Michael Pennay, Sep 2009; Cactus deermouse by J.N.Stuart, Oct 2011}

Desert Habitats, pt.2

Pequop Mountain foothills, Great Basin Desert, Nevada by Matthew Roth, Apr 2016

Big sagebrush, Artimesia tridentata by RCWinton, Aug 2008

There are four major deserts in North America. The Great Basin runs from central Idaho to northern Arizona. It is a high altitude plateau, with very cold winters, mild summers, and few plant species characterized by big sagebrush, Artimesia tridentata.

The Mohave Desert, a small area covering southern Nevada and southeastern California, is known for its cold, rainy winter season resulting in hard freezes leaving little water available. The Joshua tree, Yucca brevifolia, a yucca variety growing above 3000′, is the tallest plant in the area.

Joshua tree, Yucca brevifolia, by Melissa Delzio, May 2011

The Chihuahuan Desert, covering the high altitudes of northern Mexico ,is subject to hard freezes from arctic winds scouring its surface. Winter rains occasionally occur supporting a rich diversity of low shrubs and small cacti.

The Sonoran Desert, covering southern Arizona and the Baja Peninsula, has high and low altitudes, hot to mild temperatures, and periodic rainfalls. The winter season, with mild temperatures, does not limit the plant and animal diversity as much as in the other three, colder deserts. The Sonoran Desert, which includes several habitat types, supports a rich variety of species including 2000+ plants, 350+ birds, 100 reptiles, and 30 native fishes.

Desert plants exhibit many similar features that make them well-adapted to the hot, dry conditions of their native habitat. Most are succulents, plants with thick, fleshy stems to retain water for use during hot, dry periods. Plants often have spines in place of leaves to reduce the surface area exposed to wind and heat, greatly reducing water loss from evaporation. Spines also add a layer of protection to prevent animals from eating the plant. Stems are green, containing chlorophyll and water, and this is where photosynthesis takes place. Bloom periods and pollination occur during winter or nighttime when cooler temperatures prevail.

Creosote bush, Larrea tridentata, in flower by Malcom Manners, Apr 2017

Century plant, Agave americana, by J.Maughn, Mar 2020

Several distinctive native species characterize North American deserts including cacti, succulents, and other plant varieties with spines. The creosote bush, named for its distinctive antiseptic smell, grows three to nine feet tall and has small yellow flowers. This plant grows in colonies of cloned bushes which may live for long periods as epitomized by the King Clone of the Mohave Desert, estimated to be about 12,000 years old. The century plant, another long-lived plant, is a species of agave noted for its large cluster of wide leaves with spiny edges. The plant may live up to 30 years, but flowers only once, then dies.

^{Clockwise from top: Prickly pear by Fishfoot, Mar 2018; Prickly pear buds by Diandra Rodriguez, Nov 2011; Prickly pear cacturs in bloom by Stepan Mazurov, May 2009; Prickly pear cactus glochids by Tracie Hall, Nov 2017}

Often seen cacti include the prickly pear cactus which is actually a group of several species all native to North America. Modified stems, called pads, are often mistaken as leaves. These store water, photosynthesize food and sugars, and produce flowers. All species grow long, single spines in addition to glochids, clusters of very fine, tiny spines. Glochids are often not noticeable but can be easily detached if brushed against and once lodged in the skin are painful and difficult to remove. The saguaro cactus is another common plant. Its distinctive shape, with a tall central column and “arms” growing at right angles, is easily recognizable as one of the Sonoran Desert’s native species. It is the largest cactus in North America, growing to over 40′ high, and living 100 years or more. White, waxy flowers open only at night to attract bats, its preferred pollinator.

Saguaro cactus by Ralph Earlandson, Apr 2017

Many natural history museums have excellent displays of plants and animals from world-wide desert biomes, including one of my favorites, the North American desert display at the Jurica-Suchy Nature Museum. In my blog next week, I will introduce some of the notable animals and their adaptations to desert life.

Desert Habitat, pt.1

A biome is a type of global habitat characterized by temperature, rainfall, latitude, elevation, and wind pattern. Plants, which are unable to move about, are used to characterize each type of biome, and are well-adapted to their native habitat. The desert biome is the driest habitat found on earth. In a desert, plants are widely spaced and are adapted to life with little or no moisture except for annual periods when brief rains may be heavy, sparse, or not occur at all. Even within these harsh conditions, plants may be present supporting a rich diversity of species.

_{Clockwise above: Hidden Valley, Joshua Tree solitude by Don Graham, Apr 2013; Sonoran Desert sunset by Jasper Nance, May 2009; Sonoran Desert layers by Art DiTommaso, Apr 2020; Mohave Desert by Melissa Delzio, May 2011}

A common factor of all deserts is the aridity or lack of moisture. Aridity can be determined by how much water is available in the habitat combined with the rates of evaporation from heat, radiation, and wind exposure. Another consideration in determining aridity is how much moisture the air can hold. Neither extremely hot nor extremely cold air easily retains moisture. Freely running water is only available in the desert for the briefest period of time immediately following a rainfall, a scarce and unpredictable event.

Deserts form in areas where dry air predominates. Understanding how weather influences the Earth’s surface helps to identify where to find the world’s desert regions. At the equator, air is warmed by direct sunlight causing it to rise and absorb large amounts of water from the oceans. When the warm air mass encounters cooler air at higher altitudes, it spreads out both northward and southward. Cooler air causes the absorbed moisture to condense into rain in tropical latitudes. The outward moving air mass, now dryer and cooler, also begins to fall back to the earth’s surface, picking up heat from the sun’s radiation and the hot ground. Air masses generally descend and move back towards the equator around 30˚ latitude, which is where many deserts occur.

Rain shadow on leeward side of mountains on Oahu by Loren Javier, Jun 2010

Exploring Greenland’s grass and Dry shrub vegetation by Eugene Kaspersky, Jul 2016

Deserts can also be formed from rain shadows and temperature extremes. As prevailing winds encounter mountains, air is forced up the windward side and flows down the leeward side. As air rises, it cools, once again condensing any moisture into rain which falls on the windward side. Dry air coming over the mountain forms a rain shadow that leaves little moisture for the habitats on the leeward slopes. Temperature extremes occur in both hot and cold regions. Dry, hot air descending from the tropics form warm deserts. Cold, dry air from polar winds form cold deserts such as those found in Antarctica and Greenland.

Desert temperatures vary widely, both daily and seasonally. Dry air and cloudless skies allow a maximum amount of solar energy to reach the surface where it is absorbed and converted to heat, raising daytime temperatures dramatically. At night, air temperatures plummet as solar radiation ceases and heat is quickly wicked away into the cooler atmosphere. Temperatures may fluctuate as much as 100˚ in a 24-hour period. Ultraviolet radiation also presents other challenges to living organisms. Intense sunlight can damage skin cells, degrade retinal tissue, and destroy chlorophyll molecules in plants.

Rain in the Sonora Desert summer monsoon season by Kevin, Aug 2013

Green Sonoran Desert after brief winter rain by Wayne S. Grazio, Fwb 2017

Deserts experience seasons, just as those found in other biomes. In desert areas of Arizona, there are five recognized annual seasons. Spring, February through April, is characterized by mild temperatures and windy days. It is a dry season as warm winds wick away all exposed moisture. Summer, in May and June, is hot and dry, with many species remaining dormant to escape the heat. Summer monsoons, July through mid-September, signals a change in wind direction bringing moister air northward from the tropics. Frequent thunderstorms occur most years providing a period of replenishment for shrubs and trees. Autumn, in October and November, returns to warm and dry conditions. Winter comes in December and January bringing in mild temperatures and the possibility of a few rain showers.

The climate of the world’s deserts makes survival difficult, but many species have adapted to these conditions in some remarkable ways. Next week, we will investigate the desert regions of North America and their vast diversity of life.

_{Clockwise above: Blooming hedgehogs by Jasper Nance, Apr 2010; Desert globemallow by Take-A-Hike Arizona, Mar 2009; Desert woollystar, Eriastrum eremicum, Sonoran Desert by SSBiker1, May 2011}