Category: Vertebrates

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A Rocky Relationship with the Desert

Chuckwalla Lizard Basking
Copyright 2010 Cameron Rognan

On a recent trip to the Red Cliffs Desert Reserve in St. George, I learned about a creature with an amazing sense of place. The chuckwalla is a large member of the lizard family which resides in the desert southwest, an area well known for its temperature extremes. Like many other desert dwelling creatures, the chuckwalla has evolved a unique set of adaptations that enable it to thrive in its environment.

Chuckwallas live almost exclusively in rocky areas, and these rocks are the key to their survival. As cold-blooded creatures, they cannot regulate their own temperature, and instead rely on the environment to warm and cool their bodies. The chuckwalla’s flat body shape allows it to warm rapidly on a cool morning by pressing itself tightly to a rock in the sun. This behavior also allows it to quite literally keep a ‘low profile’ from predators. Another temperature control adaptation involves the chuckwalla’s color. While individuals exhibit regional variations from black to brown to yellow, they also have the ability to adjust their skin color to best absorb or reflect sunlight and therefore help regulate their body temperature. During the day, temperatures often soar higher than a chuckwalla can handle, and the lizards retire to the cool shade of the rocks.

Chuckwalla Lizard in a Crevice
Copyright 2010 Cameron Rognan

Apart from helping chuckwallas maintain their temperature, rocks also play a key role in the lizard’s defense against predators, including coyotes and birds of prey. When threatened, a chuckwalla will retreat to the nearest crack or crevice and take in large gulps of air. These big breaths inflate the chuckwalla’s chest cavity like a balloon, wedging its body tightly to the rocks around it – a brilliant move which makes the lizard nearly impossible to pull out by force. Most predators will soon give up and move on to find an easier meal. This behavior gives a whole new meaning to the chuckwalla’s ability to ‘fit’ its environment.

Thank you to Rocky Mountain Power Foundation for supporting the research and development of this Wild About Utah topic.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Chuckwalla Lizard
Copyright 2010 Cameron Rognan

Credits:

Photos: Courtesy & Copyright Cameron Rognan
Text: Andrea Liberatore, Stokes Nature Center
Additional Reading:

Stebbins, Robert C. 2003. Peterson Field Guides: Western Reptiles and Amphibians, Third Edition. New York: Houghton Mifflin Company., https://www.amazon.com/gp/product/0395982723

Arizona-Sonora Desert Museum, “Reptile and Amphibian Accounts: Chuckwalla” (Sauromalus obesus) https://www.desertmuseum.org/books/nhsd_chuckwalla.php (Accessed Nov 22, 2010)

Cooper, W.J. et al, 2000. Lizard Antipreditory Behaviors Preventing Extraction from Crevices. Herpetologica, 56(3): 394-401

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Sage Grouse, Pronghorn Antelope and Fences

Sage Grouse, Pronghorn Antelope and Fences: Greater Sage Grouse, Courtesy US FWS, images.fws.gov, Stephen Ting, Photographer
Greater Sage Grouse
Courtesy US FWS
Stephen Ting, Photographer

As Robert Frost famously wrote in his poem, Mending Wall, “Good fences make good neighbors”.

Fences keep livestock from crops, children from traffic and delineate boundaries. In the intermountain West, fences are important to keep livestock where we want them and away from where we don’t. But wildlife of open sagebrush habitat did not evolve with fences. Sage Grouse and Pronghorn Antelope have had a particularly difficult time adapting.

Sage Grouse are stout, chicken-like birds found only in sagebrush, whose foliage features prominently in their diet. Sage Grouse were once abundant, but their numbers have plummeted due to habitat loss. Today they are candidates for listing as an endangered species. In flight, these large bodied birds like to skim over the sagebrush canopy and so doing, careen right into fences. One Utah study attributed 1/5 of Sage Grouse deaths to fence collisions.

[Kevin Colver recording: https://wildstore.wildsanctuary.com/collections/special-collections]

Pronghorn
Courtesy US FWS
James C. Leupold, Photographer

At dawn during the spring, male Sage Grouse congregate on ancestral dancing grounds to attract mates. The birds fly to these lek areas before sunrise so may not be able to see a fence before they collide. Other areas of special concern include the crest of low hills and the midst of wide open flats. Where grouse are common, flagging a fence or otherwise making it more visible can help considerably to reduce airborne fence collisions.

For Pronghorn Antelope, however, the top of the fence is not the issue. They are the swiftest game animal in North America. As with bison, market hunting in the 19th century decimated their populations. This trend has reversed, but here also, fences are a problem. Pronghorn are sprinters, not hurdlers and rarely jump a barrier over 3 feet tall. They choose to go under or through fencelines. A simple solution for barbed wire fences is to string smooth wire for the bottom strand at least 18 inches above the ground. This simple fence fix enables pronghorns to scoot below the fence unscathed as they migrate between winter and summer grounds

The perspective of Pronghorn Antelope and Sage Grouse could be summed up in the lyrics from a Cole Porter song: Don’t fence me in.

This is Linda Kervin for Bridgerland Audubon Society.

 

Credits:

Photos: Courtesy US FWS: Images.fws.gov
Audio: Kevin Colver, https://wildstore.wildsanctuary.com/collections/special-collections
Text: Linda Kervin, Bridgerland Audubon Society
Additional Reading:

Resources:

Lives of North American Birds. Kenn Kaufman. 1996, Houghton Mifflin Company., https://www.amazon.com/American-Peterson-Natural-History-Companions/dp/0395770173

Don’t Fence Me In: If sage-grouse had a song it would be “Don’t Fence Me In”, USDA Natural Resource Conservation Service, https://www.mt.nrcs.usda.gov/technical/ecs/biology/sagegrouse/dontfence.html

Safer Fencing Can Help Save Western Birds, Environmental Defense Fund, https://www.edf.org/article.cfm?contentID=9126

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The Mysterious Salamander

The Mysterious Salamander: Tiger salamander egg mass, Copyright 2009 Jason Jones, Utah Division of Wildlife Resources
Tiger salamander egg mass
Copyright 2009 Jason Jones
Utah Division of Wildlife Resources
Salamanders have long been a source of mystery for humans and their name reflects some of this mystique. The word salamander has its roots in an Arab-Persian word meaning ‘lives in fire’, reflecting an early belief that salamanders could walk through fire unscathed. Mentioned by Aristotle, Aesop, and Shakespeare, this myth likely arose from salamanders that fled the fireplace once their cozy home in the woodpile was disturbedThe Mysterious Salamander

Utah is home to only one of the world’s more than 500 salamander species. Our tiger salamanders can live in a multitude of different habitats, so long as there is access to fresh water. Because of their need to stay moist, salamanders live a life often hidden from view – spending much of their time underneath rocks, leaves, and other debris. But in early spring, these unique creatures become more active and leave their homes in search of a mate.

Long-toed salamander larvae
in an egg
Copyright 2007 Jason JonesUtah Division of Wildlife Resources

The salamander lifecycle is similar to that of a frog. Eggs are laid in a pond or other source of still water, and hatch into larvae called efts, which look quite like their frog counterpart, the tadpole. After spending a few weeks in the larval stage, individuals metamorphose into an adult.

While modern science has debunked a lot of salamander myths one big mystery still remains. Not all salamanders undergo metamorphosis to become what we recognize as an adult salamander. Some remain in the larval form their entire life, and are even able to reproduce as larvae. This phenomenon, called paedomorphism, has been documented in a number of salamander species, and scientists don’t really understand why or how it happens. Some speculate that the ability to morph or not helps salamanders overcome environmental challenges, such as competition for resources, lack of water, or increased predation.

Tiger salamander eft
Copyright 2007 Jason Jones
Utah Division of Wildlife Resources

Unfortunately, this amazing adaptation has not helped salamanders overcome recent decreases in population that baffled scientists for many years. At one time mysterious, scientists now understand that salamanders are some of the first species to show the effects of pollution in their environment. Now that this particular salamander mystery has been solved, these animals are playing an increasingly important role in determining ecosystem health which may help save many other species.

For more information and photographs of tiger salamanders, please visit our website at www.wildaboututah.org. Thank you to the Rocky Mountain Power Foundation for supporting the research and development of this Wild About Utah topic.

Adult tiger salamander
Copyright 2002 Richard Fridell
Utah Division of Wildlife Resources

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.

Credits:

Photos:

Courtesy & Copyright Jason Jones, Utah Division of Wildlife Resources
Courtesy & Copyright Richard Fridell, Utah Division of Wildlife Resources
Courtesy & Copyright Krissy Wilson, Utah Division of Wildlife Resources
Text: Andrea Liberatore, Stokes Nature Center

Adult tiger salamander,
Copyright 2002 Krissy Wilson
Utah Division of Wildlife Resources

Additional Reading:

Donel, M., Joly, P., Whiteman, H.H. 2005. Evolutionary Ecology of Facultative Paedomorphosis in Newts and Salamanders. Biological Review 80 663-671,

https://onlinelibrary.wiley.com/doi/10.1017
/S1464793105006858/abstract

Grzimek’s Animal Life Encyclopedia, Second Edition. 2003. Volume 6: Amphibians. Farmington Hills, MI: Thompson Gale, https://www.amazon.com/Grzimeks-Animal-Life-Encyclopedia-Amphibians/dp/0787657824

Stebbins, Robert C. 2003. Peterson Field Guides: Western Reptiles and Amphibians, Third Edition. New York: Houghton Mifflin Company., https://www.amazon.com/Field-Western-Reptiles-Amphibians-Peterson/dp/0395982723

Whiteman, Howard H. 1994. Evolution of Facultative Paedomorphosis in Salamanders. The Quarterly Review of Biology 69(2) 205-220, https://www.jstor.org/pss/3037717

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Owl Vision

Barn Owl Sleeping in a Tree
Copyright © 2010 Mike Fish

Hi I’m Holly Strand.

Great-horned and other nocturnal owls have phenomenal nighttime vision. In some respects—they see much better by night than we can by the light of the sun. The visual acuity of owls springs from a number of interesting adaptations.

Of course you’ve noticed that owls have big eyes. If our eyes were in the same proportion to the size of our head, they would be the size of grapefruits! Large owl corneas and lenses help maximize the amount of light received by the retina.

There are two types of photo receptors in the retina. Cones operate in bright light and give fine detail and color vision. Rods work with much less light but compromise somewhat on detail and color. Owl eyes contain considerably more rods than cones while the eyes of daytime animals–like us –contain many more cones than rods.

Great Horned Owl
Copyright © 2010 Mike Fish

Owls –and other nocturnal creatures—have a mirror-like structure behind the retina called a tapetum. Light passes through the rods and cones, strikes the tapetum and is reflected back through the eye to the light source. The tapetum ensures that any light unabsorbed by receptor cells is reflected back through the eye. This gives the receptor cells a second chance at stimulating the rods.

Owls, like most predators, have eyes positioned forward on the face and looking in the same direction. The resulting binocular vision gives the owl a three dimensional perspective. By accurately sensing depth, the owl can zero in on a tasty little mouse scurrying across a field and make adjustments on the wing as it closes in for a kill. To help triangulate even more precisely, owls will often bob or weave their heads to get several viewpoints of an object.

Finally, because of their unique eye structure, owls cannot move their eyes within the sockets. No worries! The owl just moves its whole head instead. On an exceptionally mobile neck, an owl head can rotate at least 270 degrees from side to side and 90 degrees up and down.

For some great pictures of owls and their enigmatic eyes, go to www.wildaboututah.org

For Wild About Utah, I’m Holly Strand.

Credits:

Photos: Courtesy and Copyright 2010 Mike Fish

Text: Holly Strand

Sources & Additional Reading:

Cornell Lab of Ornithology. https://www.birds.cornell.edu/

Utah Division of Wildlife Resources. Utah Conservation Data Center. https://dwrcdc.nr.utah.gov/ucdc/

Scholz, Floyd. 2001. Owls. Mechanicsburg PA: Stackpole Books

Sparks, John and Tony Soper. 1989. Owls: Their Natural and Unnatural History. NY: Facts on File.