A colorful, charismatic species—the eastern collared lizard (Crotaphytus collaris)—is center-stage in a woody plant management project near Kansas City, Missouri. Critical habit for the collared lizard and other unique species are Missouri glades, scattered outcrops of exposed bedrock embedded in open woodland. These hot, dry, desert-like microclimates support a variety of species including tarantulas, scorpions, prickly pear, and reptiles.
“The collared lizard is a key indicator species on glades; when their numbers decline we know something is wrong with their habitat,” explains Larry Rizzo, Natural History Biologist with Missouri Department of Conservation in Kansas City, Missouri. “Jackson County is the northeastern tip of the collared lizard range, which includes much of northern Mexico and the southwestern United States.”
A Species of Conservation Concern, eastern collared lizard populations have shown a decline in Missouri due to loss of their glade habitat. Rizzo is working with U.S. Army Corps of Engineers and Jackson County Parks and Recreation to improve habitat for this species in Jackson County.
Rizzo explains that fire suppression beginning more than 50 years ago allowed Eastern red cedar (Juniperus virginiana) trees that were once confined to steep cliffs, river bluffs, and rock outcrops, to invade glades. The resulting tree canopy completely altered glade habitats and the species that depend on them for survival. Cooler, more shaded habitats caused a decline in lizard reproduction, and dense woodlands formed a barrier to lizard dispersal between glades.
“Well into the 1960s there were collared lizards in Jackson County, but those populations gradually declined as tree canopy increased,” says Rizzo. In the mid-1980s a dam was built in the eastern part of the county, and limestone riprap placed on the face of the dam. The riprap and associated limestone quarry provided safe habitat for a small population of collared lizards that migrated to the disturbed area. A third isolated population of lizards was also found in a nearby glade.
Gene flow* is an important source of genetic variation and critical for maintaining healthy collared lizard populations. “Our problem at this site was that collared lizards on the glade couldn’t disperse and interact with either the quarry or the dam populations because of dense tree canopy,” explains Rizzo. “The lizard will tolerate about 20 to 30 percent canopy, but anything more than that becomes a significant barrier to their movement.”
To connect the three populations of collared lizards and improve their habitat, Rizzo and others began removing some of the trees in the project area. The goal is to remove all woody shrubs and trees except native post oak (Quercus stellata) and chinkapin oak (Quercus muehlenbergii) from the glade and within a 50-foot wide connecting corridor between the glade and limestone quarry. An open canopy allows sunlight to warm the soil surface making it easier for lizards to disperse from the glade.
Woody vegetation control methods include mechanical removal with chainsaws and basal bark herbicide application. “We use chainsaws to cut large eastern red cedar and use a basal bark application of Garlon® 4 Ultra specialty herbicide (1 quart) plus Bark Oil Blue (2 quarts) to treat smaller cedar trees,” explains Rizzo. “Red cedar doesn’t resprout after cutting, so we don’t have to apply herbicides to the cut surface of the larger trees.” Some of the other woody vegetation such as redbud (Cercis Canadensis), red oak (Quercus rubra), hackberry (Celtis occidentalis), elm (Ulmus Americana), honey locust (Gleditsia triacanthos) and exotic honeysuckle (Lonicera maackii) resprout following cutting, so a basal bark or cut surface treatment with Garlon 4 Ultra and Bark Oil Blue is applied. Control averages about 80 percent depending on the tree species, size, and thickness of the bark.
Ultimately Rizzo would like to include fire in the control program to periodically remove the woody understory, duff and litter, help control prickly pear cactus (Opuntia sp.), and other invasive species like exotic honeysuckle. “If we could get approval to use fire to mimic historical burns in this area we could expand our ability to enhance the habit for collared lizards and other species relying on glade and open woodland habitat.”
Conservation measures taken in Jackson County to reduce the woody canopy have benefited a variety of wildlife including other lizard species and snakes, and reduced invasion of exotic honeysuckle. Future plans for the project area include reintroduction of native forbs and grasses such as scaly blazing star (Liatris squarrosa), purple coneflower (Echinacea purpurea), and sideoats grama (Bouteloua curtipendula) to enhance glade diversity.
MISSOURI IS HOME TO 13 SPECIES OF LIZARDS, all of which are harmless and non-venomous. Like other reptiles, lizards thermoregulate or adjust their body temperature by moving to different areas of their environment to warm up or cool down. This external means of keeping warm is called ectothermy, or external heating and is the reason open, desert-like, sunlit glades are critical habitat for lizards.
The collared lizard (Crotaphytus collaris) can reach up to a foot in length including the tail. The name comes from the lizards’ distinct coloration, which includes bands of black around the neck and shoulders that look like a collar. Like some other lizard species, collared lizards are capable of running on their hind legs for short distances, looking like small theropod dinosaurs. Male collared lizards are much more brightly colored than females, ranging from dark to light green to a beautiful cobalt blue in some areas. Females are typically varying shades of brown with red markings during the breeding season. Collared lizards are the official state reptile of Oklahoma.
SAVANNAS, GLADES AND WOODLANDS in Missouri are distributed in a landscape mosaic based on soil depth and bedrock type. Glades are treeless or sparsely wooded openings with bedrock at or near the surface. In pre-European settlement, glades sustained small herds of bison, elk, and deer along with other endemic species uniquely adapted to these particular habitats. Savannas or woodlands with a canopy cover of 10 to 50 percent and herbaceous groundcover often surround glades. Savannas, woodlands and glades are strongly influenced by the frequency, intensity, and seasonal variation in fire occurrence.
*Gene flow—also called migration—is any movement of genes from one population to another. If genes are carried to a population where those genes previously did not exist, gene flow can be a very important source of genetic variation.
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Published August 2014; reviewed and revised June 2018.