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Phrynosoma coronatum blainvilli

(Coast Horned Lizard)

Interesting Facts

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Common Names

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Common Names in English:

Coast Horned Lizard

Description

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Habitat

P. c. blainvillei is found in a wide variety of vegetation types including coastal sage scrub , annual grassland, chaparral , oak woodland, riparian woodland and coniferous forest (Klauber, 1939; Stebbins, 1954). In inland areas, this species is restricted to areas with pockets of open microhabitat , created by disturbance (e.g. , floods, fire, roads, grazed areas, fire breaks ) (Jennings and Hayes, 1994).

Biology

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Diet

Horned lizards of the genus Phrynosoma are primarily ant-eating reptiles whose dietary habits are well known (Montanucci, 1981; Pianka and Parker, 1975; Powell and Russell, 1984; Rissing, 1981; Turner and Medica, 1982). Up to 90% of the diet of P. c. blainvillei consists of native harvester ants (Pogonomyrmex spp. ) (Pianka and Parker, 1975), and this species does not appear to eat non-native Argentine ants (Jennings and Hayes, 1994) that have replaced native ants in much of southern California (Ward, 1987). Other slow moving insects, such as beetles, flies, and caterpillars are consumed opportunistically when encountered (Presch, 1969; Pianka and Parker, 1975). Whitford and Bryant (1979) studied the predator and prey relationship of the closely related Phrynosoma cornutum and determined some interesting results which may apply to P. coronatum since they are so closely related and share the same resource base . They found two ant species to be the most important prey for P. cornutum: Pogonomyrmex desertorum and Pogonomyrmex rugosus; P. californicus was also found to be a prey item, however, because few colonies are active during the summer when horned lizards are active, it was considered a minor prey species. They found that at a single stop, the maximum number of ants eaten by P. cornutum per species was: 18 P. californicus, 29 P. rugosus, and 25 P. desertorum. The dietary species composition of individual horned lizards varied from one species to four and the total number of ants ingested in a day varied from approximately 30 to >100 per day.

In addition, Whitford and Bryant (1979) found that the lizards feed most often on ants that were not associated with nest discs or foraging columns and took only a few ants at any one place. When active, P. rugosus was preferred over P. desertorum (based on a larger number taken), however they did not completely switch to P. rugosus. Because P. rugosus activity was found to be unreliable, alternate prey is expected to be utilized (Whitford & Bryant, 1979). Hatchling P. cornutum was found by Whitford & Bryant to feed exclusively on P. rugosus and P. desertorum, "taking an average of three harvester ants per bout and retreating to the shelter of a low shrub or grass where they remained for about 20-30 minutes before feeding again.”

Reproduction

In southern California, the male reproductive cycle begins during mid to late March and ends in June as testes decrease in size. Testes become their maximum size during Spring with sperminogenesis in progress (Goldberg, 1983). Female P. c. blainvillei are oviparous , laying a clutch of 6-17 eggs between May and July each year (Stebbins, 1954; Howard, 1974; Goldberg, 1983). Hatchlings appear in late July to early August, and require 2 - 3 years to reach reproductive age (Stebbins, 1954; Howard, 1974; Pianka and Parker, 1975; Goldberg, 1983).

After reviewing the data (Stebbins, 1954; Pianka and Parker, 1975; Howard, 1974), Goldberg (1983) found a range of average clutch sizes from various studies ranging from 11 to 12.5 individuals. Goldberg (1983) also found that P. coronatum has the potential to produce multiple clutches during the Spring.

Behavior

The daily diurnal activity of P. c. blainvillei is distinctive. As surface temperatures reach >19oC (almost 15 degrees Celsius below temperatures of normal activity), just prior to sunrise, this taxon emerges from burial sites in the substrate into a position that allows them to bask in the first rays of the sun (Heath , 1965; Hagar, 1992). Heath (1962) found that two distinct behavior patterns initiate daily activity; (1) the lizards "may move upward in the sand until their heads are exposed and remain in this position until warmed to their activity levels; (2) alternately, they emerge completely and begin basking in a fully exposed position.” He also found a similarity in emergence times between two groups of P. coronatum and P. cornutum, suggesting the operation of an endogenous or circadian rhythm .

High site fidelity is often exhibited by P. c. blainvillei, as effective thermoregulation (optimum: 29-39 degrees Celsius) requires familiarity with their surroundings (Heath, 1965). Midday temperatures over 40oC are avoided as P. c. blainvillei bury themselves in the substrate, reemerging in the later afternoon to resume full activities (e.g. , feeding, territorial , and reproductive).

Tollesturp's (1981) observations suggest that olfactory cues are important in Phrynosoma's daily activities, including courtship , feeding, sex recognition, and conspecific interactions . In addition, they were observed to apparently mark sites by partially extruding the cloaca and rubbing it back and forth on the substrate.

Contrary to Heath (1962), Whitford and Bryant (1979) did not observe activity in P. cornutum until approximately two hours after sunrise, and most feeding and other activity was confined to the morning hours. Typical morning activity observed by Whitford and Bryant involved "sitting for 30 seconds to several minutes, walking followed by elevated sitting, lasting from a few seconds to several minutes, terminated by a feeding bout or further walking, then resumption of elevated sitting.” They also found that a significant portion of the daily activity of P. cornutum involves shrub climbing and movement in the shrub canopy. Through the middle part of the day, the lizards positioned themselves in a shrub canopy where the ambient temps ranged from 35 to 40 degrees C. Their feeding corresponded with the peak activity patterns of harvester ants , between the hours of 0900 and 1100 (Whitford and Ettershank, 1975; Whitford, et. al., 1976). As expected, the bulk of thermoregulatory basking occurred in the early morning and late afternoon.

Survival: The defense that P. c. blainvillei most often uses against approaching predators is to depend on their cryptic appearance and simply lie motionless (Jennings and Hayes, 1994). Klauber (1939) documented change in body coloration to match the soil or sand on which they were found. Other methods used include hissing, inflating lungs to increase apparent size (Pianka and Parker, 1975; Munger, 1986; Sherbrooke, 1981), raising their horns by lowering their snout (Pianka and Parker, 1975; Sherbrooke, 1981), squirting blood from the corner of the eye (which seems to repel dogs and cats) (Presch, 1969; Pianka and Parker, 1975), tilting the body when irritated (Milne and Milne, 1950; Smith, 1946; Tollestrup, 1981), presenting a bristling of scales of the back while standing well up on the legs (Bryant, 1911), and running a short distance before flattening out or burrowing several centimeters under the ground (Presch, 1969). When P. coronatum flattens its body, it usually tucks its head down, exposing its horns, and often charges the enemy (Winton, 1916). An additional defense mechanism may be based on learned avoidance by predators suggested by reports of snakes dying while trying to swallow Phrynosoma which are well documented in the literature (Klauber, 1972; Milne and Milne, 1950; Van Denburgh, 1922; Vorhies, 1948; Wright and Wright, 1957).

The work conducted by Whitford and Bryant (1979) suggests that the coevolution of a foraging strategy in relation to the responses of their prey has allowed the horned lizard to survive with a potentially limited resource base .

Socio-Spatial Behavior: The literature contains conflicting data on the social behavior of P. coronatum. According to Carpenter (1967), the typical pattern of Iguanid courtship includes push-ups, head-bobs, a prancing strut, grasping of the female by the nape of the neck, and male mounting the female dorsally (Carpenter, 1967; Carpenter and Ferguson, 1977). Lynn (1965) found "no evidence of territoriality , no evidence of any type of social hierarchy, no evidence that the display (head-bob/push-up) is used in sex or species recognition, and no evidence that the display is used on courtship." Stamps (1977) speculates that horned lizards have only simplified displays and lack territorial defense. Contrary to these reports, Tollestrup (1981) found that P. coronatum utilizes a diverse repertoire of displays for species recognition, courtship and sex; including head-bob (a vertical motion of the head; (Lynn (1965) described this as "three (sometimes four) quick bobs , a bob with a quick upward movement and a slow downward movement, a slow bob); push-up (an extension of the forelimbs that raises the front part of the body); tail-curled-up (with all four limbs extended or the body pressed flat against the substrate, the tail is curled up over the body); and scratching (the two forelimbs are moved alternately with a scratching or pawing motion usually without the claws in contact with the substrate). Tollestrup (1981) observed that displays between males are usually performed from an elevated perch such as a gopher mound or cow dung, and are characterized by a frequency increase in head-bobs and push-ups, and by the use of the rocking display. One male would then run toward the other, each continuing to display. "Males presented their vents with their tails curled up over the back to other males and in each case, the male with the curled tail moved out of the area" (Tollestrup 1981). Tollestrup observed no biting or combat with the horns. Using a radiotelemetry study, Munger (1984) found that horned lizards utilize limited home ranges , occupying areas much smaller than they would if they moved randomly. His data further suggest that there is a reduction in home range overlap, and contrary to expectation, overlap between sexes tended to be less than overlap between individuals of the same sex (Munger, 1984). In Whitford and Bryant's 1979 study, the closely related P. cornutum moved an average of 46.8 meters per day (range = 9-91 m ). They also found that an individual horned lizard moved over a zigzag course during a day but rarely crossed its own trail .

P. c. blainvillei emerges from hibernation in March, and becomes surface active in April through July, after which most adults estivate (summer hibernation) (Hagar, 1992). The adults reappear again briefly in late summer and return to overwintering sites between August and early October depending upon elevation (Klauber, 1939; Howard, 1974; Hagar, 1992).

Taxonomy

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Synonyms

Agama coronatum Blainville • Phrynosoma blainvillii Gray • Phrynosoma coronatum blainvillii Gray • Phrynosoma frontalis Van Denburgh

Similar Species

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Members of the genus Phrynosoma

ZipcodeZoo has pages for 27 species and subspecies in this genus:

P. asio (Giant Horned Lizard) · P. blainvillii (San Diego Horned Lizard) · P. braconnieri (Short-Tail Horned Lizard) · P. cerroense (Cedros Island Horned Lizard) · P. cornutum (Texas Horned Lizard) · P. coronatum (Blainville Horned Lizard) · P. coronatum blainvilli (Coast Horned Lizard) · P. coronatum blainvillii (Coast Horned Lizard) · P. coronatum frontale (California Horned Lizard) · P. ditmarsi (Rock Horned Lizard) · P. douglasii (Pygmy Horned Lizard) · P. douglasii douglasii (Pigmy Short-Horned Lizard) · P. douglassii (Eastern Short-Horned Lizard) · P. douglassii douglassii (Pigmy Short-Horned Lizard) · P. douglassii hernandesi (Mountain Short-Horned Lizard) · P. douglassii ornatissimum (Desert Short-Horned Lizard) · P. douglassii ornatum (Salt Lake Short-Horned Lizard) · P. hernandesi (Greater Short-Horned Lizards) · P. mcallii (Flat-Tailed Horned Lizard) · P. modestum (Round-Tailed Horned Lizard) · P. orbiculare (Mexican Horned Toad) · P. platyrhinos (Desert Horned Lizard) · P. platyrhinos calidiarum (Desert Horned Lizard) · P. platyrhinos platyrhinos (Desert Horned Lizard) · P. solare (Regal Horned Lizard) · P. taurus (Mexican Horned Lizard) · P. wigginsi (Gulf Coast Horned Lizard)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Last Revised: 2012-07-18