Coast horned lizard Phrynosoma coronatum blainvilli Class: Reptilia Order: Squamata Family: Iguanidae Dudek and Associates Species Accounts Status: Federal: None State: State Protected Species, California Species of Special Concern Data Characterization Abundant information is available for P. c. blainvillei, however, more information is needed regarding dispersal, hibernation site requirements, and population dependance on native ants. The U.C. Riverside database provides 310 records distributed throughout the planning area, of which 98 are precise enough to hold an x and y coordinate. The metadata show that of the 98 records, 79 include date information: 11 records from 1995 to 1999; 46 records from 1990 to 1994; 14 records from 1980 to 1989; and the rest of the records from 1921 to 1979. Habitat and Habitat Associations 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). Biogeography Historically, Phrynosoma c. blainvillei was distributed from the Transverse Ranges in Kern, Los Angeles, Santa Barbara, and Ventura counties southward through the Peninsular Ranges of southern California to Baja California (Jennings, 1988). P. c. blainvillei seems to have disappeared from about 45% of its former range in southern California, in particular on the coastal plain where it was once common (Hayes and Guyer, 1981) and in riparian and coastal sage scrub habitats on the old alluvial fans of the southern California coastal plain (Bryant, 1911, Van Denburgh, 1922). In California, Phrynosoma c. blainvillei ranges from the Transverse Ranges south to the Mexican border west of the deserts, although the taxon occurs on scattered sites along the extreme western desert slope of the Peninsular Ranges (Jennings, 1988). The known elevation range of this species is from 10 meters at the El Segundo dunes (Los Angeles County) to approximately 2,130 meters at Tahquitz Meadow, on San Jacinto Mountain, in Riverside County. Phrynosoma c. blainvillei is thought to intergrade with P. c. frontale in extreme southern Kern county and northern Santa Barbara, Ventura, and Los Angeles counties (Reeve, 1952; Montanucci, 1968; Jennings, 1988). Range This species is distributed throughout western Riverside County. No specific population aggregations are apparent within the planning area. Key Populations in Planning Area Suitable habitats up to 2,100 meters in elevation. Biology Genetics: According to Montanucci (1989), specialization for myrmecophagy (ant- eating) in Phrynosoma appears to have involved the following morphological changes: (1) a reduction or loss of the epipterygoid; (2) reduction of the coronoid process; (3) reduction in the diameter of the mandibular ramus; (4) reduction in the area posterior to the coronoid process, and a concomitant increase in the length of the tooth row, possibly accomplished by a slight shift in the position of the coronoid. In addition to morphology and dietary information, behavioral information also corroborates the specialization for myrmecophagy in Phrynosoma (Montanucci, 1989). 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." Daily Activity: 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. 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. Dispersal: No information on dispersal is available. Threats The specialized diet and habitat requirements, site fidelity, and cryptic defense behavior make P. c. blainvillei highly vulnerable. Commercial collecting, and habitat loss due to agriculture and urbanization are the main reasons cited for the decline of this taxa. Most surviving populations inhabit upland sites with limited optimal habitat. Many of these sites are on marginally suitable Forest Service land (Jennings and Hayes, 1994). However, the most insidious threat to P. c. blainvillei is the continued elimination of its food base by exotic ants. Argentine ants colonize around disturbed soils associated with building foundations, roads and landfills, and expand into adjacent areas, eliminating native ant colonies (Ward, 1987). Under these conditions P. c. blainvillei populations have become increasingly fragmented, and have undergone the added stress of a number of other factors, including fire, grazing, off-road vehicles, domestic cats, and development (Jennings and Hayes, 1994). This taxon is unable to survive habitats altered by development, agriculture, off-road vehicle use, or flood control structures (Goldberg, 1983). Special Biological Considerations 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). Literature Cited Baur, B. 1979. Pfledge und "Zucht" der Reisenkrotenechse, Phrynosoma asio (reptilia: Sauria: Iguanidae). Salamandra 15:1-12. Bruner, H.L. 1907. On the cephalic veins and sinuses of reptiles, with description of a mechanism for raising the venous blood pressure in the head. Amer. Jour. Anat., 7:1-117, 17 figs., 3 pls. Bryant, H. C. 1911. The horned lizards of California and Nevada of the genera Phrynosoma and Anota. Univer. California Publ. Zool. 9:1-84. Burleson G.L. 1942. The source of blood ejected from the eye by horned toads. Copeia 1942, No. 4. Dec 28. Pp. 246-248. Herpetologica. 1989. 45(2). Pp 208-216. Carpenter, C. 1962. Aggression and social structure of iguanid lizards. Pp. 87-105 In: W.W. Milstead (Ed.), Lizard Ecology: A symposium. Univ. Missouri Press, Columbia. Carpenter, C. 1967. Aggression and social structure of iguanid lizards. Pp. 87-105. IN:W.W. Milstead (Ed.), Lizard Ecology: A Symposium. Univ. Missouri Press, Columbia. Carpenter, C.C. and G.W. Ferguson. 1977. Variation and evolution of stereotyped behavior in reptiles. Pp. 335-554. In: C Gans and D.W. Tinkle (Ed.), Biology of the Reptilia. Vol 7. Academic Press, London. Goldberg, S.R. 1983. The reproduction of the coast horned lizard, Phrynosoma coronatum in Southern California. The Southwestern Naturalist. Vol 28, No. 4 Pp. 478- 479. Grey (1946)- San Diego horned Lizard Phrynosoma coronatum blainvillei. In: Smith H.M. 1946. Handbook of Lizards. Pp. 293-295. Comstock Publ. Assoc., Ithaca, New York. Hagar, S. B. 1992. Surface activity, movement, and home range of the San Diego horned lizard, Phrynosoma coronatum blainvillei. Master's Thesis, California State University, Fullerton. Hayes, M. P., and C. Guyer. 1981. The herpetofauna of Ballona. Pp. H1 - H80 In: R. W. Schreiber (editor), The biota of the Ballona region, Los Angeles County. Supplement I, Marina Del Rey/Ballona Local Coastal Plan, Los Angeles County Natural History Museum Foundation, Los Angeles, California. Heath, J. E. 1965. Temperature regulation and diurnal activity in horned lizards. Univ. California Publ. Zool. 64:97-136. Heath, J.E. 1962. Temperature-Independent morning Emergence in Lizards of the Genus Phrynosoma. Science. Vol 138. Pp. 891-892. Howard, C. W. 1974. Comparative reproductive ecology of horned lizards (genus Phrynosoma) in southwestern United States and northern Mexico. Journal of the Arizona Academy of Science 9(3):108-116. Jennings, M. R. 1988. Phrynosoma coronatum. Catalogue of American Amphibians and Reptiles:428.1-428.5. Jennings, M. R., and M. P. Hayes. 1994. Amphibian and reptile Species of Special Concern in California. Final report submitted to California Department of Fish and Game, Inland Fisheries Division, Rancho Cordova, California, under Contract 8023. Klauber, L. M. 1972. Rattlesnakes, Their Habits, Life Histories, and Influence on Mankind. Univ. Calif. Press, Berkeley and Los Angeles, California. Southwestern Naturalist 28(4):478-479. Klauber, L. M. 1939. Studies of reptiles life in the arid southwest. Part I, Night collecting on the desert with ecological statistics; Part II, Speculations on protective coloration and protective reflectivity; Part III, Notes on some lizards of the southwestern United States. Bulletin of the Zoological Society of San Diego (14):1-100. Lynn, R.T. 1965. A comparative study of display behaviour in Phrynosoma (Iguanidae). Southwest nat. 10:25-30. Milne, L.J., and M.J. Milne. 1950. Notes on the behaviour of horne toads. Amer. Midl. Nat. 44:720-741. Milne, L.J. 1938. Mating of Phrynosoma coronatum. Copeia 1938:200-201. Montanucci, R. R. 1968. Notes on the distribution and ecology of some lizards in the San Joaquin Valley, California. Herpetologica 24(4):316-320. Montanucci, R.R. 1981. Habitat separation between Phrynosoma douglassi and P. orbiculare (Lacertlia: Iguanidae) in Mexico. Copeia 1981:147-153. Montanucci, R.R. 1989. The relationship of morphology to diet in the horned lizard genus Phrynosoma. Herpetologica. 1989. 45(2), pp 208-216. Munger, J.C. 1984. Home Ranges of Horned Lizards (Phrynosoma): circumscribed or exclusive? Oecologica (Berlin) 62:351-360. Munger, J.C. 1984. Home ranges of horned lizards (Phrynosoma): circumscribed and exclusive? Oecologia (Berlin) (1984) 62:351-360. Pianka, E. R., and W. S. Parker. 1975. Ecology of horned lizards: A review with special reference to Phrynosoma platyrhinos. Copeia 1975(1):141-162. Powell, G.L. and A. P. Russel. 1984. The diet of the eastern short horned lizard (Phrynosoma douglassi brevirostre) in Alberta, and its relationship to sexual size dimorphism. Can. J. Sci. 62:428-440. Presh, W. 1969. Evolutionary osteology and relationships of the horned lizard genus Phrynosoma (family Iguanidae). Copeia 1969:250-275. Reeve, W. L. 1952. Taxonomy and distribution of the horned lizard genus Phrynosoma. University of Kansas Science Bulletin 34(14):817-960. Rissing, S.W. 1981. Prey preferences in the desert horned lizard: Influence of prey foraging method and aggressive behavior. Ecology 6: 1031-1040. Schoenherr, A.A.1976. The Herptofauna of the San Gabriel Mountains Los Angeles, California Including Distribution and Biogeography. Special Publication of the Southwestern Herpetologist's Society, February 1, 1976. Sherbrooke, W.C. 1981. Horned Lizards: Unique reptiles of western North America. Southwest Parks and Monuments Assoc. Globe, Arizona. Smith, H.M. 1946. Handbook of lizards. Comstock Publ. Co., Ithaca New York. Stamps, J.A. 1977. Social behavior and spacing patterns in lizards. Pp. 265-334. IN: C.Gans and D.W. Tinkle (Eds.), Biology of the Reptilia. Vol. 7. Academic Press, London. Stebbins, R. C. 1954. Amphibians and reptiles of western North America. McGraw-Hill Book Company, New York, New York. Tollestrup, K. 1981. The social behavior and displays of two species of horned lizards, Phrynosoma platyrhinos and Phrynosoma coronatum. Herpetelogica 37(3):130-141. Turner, F.B. and P.A. Medica. 1982. The distribution and abundance of the flat-tailed horned lizard (Phrynosoma mcallii). Copeia 1982:815-823. Van Denburgh, J. 1922. The reptiles of Western North America; an account of the species known to inhabit California, Oregon, Washington, Idaho, Utah, Nevada, Arizona, British Columbia, Sonora, and Lower California. Volume I. Lizards. Occasional Papers of the Academy of Sciences (10):1-611. Vorhies, C.T. 1948. Food items of rattlesnakes. Copeia 1948:302-303. Ward, P. S. 1987. Distribution of the introduced Argentine ant (Iridomyrmex humulis) in natural habitats of the lower Sacramento Valley and its effects on the indigenous ant fauna. Higardia 55(2):1-16. Whitford, W.G., and M. Bryant. 1979. Behavior of a predator and its prey: the horned lizard (Phrynosoma cornutum) and harvester ants (Pogonomyrmex spp.). Ecology. 60(4):686-694. Whitford, W.G., and G. Ettershank. 1975. Factors affecting foraging activity in Chihuahuan desert harvester ants. Environmental Entomology. 4:689-696. Whitford, W.G., P. Johnson, and J. Ramirez. 1976. Comparative ecology of the harvester ant Pogonomyrmex barbatus (F. Smith) and Pogonomyrmex rugosus (Emery). Insectes Sociaux. 23:117-132. Winton, W.M. 1916. Habits and behaviour of the Texas horned toad, Phrynosoma coronatum. Copeia 1916:81-84. Wood, S.F. 1936. Courting behaviour of some western lizards. Copeia 1936:177. Wright A.H. and A.A. Wright. 1957. Handbook of snakes. Comstock Publ. Assoc., Ithaca, New York.