Elliott Chaparral Reserve

31 Mar, 05 PM - 29 Jul, 05 PM

Blainville?s Horned Lizard (BHL; Phrynosoma blainvillii) historically occurred throughout much of coastal and inland California. This species, until recently recognized as two subspecies, the Coast Horned Lizard (P. coronatum frontale) and the San Diego Horned Lizard (P. c. blainvillei), is thought to have disappeared from at least 45% of its original range (Jennings and Hayes, 1994). The actual range contraction may be even greater as this species is closely tied to Coastal Sage Scrub, a habitat type thought to have declined by 85-90% in southern California (Alberts et al. 1993). In addition to habitat loss, urban encroachment is allowing the non-native argentine ant (Linepithema humile) to invade and dramatically alter the native ant community (Sanders et al. 2003), including displacement of the harvester ant species (Messor and Pogomyrmex sp.) that are the primary prey of BHL (Suarez et al. 1998). Because horned lizards are dietary specialists, the loss of their primary prey may substantially affect the persistence of this species in areas near development. Currently BHL is included on the State of California?s Special Animal list (as the two subspecies mentioned above), and in many county planning documents. One key to the development of conservation plans for this unique Californian lizard will be a detailed understanding of the food resource needs of BHLs. Very little is actually known about the details of the foraging behavior of horned lizards. A few studies have looked at whether or not horned lizards are active or ambush foragers (Perry, 2007), and the type and number of individual ants eaten per day has been determined (Pianka and Parker, 1975; Whitford and Bryant, 1979). It is also known horned lizards may predate certain ant species based on the ant?s aggressive tendencies (Rissing, 1981). However, the relationship between the number of ant colonies used per individual lizard in a population, and particularly, their pattern of colony use (i.e. do they feed at the same colonies each day or do they alter colony use) is poorly understood. Because horned lizards consume more ants than any single colony can provide, the lizards must use multiple mounds to meet their energy needs. (Munger, 1984) attempted to determine if horned lizards forage at multiple mounds in an optimal way; however, his study was based on single observations of individual lizards. The purpose of the proposed study is to conduct repeated, sequential observations of the foraging behavior of individual BHLs. By following individual lizards, a more complete, detailed analysis of horned lizard foraging behavior can be compiled. Specifically, I plan to test if horned lizards forage at harvester ant mounds in their activity areas in a non-random way. For example, do they appear to limit their movements and behaviors in order to minimize the risk of predation while maximizing feeding opportunities? Also, by observing the lizards over several months, I plan to assess whether BHLs use the ant colonies in an efficient manner. For example, how often is a particular mound visited, or is there a pattern to the sequence in which BHLs visit the mounds? As all horned lizards rely on crypsis for predator avoidance, telemetry is necessary to repeatedly locate specific individuals for observation. Only adult lizards greater than 35 g will be selected to receive transmitters to minimize the transmitter/body mass ratio (< 10 %). The lizards will be searched for by vehicle and on foot and captured by hand. Once captured each lizard will be measured (snout-vent length, body mass and other morphometric measurements) and sexed. In addition, all study animals will receive passive integrated transponder tags implanted subcutaneously in the left inguinal region, as per IUCN recommendations. Prior to implantation, the site will be thoroughly cleaned with isopropyl alcohol. This technology is used widely in zoos and wildlife studies and causes no short term or long term distress or harm (Keck, 1994). Because this project will require an extensive amount of man-hours for the behavioral observations only 12 to 15 will be followed in 2009. Furthermore, several undergraduate students will be recruited and trained to assist with conducting the foraging behaviors. Each lizard will be followed for three consecutive days, three times during the study period (~ mid-April through July 2009). The lizard?s overnight location will be located using telemetry the evening before each observation day, and observations will begin near dawn the next day before the lizard emerges. The lizard?s movement and feeding will be observed using binoculars at a distance of ~ 10 m, or greater if the lizard seems aware of the observer?s presence. Each feeding bout will be recorded, the number of food items eaten approximated, and the source of the prey marked with flagging. At the end of the study, all harvester ant colonies in the study area will be mapped using GPS and the activity (home range) areas determined using GIS. REFERENCES Alberts, A.C., A.D. Richman, D. Tran, R. Sauvajot, C. McCalvin, and D.T. Bolger. 1993. Effects of habitat fragmentation on populations of native and exotic plants in southern California coast scrub. Pages 103-110 in Interface Between Ecology and Land Development in California, ed. by J.E. Keeley. Southern California Academy of Sciences, Los Angeles, California. Jennings, M.R. and M.P. Hayes. 1994. Amphibian and Reptile Species of Special Concern in California. Final Report to the California Department of Fish and Game for Contract number 8023, California Department of Fish and Game, Inland Fisheries Division, Cordova, California. Keck, M. B. 1994. Test for detrimental effects of PIT tags in neonatal snakes. Copeia 1994: 226-228. Munger, J.C. 1984. Optimal Foraging? Patch use by horned lizards (Iguanidae: Phrynosoma). The American Naturalist 123: 654-680. Perry, G. 2007. Movement patterns in lizards: measurement, modality, and behavioral correlates. Pages 13-48 in Lizard Ecology, ed. by S.M. Reilly, L.D. McBrayer, and D.B. Miles. Cambridge University Press, New York, New York. Pianka, E.R. and W.S. Parker. 1975. Ecology of horned lizards: A review with special reference to Phrynosoma platyrhinos. Copeia 1975: 141-162. Rissing, S.W. 1981. Prey preferences in the desert horned lizard: influence of prey foraging method and aggressive behavior. Ecology 62: 1031-1040. Sanders, N.J., N.J. Gotelli, N.E. Heller, and D.M. Gordon. 2003. Community disassembly by and invasive species. Proc. Nat. Acad. Sci 100:2474-2477 Suarez A.V., D.T. Bolger and T.J. Case. 1998. The effects of fragmentation and invasion on the native ant community in coastal southern California. Ecology 79:2041?2056 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: 686-694.

Visit #17405 @Elliott Chaparral Reserve

Approved

Under Project # 19630 | Research

The Foraging Ecology of Blainville's Horned Lizard

graduate_student - California State University (CSU), San Marcos

Reservation Members(s)

Kenneth Morgan Mar 31 - Jul 29, 2009 (121 days)
Kenneth Morgan Mar 31 - Jul 29, 2009 (121 days)
Group of 2 Undergraduate Student Mar 31 - Jul 29, 2009 (121 days)

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Grounds use only 4 Mar 31 - Jul 29, 2009