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Ecology and Ontogenetic Variation of Diet in the Pigmy Short-Horned Lizard (Phrynosoma douglasii)

Megan E. Lahti and Daniel D. Beck
The American Midland Naturalist
Vol. 159, No. 2 (Apr., 2008), pp. 327-339
Stable URL: http://www.jstor.org/stable/20491337
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Ecology and Ontogenetic Variation of Diet in the Pigmy Short-Horned Lizard (Phrynosoma douglasii)
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Abstract

To date, the diet of the pigmy short-horned lizard (Phrynosoma douglasii) is not known. We report the diet of the pigmy short-horned lizard to determine whether it shows a more generalized diet, similar to other short-horned lizards or a more specialized diet consisting primarily of ants. We compare variation in diet among habitat variables and age/sex classes. We also compare ant head capsules consumed among age/sex classes to determine if lizard groups consume ants of varying size and diversity proportional to their body sizes. Similar to other short-horned lizards, P. douglasii consumes relatively lower proportions of ants (71%) than highly myrmecophagous horned lizard species, followed by pebbles (13%) and Coleopteran insects (11%). Aside from terrain, diet varies among all habitat variables measured, but especially among age and sex classes; neonates feed almost exclusively on ants (89%) while adults consume fewer ants (72%) and yearlings consume the lowest proportion of ants (60%). Most ants consumed by adults represent a single ant genus (Camponotus), while yearlings and neonates consume multiple ant genera of smaller sizes (Camponotus, Pheidole, Tetramorium). We found a significant positive correlation between lizard SVL and the size of ant heads in the diet of P. douglasii. These results are important in understanding variation in diet and ecology of the pigmy short-horned lizard and also in addressing foraging and diet in other insectivorous Phrynosomatid lizards, particularly horned lizards.

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