Wednesday, August 4, 2010 - 10:50 AM

COS 53-9: Amphibians and reptiles as indicator species in urban areas: the importance of life-history and spatial scale

Kyle Barrett, University of Georgia

Background/Question/Methods Over one-half of the world’s population now resides in urban areas, and the proportion in the U.S. is even higher.  Urban development is known to negatively affect a wide range of taxa, and for some groups, the pattern of response to development is more predictable than others.  For example, stream ecologists have developed groups of invertebrates that can generally be thought of as sensitive or tolerant to stream degradation.  Amphibians, are the other hand, are widely regarded as being a group that is collectively sensitive to development or other pressures.  At least one recent study has questioned this conventional wisdom.  Reptiles are another taxa experiencing documented declines, and reptiles are often monitored along with amphibians.  To quantify amphibian and reptile sensitivity to urban land use, I monitored stream- and riparian-dwelling herpetofauna for two years.  Based on these data and data from previous studies reporting on herpetofaunal species richness patterns in urban streams, I present ideas regarding which members of this group are most sensitive to development.  I also address the spatial scale of development that best predicts species richness and abundance patterns.

Results/Conclusions I found that amphibians are particularly sensitive to urban development.  Only four amphibian species were estimated as present in the three urban streams surveyed, whereas I estimate between 12 and 14 species in non-urbanized streams.  Contrastingly, reptiles were more species rich in urban riparian areas relative to other land use types.  Within the amphibians, data from previous work indicates that salamander density is best predicted by development at the watershed-scale.  Data collected as part of this study suggest the same pattern does not hold for anurans.  Anuran counts (as indexed from automated recording devices) were best predicted by the amount of deciduous forest within a 1 km buffer of the monitoring point.  The data suggest that monitoring protocols designed to evaluate effects of a stressor on herpetofauna are likely to be flawed if they do not separately evaluate amphibians and reptiles.  Furthermore, within the amphibians it is important to appreciate that salamanders are subjected to land use patters far beyond the stream edge, as stream beds act as an attractor of non-point source pollutants and increased runoff in urban areas.  Anurans are not subjected to this same dynamic and therefore respond to land use patterns at a much smaller scale.