Image by Brady Poteet
Characterizing Post-breeding Terrestrial Habitat
of the American Toad (Anaxyrus americanus) in
York County, Pennsylvania
Image taken from Pixgood.com
Brady Poteet
Department of Biological Sciences, York College of Pennsylvania, York, PA 17403
Introduction
Methods
Discussion
Top model suggests that soil and air temperature
are the environmental variables that most influence
the presence or absence of A. americanus.
Amphibian populations have been declining in the
past several decades with habitat destruction being
the principle offender (Gallant et al 2007).
Created random sampling points on maps of the study areas using ArcGIS (Figure 1).
The aquatic habitat of amphibians in the order
Anura has been well documented, but the
terrestrial habitat of these amphibians has not been
well defined (Mitrovich et al 2011).
When a sample point was reached, a 30x30 meter plot was established with a 1x1 meter
plant quadrat In the center of the plot.
The American Toad is currently listed as abundant
(PAHerps 2013). However, this species may
eventually experience declines much like its close
relative, the Fowler’s toad.
Traveled to sampling points using a handheld GPS.
Since humidity did not differ between present and
absent plots, it is possible that A. americanus is able
to effectively exploit moist microhabitat in order to
avoid desiccation (Rittenhouse et al. 2008).
 Environmental variables such as air temperature, soil temperature, relative humidity, and
vegetation cover were recorded in the center of each plot using a Vernier Lab Quest data
Collection device. Vegetation type was also recorded.
A. americanus can effectively travel to and occupy
habitat that is several hundreds of meters away from
water sources (Forester et al, 2006; Miaud, Sanuy,
and Avrillier, 2000).
 A thorough search for toads was conducted within each plot. When a toad was encountered,
the sex and snout to vent length of the individual were recorded. Environmental variables were
also recorded wherever a toad was located.
Figure 1. Map of Nixon county park with
randomly generated sampling points.
Characterizing terrestrial habitat has tremendous
potential for conserving both the American toad and
related terrestrial anuran species that are
threatened or endangered.
Results
Future Studies
Table 1. Multiple logistic regression analysis using model selection with AIC scores. The top
models are within 2 ∆AIC of the best model (above line) with the null model for comparison.
Hypotheses
American toads favor habitats that offer:
•Mild air temperature (20oC to 25oC)
•Mild soil temperature (20oC to 25oC)
•High relative humidity
•Moist soil
 Location of American toads will be independent of
proximity to water sources
Study Area
Image taken from Google Maps
Model Name
K
AICc
∆AICc
AICc Weight
ta + ts + (1|Quadrat)
ts + hum + (1|Quadrat)
vcover + ts + (1|Quadrat)
ts + (1|Quadrat)
ta + ts + hum + (1|Quadrat)
(1|Quadrat)
4
4
4
3
5
2
24.80
25.29
25.64
26.37
26.87
31.88
0.00
0.49
0.84
1.57
2.07
7.08
0.22
0.17
0.14
0.10
0.08
0.01
ts= soil temperature
ta= air temperature
hum= humidity
Vcover= vegetation cover
ms= soil moisture
Quadrat= plot (random effect)
For Soil Temperature: Model average estimate= 8.98, Unconditional SE= 10.63,
95 % Unconditional confidence interval: -11.84 , 29.81
 16 American toads were located.
• 3 juveniles within Nixon county
park. 9 juveniles and 4 adults on
private land.
Future studies should aim to obtain larger sample
sizes in order to create spatial habitat models that could
further the characterization of A. americanus habitat.
Future studies should broaden the sampling locations
to further improve the habitat characterization of A.
americanus within York County.
Figure 2. Mean soil temperature of plots where A. americanus was
absent (n=14) compared to mean soil temperature where A.
americanus was present (n=20). Error bars represent 95% CI. Means
differ significantly (*) between absent and present plots (MannWhitney test, P<0.0001, U=30.00).
 Multiple logistic regression analysis
yielded 24 possible models.
• Top 5 models = ∆AICc < 2.0
• Soil temperature, air
temperature, humidity, and
vegetation cover were included in
the top models (Table 1).
Air temperature, humidity, and soil moisture is
variable in American toad post-breeding habitat.
 American toads occupy habitat independent of
proximity to water sources.
The American toad is a true habitat generalist.
Literature Cited
Forester, D.C. et al. 2006. Post-breeding dispersal and summer home range of female American Toads (Bufo americanus). Northeastern
Naturalist 13(1):59-72.
 A. americanus juveniles were found
in habitat both near and far away from
major water sources at differing
elevations within Nixon county park
(Figure 3).
 A. americanus juveniles were found
on different soil types within Nixon
county park (Figure 4).
Conclusions
During the post-breeding season, American toads
prefer to occupy habitats that offer higher soil
temperature.
 Soil temperature was significantly
higher in plots where A. americanus
was present.
Sampling for toads took place primarily in Richard
Nixon county park and William Kain county park in
York county, Pennsylvania. Sampling also occurred on
private land approximately 10 miles east of this
location near Red Lion, Pennsylvania.
A. americanus can occupy habitats that offer a
variety of vegetation cover, vegetation types, and soil
types.
Gallant, A.L. et al. 2007. Global rates of habitat loss and implications for amphibian conservation. Copeia 2007(4):967-979.
Mitrovich, M.J. et al. 2011. Habitat use and movement of the endangered Arroyo toad (Anaxyrus californicus) in coastal southern California.
Journal of Herpetology 45(3):319-328.
Miaud, C., Sanuy, D., Avrillier, J. 2000. Terrestrial movements of the natterjack toad Bufo calamita (Amphibia, Anura) in a semi-arid,
agricultural landscape. Amphibia-Reptilia 21:357-369.
PAHerps. Available from: http://www.paherps.com/herps/frogs-toads/american_toad/. Accessed 2014 July 20.
Figure 3. Topography and water source proximity in
Nixon county park. Two A. americanus juveniles were
found near the stream, while another was found over
200 meters away from a major water source at an
elevation 140 feet higher.
Rittenhouse, T.A.G. et al. 2008. The role of microhabitats in the desiccation and survival of anurans in recently harvested oak-hickory forest.
Copeia 2008(4):807-814.
Figure 4. Soil types found in Nixon county park. A.
americanus was found on two dissimilar soil types:
Codorus silt loam, and Mt. Airy and Manor Soil, 8-25%
slope, very stony.
Acknowledgements
I would like to thank Dr. Bridgette Hagerty for her
guidance, expertise, and support throughout this study.