American Toad
EASTERN AMERICAN TOAD
Bufo a. americanus
 
INTRODUCTION
The American toad is among the most well recognized amphibians of southern New England. It is found throughout Rhode Island, ranging from relatively pristine forest patches in western Rhode Island to somewhat degraded urban areas in the Providence area. American toads often frequent shaded yards and parks after a spring rain, as they generally prefer areas where conditions are moist and food sources abundant. Toad populations appear to be relatively secure in the region, with the major cause of mortality seemingly attributed to road activity during peak migrations. The far less common Fowler's toad (Bufo fowleri) is similar in appearance and can easily be mistaken for an American toad- especially as juveniles and young adults. To add to the confusion, these two species are thought to hybridize in areas where habitat is suitable to both species. American toads are a facultative vernal pool species.

 
IDENTIFICATION

  • The American toad is a rotund, terrestrial frog with a large-wide head, short limbs, and rough, warty skin.
  • Mature females are significantly larger than males and feel noticeably rougher in texture when handled.
  • Commonly, the spotted dorsum is dominantly brown in color, but there is much variation. Individuals vary from brick-red to olive to greenish gray to nearly black; furthermore, coloration may change depending upon the season, environment, time of day, age, and sex.
  • The chest and forward part of the abdomen is cream-colored and speckled with small black flecks or spots. Fowler's is immaculate- white with no dark flecking.
  • Males have dark throats (Dickerson 1906).
  • The colors of the usually roundish spots on the dorsum also vary. Shades of red, brown, and black have been noted. Female's dorsal warts may be noticeably pointed (Hunter et al. 1999).
  • In the American toad, each of the larger spots contains 1-2 round warts (small glands). Fowler's Toads tend to have 3-4 warts per spot. The legs, feet, and thighs are also warty.
  • The two cranial ridges on top of the head have lateral branches extending behind the eye. Behind these ridges are the large, bean-shaped parotid glands. The parotid glands are either separated from the cranial ridge behind the eye, or connected with it by a short spur (Hunter et al. 1999). On Fowler's toad, the cranial ridges and parotid glands touch completely.
  • A light, narrow mid-dorsal stripe may be present. Fowler's Toad has a light mid-dorsal stripe.
  • Breeding males have enlarged, darkened nuptial pads on the dorsal (upper) surface of the thumbs that are used to grasp the female during amplexus. During the breeding season, the nuptial pads are the most useful characteristic to distinguish genders.
  • During the breeding seasons females tend to be more reddish overall.
  • Voice: A long trilling whistle, lasting 6-30 seconds, with some individual variation in pitch and tone (Gage 1904; Wright and Wright 1949; Conant and Collins 1991).
American toad

(1) American Toad color variation.
(2) Notice the cranial ridge
and parotid gland behind the eye
(3) top photo: mid-dorsal stripe

American Toad
 
SIZE
AGE / SEX SVL (SNOUT VENT LENGTH) (cm)
SAMPLE SIZE

AVERAGE

RANGE

Std. Deviation

ADULT FEMALE

7.1

6.0- 8.7

0.7

68

ADULT MALE

6.1

5.1- 7.2

0.5

146

JUVENILE

3.3

0.8

1.3- 5.7

309

METAMORPH

1.6

0.7- 2.3

0.3

360



AGE/ SEX
MASS (g)
SAMPLE SIZE

AVERAGE

RANGE

Std. Deviation

ADULT FEMALE

43.5

16.4- 75.3

15.1

68

ADULT MALE

26.3

13.7- 38.4

5.0

146

JUVENILE

4.5

0.5- 15.7

3.5

309

METAMORPH

0.4

0.1- 1.0

0.2

360





American toad

 
RELATIVE ABUNDANCE
Rhode Island
Common, much more likely to be detected during the breeding season in permanent ponds or ponds that often do not dry every year.
  two toads  
Regional
Despite some localized extirpations and high road mortality, American toads are presently thought to be abundant and widespread in southern New England (Klemens 1993).
 
DISTRIBUTION
Rhode Island
American Toads are widespread throughout mainland Rhode Island, but are absent from some of the state's many islands. We found evidence of American toads breeding (egg masses and larva) in 10 of 119 randomly-selected ponds in Rhode Island during research in 2000 (Paton and Egan 2001).
Regional
Widespread and common (Klemens 1993; DeGraaf and Yamasaki 2001).
General
Found throughout eastern North America from Hudson's Bay in northern Canada to the southern United States, except for Florida's Gulf Coast, coastal areas in the southeast, parts of New Jersey, Long Island, New York (Klemens 1993).
 
HABITAT NON BREEDING
In general, American toads spend only a few weeks at breeding sites, then disperse into the upland and are solitary and seldom seen. American toads are believed to be habitat generalists because they are found in all forest types in New England and most non-forested habitats with the exception of high-elevation habitats (alpine and Krummholz) (DeGraaf and Yamasaki 2001). When encountered, they are found in a variety of habitats including: forests- deciduous and evergreen, shrublands, open fields, residential yards, urban parks, and fringes of water bodies (Hunter et al 1999). Toads may be seen throughout the fall, especially after a rainy night, until the weather turns cold. When winter sets in, toads burrow deep into soft soils or forest floor litter and hibernate until the following spring. Unfortunately, little is known in our area about the wintering habitats and requirements of American Toads (Raithel unpubl. ms).
 
HABITAT BREEDING
American toads breed primarily in permanent fresh water, but alternative breeding sites include: temporary pools, ditches, old beaver flowages, flooded gravel pits, artificial ponds, coves in large lakes, floodplains of rivers, and shallow portions of streams. The common requirement among these habitats seems to be areas of shallow water (Klemens 1993; Hunter et al.1999). In Rhode Island, we found that American toads were most likely to breed in permanent ponds, although they occasionally were detected in ponds that dried by the end of July (Paton and Egan 2001).

Ponds used by breeding American toads can be found in a number of habitats located from sea level to mountain elevations-ranging from suburban backyards in gardens and woods to mountain wilderness; nearly any place where toads can find hiding places, some moisture, and an abundance of insects and other invertebrates for food (Conant and Collins 1991).
 
HYDROLOGY
Found in ponds with a variety of hydroperiods, although they tend to breed more frequently in permanent ponds (Paton and Egan 2001).

hydrology data

 
MOVEMENT CHRONOLOGY
Adult immigration
American toads typically immigrate to breeding ponds in southern Rhode Island during the last week of April (Paton and Crouch In press).

Metamorphs emigration
We found peak emigration of American toad metamorphs to be at the end of July, approximately 3 months after peak immigration of adults (Paton and Crouch In press). However, Klemens (1993) reported metamorphosing young as early as 10 June in Connecticut.

movement data



Movement phenology of American Toad. Data gather over a three year period in 10 ponds surrounded by drift net fences.
(Paton et al. 2000; Paton and Crouch In press).

 
REPRODUCTION
The breeding season for American toads is temperature dependent, peaking typically during mid-April in Rhode Island (Paton and Crouch In press). When environmental conditions are optimal, males toads move to breeding sites. Arriving prior to the females, males begin their harmonious trilling. Females, lured by the call of males, arrive a few days later. Breeding typically occurs within two weeks of emergence and is usually brief, commonly less than 15 days, but calling can continue sporadically until early July (Knox 1999), although Klemens (1993) reported breeding choruses in Connecticut only from mid-March through early June. toads in amplexus
American toads in amplexus
(male is on top of female)

 
EGG MASS

Gelatinous eggs are laid in two long thin parallel strings usually spiraling on the open bottom or entangled in submerged vegetation. The development of the thousands of eggs- numbering from 4,000 to 12,000 eggs (Degraaf and Rudis 1983)- is partially temperature dependent, but hatching usually occurs within 3 to 12 day (Knox 1999).

American toad egg strings can be separated from Fowler's toads by the presence of an inner layer in the gelatin tube and partitions separating the eggs, which are usually in single file (Wright and Wright 1949).

toad eggs
Strand of American toad eggs

 

 
LARVAE

The unicolored black tail musculature and body, the transparent ventral and dorsal fins, and the rounded tipped tail makes the toad tadpole readily distinguishable all other Rhode Island amphibians except Fowler's Toad. Eyes are dorsal. All other species of tadpoles in Rhode Island, except Fowler's toad, have lateral or dorsal-lateral eyes.

After hatching, the tadpoles tend to school in the shallow, sunny waters feeding on suspended matter, algae, plants, and carrion. Basking in these warmer waters raises body temperature and thereby increases metabolic rate and accelerates development (Klemens 1993). Tadpole metamorphosis is complete in 5 to 10 weeks.

toad tadpole
American toad tadpole



 
METAMORPHS
  toad metamorph
Dorsal view

toad metamorph
Ventral view
 
JUVENILES
Age to maturity: According to Dickerson (1906) American toads reach sexual maturity in 3 to 4 years; however, Hamilton (1934) found toads mature a bit sooner - in 2 to 3 years.
 
FOOD
Adults
Adult American toads feed from dawn through evening hours; however, foraging activities decline during periods of high temperatures. They feed primarily on invertebrates with the type of prey generally determined by availability and abundance -though studies have shown that toads can be selective (Hunter et al 1999). Common food types include: adult and larval terrestrial and aquatic insects, arthropods, slugs, and earthworms, sowbugs, spiders, centipedes, and millipedes (Klemens 1993; Degraaf and Rudis 1983). The benefits of American toads have been known since at least 1915. Mattoon (2001) quoted from a study by Kirkland, in a US Department of Agriculture report, who documented the stomach contents of 149 toads, and found pest species including gypsy moths, tent caterpillars, and beetles account for 62% of the toads diet. He estimated one adult toad may consume 10,000 pest insects in a 90-day period.
Larvae
 
PREDATION
Adults
Predominate toad predators include nocturnal mammals, particularly raccoons and skunks, and a variety of snakes including: garter (Thamnophis s. sirtalis), hognose (Heteroden platyrhinos), and water snakes (Nerodia s. sipedon). Toads employ anti-predator defenses including camouflage, escape by burrowing, ejection of urine, and noxious or toxic skin secretions released from enlarged parotid glands and warty skin (Knox 1999). The secretions are mainly cardiotoxic steroids which some mammalian predators (including domestic dogs and cats) painfully learn to avoid (Knox 1999).
Larvae
 
CONSERVATION CONCERNS
Presently thought to be relatively secure in the region (Klemens 1993; DeGraaf and Yamasaki 2001).
spring peeper
NEXT SPECIES
gray treefrog