More info for the term:
coverBreeding: Great Basin spadefoots breed in spring and early summer.
Hovingh and others [
10] reported that in the Bonneville Basin of Utah,
breeding occurred from April to mid-June. Breeding after early summer
is probably uncommon. Spring rains usually provide the stimulus for
males to emerge from their burrows for breeding, although unlike other
spadefoots (Scaphiopus spp.), Great Basin spadefoots do breed during
periods of no rainfall. The stimulus for emergence for breeding in the
absence of rain is unknown. Males move to breeding waters first and
begin vocalizing. Female Great Basin spadefoots move to breeding waters
after only a few males are vocalizing [
10].
Each female produces several hundred eggs contained in a sticky gel.
The female deposits her fertilized eggs in several different locations
within the breeding water: on vegetation, rocks, or anything else that
anchors the eggs. After mating, females return to their burrows.
Males stay at the breeding pool and continue vocalizing until females
stop arriving (presumably because all females in the vicinity have
mated); then the males also return to their burrows [
3].
Mature egg and tadpole stages of development. Photos by Gary Nafis.
Development: Developing rapidly helps Great Basin spadefoots avoid
desiccation and consequent death in their arid environment. Great Basin
spadefoot eggs probably hatch within 2 to 3 days of deposition [
15].
Tadpole development and metamorphosis is complete within 4 to 8 weeks,
depending upon temperature, food quality, and food quantity. Brown [
4]
found that recently fertilized Great Basin spadefoot egg masses,
collected on 20 May from a temporary pond in eastern Washington and
placed in an aquarium, hatched a day later. Hindlegs of tadpoles in the
aquarium developed by 18 days of age, and forelimbs developed by 31
days. Tadpole body mass was greatest at 33 days, when complete head
reorganization (eyes, ears, jaws, muscles, and gill absorption) was
complete. Tail length was greatest 30 days after hatching; the tail was
reabsorped 40 days after hatching [
4]. In the wild, temporary waters
frequently dry out and tadpoles die before larval development is
complete [
3,
4]. Rate of tadpole development may vary with breeding pool
type. In Texas, tadpoles of a related species, Couch's spadefoot
(Scaphiopus couchii), were found to develop more slowly in permanent
waters than in temporary ponds [
14].
Young morphs (metamorphosed preadults) are small; Nussbaum and others
[
15] reported that recently metamorphosed Great Basin spadefoots in
north-central Oregon averaged 0.8 inch (19 mm) in length [
16]. (Adults
are from 1.5 to 2.5 inches [3.7-6.4 cm] long [
18].) Great Basin
spadefoots have high surface-to-volume ratios as morphs. Consequently,
they are highly susceptible to desiccation and seek shade cover
immediately after emerging from breeding pools. Young spadefoots grow
rapidly. Under laboratory conditions, Couch's spadefoot morphs showed a
110 percent increase in length and over a 1,100 percent increase in mass
in a 3-month period [
16].
Hibernation: Spadefoots accumulate fat rapidly in summer. They are
dormant in fall and winter, with dormancy and apparently triggered by
photoperiod [
16]. Spring emergence may be triggered by increased
moisture in the burrow [
3].
Spadefoots extend their dormancy period during drought, and can
apparently remain dormant or mostly dormant for long periods of time.
Fat reserves are metabolized slowly during dormancy, and females may
reabsorb their eggs if spring rains do not occur. Mayhew [
12]
speculated that Couch's spadefoots in the extremely arid Imperial Valley,
California, survived a 20-year local drought by remaining dormant except
during rare summer thunderstorms.
