Western Toad - Timing of Major Life Events

Timing of Major Life Events

Western toads are active from January to October, depending on latitude and elevation. Boreal toads in one Colorado population used natural chambers near a small stream bed. The high water table, constantly flowing stream, and deep winter snow served to maintain the air temperature within the hibernaculum at a point slightly above freezing. Emergence from hibernation followed a few days of warm temperatures that freed the entrance and increased temperatures within the chamber to about 39.2 °F (4 °C).

At low elevations western toads are active at night; at high elevations and in the northern parts of their range they are diurnal. Body temperature of western toads is closely correlated with the substrate temperature. Basking and conduction from the substrate are primary means of increasing body temperature and cooling is achieved by evaporative cooling and conduction of heat to a cooler medium. Diurnal and nocturnal activity are often related to seasonal changes in temperature; most western toads are diurnal during the spring and fall but are nocturnal during the warmer summer months.

In central Oregon, the minimum breeding age for male western toads is 3 years, and probably 4 or 5 years for females. California toads are reported as sexually mature at 2 years of age. Male western toads breed every year; females breed at less regular intervals, depending on individual condition and previous years' breeding effort. Sex ratios differ according to habitat type; males are more numerous in wet areas and females are more numerous in dry habitats.

Eggs are laid in open water from February to July, with peak activity occurring in April. Timing of egg-laying activity varies with elevation and weather conditions. In Colorado, initiation of breeding was correlated with the onset of warming weather and initiation of snowpack melting. Eggs are usually laid in late May or early June. In western Montana, a few males were present on the shores (of two gravel pits) by May 11, 1967, and by May 14, each pond contained at least 30 males. Males were spaced at least 1 foot (0.3 m) apart, all facing the shore Eggs are laid in gelatinous strings of 13 to 52 eggs per inch, in masses of up to 16,500 per.clutch. Egg development rate is partially dependent on temperature; hatching times vary.

Metamorphosis is usually completed within 3 months of egg laying. The time required for metamorphosis is given as 30 to 45 days for the boreal toad and 28 to 45 days for the California toad.

Female western toads at least 10 to 11 years of age have been reported. In Colorado, boreal toads probably attain a maximum age of at least 9 years.