Timeline of nuptial pad growth across frog maturation stages

The development of nuptial pads is not a one-time event but a cyclical process that occurs annually throughout a male frog's mature life.

• Juvenile Stage: Young, sexually immature males have smooth thumbs with no trace of nuptial pads.
• First Maturation: During their first breeding season after reaching sexual maturity, the pads will develop for the first time, often appearing smaller and less pronounced than in older, larger males.
• Pre-Breeding Season (Annual): As environmental cues like increasing daylight and temperature signal the start of the breeding season, androgen levels rise. Over several weeks, the pads begin to swell, darken, and the keratinized spines emerge from the skin.
• Peak Breeding Season: The pads reach their maximum size, roughness, and pigmentation. They are fully functional and remain this way for the duration of mating activity.
• Post-Breeding Season: Once the breeding season ends, androgen levels plummet. The pads regress, the keratinized spines are shed, and the skin on the thumbs becomes smooth again, conserving energy until the next year.