Estimation of temporary emigration in male toads

Area of Science:

• Ecology
• Wildlife Biology
• Amphibian Conservation

Background:

• Male boreal toads (Bufo boreas) are generally assumed to exhibit high site fidelity, returning to breeding grounds annually.
• However, the extent of annual return and factors influencing temporary absence are not fully understood.

Purpose of the Study:

• To estimate temporary emigration rates in male boreal toads at three distinct Colorado breeding sites.
• To investigate site-specific and temporal variations in temporary emigration.
• To explore potential relationships between temporary emigration and weather variables.

Main Methods:

• Utilized Pollock's robust design, a capture-recapture statistical framework.
• Collected data over multiple years (1992-1998) across three study sites in Colorado.
• Analyzed probabilities of male toads being absent from breeding sites in given years.

Main Results:

• Confirmed that not all male boreal toads return to breeding sites annually, challenging previous assumptions.
• Demonstrated significant variation in temporary emigration probabilities, ranging from 10% to 95% across sites and years.
• Found weak evidence for increased return probability after a year of absence; state-dependent emigration was not supported.
• Observed imprecise estimates for the impact of weather variables on temporary emigration.

Conclusions:

• Temporary emigration is a notable phenomenon in male boreal toad populations, varying considerably by location and time.
• The assumption of consistent annual breeding site return for male boreal toads may not hold true.
• Further research is needed to precisely determine the influence of environmental factors on toad emigration patterns.