Complementary Gompertz survival models: decreasing alive versus increasing dead

Area of Science:

• Ecology
• Population Dynamics
• Biostatistics

Background:

• Survival patterns in animal populations are crucial for ecological understanding.
• Classical Gompertz models describe survival but may not capture all observed patterns.
• Existing models often assume a simple exponential decay in population size over time.

Purpose of the Study:

• To introduce and validate an alternative Gompertz model for animal survival.
• To differentiate between standard and alternative Gompertz survival curves.
• To analyze factors influencing which survival model best fits a population.

Main Methods:

• Mathematical modeling of two asymmetric sigmoid survival forms.
• Comparison of standard Gompertz (decreasing alive) and alternative Gompertz (increasing dead) models.
• Analysis of published survival data from various animal populations.

Main Results:

• Identified two distinct animal survival patterns fitting asymmetric sigmoid curves.
• The alternative Gompertz model accurately predicts "non-Gompertzian" survival plots.
• Survival mode varied based on sex, genetic strain, nutrition, and activity levels.

Conclusions:

• Animal survival can be modeled by either standard or alternative Gompertz functions.
• The alternative model captures survival dynamics not explained by traditional assumptions.
• Environmental and genetic factors significantly modulate population survival trajectories.