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Announcements

  • 1st Midterm Exam

    • Date: Next Monday, a half midterm

    • Format: 25 minutes, 2 pages, approximately 6 questions.

    • Coverage: Entire course content through spatial organization and movements, including lectures and readings this week.

    • Arrangements for specific students: Those with special arrangements may leave after the lecture and exam distribution.

  • Office Hours Changes

    • No office hours today (due to another commitment).

    • Rescheduled to tomorrow (Friday) at 11 AM.

Lecture Overview

  • Demography and Wildlife Conservation

    • Understanding population data is critical; don’t memorize numbers but instead focus on understanding calculations and their relevance.

Population Data Columns

  1. Column 1: Age ( X Series)

    • Data on age in years; typically in 1-year intervals.

  2. Column 2: Survival Data ( NX Series)

    • Example: 337 baby Belding’s ground squirrels; 130 survived after year one, indicating some died, while some may have emigrated.

    • Importance of tracking population changes over time.

  3. Column 3: Number Dying ( DX Series)

    • Calculated through subtraction of surviving from initial count (e.g. 337 - 130 = 207 died in year one).

  4. Column 4: Proportion Dying ( QX Series)

    • Calculated by dividing the number dying by initial population.

    • High juvenile mortality followed by stabilization around 50% annual survival.

  5. Column 5: Survival Probability ( LX Series)

    • Calculated by dividing the number alive at each age by the initial population number.

    • Enables comparison across populations.

  6. Column 6: Expected Female Offspring ( MX Series)

    • Average number of female offspring each female produces at each age, calculated based on litter size among others.

  7. Column 7: Reproductive Output ( LXMX Series)

    • Combines survival probability with expected reproductive output to measure total female offspring expected from each age-group.

Key Concepts of Demography

  • Net Reproductive Rate (R_0)

    • Expected number of female offspring produced in a lifetime; critical for understanding population viability.

    • R_0 > 1: increasing population

    • R_0 < 1: declining population

  • Survivorship Curves

    • Type 1: High juvenile survival, steep decline in old age (e.g., hippos, humans).

    • Type 2: Constant mortality rate regardless of age (e.g., some birds and mammals).

    • Type 3: High juvenile mortality but high annual survival after reaching a certain age (e.g., sea turtles, some insect species).

Practical Application and Conservation Considerations

  • Age of First Reproduction

    • Critical demographic factor influencing population growth and conservation efforts. Delayed reproduction can hinder recovery in endangered species.

  • Reproductive Value

    • Expected offspring a female will produce for the rest of her life; vital for prioritizing conservation efforts towards females that can contribute more effectively to population recovery.

Next Steps

  • Will continue on reproductive value and its importance in population management on Friday.